Combined Spinal-Epidural Anesthesia?

Joseph Eldor, MD

Preface
Origin
Soresi technique
Curelaru technique
Needle-through-needle technique
Eldor needle technique
Huber needle technique
Eldor, Coombs and Torrieri technique
Indications
Problems
The twin theory
Failed spinal or epidural anesthesia
One needle technique for combined spinal-epidural anesthesia
Aspiration pneumonia prevention by the CSEA
Intraoperative challenges
Anesthesia and public image
Huber needle and Tuohy catheter
Total spinal anesthesia: The origin of CSEGA
What is anethesia?
Use of ephedrine in CSEGA
Cardiovascular effects of CSEGA
Cord ischemia and preemptive analgesia
CSEA for Cesarean section
Corning
Bier
A new look at the lumbar extradural space pressure
Do not rotate the epidural needle
Epidural rostal augmentation of spinal anesthesia
Metallic particles in the needle-through-needle technique
Superselective spinal anesthesia
CSEA in uncommon disease
CSEA for laparoscopic operations
Postoperative epidural analgesia
Unilateral spinal anesthesia
CSEA for abdominal operations
CSEA for thoracic operations
Anesthetic risk factors
Medico-legal aspects of CSEA
Spinal opioid pruritus and emesis
Endocrine responses to spinal or epidural anesthesia
Epidural unilateral blockade
Combined spinal-epidural anesthesia: The anesthesia of choice
Epidural catheter strength
Epidural catheter paresthesias
CSEA and anticoagulation
Combined spinal-epidural analgesia in labor
Combined spinal-epidural anesthesia for orthopedic operations
Combined end-multiple lateral holes (CEMLH) epidural catheter
Double-hole pencil-point spinal needle
Epidural catheter test dose in the combined spinal-epidural anesthesia
Spinal and epidural opioid analgesia
The choice of the anesthesiologists
Epidural catheter malposition
Woolley and Roe case
Anesthetic costs
From the skin to the spinal-epidural spaces
Myint case
Spinal needles
Meningitis post spinal-epidural anesthesia
Preemptive analgesia and combined spinal-epidural anesthesia
Sympathetic innervation and CSEA
The politics of anesthesiology
Preconclusion
Conclusion

Preface

CSEA (combined spinal-epidural anesthesia) and CSEGA (combined spinal-epidural-general anesthesia) are new modalities of anesthesia for almost any patient at any age. This book highlights the subject from various points of view. It doen`t intend to teach. It`s goal is to encourage the anesthesiologists to practise what they already know in the best way they think is good for themselves while being a patient. It is a kind of a balanced anesthesia which uses techniques instead of drugs to accomplish the ideal kind of anesthesia for the patients. This new frontier in anesthesia should open a new era of anesthetic quality and cost-effectiveness. However, in the second edition of Principles and Practice of Obstetric Analgesia and Anesthesia, edited by Bonica JJ and McDonald JS, and published in 1995 by Williams & Wilkins, there are 1344 pages. The chapter on epidural analgesia and anesthesia contains 127 pages. That on subarachnoid block - 26 pages. On subarachnoid/epidural combination there is only half a page with only 2 references in the chapter on cesarean section. So, the new combined spinal-epidural anesthesia gained only 0.03% of the space in a book published in 1995 on the practice of obstetric analgesia and anesthesia. This is really not its present worth, neither its future...

"It has long been an axiom of mine that the little things are infinitely the most important" (Arthur Conan Doyle).

"If pain could have cured us we should long ago have been saved" (George Santayana).

"The greatest evil is physical pain" (St. Augustine of Hippo).

Origin

The first epidural analgesia was done by Corning (1) in 1885 inadvertently. Lumbar dural puncture was introduced in 1891 by Wynter (2) in England and Quincke (3) in Germany. Von Ziemssen (4) in 1894 suggested the feasibility of injecting drugs by means of lumbar dural puncture. Bier (5), a surgeon at the Royal Chirurgical Clinic in Kiel, was the first to inject cocaine into the spinal space. It was between August 16 and 27, 1898. It took 52 years since Corning`s discovery of the epidural analgesia and 39 years since Bier`s spinal anesthesia that these two compartments were first combined by Soresi (6) in 1937. It took another 42 years until Curelaru (7) in 1979 used this combined spinal-epidural anesthesia again. Even the discoveries of Corning and Bier are 13 years apart. However, the first anesthesia (maybe it was combined spinal-epidural anesthesia - who knows?...) was done by God (8) "caused a deep sleep to fall upon Adam" for rib extraction. The combined approach can also have its origin in the Bible: "Two are better than one" (9). Or you can look at it from Mark Twain`s point of view: "Name the greatest of all the inventors. Accident". 1. Corning JL. Spinal anaesthesia and local medication of the cord. NY Med J 1885;42:483-485 2. Wynter WE. Lumbar puncture. Lancet 1891;1:981-982 3. Quincke HI. Die technik der lumbalpunktion. Verh Dtsch Ges Inn Med 1891;10:321-331 4. Von Ziemssen HW. Allgemeine behandlung der infektionskrankenheiten. Jena 1894 5. Bier A. Versuche uber Cocainisirung des Ruckenmarkes. Dtsch Ztschr Chir 1899;51:361-369 6. Soresi AL. Episubdural anesthesia. Anesth Analg 1937;16:306-310 7. Curelaru I. Long duration subarachnoid anaesthesia with continuous epidural block. Praktische Anasthesie Wiederbelelung und Intensivtherapie 1979;14:71-78 8. Genesis 2:21 9. Ecclesiastes 4:9

Soresi technique

Soresi (1) used a fine needle without stilet and introduced it into the epidural space using the hanging drop technique. While in the epidural space he injected 7-8 ml of dissolved novocain. Then he pierced the dura and poured another 2 ml of dissolved novocain into the spinal space. This gave his patients anesthesia for a period of 24-48 hours! He and his colleagues employed this method in over 200 patients. He concluded that "by combining the two methods many of the disadvantages of both methods are eliminated and their advantages are enhanced to an almost incredible degree". 1. Soresi AL. Episubdural anesthesia. Anesth Analg 1937;16:306-310

Curelaru technique

Forty two years later, the Swedish anesthesiologist, Curelaru (1), while working in Bucharest, Romania, tested on 150 patients the method of spinal anesthesia with continuous epidural block. The punctures of the epidural and subarachnoid spaces were done through two intervertebral spaces. The puncture of the epidural space was performed 1-2 intervertebral spaces higher than the subarachnoid. Anesthesia was always started with the introduction of an epidural catheter. After introducing the epidural catheter, the puncture of the subarachnoid space was done, followed by subarachnoid injection of the anesthetic solution. Curelaru concluded its advantages as "the possibility of obtaining a high quality conduction anaesthesia, virtually unlimited in time, the ability to extend over several anatomical regions the surgical field, minimal toxicity, the absence of postoperative pulmonary complications and the economy". 1. Curelaru I. Long duration subarachnoid anaesthesia with continuous epidural block. Praktische Anasthesie Wiederbelelung und Intensivtherapie 1979;14:71-78

Nedle-through-needle technique

Coates (1) from England and Mumtaz, Daz and Kuz (2) from Sweden, in two separate letters in the same issue of Anaesthesia, in 1982, first described the insertion of a long spinal needle through the epidural needle for performing the combined spinal-epidural anesthesia. Coates found the technique "simple, reliable and relatively quick to perform". After injecting the anesthetic solution into the subarachnoid space, the spinal needle is withdrawn and an epidural catheter is threaded through the same lumen of the epidural needle, through which the spinal needle was inserted. 1. Coates MB. Combined subarachnoid and epidural techniques. A single space technique for surgery of the hip and lower limb. Anaesthesia 1982;37:89-90 2. Mumtaz MH, Daz M, Kuz M. Combined subarachnoid and epidural techniques: Another single space technique for orthopaedic surgery. Anaesthesia 1982;37:90

Eldor needle technique

The Eldor needle (1) was first described in 1990. The Eldor needle is a combined spinal-epidural needle which is composed of an 18 gauge epidural needle with a 20 gauge spinal conduit. This is a specialized needle for the combined spinal-epidural anesthesia. There is no need of long spinal needles. The epidural catheter can be inserted before the spinal anesthetic injection. The Eldor needle facilitates the insertion of very small gauge spinal needles through its spinal conduit, so significantly reduces the incidence of post-dural puncture headache. There is no danger of epidural catheter protrusion through the dural hole made by the spinal needle. There are no metallic particles production while the spinal needle passes through the bent epidural needle tip, as in the needle-through-needle technique. The procedure of the Eldor needle is quite simple and straightforward. First, the spinal needle is introduced into the guide needle as far as the distal end of the latter. Then, the now Eldor needle is introduced into the selected intervertebral space and the epidural space is located using the well-known indicator methods. After that the epidural catheter is introduced into the epidural space, confirming its position by the test dose technique. Then, the spinal needle is slowly pushed in to puncture the dura, until cerebrospinal fluid is obtained. The anesthetic solution is injected through the spinal needle into the spinal space. Subsequently, the spinal needle is slowly withdrawn from the guide needle and then the Eldor needle is withdrawn, leaving the epidural catheter in position in the epidural space. 1. Eldor J, Guedj P. Une nouvelle auguille pour l`anesthesie rachidienne et peridurale conjointe. Ann Fr Anesth Reanim 1990;9:571-572

Huber needle technique

Huber (1), the inventor of the "Tuohy" epidural needle, also patented in 1953 an hypodermic needle with an "auxiliary outlet being disposed in transverse alignment with the channel outlet" (2). Hanaoka (3) described in 1986 its use in 500 patients. This needle has a very small hole behind the epidural needle tip ("back eye"). A small gauge spinal needle is inserted through that hole and punctures the dura. After withdrawing the spinal needle an epidural catheter is introduced through the epidural needle. 1. Eldor J. Huber needle and Tuohy catheter. Reg Anesth 1995;20:252-253 2. Huber RL. Hypodermic needle. US Patent No. 2,748,769 3. Hanaoka K. Experience in the use of Hanaoka`s needles for spinal-continuous epidural anaesthesia (500 cases). 7th Asian Australasian Congress of Anaesthesiologists Abstracts. Hong Kong, 1986;161-162

