Transient Neurological Symptoms After Isobaric Subarachnoid Anesthesia with 2% Lidocaine: The Impact of Needle Type
From the *Obstetric Anesthesia Unit, and †Department of Anesthesia, Edith Wolfson Medical Center, Holon, Sackler Faculty of Medicine, Tel Aviv University, Israel; ‡Outcomes Research Group, Cleveland, Ohio; §Department of Epidemiology, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva; [//]Department of Statistics, Haifa University; and ¶Department of Urology, Edith Wolfson Medical Center, Holon, Sackler Faculty of Medicine, Tel Aviv University, Israel.
study was the final thesis for Victoria Gurstieva
and was accepted as partial fulfillment for Master's Degree in Public Health
(MPH) at the
Table of Contents:
≪ The Differential Effect of Cyclosporine on Hypnotic Response
and Pain Reaction in Mice.
≫ Recovery Profiles of General Anesthesia and Spinal Anesthesia for Chemotherapeutic Perfusion with Circulatory Block (Stop-Flow Perfusion).
· Figure 1
· Table 1
· Table 2
· Table 3
BACKGROUND: The reported incidence of transient neurological symptoms (TNS) after subarachnoid lidocaine administration is as high as 40%. We designed this clinical trial to determine the incidence of TNS with two different pencil-point spinal needles: one-orifice (Atraucan) and two-orifice (Eldor) spinal needles.
METHODS: Ninety-nine ASA physical status I or II patients undergoing surgical procedures of the urinary bladder or prostate were prospectively allocated to receive spinal anesthesia with 40 mg, 2% isobaric lidocaine plus fentanyl injected through either a 26-gauge Atraucan (n = 52) or a 26-gauge Eldor (n = 47) spinal needle. During the first three postoperative days, patients were observed for postoperative complications, including TNS. The primary end-point for this trial was the percentage of TNS in both double- and single-orifice spinal needle procedures.
RESULTS: The incidence of TNS was higher when spinal anesthesia was done through the Atraucan needle (28.8% vs 8.5%, P = 0.006). Fifty percent of the patients in the double-orifice group versus 100% of the single-orifice group developed TNS after surgery in the lithotomy position (P = 0.014). The relative risk for developing TNS with the Eldor needle was 0.29 (95% CI: 0.07–0.75) compared with the Atraucan needle.
Transient neurological symptoms (TNS) are characterized by postoperative pain or dysesthesia in the buttocks or lower extremities. The cause of TNS has been investigated in several studies in association with lidocaine concentration (1), osmolarity (2), dextrose concentration (2), lithotomy position (3), ambulatory surgery (3), and early ambulation (4). The only factors found to be associated with increased risk of TNS were lidocaine spinal anesthesia, the lithotomy position, and ambulatory surgery (4). Pooling and maldistribution of local anesthetic encountered with the use of pencil-point spinal needles (5) or spinal microcatheters (6) were suggested to have a causative effect for neurological injury, but not TNS. The Eldor spinal needle (Fig. 1) has two rounded opposing lateral orifices at its pencil-point tip (7) that might affect the dispersion of local anesthetic. However, a single study comparing the block characteristics achieved by this needle versus a single-orifice Sprotte needle found no differences in the quality of the block (8). In this randomized single blinded comparison study using 2% lidocaine in patients undergoing surgical procedure of the urinary bladder or prostate, we evaluated the newly shaped Eldor spinal needle specifically with regard to the incidence of TNS.
Figure 1. Spinal needle types. (a) Double-orifice: Eldor needle. (b) Single-orifice: Atraucan.
After obtaining approval of the IRB and written patient informed consent, 99 ASA physical status I and II patients scheduled for suprapubic prostatectomy or transurethral resection of prostate, under spinal anesthesia, were randomized blindly to receive spinal anesthesia with 40 mg, 2% plain preservative-free lidocaine (Rafa Laboratory, Jerusalem, Israel) plus 15 µg fentanyl (Janssen Cilag, Kibbutz Shefaim, Israel), injected through either a 26-gauge pencil-point, Eldor needle with two lateral opposing orifices at its tip (TSK Laboratory, Baldoyle Ind, East Dublin, Ireland) or a 26-gauge, single-orifice Atraucan cutting-point double-bevel needle (B. Braun, Melsungen AG, Germany). Randomization was performed using a cluster design, in which patients belonging to a specific session and undergoing a urology procedure of prostate or urinary bladder were given spinal anesthesia with the same type of needle. Patients were randomly allocated to have their spinal anesthesia performed by one of the two types of needles. Needles were kept in sealed envelopes marked with the session number, using random number tables.
