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© 1999 International Anesthesia Research Society
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Abstract |
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Using the single level needle-through-needle technique for combined spinal-epidural anesthesia (CSE) may introduce very fine metal particles abraded by the spinal needle from the inner ground edge of the Tuohy needle into the patient. Either the local anesthetic administered epidurally or the peridural catheter may also pass intrathecally through the hole in the dura made by the spinal needle. To examine these concerns, the needle-through-needle technique was simulated in an in vitro model (18-gauge Tuohy needle; 27- or 29-gauge Quincke needle). The presence of abraded metal particles was identified by atomic absorption spectrography (AAS). The needles were then examined under an electron microscope. Metal particles could not be identified by using AAS in the needle-through-needle technique after normal clinical use, nor could traces of use be revealed by using an electron microscope to examine the Tuohy needle. With intentionally rough handling and caudal orientation of the spinal needle tip, minimal scratches could be seen by using an electron microscope, but there were no metal particles detected by AAS. In an anatomical preparation, the possible passage of the epidural catheter anesthetic through the dural puncture hole into the cerebrospinal fluid compartment was investigated endoscopically. Neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy. We conclude that the needle-through-needle-technique is an acceptable way of performing CSE anesthesia. Endangering the patient by an unintentionally intrathecal misplacement of the epidural catheter seems to be very unlikely based on our in vitro model if small spinal needles (27- or 29-gauge) are used.
Implications: Atomic absorption spectrography shows no contamination of the intrathecal compartment by abraded metal particles from the Tuohy needle by combined spinal-epidural anesthesia with the needle-through-needle technique. In vitro, neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy.
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Combined spinal-epidural anesthesia (CSE) has the advantages of both techniques. Spinal administration of the local anesthetic guarantees a rapid onset of action, good motor relaxation, and reliable analgesia with less local anesthetic and, thus, lower overall toxicity. The epidural catheter enables the analgesic action to be prolonged by administering top-up doses, providing optimal postoperative pain therapy (1–3).
CSE can be performed reliably and quickly with the needle-through-needle technique. However, it is alleged that tiny metal particles that may pass into the epidural or spinal compartment are abraded from the inner edge of the epidural needle by the spinal needle in this technique (4,5). Our first hypothesis was that metal particles can be abraded from both types of needles; our second hypothesis was that the catheter may inadvertently pass through the puncture hole into the dura and that greater amounts of local anesthetic could pass through the dural hole into the spinal compartment.
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Methods |
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To detect the penetration of traces of steel into the cerebrospinal fluid (CSF) compartment, the needle-through-needle CSE technique was simulated experimentally in the laboratory. A test tube (20 mL) flushed free of metal was closed with a inert plastic foil, then perforated with an 18-gauge Tuohy needle (B. Braun AG, Melsungen, Germany). CSE was simulated through the lumen of the Tuohy needle with a 27- or 29-gauge Quincke spinal needle.
A puncture was simulated with the needle-through-needle technique by pushing the spinal needle through the Tuohy needle. This was done two- or fivefold, each kind of simulation executed five times, the orientation of the spinal needle bevel perpendicular (90°) to that of the Tuohy needle. To detect metal particles that may have remained in the Tuohy needle after puncture, the lumen of the needle was flushed with 0.5 mL of 0.5% bupivacaine after every puncture, and the fluid was collected. To deliberately abrade metal particles, the spinal puncture was executed three times by force. Each time, the spinal needle was introduced so that the bevel of the spinal needle lay opposite that of the Tuohy needle.
The puncture needles contained the alloy constituents specified in Table 1 (manufacturer's information). To quantify the introduction of trace metal into the CSF compartment, the alloy components in the flushing solution were measured before use (control) and after twofold and fivefold puncture simulation. The high-grade steel of manufactured needles is inert, and detection of metal ions is only possible after oxidative acid dissolution of the rinsing fluid. This was attained with high-purity concentrated nitric acid (Suprapur®; Merck, Germany). Thereafter, the alloy constituents chromium, nickel, and manganese were determined quantitatively by using an electrothermal atomic absorption spectroscopy (AAS) with Zeeman background compensation (6,7). The minimal detection limits for chromium (0.01 mg/L), manganese (0.005 mg/L), and nickel (0.1 mg/L) amount to a one-thousandth of the liquor concentration and a one-hundredth of the concentration in fat free body mass (6,7).
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The spinal and epidural needles were investigated by using a scanning electron microscope (magnification up to x1000x) for traces of use (application abrasion) before and after performance of the punctures.
To determine intrathecal passage of the epidural catheter or local anesthetic through the dural puncture site, the needle puncture was observed using endoscopy in a cadaver model. A section of human spinal compartment containing the lumbar vertebrae (T12-L5) was removed from an unfixed body with the accompanying back musculature. Retaining the physiological lordosis of the spine, a rigid 4-mm endoscope with 0° optical system (Storz, Tuttlingen, Germany) was introduced into the intrathecal compartment from the lumbosacral transition cranially. The spinal canal was filled with a fluid with physical characteristics comparable to CSF, and physiological pressure was simulated using a 25-cm water column (8,9). The spinal and epidural compartment were closed by ligature above T12.