Eldor, Coombs and Torrieri technique

Eldor (1) and Torrieri (2) described in separate letters, in 1988, an epidural needle with a spinal needle attached to it. Through the spinal needle a longer spinal needle is inserted into the subarachnoid space, while an epidural catheter is introduced through the epidural needle into the epidural space. A few months before the publication of these letters, Coombs (3) applied for a patent on the same device. 1. Eldor J, Chaimsky G. Combined spinal-epidural needle (CSEN). Can Anaesth Soc J 1988;35:537-8 2. Torrieri A, Aldrete JA. Letter to the Editor. Acta Anaesthesiologica Belgica 1988;39:65-66 3. Coombs DW. Multi-lumen epidural-spinal needle. US Patent No. 4,808,157

Indications

Combined spinal-epidural anesthesia is like "to paint the fence" from both its sides. The indications are those of the spinal or epidural alone and even more. Rawal (1) made a survey in 17 European countries on their anesthetic choices in 1992. 17% of the procedures were performed under central blocks. Among these blocks - 56% were spinal; 40% - epidural and 4% - combined spinal-epidural anesthesia. The commonest indication for combined spinal-epidural blocks was hip replacement surgery (28.2%), followed by hysterectomy (19%), knee surgery (14.4%), Cesarean section (14%), emergency Cesarean section (13%), femur fracture in elderly patients (7.2%) and prostatectomy (5.6%). This under-utility of regional anesthesia (only 17% of the procedures) is in contrast to how the anesthesiologists would like to be anesthetized in case they need an operation: In 1986, Broadman et al. (2) confirmed that 92% of the anesthesiologists preferred regional over general anesthesia for their own hypothetical surgery, while 74% preferred a regional technique for their own elective extremity surgery. This is in accordance with a previous survey done in 1973 by Katz (3) in which 68% of the American anesthesiologists surveyed preferred regional anesthesia for their own anesthetic during an unspecified elective surgical procedure. The spectrum of indications for the combined spinal-epidural anesthesia ranges from labor analgesia (4,5) to high abdominal and even thoracic and head operations (6) by the adjuvant use of an endotracheal tube ventilation. The dosages of the local anesthetics with or without opioids that are injected into the spinal and epidural spaces are now evaluated in various hospitals around the world. The dosage combinations are enormous. The story has only begun. 1. Rawal N. European trends in the use of combined spinal epidural technique - A 17-nation survey. Reg Anesth 1995;20 (Suppl):162 2. Broadman LM, Mesrobian R, Ruttiman U, McGill WA. Do anesthesiologists prefer a regional or a general anesthesia for themselves? Reg Anesth 1986;11:557 3. Katz J. A survey of anesthetic choice among anesthesiologists. Anesth Analg 1973;52:373-5 4. Abouleish A, Abouleish E, Camann W. Combined spinal-epidural analgesia in advanced labour. Can J Anaesth 1994;41:575-8 5. Arkoosh VA, Sharkey SJ, Norris MC, Isaacson W, Honet JE, Leighton BL. Subarachnoid block analgesia: Fentanyl and morphine versus fentanyl and morphine. Reg Anesth 1994;19:243-246 6. Eldor J. Combined spinal-epidural-general anesthesia. Reg Anesth 1994;19:365-6

Problems

Blumgart et al. (1) found that the mechanism of extension of spinal anesthesia by extradural injection of local anesthetics is largely a volume effect. Using extradural saline 10 ml and extradural bupivacaine 0.5% 10 ml - the extension of the block was found to be similar in the saline or the bupivacaine groups, and significantly faster than the group which received no extradural injection after spinal injection of 1.6-1.8 ml of 0.5% hyperbaric bupivacaine. Suzuki et al. (2) found that spinal puncture with a 26 gauge spinal needle, with no spinal anesthetic injection, immediately before epidural injection of 18 ml 2% mepivacaine resulted in rapid caudal spread of analgesia as compared to an epidural anesthetic alone. They attributed it to the flow of local anesthetic into the subarachnoid space through the perforation produced by the spinal needle. In all the techniques, except the Eldor needle and Curelaru`s double-space techniques, there is inability to perform the epidural catheter test dose due to the fact that the epidural catheter is inserted after the subarachnoid local anesthetic injection. This can result in epidural catheter malposition in the subarachnoid space or intravascular with a danger of total spinal, delayed cardiorespiratory arrest due to opioid overdosage (3,4) or convulsions. Due to the insertion of the spinal needle through the bent tip of the epidural needle in the needle-through-needle technique there is friction that produces metallic microparticles that can be introduced further into the epidural space by the epidural catheter insertion (5,6). If there is a delay in epidural catheter threading in the needle-through-needle technique there is a partial spinal anesthesia while using the hyperbaric anesthetic solution (7), with the need to supplement it further through the epidural route. The incidence of epidural needle or catheter unintentional dural puncture ranges from 2.5% (8) to 0.6% (9) and even 0.26% (10). However, using the needle-through-needle technique the chances are greater because of the same pathway shared by the spinal needle and the epidural catheter in the epidural space and the force exerted by the friction between the spinal needle and the epidural needle`s tip that can advance forward the epidural needle causing an unrecognized dural tear by the epidural needle, through which an epidural catheter can be threaded inadvertently. 1. Blumgart CH, Ryall D, Dennison B, Thompson-Hill LM. Mechanism of extension of spinal anaesthesia by extradural injection of local anaesthetic. Br J Anaesth 1992;69:457-460 2. Suzuki N, Koyanemaru M, Onizuka S, Takasaki M. Dural puncture with a 26-gauge spinal needle affects epidural anesthesia. Reg Anesth 1995;20 (Suppl):118 3. Myint Y, Bailey PW, Milne BR. Cardiorespiratory arrest following combined spinal epidural anaesthesia for caesarean section. Anaesthesia 1993;48:684-686 4. Eldor J, Guedj P, Levine S. Delayed respiratory arrest in combined spinal-epidural anesthesia. Reg Anesth 1994;19:418-422 5. Eldor J, Brodsky V. Danger of metallic particles in the spinal-epidural spaces using the needle-through-needle approach. Acta Anaesthesiol Scand 1991;35:461 6. Eldor J. Metallic particles in the spinal-epidural needle technique. Reg anesth 1994;19:219-220 7. Fan SZ, Susetio L, Wang YP, Cheng YJ, Liu CC. Low dose of intrathecal hyperbaric bupivacaine combined with epidural lidocaine for cesarean section - a balance block technique. Anesth Analg 1994;78:474-7 8. Dawkins CJM. An analysis of the complications of extradural and caudal block. Anaesthesia 1969;24:554-563 9. Tanaka K, Watanabe R, Harada T, Dan K. Extensive application of epidural anesthesia and analgesia in a university hospital: Incidence of complications related to technique. Reg Anesth 1993;18:34-38 10. Macdonald R, Lyons G. Unintentional dural puncture, Anaesthesia 1988;43:705

The twin theory

Spinal anesthesia is a safe, cost-effective and reliable form of anesthesia. Many anesthesiologists would regard the epidural as an insurance against unsatisfactory spinal anesthesia, aiming to provide complete anesthesia by the subarachnoid route (1). Another approach is the use of a minimal dose of spinal anesthesia for a shorter duration with the flexibility of epidural reinforcement if necessary. For many years in many anesthetic departments around the world there was a philosophy that extradurals are for young people and the intrathecal route for the old, with few exceptions. Seeberger et al. (2) addressed the question: Is the spinal or the epidural technique better? Two hundred and two patients younger than 50 years underwent spinal or epidural anesthesia. Spinals were performed with 24-gauge Sprotte needles and epidurals with 18 gauge Tuohy needles and catheters. The failure rate of both techniques was 5%. Patient acceptance was high in both groups (97% in the spinal; 93% in the epidural). The authors concluded that spinal anesthesia was superior, because of better quality of anesthesia, no risk of intoxication, less time needed to perform the block, and less expensive kits. However, using the combined spinal-epidural anesthesia there is no more a question of which is better, as Greene and Brull (3) wrote: "Epidural and spinal anesthesia are indeed related to each other, but only to the same extent as cousins, or, at best, siblings; monozygotic twins they are not". 1. Brownridge P. Epidural and subarachnoid analgesia for elective caesarean section. Anaesthesia 1981;36:70 2. Seeberger MO, Lang ML, Drewe J, Schneider M, Hauser E, Hruby J. Comparison of spinal and epidural anesthesia for patients younger than 50 years of age. Anesth Analg 1994;78:667-73 3. Greene NM, Brull SJ. Physiology of spinal anesthesia. 4th ed. Baltimore:Williams & Wilkins, 1993, p.IX

