ELDOR AMNIOCENTESIS NEEDLE : A NEW DOUBLE HOLE PENCIL POINT ATRAUMATIC NEEDLE FOR AMNIOCENTESIS
A new amniocentesis needle which has an atraumatic pencil point tip and two opposite circular side holes at the tip is described herein.
Unlike the current used Quincke spinal needle for amniocentesis this new needle separates the uterine fibers instead of tearing it. It may reduce bleeding, uterine contractions and fetal injury in case it inadvertently contacts the fetus.
Amniocentesis; spinal needle (Quincke, Eldor).
Prior to the introduction of simultaneous ultrasound examination and sonographic guidance of the needle, amniocentesis was associated with infrequent but serious fetal complications, including pneumothorax, laceration of the spleen, hematoma of the thorax, and head and eye injury (1,2).
The typical amniocentesis needle is a 8.9 cm, 22-gauge Quincke spinal needle. The incidence of inadvertent needle contact with the fetus using the current technique is 0.4% (7 of 1,458) (3).
Significant blood contamination of the amniotic fluid after amniocentesis occurs in every instance if evaluated at a "second look" procedure; the blood contamination is higher when an anterior placenta is traversed with the needle (4).
Failure to aspirate amniotic fluid during amniocentesis can be due to several causes: The needle tip may be against the fetus, umbilical cord, or placenta; secondary to debris in the needle lumen; tenting of the membranes (5,6).
A fetus can move onto a needle if it is not placed deep enough and also, a posterior placenta can thrust against a needle by a contraction during aspiration, either leading to injury or bleeding when the needle tip is sharp.
A new needle that may overcome these disadvantages of the current used needle is described herein:
Greene (7) described in 1926 a spinal needle with a point that is "round, tapering, and sharp".
This was the result of experiments made by him during 1923 (8) and his experience
since then that brought him to the conclusion that "postpuncture headache is caused by
trauma to the spinal dura sufficient to result in excessive leakage of cerebrospinal
fluid to the point at which the brain is left without a water cushion". His experiments
demonstrated that a greater trauma was produced by the use of a needle with a blunt
cutting point than by a needle of the same caliber with a point rounded, tapering and
sharp. He found also that it was possible to pass a small sharp, round, tapering pointed
instrument between the fibers of a spinal dural sac, suspended and filled with water,
without cutting any of them. He performed 215 consecutive punctures with his needle,
with a headache incidence of two in the series. In many instances the puncture was
done during the noon hour, and the patient resumed his work for the remainder of the
Kirschner (9) in 1931 described a needle for spinal anesthesia with an opening in
the shaft just proximal to the beveled closed end. Such a needle was recommended to
aid in the more accurate control of the duration and extent of anesthesia, since it
could be manipulated to permit the injection of solution in the stream flowing parallel
to the long axis of the spinal fluid column rather than against the side of the canal
Hart and Whitacre (10) described in 1951 their pencil-point spinal
needle, known since as the Whitacre needle.
Sprotte, Schedel and Pajunk (11) in 1987 modified the Whitacre needle, known since as the Sprotte needle. The FDA approves only the use of the pencil-point spinal needle in the needle-through-needle or the Eldor needle techniques for the combined spinal-epidural anesthesia. However, the long orifice of 24 gauge Sprotte spinal needles may result in failed spinal anesthetics when they are used, since this length exceeds the 1 mm thickness of human lumbar dura (12). Sprotte has modified this device by reducing the length of the orifice.
Sosis et al. (12) compared in vitro the 1.8 mm long laterally placed orifice of the original version of the Sprotte spinal needle with the 1.0 mm long new Sprotte needle. They found that the flow of water through the needle was not reduced after the orifice length was reduced by 44%.
Lipov et al.(13) examined whether the window design of Sprotte pencil
point needles leads to deformation under lateral or axial loading conditions. They
examined the 22- and 24-gauge Sprotte, 22- and 25-gauge Whitacre and 22- and
25-gauge Quincke needles. The force needed to bend the Sprotte needles was less than
needed for the Whitacre and Quincke needles of similar size when lateral or axial
pressure was applied. Examination of the needle tips demonstrated that the Sprotte
needles were most likely to bend at the needle window, while the Quincke and
Whitacre needles deformed at the point of clamping. They concluded that the Sprotte
needles have an inherent design weakness to lateral and axial pressure, which may
result in a greater number of needle tip deformations upon needle insertion. The
nature of this deformation may result in difficulty in needle withdrawal and possibly
fracture of the needle tip.
A new pencil-point spinal needle is described: It is named double-hole pencil-point (DHPP) spinal needle (Eldor spinal needle) , and is composed of a blunt ogival tip and two circular holes opposing each other just proximal to the tip (Fig. 1). The area of the
two holes is almost the same as of the single hole Sprotte needle`s area, which enables
more rapid CSF reflux. The anesthetic solution injection spreads through both holes.
There is a possible advantage of a more diffuse anesthetic distribution and less
anesthetic solution dosage. The DHPP spinal needle allows anesthetic solution injection
when one of the holes is obstructed by a tissue fragment, through the opposite hole.
Using the DHPP spinal needle is like inserting two Whitacre needles in the same
interspace, from the point of view of the hole`s area. There is a possibility to avoid the
risk of needle deformation due to bending at the window, as it is the case with the
Sprotte needle. In this respect it is more like the Whitacre needle. However, unlike the
Whitacre needle there is a possibility of a two times rapid CSF reflux, because of a
double orifice area.
The same rules that are now the state of the art in spinal anesthesia can be applied to Amniocentesis as well. This Atraumatic needle tip for amniocentesis can facilitate the aspiration of the amniotic fluid through its bilateral holes, avoid amniotic tenting, reduce amniotic bleeding and maternal pain upon its insertion.
It may also avoid coring of maternal tissue that may be introduced into the uterus.
Unlike the current Quincke needle this Eldor amniocentesis needle has atraumatic characteristics. It intends to separate the fibers of the uterus and thus avoiding unnecessary intrauterine bleeding which occurs in almost every case when the Quincke spinal needle is used for Amniocentesis.
Joseph Eldor, MD
Department of Anesthesia
Misgav Ladach General Hospital, Jerusalem, Israel
I would like to thank Jason C. Birnholz, M.D., AmnioNet, Oak Brook, Illinois, USA, for reviewing the manuscript.
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8. Greene HM. A technic to reduce the incidence of headache following lumbar puncture in ambulatory patients with a plea for more frequent examinations ofthe cerebrospinal fluids. Northwest Med 1923;22:240
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13. Lipov EG, Sosis MB, McCarthy RJ, Ivankovich AD. Does the design of the Sprotte spinal needle reduce the force needed to deform the tip? J Clin Anesth 1994;6:411-413