Excluded from the study were patients with a history of chronic pain, presence of neurological disease, diabetes mellitus, smoking of more than 10 cigarettes per day for more than 3 yr, chronic use of analgesic medications, and body mass index >30.
Premedication consisted of oral diazepam, 7.5 mg, 1
h before surgery. Intraoperatively, monitors were
applied as per ASA guidelines. Before spinal anesthesia was performed, 10 mL/kg of lactated Ringer's solution was administered IV
over 20 min. With the patient in the sitting or left lateral decubitus position, the patient's skin was prepped with a
10% solution of povidone iodine in isopropyl alcohol
(Fisher Pharmaceutical Labs, Tel Aviv,
Arterial blood pressure was recorded at
1 min intervals for the first 20 min and at 5 min intervals thereafter, until
complete (motor and sensory) recovery from spinal anesthesia. Hypotension was
defined as a decrease in systolic blood pressure of >
The primary outcome for this trial was the percentage of TNS in both double- and single-orifice spinal needle procedures. Initially, the sample size was based on one planned analysis at the end of the study. A sample size of 150 patients in each group was calculated to achieve 80% power and a two-sided [alpha] of 0.05, assuming a 12.5% and 25% incidence of TNS in the double- and single-orifice groups, respectively. After 99 patients were enrolled in the study, a safety concern was raised by the physicians who were involved in data collection due to the clinical impression of frequent TNS. Although the overall incidence of TNS was not increased, the possibility of a large group disparity raised ethical concerns that led to the decision of data unblinding. Before unblinding the data, the statistician and the IRB were informed regarding our clinical suspicion of frequent TNS. The course of action decided at that stage was to terminate the study in case of verification of a significantly frequent incidence of TNS in the interim analysis. Interim analysis at that point revealed a 19% overall incidence of TNS with 8.5% and 28.8% in the double- and single-orifice groups, respectively. Because of ethical concerns, a decision was then made to terminate the study.
The difference in TNS rates in the
collected data was then analyzed by group sequential (interim) analysis
methods, and results were found to be consistent with a statistically
significant difference of >17.8% between the two groups. The interim
analysis was performed by a statistician who decided on the criteria by which
the study would be discontinued. This boundary was calculated based on the
previously specified power, significance level, and effect sizes. The boundary
shape (determined after data unblinding) was set
according to Pocock (9). Such an approach
requires a predetermined number of interim analyses. Because such a judgment
had not been determined at the study design phase, the number of analyses was ad
hoc set to four. These calculations led to a maximal sample size of 200
patients in each group, with four interim analyses, after enrollment of 50
patients per group. The number of patients in each group at time of study
termination matched the number of patients needed for first data analysis (
The boundaries for achieving a two-sided statistical significance of 0.05 were a difference in TNS rate of 17.8%, 12.6%, 10.3%, and 8.9% in each interim analysis, respectively. For further details, see Jennison and Turnbull (10). Adjustments to the P value and the confidence interval, comparing TNS rates, were done using analysis time ordering.
Univariate comparisons of the patients' characteristics were performed using unpaired t-test, [chi]2, or Fisher's exact test. The Fisher's exact test was used when the expected values in a cell were less than five. Stratified analysis and Mantel-Haenszel relative risk and 95% confidence intervals were used to examine potential confounders. For variables significantly different between groups in the univariate analysis, odds ratios and 95% confidence intervals were obtained from multiple logistic regression analysis to estimate their independent contribution to TNS. The module used for statistical analysis was Seq Trial 2 (2002) in 5-Plus 6, 2 ©, 2003, Insightful Corp.
During the 6-mo study period, 152
patients underwent urology procedures under spinal anesthesia. Of them, 99
(65.1%) fulfilled the inclusion criteria and agreed to participate in the
study. Excluded from the study were patients with diabetes mellitus (14.5%),
obesity (8.6%), technical difficulties in performing spinal anesthesia (4.6%),
refusal to participate (3.3%), neurological problems (2%), and other reasons
(2%). There were no differences in the patients' demographics, surgery
characteristics and quality, and duration of spinal anesthesia (Table 1).