Failed Spinal or Epidural Anesthesia

Failure of regional anesthesia has been reported to be in the order of 4% (1,2). The failure rate of spinal anesthesia alone ranged between 3.1% - 17% involving 100 to 1,891 patients respectively (3,4). Johr et al. (5) investigated the incidence of failed spinal anesthesia in a Swiss teaching institution. Of 3,004 blocks 197 (6.5%) did not provide satisfactory analgesia. The 197 failures included: absent blockade - 36; failure to obtain CSF - 6; level too low - 90; duration too short - 36; intensity too weak - 28; unclear - 1. However, 531 (17.4%) blocks were excessively high (45 - cervical level; 2 - required intubation). The management of the 197 failed blocks included: additional spinal anesthesia - 117; epidural anesthesia - 2; local infiltration - 1; general anesthesia - 30; IV supplementation - 47. Manchikanti et al. (6) found that the failure rate with sole use of spinal anesthesia ranges between 0.46% and 35% . Epidural analgesia sometimes falls short of perfection due to the variable "compartmentalisation" of the epidural space (7). Shesky et al. (8) studied in 1983 the dose-response of bupivacaine for spinal anesthesia. Sixty males having transurethral surgery were studied using 10-, 15- and 20 mg doses of glucose-free bupivacaine as either a 0.5 or a 0.75% solution. Both 15 and 20 mg of either concentration of bupivacaine provided satisfactory spinal anesthesia. However, three of 20 patients receiving 10 mg dose required supplementation with general anesthesia. Lyons et al. (9) used a 26G spinal needle through the Tuohy epidural needle for the combined spinal-epidural anesthesia. Unsuccessful spinal anesthesia occurred in 8 of the 50 patients (16%). In four patients, anesthesia was provided by the epidural route, while in the remainder another intrathecal injection was made using a different intervertebral space. Lesser et al. (10) evaluated the use of a 30G spinal needle through the Tuohy epidural needle for the combined spinal-epidural anesthesia. Unsuccessful spinal anesthesia was in 12 of the 50 patients (24%) studied. Six failures were due to unsuccessful dural puncture and six to inadequate block. Due to requirement of large doses of local anesthetics for epidural block there is a risk of toxic complications (11,12). In spite of large doses epidural block may fail to provide adequate analgesia in up to 25% of patients due to difficulty in blocking sacral roots (13-15). Failure to obtain CSF when using the needle-through-needle technique may occur despite successful dural puncture if the needle orifice is occluded, for example by a nerve root. It may also happen if dural puncture has failed to occur because the spinal needle is too short or is placed too laterally as the epidural needle may have entered the epidural space at an angle (16). One technical problem of the needle-through-needle method is the occasional difficulty in threading the catheter into the epidural space after injection of the spinal solution. If some minutes are spent in replacing the epidural needle, the spinal solution may become relatively "fixed" on the dependent side (17). However, when spinal and epidural anesthesia are combined, recourse to general anesthesia becomes a very rare event. 1. Milne MK, Lawson JIM. Epidural analgesia for Caesarean section. A review of 182 cases. Br J Anaesth 1973;45:1206-10 2.Moir DD. Local anaesthetic techniques in obstetrics. Br J Anaesth 1986;58:747-59. 3. Tarkkila PJ. Incidence and causes of failed spinal anesthetics in a university hospital: a prospective study. Reg Anesth 1991;16:48-51 4. Levy JH, Islas JA, Ghia JN, Turnbull C. A retrospective study of the incidence and causes of failed spinal anesthetics in a university hospital. Anesth Analg 1985;64:705-10 5. Johr M, Hess FA, Balogh S, Gerber H. Incidence and management of failed spinal anaesthesia in a teaching institution: A prospective evaluation of 3,004 epidural blocks. Acta Anaesthesiol Scand 1995;39:A421 6. Manchikanti L, Hadley C, Markwell SJ, Colliver JA. A retrospective analysis of failed spinal anesthetic attempts in a community hospital. Anesth Analg 1987;66:363-6. 7. Husemeyer RP, White DC. Topography of the lumbar epidural space. A study in cadavers using injected polyester resin. Anaesthesia 1980;35:7-11. 8. Sheskey MC, Rocco AG, Bizzari-Schmid M, Francis DM, Edstrom H, Covino BG. A dose-response study of bupivacaine for spinal anesthesia. Anesth Analg 1983;62:931-5. 9. Lyons G, Macdonald R, Mikl B. Combined epidural/spinal anaesthesia for Caesarean section: Through the needle or in separate spaces? Anaesthesia 1992;47:199-201. 10. Lesser P, Bembridge M, Lyons G, Macdonald R. An evaluation of a 30-gauge needle for spinal anaesthesia for Caesarean section. Anaesthesia 1990;45:767-8. 11. Abouleish E, Bourke D. Concerning the use and abuse of test doses for epidural anesthesia. Anesthesiology 1984;61:344-5. 12. Thorburn J, Moir DD. Bupivacaine toxicity in association with extradural analgesia for Caesarean section. Br J Anaesth 1984;56:551-3. 13. Larsen JV. Obstetric analgesia and anaesthesia. Clinics in Obst Gyn 1982;9:685-710. 14. Thorburn J, Moir DD. Epidural analgesia for elective Caesarean section. Technique and its assessment. Anaesthesia 1980;35:3-6. 15. Kileff ME, James FM, Dewan DM, Floyd HM. Neonatal neurobehavioral responses after epidural anesthesia for Cesarean section using lidocaine and bupivacaine. Anesth Analg 1984;63:413-7. 16. Patel M, Samsoon G, Swami A, Morgan BM. Flow characteristics of long spinal needles. Anaesthesia 1994;49:223-225. 17. Carrie LES. Epidural versus combined spinal epidural block for Caesarean section. Acta Anaesthesiol Scand 1988;32:595-596.

One needle technique for combined spinal-epidural anesthesia

Vitenbeck (1), in 1980, described the use of combined spinal-epidural anesthesia in 210 patients using the same needle for the spinal and the epidural injections. He first injected 1-2 ml Dicaine 0.2% into the subarachnoid space. Five minutes later he injected through the same needle, which was withdrawn into the epidural space, 25-37 ml of Dicaine 0.2-0.3% in distilled water with adrenaline 1:1,000. Anesthesia lasted for 2.5-3.5 hr. In only 3 patients he needed to induce general anesthesia because the operation lasted more than the effect of the regional anesthesia. Only 2 patients (0.9%) had postdural puncture headaches. 1. Vitenbeck IA. Associated spino-peridural anesthesia as a variant of conduction anesthesia during operation. Vestn Khir 1981;126:123-128.

Aspiration pneumonia prevention by the CSEA

In a review of maternal mortality published in 1991 (1) Glassenberg quoted statistics collected up to the mid-1980`s in the UK, USA and Sweden. Over the preceding decade, aspiration as a cause of maternal death had fallen to two deaths per million births, or one death per 30,000 anesthetics, still seven times the aspiration fatality rate for the non-obstetric surgical population, and closely associated with failed intubation. Dennis W. Coombs (2) wrote in 1983 an editorial entitled "Aspiration pneumonia prophylaxis". He said that "unfortunately, the magic prophylactic bullet is not available yet for all situations". However, instead of a "cimetidine prophylaxis" it is suggested to use the "CSEA prophylaxis"... 1. Glassenberg R. General anaesthesia and maternal mortality. Semin Perinatol 1991;15:386-396. 2. Coombs DW. Aspiration pneumonia prophylaxis. Anesth Analg 1983;62:1055-8.

Intraoperative challenges

Although developments in anesthesia and surgery have improved overall surgical outcome during recent decades, there is still concern about the detrimental effects of operative procedures, such as myocardial infarction, pulmonary complications, thromboembolism, gastrointestinal paralysis, immunosuppression,etc., that cannot be attributed solely to imperfections in surgical technique (1). Edwards et al. (2) studied 100 patients undergoing transurethral surgery, who were allocated randomly to receive either general or spinal anesthesia. The overall incidence of myocardial ischemia increased from 18% to 26% between the preoperative and postoperative periods, but no significant difference between the two anesthetic techniques. Nakatsuka et al. (3) used spinal anesthesia combined with epidural anesthesia in nine patients with ischemic heart disease having femoral-distal artery bypass surgery. A 20-gauge epidural catheter and a 24-gauge spinal catheter were inserted. Epidural anesthesia was initiated using 10-12 ml of 2% lidocaine and switched to continuous epidural anesthesia with 0.5% bupivacaine (5-7 ml/hr). Spinal bupivacaine 0.75% was injected up to 5 mg through the spinal catheter as needed to manage surgical pain of lower leg and foot. Seven out of 9 patients required additional spinal anesthesia. Juelsgaard et al. (4) examined continuous spinal anesthesia vs single dose spinal anesthesia vs general anesthesia in 44 elderly patients scheduled for hip surgery and receiving medication for angina or displaying ECG signs of coronary sclerosis. In the continuous spinal anesthesia they injected 1.5 ml isobaric bupivacaine 0.5% with 0.5 ml increments to establish T10 anesthesia. In the single dose spinal anesthesia group they injected 2.5 ml isobaric bupivacaine 0.5%. The general anesthesia consisted of fentanyl, thiopentone, N2O/O2 and enflurane. There were only 3 hypotensive events in the continuous spinal group (3/10 patients) compared to 24/13 patients in the single dose spinal group and 29/11 patients in the general anesthesia group. There was only 1 ischemic event in the continuous spinal group compared to 93 ischemic events in the single dose spinal and 11 in the general anesthesia group. These benefits of continuous spinal anesthesia can be obtained also in the combined spinal-epidural anesthesia, while the spinal injections can be done in incremental doses of 0.5 ml plain bupivacaine through the spinal needle or at a reduced dose of 1-1.5 ml injected slowly into the spinal space, and then supplemented by the epidural route, if necessary. 1. Kehlet H. Postoperative pain relief: A look from the other side. Reg Anesth 1994;19:369-377. 2. Edwards ND, Callaghan LC, White T, Reilly CS. Perioperative myocardial ischemia in patients undergoing transurethral surgery: a pilot study comparing general with spinal anaesthesia. Br J Anaesth 1995;74:368-372. 3. Nakatsuka M, Long SP, Shy DG. Spinal anesthesia combined with epidural anesthesia for peripheral vascular emergency with dual catheters. Anesth Analg 1994;78:S309. 4. Juelsgaard P, Sand NPR, Felsby S, Dalsgaard J, Brink O, Thygesen K. Continuous spinal anaesthesia vs single dose spinal anaesthesia vs general anaesthesia: Perioperative holter monitoring of patients with coronary atherosclerosis. Acta Anaesthesiol Scand 1995;39:A428