In 10 series of experiments, the epidural compartment was punctured with an 18-gauge Tuohy needle. With the bevel of the needle in caudal alignment, the spinal puncture (27- or 29-gauge Quincke needle) was performed with the needle-through-needle technique. The bevel of the Quincke needle was rotated 90° in relation to the Tuohy needle. After spinal puncture, the opening of the Tuohy needle was turned 180° to cranial alignment, and a peridural catheter was inserted. The rotation resulted in a greater distance between the dural hole and the epidural catheter than leaving the Tuohy needle in the original placement. Thereafter, 15 mL of an isobaric local anesthetic (bupivacaine 0.5%) marked with a small amount of methylene blue was administered through the catheter. The internal side of the intrathecal compartment was examined endoscopically for penetration of the epidural catheter or anesthetic. In a similar way, the endoscope was inserted into the epidural compartment to visualize the movements of the epidural catheter in this compartment.
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Results |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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After performing CSE using the needle-through-needle technique, no increased alloy components were detected in the rinse solution after either twofold or fivefold puncture compared with the control measurements (Table 2).
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After five punctures with the needle-through-needle technique, handling the needle as in normal clinical practice, no traces of use could be detected by electron microscopy on the inner ground edge of the Tuohy needle (Figure 1). Figure 2 shows the tip of the 29-gauge Quincke needle before and after five punctures. There was no damage to the surface by contact with the Tuohy needle.
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Slight scratches could be seen on the Tuohy needle when the puncture was performed in an intentionally rough and powerful way with an opposite orientation of the bevel of the spinal needle in relation to the Tuohy needle. There were no essential differences between these scratches and those remaining from the production of the Tuohy needles. No greater defects that might indicate abraded metal particles could be visualized, even with 4000-fold magnification (Figure 3).
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With first caudal alignment of the Tuohy needle bevel for spinal anesthesia with the Quincke needle (CSE), then cranial direction of the needle tip of the Tuohy needle in moving the peridural catheter forward, the dural puncture and the outlet of the epidural catheter are more than 5 mm apart. Even when the catheter was moved forward directly under endoscopic control of the epidural compartment to the site of dural puncture, the peridural catheter could not be moved forward into the intrathecal compartment. Figure 4 shows the size relationship of a dural puncture with a 27-gauge and 29-gauge Quincke needle and a epidural catheter under 50-fold magnification.
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Even 1 h after epidural administration of 20 mL of methylene blue-dyed local anesthetic (bupivacaine 0.5%, isobaric), no passage of the local anesthetic into the intrathecal compartment could be detected under continuous endoscopic monitoring.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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The advantages of both spinal and epidural anesthesia are combined using the CSE technique. Brownridge (1) described CSE as the ideal technique as early as 1981, because spinal anesthesia fulfills the essential requirements for ideal operating conditions and a catheter in the epidural space offers flexibility and efficiency of postoperative analgesia. The CSE, however, is more comfortable for the patient if there is only one puncture. The needle-through-needle technique is the most technically simple and inexpensive method.
However, the needle-through-needle technique has encountered criticism because there are concerns that ultrafine metal particles could be abraded from the inner edge of the Tuohy needle, which may subsequently pass into the spinal compartment. In a case report, Eldor (5) describes microscopic traces of use detected on the inside edge of the Tuohy needle after a needle-through-needle puncture.
In our study, we were not able to detect any traces of use on the Tuohy needle even with 1000-fold magnification, provided that the in vitro experiment was performed with the same careful technique as a puncture under clinical conditions. Even using the very sensitive AAS method, we could not detect abraded metal particles in an artificial intrathecal compartment or in the solution we used for rinsing the Tuohy needles after passage of the spinal needle.
Slight scratches of use were detected by electron microscopy on the inner edge of the Tuohy needle if the spinal needle bevel was opposite to the bevel of the Tuohy needle and inserted roughly. There were no abrasions of metal, only slight scratches in the material of the Tuohy needle. These scratches were no deeper than scratches remaining from the production of the needle. The detection of alloy constituents with AAS did not differ from the control value.
The method of AAS is very sensitive and is well established in forensic toxicology for detecting small amounts of dissolved metals in blood for the diagnosis of intoxication (10). The relatively high values of alloy constituents in the control measurements with relatively great standard deviations are most likely explained by the bevel cut. Changes after the needle-through-needle-puncture would have been detected by the very sensitive AAS.
At the end of the 1950s, there were warnings against the use of spinal needles without introducer needles because foreign material and punch cylinders of skin and the connective tissue may be inadvertently introduced into the spinal canal (11,12). The epidermal cells implanted in this way were considered responsible for rare cases of intraspinal lumbar epidermoid tumors (13,14). Against this background, the care taken to avoid transmission of other foreign materials into the spinal canal is understandable. Our investigation results indicate that concern about the introduction of metal particles into the spinal cavity with the needle-through-needle technique is unfounded. The alloy constituents measured by using AAS after two and five simulated spinal punctures with the epidural needle do not differ significantly from the control values.
