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Atraumatic vs. Standard Needles for Diagnostic Lumbar Puncture



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Am Fam Physician. 2001 May 1;63(9):1837-1838.

Lumbar puncture is a common and important diagnostic procedure, but it may present technical difficulties and be complicated by headache. The incidence of headache following similar interventions, such as spinal anesthesia and myelography, is approximately one half of that following lumbar puncture because smaller net volumes of fluid are removed and smaller needles are used. Since the 1920s, advocates for atraumatic (“blunt”) needles have argued that use of a smaller, tapered needle with a blunt tip results in separation of dural fibers rather than severing of tissues and, thus, results in fewer complications. Conversely, opponents of blunt needles contend that the increased technical difficulties associated with their use cause longer and more complicated attempts at lumbar puncture with more failed procedures. Thomas and colleagues directly compared the two types of needles in a randomized, controlled trial of lumbar punctures in the neurology department of a university teaching hospital.

Seven residents received standard training in lumbar puncture, including watching the manufacturer's videotape on the use of atraumatic needles. For at least one month, they performed lumbar punctures with both types of needles. They were allowed four attempts with the allocated needle type before they changed to the alternative needle. If two attempts with the alternative needle were unsuccessful, a senior colleague was called. The protocols for lumbar puncture and aftercare were standardized and identical for all procedures. Recorded patient data included age, sex, body mass index and presumptive diagnosis. Patients were contacted one week after the procedure to ascertain incidence, type, duration and severity of headache, including the use of analgesia. The information recorded about the procedure included number and duration of attempts, opening and closing pressure, volume of fluid removed and volume of local anesthetic used. Visual analog scales were used to record the discomfort experienced by the patients and the degree of difficulty perceived by the residents.

The 48 patients who were followed after the use of standard needles were identical to the 49 on whom atraumatic needles were used in procedural measurements such as opening and closing pressures, volume of fluid removed and volume of local anesthetic used. Patient characteristics were also identical except for higher body mass in the standard needle group. In eight patients, lumbar puncture was unsuccessful after four attempts with an atraumatic needle but successful with a standard needle. After 24 hours, patient ratings of headache were similar in the two groups, but the mean reported severity of headache was reduced in the atraumatic needle group (0.93 compared with 1.5 in the standard needle group: P = 0.11). After one week, the incidence of moderate or severe headache was significantly reduced in the atraumatic needle group. Seven patients reported moderate headache, and seven reported severe headache following use of atraumatic needles compared with eight reports of moderate headache and 18 of severe headache following standard needle use. Patients on whom the standard needle was used were more likely to seek medical advice or use analgesia during the week following the procedure. Two patients, both from the standard needle group, were admitted to the hospital in the week following the procedure. The duration of procedures did not vary with type of needle used, but the residents reported greater difficulty with the atraumatic needle. The risk of multiple attempts was significantly related to patient body mass index. Although atraumatic needles were associated with more than one attempt, this was not statistically significant. Patients did not perceive any difference between the two needle types in terms of discomfort during the procedure.

The authors conclude that atraumatic needles significantly reduced the incidence of severe to moderate headache and the need for medical care following diagnostic lumbar puncture. They calculate that one headache is avoided for every four patients when atraumatic needles are used. Similarly, one medical intervention is avoided for every three patients. The potential savings in discomfort and use of health resources must be balanced against the implications of greater technical difficulty associated with use of atraumatic needles. An estimated one patient in every seven requires more than one attempt when atraumatic needles are used. Atraumatic needles cost approximately seven times more than standard needles, but the increased cost (about $7.67 per needle) is offset by the reduced utilization of medical care following the procedure. The authors suggest that atraumatic needles be more widely used, except in patients with high body mass indexes and in certain clinical situations in which standard needles have clear advantages.

Thomas SR, et al. Randomised controlled trial of atraumatic versus standard needles for diagnostic lumbar puncture. BMJ. October 21, 2000;321:986–90.

editor's note: Aside from the needles, the determining factor in successful lumbar puncture and avoidance of complications is the skill of the operator. The benefits of using atraumatic needles will not be realized unless residents and physicians are given opportunities to practice. With hospital and other opportunities increasingly restricted by short lengths of stay, simulators and workshops are needed to enable us all to develop and retain the “feel” for this and other procedures. Watching videotapes is not sufficient, and our patients do not deserve to suffer because our dexterity has diminished in once-common skills like lumbar puncture or even starting intravenous lines. Beyond hospitals providing “skills labs,” major conferences and CME gatherings should feature opportunities to practice skills requiring manual dexterity.—a.d.w.

 

Copyright © 2001 by the American Academy of Family Physicians.
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