Anesthesia and public image

Swinhoe and Groves (1) pinponted again the low public image of anaesthesiology and anaesthesiologists. Their paper was commented by anaesthesiologists from other countries who showed the same trend (2,3). Keep and Jenkins (4) showed in 1978 the same finding that only 67% (65% in Swinhoe and Groves` report) of the patients thought an anaesthesiologist was a medical doctor. Their conclusion was that there is a need to give information sheets to patients preoperatively on the ward. It is possible to attack this genuine problem from another point of view: In 1973, Katz (5) surveyed American anesthesiologists and found that 68% preferred regional anaesthesia for their own anaesthetic during an unspecified elective surgical procedure. In 1986, Broadman et al (6) confirmed that a majority of anaesthesiologists still preferred regional over general anaesthesia for their own extremity surgery. In their survey, 92% of the anaesthesiologists preferred regional over general anaesthesia for their own hypothetical emergency surgery, while 74% preferred a regional technique for their own elective extremity surgery. It is possible that if most anaesthetics are done by the regional techniques there will be much time for the awakened patient to learn that the person at the top of the operating table is not less important than the person who stands behind the sterile curtain... and both of them are medical doctors. So, anesthesiologists have to treat their patients as they would like to be treated while they are patients - and they have already chosen : Regional anaesthesia. This shift in the anaesthetic profession towards the regional techniques will be also a shift in the public recognition and appreciation of anesthesiology and anesthesiologists. 1. Swinhoe CF, Groves ER. Patient`s knowledge of anaesthetic practice and the role of anaesthetists. Anaesthesia 1994;49:165-6. 2. Gajraj NM, Bala AS. Patient`s knowledge of anaesthetists. Anaesthesia 1994;49:559. 3. Ali S, Vivekanaandan P, Tierney E. Patient`s perception of the anaesthetist and anaesthesia. Anaesthesia 1994;49:644-5. 4. Keep PJ, Jenkins JR. As others see us. The patient`s view of the anaesthetist. Anaesthesia 1978;33:43-5. 5. Katz J. A survey of anesthetic choice among anesthesiologists. Anesth Analg 1973;52:373-5. 6. Broadman LM, Mesrobian R, Ruttiman U, McGill WA. Do anesthesiologists prefer a regional or a general anesthetic for themselves? Regional Anesthesia 1986;11:S57.

Huber needle and Tuohy catheter

Total spinal anesthesia: The origin of CSEGA

What is anesthesia?

Definitions of the state of anesthesia: 1. Drug-induced unconsciousness; the patient neither perceives nor recalls noxious stimulation (1). 2. Reversible oblivion and immobility (2). 3. Paralysis, unconsciousness, and attenuation of the stress response (3). 4. Sensory block, motor block, blocking of reflexes, and mental block (4). 5. All separate effects used to protect the patient from the trauma of surgery (5). Jorgensen et al. (6) studied the anesthetic choice of 705 patients of outpatient surgery candidates prior to speaking to the anesthesiologist. Sixty five percent preffered general anesthesia, 22% - spinal anesthesia, and 12% were unsure. Of those who had spinal anesthesia previously, only 33% would select it in the future. Conversely, 70% of patients who had general anesthesia would prefer it again. Concerns about spinal anesthesia were : paralysis, nerve damage, being awake, infection, inadequate anesthesia, backache, fear of needle and headache. The use of regional anesthesia in residency training programs has increased from 21.3% in 1980 to 29.8% in 1990, primarily because of a two-fold rise in the use of epidural anesthesia (7). Advantages of spinal anesthesia: Obviates the need for deep general anesthesia, profound muscle relaxation, cheap, easy to perform, danger of toxic drug signs - negligible. Disadvantages of spinal anesthesia: hypotension, postoperative headache, some patients prefer to be asleep during operation. The combined spinal-epidural anesthesia combines the rapid onset and good muscle relaxation of subarachnoid block with the ability to supplement analgesia through the epidural catheter, intraoperatively and after the operation. Reynolds et al. (8) using plain lumbar x-rays and CT after injection of iodized oil into the extradural space of 19 subjects recorded the depth of the extradural space at the caudal end: 8.3 �1.95 mm (at the level of T12). Westbrook et al. (9) found even a smaller ligamentum flavum-dura mater depth at the L2-3 level: 3.95�1.1 mm by using the magnetic resonance imager of 39 subjects. Pitkin (10) describing spinal anesthesia in 1928 wrote that "in 1912, its use was confined to very elderly people, those considered as `bad risks` and to whom we were afraid to give ether". Koster (11) described in 1928 his experience of spinal anesthesia also in operations of the head, neck and thorax. He wrote: "Any one who can do a lumbar puncture can induce spinal anesthesia; the method is reasonably `fool proof` ". Babcock (12) in 1928 summarized his experience of 24 years with spinal anesthesia: "In no other known way can so profound and extensive an anesthesia be produced by so small a dose of a drug and with so little general toxicity". Bromage (13) stated in 1967 that "the beautiful precision and economy of a subarachnoid block is lacking in epidural anesthesia". Greene and Brull (14) in their preface to the fourth edition of "Physiology of Spinal Anesthesia" have written: "Epidural and spinal anesthesia are indeed related to each other, but only to the same extent as cousins or, at best, siblings; monozygotic twins they are not". 1. Prys-Roberts C. Anaesthesia: a practical or impractical construct? Br J Anaesth 1987;59:1341-5. 2. Eger EI. What is general anesthetic action? Anesth Analg 1993;77:408-9. 3. Pinsker MC. Anesthesia: a pragmatic construct. Anesth Analg 1986;65:819-27. 4. Woodbridge PD. Changing concepts concerning depth of anesthesia. Anesthesiology 1957;18:536-50. 5. Kissin I, Gelman S. Components of anaesthesia. Br J Anaesth 1988;61:237-42. 6. Jorgensen NH, Harders M, Hullander RM, Leivers D. Survey of preference for spinal vs. general anesthesia: Education makes a difference. Reg Anesth 1993;18:S53. 7. Kopacz DJ, Bridenbaugh LD. Are anesthesia residency programs failing regional anesthesia? The past, present and future. Reg Anesth 1993;18:84-87. 8. Reynolds AF, Roberts PA, Pollay M, Stratemeier PH. Quantitative anatomy of the thoracolumbar epidural space. Neurosurgery 1985;17:905-907. 9. Westbrook JL, Renowden SA, Carrie LES. Study of the anatomy of the extradural region using magnetic resonance imaging. Br J Anaesth 1993;71:495-498. 10. Pitkin GP. Controllable spinal anesthesia. Am J Surg 1928;5:537-553. 11. Koster H. Spinal anesthesia, with special reference to its use in surgery of the head, neck and thorax. Am J Surg 1928;5:554-570. 12. Babcock WW. Spinal Anesthesia. An experience of twenty-four years. Am J Surg 1928;5:571-6. 13. Bromage PR. Physiology and pharmacology of epidural analgesia. Anesthesiology 1967;28:592-622. 14. Greene NM, Brull SJ. Physiology of spinal anesthesia. Williams & Wilkins, 4th ed., 1993.

Use of Ephedrine in CSEGA

Ephedrine is the sympathomimetic drug which is most widely used to sustain blood pressure during spinal anesthesia. The active principal was isolated from the chinese herb ma huang in 1885 by Yamanashi (1). Butterworth et al. (2) found that a mixed adrenergic agonist such as ephedrine more ideally corrected the noncardiac circulatory sequelae of total spinal anesthesia in dogs than did either a pure alpha (phenyl-ephrine) or a pure beta-adrenergic agonist (isoproterenol). Butterworth et al. (3) also demonstrated in dogs the effectiveness of dobutamine and dopamine as possible alternatives to ephedrine for the pharmacologic correction of the noncardiac circulatory sequela of total spinal anesthesia. Goertz et al. (4) investigated the effect of ephedrine on left ventricular function in patients without cardiovascular disease under high thoracic epidural analgesia combined with general anesthesia. Ephedrine improved left ventricular contractility without causing relevant changes of left ventricular afterload. 1. Goodman L, Gilman A. The pharmacological basis of therapeutics. New York, The Macmillan Co., 1941, p.1383. 2. Butterworth JF, Piccione Jr W, Berrizbeitia LD, Dance G, Shenim RJ, Cohn LH. Augmentation of venous return by adrenergic agonists during spinal anesthesia. Anesth Analg 1986;65:612-6. 3. Butterworth JF, Austin JC, Johnson MD, Berrizbeitia LD, Dance GR, Howard G, Cohn LH. Effect of total spinal anesthesia on arterial and venous responses to dopamine and doputamine. Anesth Analg 1987;66:209-14. 4. Goertz AW, Hubner C, Seefelder C, Seeling W, Lindner KH, Rockemann MG, Georgieeff M. The effect of ephedrine bolus administration on left ventricular loading and systolic performance during high thoracic epidural anesthesia combined with general anesthesia. Anesth Analg 1994;78:101-5.

Cardiovascular effects of CSEGA

Cord ischemia and preemptive analgesia

Breckwoldt et al. (1) investigated the effect of intrathecal tetracaine on the neurological sequelae of spinal cord ischemia and reperfusion with aortic occlusion in rabbits. They found that intrathecal tetracaine significantly and dramatically abrogated the neurological injury secondary to spinal cord ischemia and reperfusion after aortic occlusion at 30 minutes. Peripheral tissue injury provokes two kinds of modification in the responsiveness of the nervous system: peripheral sensitization and central sensitization. The optimal form of pain treatment may be one that is applied both pre-, intra-, and postoperatively to preempt the establishment of pain hypersensitivity during and after surgery. Woolf and Chong (2) in their review of preemptive analgesia concluded that "although evolution has conserved sensitization in humans, the capacity to inflict `controlled injury` during surgery has clearly not been anticipated". 1. Breckwoldt WL, Genco CM, Connolly RJ, Cleveland RJ, Diehl JT. Spinal cord protection during aortic occlusion: Efficacy of intrathecal tetracaine. Am Thorac Surg 1991;51:959-63. 2. Woolf CJ, Chong MS. Preemptive analgesia - treating postoperative pain by preventing the establishment of central sensitization. Anesth analg 1993;77:362-79.