There were 47 procedures performed with the Eldor
Table 1. Demographic and Clinical Characteristics of Patients According to the Type of Needle Used for Spinal Anesthesia
Table 2. Symptoms Reported Within 72 h of Surgery by Type of Needle Used for Spinal Anesthesia
Table 3. Odds Ratio (95% Confidence Interval) of the Association Between the Type of Needle, Type of Surgery, and Positioning During Spinal Anesthesia, and Transient Neurological Symptoms
Our study suggests that TNS is more common after spinal anesthesia with 2% isobaric lidocaine, plus fentanyl, when a single-orifice cutting point (Atraucan) needle is used in patients undergoing urology procedures. Our report on the incidence of TNS is similar to the previously reported incidence with lidocaine (14.2%) and prilocaine (4%) for the same type of surgery with spinal anesthesia performed through 25-gauge to 29-gauge Quincke needles (11). Other studies report an incidence of TNS ranging from 4% to 37% (12–17). Although most local anesthetics are associated with TNS (12,18–23), it occurs most frequently with lidocaine. The type and duration of surgery and patient position during surgery may also add to the variability of the factors implicated with the TNS (3,12,14,17). All these variables were assessed in our study and were not found to be confounding for the association between the needle type and incidence of TNS. The precise etiology of TNS has not been elucidated, with previous theories having postulated local anesthetic toxicity (17,24–26), needle trauma or neuronal ischemia as a result of sciatic stretching (27).
Pooling and maldistribution of local anesthetic, encountered with the use of pencil-point needles, was also suggested to cause transient neurologic deficit, but not TNS (5). This was suggested to occur after slow injection rates of 5% hyperbaric lidocaine with sacrally directed Whitacre needles, or when using spinal microbore catheters (6). Freedman et al. (3), in a large epidemiologic study of needle types (Quinke versus Whitacre), found no difference in the rate of TNS, although both were single-orifice needles with different distributions of local anesthetic. We undertook our study with the hypothesis that the type of the needle may affect the incidence of TNS and that, specifically, the two-orifice needle may produce a more uniform distribution of the local anesthetic. However, when comparing the two-orifice, 26-gauge Eldor spinal needle, with the 27-gauge Pencan (Sprotte) needle (8), there were no differences in the quality of the block consistent with our results. Although neural injury is clearly linked to anesthetic maldistribution, there was no evidence supporting the link with TNS in previous studies or the current study. For example, in our study, the maximum sensory level was similar between the groups, implying that the maldistribution of local anesthetics does not seem to be the cause of the different incidence of TNS between the groups.
A limitation of our study is the lack of homogeneity of the groups in regard to type of surgery and patient's position during the spinal administration. The difference in operative procedures stems from the nonhomogeneity of the patients in the cluster. However, despite the statistical significance of these differences when reported as univariate variables, the multivariable analysis did not identify these two variables (type of surgery and patient's position) as confounding factors when comparing the type of needle and the incidence of TNS. Also, methodology bias cannot be excluded by early termination of our study and the performance of interim analysis of the results.
The interim analysis was not planned at the study design, but was decided upon due to concerns regarding a potentially high disparity in the incidence of TNS. This necessitated the interim analysis. Statistically, it has not been determined how to address the problem of unplanned interim analysis (10). After unblinding the data, we constructed a group sequential study (interim analysis design) to match the enrolled patients' status with the previously specific study parameters. This approach allowed us to conduct an ad hoc interim analysis as if it were initially planned. We believed that this approach was suboptimal, but it yielded lesser bias than disregarding the fact of early study termination. As for the P value, the boundaries were 17% when comparing the TNS incidence for a significance level of 0.05. The adjusted P value comparing TNS incidence was P value = 0.006 with adjusted 95% CI of the difference in TNS rate of 5.6%–35%. Finally, our study was not double-blind. However, although the anesthesiologist performing spinal anesthesia was not blinded, both the investigator and the patient were unaware of the needle type used for spinal anesthesia. Therefore, it is unlikely that an investigator bias affected the results of the study. In our study, we used two types of needles: the pencil-point needle has been shown to be associated with maldistribution of photalocyanine blue dye in a spinal model, whereas the Quincke needle was not (5).
The results of our study show that the use of a single-orifice Atraucan spinal needle for the administration of 40 mg of 2% spinal lidocaine in urology surgeries was associated more frequently with TNS when compared with the use of the two-orifice Eldor needle. The reduced incidence of TNS with the use of two-orifice spinal needle may be attributable to the needle design.
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