The one-segment needle-through-needle-technique is also criticized because of the possible penetration of the epidural catheter or epidurally injected local anesthetic into the intrathecal compartment via the puncture hole in the dura. In our model of simulated physiologic intrathecal pressure conditions, we could not detect significant migration of methylene blue-dyed local anesthetic into the intrathecal compartment. The intrathecal passage of the epidural catheter did not occur, either. Even under endoscopic control, it was not possible to direct the epidural catheter through the puncture hole made by the spinal needle. However, in this study, we included only 27- and 29-gauge Quincke needles. In 1995, Holmstrom et al. (15) reported intrathecal catheter passage after the needle-through-needle-technique with a 25-gauge spinal needle. Carrie (16), one of the inventors of the needle-through-needle-technique, describes the combination with a large-gauge spinal needle as unfortunate and unnecessary.
There is some dispute whether dural puncture by the Tuohy needle plays an important role in cases of spinal perforation of the epidural catheter (17). However, the 180° rotation of the Tuohy needle seems to have no impact on trauma of the dura, as far as we could confirm by intrathecal and epidural endoscopy, because the tip of the Tuohy needle used in this study does not have a cutting bevel. Tuohy needles otherwise configured require further investigation regarding this point.
The needle-through-needle-technique is an acceptable way to perform CSE anesthesia. The results of this study suggest that contamination of the intrathecal compartment by abraded metal particles from the Tuohy needle is unlikely in the clinical setting. Endangering the patient by an unintentional intrathecal misplacement of the epidural catheter seems to be very unlikely based on our in vitro model if small spinal needles (27- or 29-gauge) are used. However, the results of an in vitro model cannot absolutely be transferred to the complex clinical settings. In clinical practice, an intrathecal perforation of the epidural catheter should always be excluded clinically if the needle-through-needle technique is performed with a fine-gauge spinal needle.
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Acknowledgments |
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The authors thank Ms. Hanschke and Mr. Fischer (Institute of Biology, Ernst-Moritz-Arndt-University of Greifswald) for preparing the electron micrograms. The August Bier Society supported us in implementing the experimental design.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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- Brownridge P. Central neural blockade and caesarean section. Anaesth Intensive Care 1979;7:33–8.[Web of Science][Medline]
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Carrie LES. Extradural, spinal or combined block for obstetric surgical anaesthesia. Br J Anaesth 1990;65:225–33.
[Free Full Text] - Coates MB. Combined subarachnoid and epidural techniques. Anesthesiology 1981;89–90.
- Eldor J, Brodsky V. Danger of metallic particles in the spinal-epidural spaces using the needle-through-needle approach [letter]. Scand 1991;35:461.
- Eldor J. Combined spinal-extradural anaesthesia in obstetrics. J Anaesth 1992;68:634.
- Jackson KW, Mahmood TM. Atomic absorption, atomic emission, and flame emission spectrometry. Chem 1994;66:252R–79R.
- Wang ST, Demshar HP. Rapid Zeeman atomic absorption determination of copper in serum and urine. Clin Chem 1993;39:1907–10.[Abstract]
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Rigler ML, Drasner K, Krejcie TC, et al. Cauda equina syndrome after continuous spinal anesthesia. Anesth Analg 1991;72:275–81.
[Abstract/Free Full Text] - Rigler ML, Drasner K. Distribution of catheter-injected local anesthetic in a model of the subarachnoid space. Anesthesiology 1991;75:684–92.[Web of Science][Medline]
- Tanaka T, Hara K, Tanimoto A, et al. Determination of arsenic in blood and stomach contents by inductively coupled plasma/mass spectrometry (ICP/MS). Forensic Sci Int 1996;81:43–50.[Web of Science][Medline]
- Brandus V. The spinal needle as a carrier of foreign material. Can Anaesth Soc J 1968;15:197–201.[Web of Science][Medline]
- Gibson T, Norris W. Skin fragments removed by injection needles. Lancet 1958;983–7.
- Choremis C, Economos D, Papadatos C, Gargoulas A. Intraspinal epidermoid tumors (cholesteatomas) in patients treated for tuberculous meningitis. Lancet 1956;437–9.
- Gros C. Intraspinal epidermoid cysts. Neurosurgery 1961;7:163–9.
- Holmstrom B, Rawal N, Axelsson K, Nydahl P-A. Risk of catheter migration during combined spinal epidural block: percutaneous epiduroscopy study. Anesth Analg 1995;80:747–53.[Abstract]
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Carrie LES. Metallic fragments and the combined spinal-extradural technique [letter]. Br J Anaesth 1992;69:662–3.
[Free Full Text] - Russel IF, Vucevic M. Spinal anesthesia for caesaren section [letter]. Anaesth 1992;68:662.
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