CSEA for Cesarean section

Corning

The first epidural anesthesia done by Corning, a New York city neurologist, in 1885 was a "walking" epidural. He injected twice 2 ml of a 3% solution of the hydrochlorate of cocaine into the epidural space of a man "addicted to sexual abuse". While standing with eyes closed, the man experienced some dizziness, but no incoordination or motor impairment was discernible in his gait. He left the office an hour or more after the injection and seemed "none worse for the experience" (1). 1. Marx GF. The first spinal anesthesia: Who deserves the laurels? Reg Anesth 1994;19:429-430

Bier

August Bier (1), on August 24, 1898, asked his assistant, Dr. Hilderbrandt, "to perform a lumbar puncture on me", 8 days after he first performed it on a 34-year-old patient for excision of a tuberculous capsule at the ankle joint. Bier wrote that he did not feel any discomfort "except for a quick flash of pain in one leg at the moment that the needle penetrated the meninges". Unfortunately, the experiment was not successful because of an error (the syringe did not fit the needle tightly... and consequently some CSF ran out and most of the cocaine was lost). No sensory loss ensued. Dr. Hilderbrandt immediately offered to submit himself to the experiment, which was successful. Both of them "went to eat after the experiments were performed on our bodies. We had no physical discomfort, we ate, drank wine, and smoked several cigars". However, next morning, after a one hour morning stroll Bier felt slight headache which increased in intensity during the course of the day. Nine days after the puncture, all the symptoms disappeared. After 3 more days, "I was able to go on a train trip without discomfort and was fit enough to participate in a strenuous 8 day hunting trip in the mountains". 1. Bier AKG, von Esmarch JFA. Versuche uber Cocainisirung des Ruckenmarkes. Dtsch Z Chir 1899;51:361-369

A new look at the lumbar extradural space pressure

The answer to the questions: Why does not the Macintosh balloon indicator deflate, or why the hanging drop technique is unreliable was given by Shah (1): The epidural space pressure is influenced by many factors. It is raised by jugular venous compression, ventilation with carbon dioxide and positive end-expiratory pressure (PEEP). The lumbar extradural pressure is increased rapidly with stimuli known to increase CSF pressure. However, the next question is what happens in the "normal" condition (without jugular venous compression or CO2 inhalation, etc.)? There is a wave pressure, which is the lumbar CSF wave pressure transmitted to the epidural space. On that subject Shah quoted an article by Hirai et al (2) published in 1982:"The arterial pressure wave in the spinal CSF originates from the choroid plexus... The pulsatile vibration of the brain parenchyma derived from the blood flow in the cerebral arteries may have enough energy to generate the spinal CSF pulse. The amplitude of the pulse wave varies directly with intracranial pressure". This citation is not exactly true in the light of an investigation published by Urayama (3). He performed system analysis on 16 adult mongrel dogs to determine the origin of the lumbar cerebrospinal fluid pulse wave. The descending thoracic aorta was occluded to evaluate the effects of the spinal arterial pulsations, and the thoracic aorta and inferior vena cava were simultaneously occluded to evaluate the effects of the spinal venous pulsations. It was concluded that, in the first harmonic wave, the components of the lumbar cerebrospinal fluid pulse wave are as follows: spinal arterial pulsations - 39.4%; spinal vascular (arteries and veins) pulsations - 77%; venous pulsations in the spinal canal - 37.6%; and the intracranial pressure pulse wave transmitted through the spinal canal from the intracranial space to the lumbar level - 23%. So, from this investigation we can learn that 77% of the lumbar cerebrospinal fluid pulse wave which is directly transmitted to the extradural space as an extradural pressure wave is originated in the vascular system (arteries and veins), and not in the brain . So, any rise in the blood pressure, which is not an infrequent observation during epidural needle insertion, can give a concomitant rise in the extradural pressure with the loss of the "negative" pressure in the extradural space and "unreliable" hanging drop and Macintosh balloon indicator techniques. 1. Shah JL. Positive lumbar extradural space pressure. Br J Anaesth 1994;73:309-314. 2. Hirai O, Handa H, Ishikawa M. Intracranial pressure pulse waveform: considerations about its origin and methods of estimating intracranial pressure dynamics. Brain Nerve (Tokyo) 1982;34:1059-1065. 3. Urayama K. Origin of lumbar cerebrospinal fluid pulse wave. Spine 1994;19:441-445

Do not rotate the epidural needle

The epidural needle rotation in CSEA using the needle-through-needle technique was first suggested in 1988 by Rawal et al. (1). However, Dr. Rawal abandoned this technique of epidural needle rotation (2) because he was convinced that "180� rotation of the epidural needle may cause dural tear". Nickalls and Dennison (3) found that the distance the spinal needle has to be advanced past the end of the Tuohy needle to just puncture the dura ranges from 0.3 to 1.05 cm. Joshi and McCarroll (4) described two sets of needle-through-needle techniques to perform the combined spinal-epidural anesthesia. They were concerned to find cerebrospinal fluid in the Tuohy needle after removal of the spinal needle. Carter et al. (5) abandoned this technique of epidural needle rotation because it increased the chance of inadvertent dural puncture by a factor of 5.6: there was also a 16.6% incidence of the epidural catheter protruding through the hole made previously by the spinal needle. Meiklejohn (6) found that "postmortem dura mater demonstrated that rotation of the epidural needle significantly decreases the force required to puncture the dura". He concluded that "once the needle has been inserted into the epidural space... it should not be moved for any reason other than to remove it". 1. Rawal N, Schollin J, Wesstrom G. Epidural versus combined spinal epidural block for cesarean section. Acta Anaesthesiol Scand 1988;32:61-6 2. Rawal N. Combined spinal-epidural needle (CSEN) for the combined spinal-epidural block - reply. Acta Anaesthesiol Scand 1989;33:618 3. Nickalls RWD, Dennison B. A modification of the combined spinal and epidural technique. Anaesthesia 1984;39:935 4. Joshi GP, McCarroll SM. Combined spinal-epidural anesthesia using needle-through-needle technique. Anesthesiology 1993;78:406-7 5. Carter LC, Popat MT, Wallace DH. Epidural needle rotation and inadvertent dural puncture with catheter. Anaesthesia 1992;47:447-8 6. Meiklejohn BH. The effect of rotation of an epidural needle. Anaesthesia 1987;42:1180-2

Epidural rostral augmentation of spinal anesthesia

Suzuki et al. (1) found that spinal puncture with a 26G spinal needle, with no spinal anesthetic injection, immediately before epidural injection of 18 ml 2% mepivacaine resulted in rapid caudal spread of analgesia as compared to an epidural anesthesia alone. They attributed it to the flow of local anesthetic into the subarachnoid space through the perforation produced by the spinal needle. Dobson et al. (2) reported of a sudden asystole 70 min after intrathecal injection of 2.75 ml hyperbaric bupivacaine 0.5% in a patient whose cardiac output was being monitored. After successful resuscitation , the height of the block was judged to be T4. According to the authors of the report, monitoring should continue for at least 90 min after induction of spinal anesthesia. Bodily et al. (3) warned that changes in position can alter the spread of sensory blockade for at least 1 hr after the intrathecal injection of a hypobaric solution. They showed that 8 ml lidocaine 0.5% (baricity 0.9985�0.0003, 25�C) produced effective spinal anesthesia for perirectal surgery in the jack-knife position. Dermatomal levels remained low (T11-L5) while the patients were in the head-down position during surgery, but rose two to six dermatomes if the patient`s head was elevated after surgery. Fast rate of injection (0.5 ml/sec) of 5 ml 0.3% bupivacaine into the subarachnoid space results in a higher maximum sensory level than slow rate injection (0.02 ml/sec) (4). Serpell et al. (5) recorded intrathecal pressure after instillation of saline boluses into the epidural space in adult ewes. Mean baseline CSF pressure was 28.5�5.5 mmHg. Five ml saline boluses (1 ml/sec) were injected at 5-minute intervals until CSF pressure exceeded 100 mmHg. Initially, a rapid increase in CSF pressure accompanied each saline bolus with a gradual return to baseline. Up to a cumulative volume of 20 ml (range 5-60), the mean value of peak CSF pressure was 53�12 mmHg and the resting pressure would return to baseline. After a cumulative injection volume of 50.5�39.5 ml (range 15-115) saline, the resting pressure progressively rose to 64.1 �17.4 mmHg to coincide with a peak CSF pressure exceeding 100 mmHg, indicating that the compliance of the spinal space had been compromised. Radiographic contrast injected into the caudal sheath revealed that initial decompression occurred via leakage into the large sacral root foramina and sheaths. Dell and Orlikowski (6) described a 26-year-old patient who received 45 ml of bupivacaine 0.25% (including a 3 ml of bupivacaine 0.5% as a test dose) within 3 hours of labour analgesia. One hour after the last dose of epidural bupivacaine, with the patient in the left lateral position, 2.5 ml of hyperbaric bupivacaine 0.5% was injected through a 25 gauge Whitacre needle into the subarachnoid space for cesarean section, because the epidural sensory block was patchy. Two minutes later, there was profound motor block of the lower limbs. At 5 min she developed paresthesias and weakness in the upper limbs and experienced difficulty in breathing. At 8 min she complained of nasal stuffiness and her trachea was intubated following rapid sequence induction of general anesthesia. The reduced CSF volume following epidural injection of a relatively large volume (45 ml) was suggested as an explanation for this high spinal anesthesia following 2.5 ml hyperbaric bupivacaine spinal injection. D`Angelo et al. (7) found a rapid cephalad spread of intrathecal sufentanil 10 �g combined with 12 ml epidural saline injection for labor analgesia. However, they have "blamed" this phenomenon only on the opioid pharmacokinetics and not the epidural saline rostral augmentation of intrathecal sufentanil. Barclay et al. (8) showed that compression of the vena cava by an abdominal binder decreases the volume of the subarachnoid space and heightens the level of spinal anesthesia. Furst and Reisner (9) described two cases of high spinal anesthesia following failed epidural blockade. They found its incidence to be 11% versus fewer than 1% in patients undergoing spinal anesthesia alone. In light of these findings, they changed their practice by reducing the dose of spinal bupivacaine by 20% in those patients in whom epidural anesthesia has proved inadequate. They also perform the spinal block in the sitting position, allowing it to "set" for 60-90 seconds prior to placing the patient supine. Gamil (10) reported a case of a parturient for cesarean section who received spinal anesthesia with 2.5 ml of 0.5% heavy bupivacaine in the sitting position. The patient was maintained in this position whilst an epidural catheter was sited in a cephalad direction. It took 15 min. Before threading the epidural catheter, the epidural space was primed with 20 ml of saline. Then the patient positioned for surgery, supported under the shoulders by three pillows. 75 min from the insertion of the spinal, at the end of surgery, 50 ml of saline was injected to the epidural space as prophylaxis against headache. 5 min later the block extended from L1 to T1. The injection of a relatively small amount of 0.5% bupivacaine into the extradural space after a subarachnoid injection of a standard dose of bupivacaine results in rapid extension of the block (11,12). Several hypotheses have been advanced to explain this enhancement of the subarachnoid block. These include leakage of extradural bupivacaine into the subarachnoid space via the hole created by the subarachnoid puncture, the existence of a "subclinical" analgesia at a higher level which is enhanced and becomes evident by perineural or transdural spread of the extradural solution, or the continuing spread of the initial subarachnoid injection independent of the extradural injection (11-14). Blumgart et al. (15) found that the mechanism of extension of spinal anesthesia by extradural injection of local anesthetics is largely a volume effect. Using extradural saline 10 ml and extradural bupivacaine 0.5% 10 ml - the extension of the block was found to be similar in the saline or the bupivacaine groups and significantly faster than the group which received no extradural injection after spinal injection of 1.6-1.8 ml of 0.5% hyperbaric bupivacaine. 1. Suzuki N, Koyanemaru M, Onizuka S, Takasaki M. Dural puncture with a 26-gauge spinal needle affects epidural anesthesia. Reg Anesth 1995;20:S118 2. Dobson PMS, Caldicott LD, Gerrish SP. Delayed asystole during spinal anaesthesia for transurethral resection of the prostate. Eur J Anaesth 1993;10:41-43 3. Bodily MN, Carpenter RL, Owens BD. Lidocaine 0.5% spinal anaesthesia: A hypobaric solution for short-stay perirectal surgery. Can J Anaesth 1992;39:770-773 4. Horlocker TT, Wedel DJ, Wilson PR. Effect of injection rate on sensory level and duration of hypobaric bupivacaine spinal anesthesia for total hip arthroplasty. Anesth Analg 1994;79:773-7 5. Serpell MG, Coombs DW, Colburn RW, Deheo JA, Twitchell BB. Intrathecal pressure recordings due to instillation in the epidural space. International Monitor on Regional Anaesthesia 1993;52 6. Dell RG, Orlikowski CEP. Unexpectedly high spinal anaesthesia following failed extradural anaesthesia for caesarean section. Anaesthesia 1993;48:641 7. D`Angelo R, Anderson MT, Philip J, Eisenach JC. Intrathecal sufentanil compared to epidural bupivacaine for labor analgesia. Anesthesiology 1994;80:1209-1215 8. Barclay DL, Renegar OJ, Nelson EW. The influence of inferior vena cava compression on the level of spinal anesthesia. Am J Obstet Gynecol 1968;101:792-800 9. Furst SR, Reisner LS. Risk of high spinal anesthesia following failed epidural block for cesarean delivery. J Clin Anesth 1995;7:71-74 10. Gamil M. Combined spinal/epidural anaesthesia for caesarean section. Anaesthesia 1994;49:545-6 11. Carrie LES. Epidural versus combined spinal epidural block for Caesarean section. Acta Anaesthesiol Scand 1988;32:595-596 12. Rawal N, Schollin J, Wesstrom G. Epidural versus combined spinal epidural block for Caesarean section. Acta Anaesthesiol Scand 1988;32:61-66 13. Rawal N. Single segment combined subarachnoid and epidural block for Caesarean section. Can Anaesth Soc J 1986;33:254-255 14. Bromage PR. Mechanism of action of extradural anaesthesia. Br J Anaesth 1975;47:199-212 15. Blumgart CH, Ryall D, Dennison B, Thompson-Hill LM. Mechanism of extension of spinal anaesthesia by extradural injection of local anaesthetic. Br J Anaesth 1992;69:457-460

Metallic particles in the needle-through-needle technique

The Tuohy needle was not originally intended to be an introducer for a spinal needle. Tuohy (1) in 1944, used a needle with a curved Huber tip for continuous spinal anesthesia, and Curbelo (2) in 1949, adapted this needle for continuous epidural block. Coates (3) and Mumtaz et al. (4) were the first to publish the possibility of inserting a long spinal needle through a Tuohy epidural needle. They encountered only two potential hazards, "possible passage of the epidural catheter through the hole in the dura mater and the possibility of subarachnoid effects from epidurally injected drugs by passage through the hole in the dura". Evans (5) applied for a patent for this instrument a year later. The long spinal needles have been available in the British market since 1985 (6). The forward end of the spinal needle is inclined at an angle of about 30� to its length when it projects by about 10 mm from the forward end of the epidural needle (5). At that inclination the spinal needle scratches the inner surface of the epidural needle tip when moving forward and backward. This friction must cause metallic microparticles. Spectral analysis of the 18-gauge epidural needle (Portex) at 20 KV (7) revealed 18.96�0.28% chromium and 68.75 �0.82% iron. The other components were: nickel, 9.35�0.57%; manganese, 1.85 �0.07%; silicone, 0.67�0.16%; and molybdenum, 0.31 �0.23%. For example, nickel implanted in rats produced a necrotic, abcesslike reaction (8). In the clinical setting, an epidural catheter is pushed through the shaft after the spinal needle is withdrawn, so the microparticles produced by the friction between the two needles can be pushed forward by the force exerted to insert the catheter into the epidural space. 1. Tuohy EB. Continuous spinal anesthesia: Its usefulness and technique involved. Anesthesiology 1944;5:142-143 2. Curbelo MM. Continuous peridural segmental anesthesia by means of a ureteral catheter. Curr Res Anesth Analg 1949; 28:13 3. Coates MB. Combined subarachnoid and epidural techniques. Anaesthesia 1982;37:89-90 4. Mumtaz MH, Daz M, Kuz M. Another single space technique for orthopaedic surgery. Anaesthesia 1982;37:90 5. Evans JM. Instrument for epidural and spinal anaesthesia: UK patent application, 1983: GB 2124503A 6. Desira WR. A special needle for combined subarachnoid and epidural block. Anaesthesia 1984;39:308 7. Kumar B, Messahel FM. Evaluation of epidural needles. Acta Anaesthesiol Scand 1987;31:96-99 8. Wigle RL. The reaction of copper and other projectile metals in body tissues. J Trauma 1992;33:14-18

Superselective spinal anesthesia

Veneziani et al. (1) described a technique of superselective spinal anesthesia for the surgical treatment of saphenectomy. The block has been performed at L2-3 with the patients laying in omolateral decubitus with respect to surgical side and injecting slowly 1% hyperbaric bupivacaine 0.5-0.6 ml and maintaining such a position for about 10-15 minutes. The 24G Sprotte spinal needle was used with an incidence of only 0.4% postspinal headache. 1. Veneziani A, Santagostino G, Matera D, Tulli G. Superselective spinal anaesthesia for the surgical treatment of saphenectomy. Acta Anaesthesiol Scand 1995;39:A430

CSEA in uncommon disease

Cherng et al. (1) described a case report of combined spinal and epidural anesthesia for abdominal hysterectomy in a 34-year-old woman with myotonic dystrophy. Patients with myotonic dystrophy have a high risk of anesthetic complications, and the anesthetic technique should aim to prevent any stimulation (chemical, mechanical or thermal), and avoid any drugs that would induce uncontrollable muscular contraction (myotonic crisis) (2). 1. Cherng YG, Wang YP, Liu CC, Shi JJ, Huang SC. Combined spinal and epidural anesthesia for abdominal hysterectomy in a patient with myotonic dystrophy. Reg Anesth 1994;19:69-72 2. Paterson RA, Tousignant M, Skene DS. Caesarean section for twins in a patient with myotonic dystrophy. Can Anaesth Soc J 1985;32:418-421

CSEA for laparoscopic operations

Ciofolo et al. (1) evaluated the respiratory effects of laparoscopy under epidural anesthesia in seven female patients scheduled for a gamete intrafallopian transfer procedure. No significant changes in the ventilatory variables were observed in the Trendelenburg position. In contrast, CO2 insufflation significantly increased minute ventilation (from 9.1�1.0 L/min to 11.8 �2.6 L/min) and respiratory rate (from 16.9�1.9 breaths/min to 23.1 �3.3 breaths/min), whereas CO2 output remained unchanged. PaCO2 remained constant throughout the study. They concluded that epidural anesthesia may be a safe alternative to general anesthesia for outpatient laparoscopy, as it is not associated with ventilatory depression. Epidural analgesia for minilaparotomy cholecystectomy improves pain relief in the immediate postoperative period, compared to intramuscular morphine (2). Reduction of the surgical stress response can be achieved by two techniques: One is to reduce the degree of tissue trauma and thereby the injury response using the "minimal invasive surgery concept"; the other is "stress-free anesthesia and surgery" providing effective pain relief, including afferent neural block (3,4), together with block of various humoral mediator cascade systems (arachidonic cascade metabolites, cytokines, etc.) as well as a maintenance of nutritional status by provision of unspecific nutrients (glutamine, arginine) or growth factors (growth hormone, etc.) (5). 1. Ciofolo MJ, Clergue F, Seebacher J, Lefebvre G, Viars P. Ventilatory effects of laparoscopy under epidural anesthesia. Anesth Analg 1990;70:357-61 2. Dahl JB, Hjortso N-C, Stage JG, Hansen BL, Moiniche S, Damgaard B, Kehlet H. Effects of combined perioperative epidural bupivacaine and morphine, ibuprofen, and incisional bupivacaine on postoperative pain, pulmonary, and endocrine-metabolic function after minilaparotomy cholecystectomy. Reg Anesth 1994;19:199-205 3. Kehlet H. Modification of responses to surgery and anesthesia by neural blockade: Clinical implications. In:Cousins MJ, Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain. Philadelphia, Lippincott, 1987:145-188 4. Kehlet H. General vs regional anesthesia. In: Rogers MC, Tinker JH, Covino EG, Longnecker DE (eds.). Principles and practice of anesthesiology. St Louis, C.V. Mosby, 1993:1218-1234 5. Kehlet H. Postoperative pain relief. A look from the other side. Reg Anesth 1994;19:369-377

Postoperative epidural analgesia

Albert Schweitzer said that "pain is a more terrible lord of mankind than even death itself". Bonica (1) wrote that "acute and chronic pain afflicts millions upon millions of persons annually, and in many patients with chronic pain and a significant percentage of those with acute pain, it is inadequately relieved". In the 1980s, surveys of patients` subjective well-being revealed an incidence of moderate or severe pain after surgery of 31-75% (2,3). De Leon-Casasola et al. (4) compared the effect on postoperative myocardial ischemia of epidural versus intravenous patient-controlled analgesia. 198 patients received either technique for 5-7 days postoperatively. Patients in the epidural group had a lower incidence of tachycardia (14% vs. 65%), ischemia (5% vs. 17%), and infarction - 0% vs. 20% of patients with ischemia in the intravenous patient-controlled analgesia group. Postoperative ileus is an undesirable response to injury and is predominantly caused by an increase in inhibitory afferent sympathetic activity (5). Postoperative continuous epidural analgesia may improve gastrointestinal motility and reduce ileus (6-9). Early oral feeding reduced the risk of septic complications (10). The positive effect of epidural local anesthetic analgesic techniques on gastrointestinal paralysis may facilitate early oral nutrition as well as reducing fatigue and convalescence. 1. Bonica J.J. History of pain concepts and pain therapy. Mt Sinai J Med 1991;58:191-202 2. Kuhn S, Cooke K, Collins M, Jones JM, Mucklow JC. Perceptions of pain relief after surgery. Br Med J 1990;300:1687-1690 3. Owen H, McMillan V, Royowski D. Postoperative pain therapy: A survey of patients` expectations and their experiences. Pain 1990;41:303-307 4. De Leon Casasola OA, Lema MJ, Karabella D, Harrison P. Postoperative myocardial ischemia: Epidural versus intravenous patient-controlled analgesia. Reg Anesth 1995;20:105-112 5. Wattwill M. Postoperative pain relief in gastrointestinal motility. Acta Chir Scand 1988;550(Suppl):140-145 6. Bredtmann RD, Herden RN, Teichmann W, Moecke HP, Kniesel B, Batdgen R, Tecklenburg A. Epidural analgesia in colonic surgery: Results of a randomized prospective study. Br J Surg 1990;77:638-642 7. Sheinin B, Asantila R, Orku R. The effect of bupivacaine on pain and bowel function after colonic surgery. Acta Anaesthesiol Scand 1987;31:161-164 8. Ahn H, Bronge A, Johansson K, Ygge H, Lindhargen J. Effect of continuous postoperative epidural analgesia on intestinal motility. Br J Surg 1988;75:1176-1178 9. Wattwill M, Thoren T, Hennerdal S, Garvill J-E. Epidural analgesia with bupivacaine reduces postoperative paralytic ileus after hysterectomy. Anesth Analg 1989;68:353-358 10. Moore FA, Philiciano DV, Andrassy REJ, McArdle AH, Booth FVM, Morgenstein-Wargnen TB, Kellum JM, Welling RE, Moore EE. Early enteral feeding, compared with parenteral, reduces postoperative septic complications: The results of a meta-analysis. Ann Surg 1992;216:172-183

Unilateral spinal anesthesia

Using the needle-through-needle technique in 80 patients for cesarean section Fan et al. (1) noted the occurrence of a unilateral spinal block with the hyperbaric 0.5% bupivacaine, "because keeping the patient in the lateral position was necessary to accomplish the epidural procedure". 1. Fan SZ, Susetio L, Wang YP, Cheng YJ, Liu CC. Low dose of intrathecal hyperbaric bupivacaine combined with epidural lidocaine for cesarean section - a balance block technique. Anesth Analg 1994;78:474-7

CSEA for abdominal operations

Guedj et al. (1) compared between spinal anesthesia and combined spinal-epidural anesthesia (CSEA) in 63 patients undergoing gynecological surgery. Spinal anesthesia (n=34) was carried out in the L3-4 interspace with the patients sitting using 15 mg of hyperbaric 0.5% bupivacaine with adrenaline. In the CSEA group (n=29) an epidural catheter was inserted through the L2-3 interspace and the spinal anesthesia in the L3-4 interspace, while the patients were sitting. In the CSEA group, excellent analgesia was obtained in all patients. In the spinal group, general anesthesia was required in 3 patients (8.8%), as anesthesia only reached the T12 level in 2 cases, and as surgery lasted longer than the spinal in the third one. Moiniche et al. (2) described a case of colonic resection with early discharge after combined subarachnoid - epidural analgesia, preoperative glucocorticoids, and early postoperative mobilization and feeding in a 59-year-old pulmonary high-risk woman. They have introduced an epidural catheter between T9-10 and a spinal catheter between L3-4. During the operation the patient was fully awake. At one time during intestinal traction, visceral pain was treated vith intravenous 100 �g fentanyl. Surgery lasted for 70 minutes. The spinal catheter was removed at the end of surgery, while the epidural catheter provided postoperative analgesia for 72 hours. Luchetti et al. (3) used the combined spinal-epidural anesthesia in 20 patients undergoing surgery for hernioplasty, saphenectomy, hemorroidectomy and varicocelectomy. The subarachnoid injection consisted of hyperbaric bupivacaine 1% 1 ml and the epidural catheter injection - bupivacaine 0.5% 3 ml + fentanyl 50 �g. Analgesia was excellent in 17 patients and good in 3. No patient needed further analgesic medication intraoperatively. Mihic and Abram (4) compared five groups of patients undergoing abdominal hysterectomy with or without appendicectomy with regional anesthesia. Two hundred patients were divided as follows: Group 1 - spinal anesthesia with hyperbaric 0.5% bupivacaine; Group 2 - as group 1 with the addition of 0.06 mg of IV buprenorphine and 2.5 mg of IV midazolam; Group 3 - epidural block with 0.75% bupivacaine; Group 4 - as group 3 with the addition of epidural morphine 1%; Group 5 - combined spinal-epidural block (as in groups 1 and 4). No case of unsuccessful blockade occurred in the combined spinal-epidural anesthesia, compared to 3-4 cases of failed block in the other groups. Four patients whose analgesia was considered to be unsuccessful had to be intubated to obtain satisfactory surgical conditions. The combination of subarachnoid and epidural block provided the best analgesia. 1. Guedj P, Eldor J, Gozal Y. Conventional spinal block versus combined spinal-epidural anaesthesia for lower abdominal surgery. Ann Fr Anesth Reanim 1992;11:399-404 2. Moiniche S, Dahl JB, Rosenberg J, Kehlet H. Colonic resection with early discharge after combined subarachnoid-epidural analgesia, preoperative glucocorticoids, and early postoperative mobilization and feeding in a pulmonary high-risk patient. Reg Anesth 1994;19:352-356 3. Luchetti M, Palomba R, Liardo A, Bardari G, Sica G. Combined spinal-epidural anaesthesia (CSEA) is effective and safe for minor general surgery. Int Monitor Reg Anaesth 1994;A97 4. Mihic DN, Abram SE. Optimal regional anaesthesia for abdominal hysterectomy: Combined subarachnoid and epidural block compared with other regional techniques. Eur J Anaesthesiol 1993;10:297-301

CSEA for thoracic operations

Kowalewski et al. (1) reported on the use of spinal anesthesia with hyperbaric bupivacaine (20-30 mg) and/or lidocaine (150 mg) with morphine (0.5-1 mg) combined with general anesthesia with alfentanil 97 �22 �g/Kg and midazolam 0.04�0.02 mg/Kg supplemented with a muscle relaxant and maintained with isoflurane (0.25-0.5%) in oxygen in 18 patients for coronary artery bypass surgery (CABG). They suggested that general anesthesia combined with spinal anesthesia may be an effective technique for CABG. Very low concentrations of inhalational agents are required to maintain unconsciousness during high spinal anesthesia (2). Epidural anesthesia attenuates the endocrine-metabolic responses to surgical stress (3), reduces intestinal paralysis (4,5) and decreases perioperative morbidity (6,7). Thoracic epidural anesthesia decreases heart rate, mean arterial pressure, cardiac output and left ventricular contractility (8,9). Dopamine effectively counters cardiovascular depression during thoracic epidural anesthesia (10,11). Dopamine effectively and dose-dependently counters cardiovascular depression induced by the anesthetic technique of combining isoflurane and thoracic epidural anesthesia (12). Animals` experiments demonstrated that spinal cord section (13) or its cooling at the T1 level (14) resulted in behavioral and electrophysiological evidence of sleep. Subarachnoid bupivacaine blockade decreased the hypnotic dose of thiopental from 3.40 �0.68 mg/Kg to 2.17�0.48 mg/Kg. The ED50 value of midazolam also decreased with bupivacaine blockade, from 0.23 mg/Kg to 0.06 mg/Kg. It was suggested that the reduction in hypnotic requirements was due to the decrease in afferent input induced by spinal anesthesia (15). Extension of the segmental block to involve the cardioaccelerator fibers (above T4) is commonly advanced as a reason to explain the bradycardia that may accompany epidural analgesia (16), however, central volume depletion may have a greater cardioinhibitory vasodepressor influence (16,17). 1. Kowalewski RJ, MacAdams CL, Eagle CJ, Archer DP, Bharadwaj B. Anaesthesia for coronary artery bypass surgery supplemented with subarachnoid bupivacaine and morphine: a report of 18 cases. Can J Anaesth 1994;41:1189-95 2. Greene NM, Brull SJ. Physiology of spinal anesthesia. 4th ed. Baltimore: Williams & Wilkins, 1993:61-8 3. Kehlet H. Modification of responses to surgery by neural blockade: clinical implications. In: Cousins MJ, Bridenbaugh PO, eds. Neural bloclkade. Philadelphia: JB Lippincott, 1988:145-188 4. Scheinin B, Asantila R, Orko R. The effect of bupivacaine and morphine on pain and bowel function after colonic surgery. Acta Anaesthesiol Scand 1987;31:161-164 5. Ahn H, Bronge A, Johansson K, Ygge H, Lindhagen J. Effect of continuous postoperative epidural analgesia on intestinal motility. Br J Surg 1988;75:1176-1178 6. Yeager MP, Glass DD, Neff RK, Brinck-Johnson T. Epidural anesthesia and analgesia in high-risk surgical patients. Anesthesiology 1987;66:729-736 7. Scott NB, Kehlet H. Regional anaesthesia and surgical morbidity. Br J Surg 1988;75:299-304 8. Reiz S, Nath S, Ponten E, Friedman A, Backlund U, Olsson B, Rais O. Effects of thoracic epidural block and the beta-1-adrenoreceptor agonist prenalterol on the cardiovascular response to infrarenal aortic cross-clamping in man. Acta Anaesthesiol Scand 1979;23:395-403 9. McLean APH, Mulligan GW, Otton P, MacLean LD. Hemodynamic alterations associated with epidural anesthesia. Surgery 1967;62:79-87 10. Lundberg J, Biber B, Henriksson BA, Martner J, Raner C, Werner O, Winso O. Effects of thoracic epidural anesthesia and adrenoreceptor blockade on the cardiovascular response to dopamine in dog. Acta Anaesthesiol Scand 1991;35:359-365 11. Lundberg J, Norgren L, Thomson D, Werner O. Hemodynamic effects of dopamine during thoracic epidural analgesia in man. Anesthesiology 1987;66:641-646 12. Raner C, Biber B, Lundberg J, Martner J, Winso O. Cardiovascular depression by isoflurane and concomitant thoracic epidural anesthesia is reversed by dopamine. Acta Anaesthesiol Scand 1994;38:136-143 13. Ho T, Wang YR, Lin TAN, Chang YF. Predominance of electrocortical sleep patterns in the "encephale isole" cat and new evidence for a sleep center. Physiol Bohemosloven 1960;9:85-92 14. Oreshchuk FA. The development of sleep on local cooling of the spinal cord. Fiziol Z (Moscow) 1960;46:1230-5 15. Tverskoy M, Shagal M, Finger J, Kissin I. Subarachnoid bupivacaine blockade decreases midazolam and thiopental hypnotic requirements. J Clin Anesth 1994;6:487-490 16. Bromage PR. Physiology and pharmacology of epidural anesthesia. Anesthesiology 1967;28:592-608 17. Arndt JO, Hock A, Stanton Hicks M, Stuhmeier KD. Peridural anesthesia and the distribution of blood in supine humans. Anesthesiology 1985;63:616-623

Anesthetic risk factors

In a survey among 1,152 Australian and New Zealand anesthetists Kitching et al. (1) evaluated the percentage of anesthetists who warn patients before operation about "material risks" like death, neurological injury, awareness, failed intubation, failed block, seizures, etc. Only 1-9% have discussed and documented these items to their patients. 55% discussed but not documented the subject of failed block compared to 2% - for failed intubation. 36-97% did not discuss these matters at all pre-operatively. 1. Kitching A, Love J, Donnan G. Mishap or negligence. Br J Anaesth 1995;74:110-111

Medico-legal aspects of CSEA

Reports of cauda equina syndrome associated with micro-bore spinal catheter use, resulted in their removal from clinical practice in the USA (1). Finucane (2) in an editorial on the dosage dilemma of spinal anesthesia for cesarean delivery wrote that "the era of the microcatheter technique was short lived... The combined spinal-epidural technique is an excellent alternative and addresses many of the issues raised. One does not have to commit to a large initial subarachnoid dose of local anesthetic, supplementation may be administered epidurally, and opioids may be administered in this fashion for postoperative pain relief". 1. FDA Safety Alert; 29.5.92 2. Finucane BT. Spinal anesthesia for cesarean section: The dosage dilemma. Reg Anesth 1995;20:87-89

Spinal opioid pruritus and emesis

Larger doses of spinal morphine result in a greater incidence of pruritus (1). Knudsen and Lisander (2) decreased the incidence of emesis post subarachnoid morphine from 58% to 17% by 20 mg metoclopramide given intramuscularly before and after the surgery. Combined use of intrathecal sufentanil and bupivacaine can reduce the incidence of pruritus due to the sole use of intrathecal sufentanil for labor analgesia. Abouleish et al. (3) used spinal injection of bupivacaine 2.5 mg and sufentanil 10 �g in the combined spinal-epidural analgesia (CSEA) and found an incidence of 21%. However, D`Angelo et al. (4) used only intrathecal sufentanil 10 �g in CSEA with an incidence of pruritus of 84%. 1. Fuller JG, McMorland GH, Douglas MJ, Palmer L. Epidural morphine for analgesia after caesarean section: A report of 4880 patients. Can J Anaesth 1990;37:636-40 2. Knudsen K, Lisander B. Metoclopramide decreases emesis after spinal anesthesia supplemented with subarachnoid morphine. Reg Anesth 1994;19:390-394 3. Abouleish A, Abouleish E, Camann W. Combined spinal-epidural analgesia in advanced labour. Can J Anaesth 1994;41:575-8 4. D`Angelo R, Anderson MT, Philip J, Eisenach JC. Intrathecal sufentanil compared to epidural bupivacaine for labor analgesia. Anesthesiology 1994;80:1208-1215

Endocrine responses to spinal or epidural anesthesia

The endocrine response measured by plasma cortisol and glucose levels was not abolished by thoracic epidural etidocaine (1). Studies have failed to dampen the endocrine metabolic response to surgical trauma by thoracic epidural anesthesia unless this has been combined with spinal anesthesia (2). 1. Dahl JB, Rosenberg J, Kehlet H. Effect of thoracic epidural etidocaine 1.5% on somatosensory evoked potentials, cortisol and glucose during cholecystectomy. Acta Anaesthesiol Scand 1992;36:378-382 2. Dahl JB, Rosenberg J, Dirkes WE, Mogensen T, Kehlet H. Prevention of postoperative pain by balanced analgesia. Br J Anaesth 1990;64:518-520

Epidural unilateral blockade

The incidence of unilateral blockade in continuous lumbar epidural anesthesia is 5.9% (1). There have been four etiologic factors described for the development of unilateral epidural blockade (2-9):1. Slow injection of small volumes, patient position, and baricity of local anesthetic solution may cause anesthetic solutions to pool on the lower side during injection; 2. A congenital median epidural septum or acquired midline adhesion may act as a diffusion barrier; 3. The epidural catheter tip may pass through an intervertebral foramen resulting in production of a unilateral paravertebral block; 4. The epidural catheter tip may be in the anterior epidural space resulting in longitudinal and ipsilateral transverse spread of local anesthetics, instead of circumferential spread around the dura. Unilateral epidural block is more common in women receiving repeat epidurals (6.6% vs. 18.3%) (10). Crawford (11) reported an incidence of two cases of inadequate epidural block (one unilateral block; one missed segment) in 17 women who received epidural analgesia after a blood patch. In a further woman the sensory level could not be extended above T10 for cesarean section. 1. Asato F, Hirakawa N, Oda M, Iyatomi I, Nagasawa I, Katekawa Y, Totoki T. A median epidural septum is not a common cause of unilateral epidural blockade. Anesth Analg 1990;71:427-9 2. Singh A. Unilateral epidural analgesia. Anaesthesia 1967;22:147-9 3. Shanks CA. Four cases of unilateral epidural analgesia. Br J Anaesth 1968;40:999-1002 4. Usubiaga JE, Dos Reis A, Usubiaga LE. Epidural misplacement of catheters and mechanisms of unilateral block. Anesthesiology 1970;32:158-61 5. Bozeman PM, Chandra P. Unilateral analgesia following epidural and subarachnoid block. Anesthesiology 1980;52:356-7 6. De Rosayro AM. A case of unilateral analgesia following epidural and subarachnoid block revisited. Anesthesiology 1981;55:478 7. Bailey PW. Median epidural septum and multiple cannulation. Anaesthesia 1986;41:881-2 8. Nunn G, Mackinnon RP. Two unilateral epidural blocks. Anaesthesia 1986;41:439-40 9. Hehre FW, Sayig JM, Lowman