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Randomised controlled trial of atraumatic versus standard needles for diagnostic lumbar puncture

S Rachel Thomas, lecturer ^a, D R S Jamieson, consultant ^b, Keith W Muir, locum consultant ^a. 

^a Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF, ^b Department of Neurology, Leeds General Infirmary, Leeds LS1 3EX

Correspondence to: K W Muir k.muir{at}clinmed.gla.ac.uk

	Abstract

Top Abstract Introduction Participants and methods Results Discussion References

Objective: To compare the ease of use of atraumatic needles with standard needles for diagnostic lumbar puncture and the incidence of headache after their use.
Design: Double blind, randomised controlled trial.
Setting: Investigation ward of a neurology unit in a university hospital.
Participants: 116 patients requiring elective diagnostic lumbar puncture.
Interventions: Standardised protocol for lumbar puncture with 20 gauge atraumatic or standard needles.
Outcome measures: The primary end point was intention to treat analysis of incidence of moderate to severe headache, assessed at one week by telephone interview. Secondary end points were incidence of headache at one week analysed by needle type, ease of use by operator according to a visual analogue scale, incidence of backache, and failure rate of puncture.
Results: Valid outcome data were available for 97 of 101 patients randomised. Baseline characteristics were matched except for higher body mass index in the standard needle group. By an intention to treat analysis the absolute risk of moderate to severe headache with atraumatic needles was reduced by 26% (95% confidence interval 6% to 45%) compared with standard needles, but there was a non-significantly greater absolute risk of multiple attempts at lumbar puncture (14%, 4% to 32%). Higher body mass index was associated with an increased failure rate with atraumatic needles, but the reduced incidence of headache was maintained. The need for medical interventions was reduced by 20% (1% to 40%).
Conclusions: Atraumatic needles significantly reduced the incidence of moderate to severe headache and the need for medical interventions after diagnostic lumbar punctures, but they were associated with a higher failure rate than standard needles.

	Introduction

Top Abstract Introduction Participants and methods Results Discussion References

Headache due to a reduced volume of cerebrospinal fluid and reduced pressure complicates a substantial proportion of lumbar punctures.^1-3 In the 1920s Greene hypothesised that complications could be reduced by using a smaller, tapered needle with a blunt tip, which would separate rather than cut dural fibres and thus reduce fluid leakage. ^{4 5} Atraumatic ("blunt") needles have been in clinical use since the 1950s, principally in anaesthetic practice, where there is substantial evidence of a reduced incidence of headache and other neurological complications after their use.⁶

Spinal anaesthesia and myelography differ from diagnostic lumbar puncture because smaller gauge needles are used, smaller volumes of cerebrospinal fluid are removed, and other fluids can be introduced. The incidence of headache after spinal anaesthesia is typically half that after diagnostic lumbar puncture. ^{2 6} Despite evidence that relevant physical characteristics of atraumatic needles, such as flow rates, are comparable to those of standard needles,⁶ there are limited data on their benefit in diagnostic lumbar puncture. Also, there is a perception that atraumatic needles are more difficult to use than standard needles. Previous studies of diagnostic lumbar puncture have potentially been confounded by comparing different needle gauges, failing to define the operators' previous experience or the length of follow up, and not addressing technical difficulties.^7-9 The Cochrane Collaboration has identified only two methodologically adequate studies of atraumatic needles for diagnostic lumbar puncture (C Sudlow, personal communication). We aimed to compare the incidence of headache with atraumatic and standard needles and to evaluate technical difficulties.

	Participants and methods

Top Abstract Introduction Participants and methods Results Discussion References

Participants
A local pilot study established the feasibility of training medical staff on rotation in the use of atraumatic needles. We considered as eligible for our study all patients attending the investigation ward of a regional neurology unit for elective diagnostic lumbar puncture between September 1998 and February 1999. We excluded patients with a history of chronic headache requiring analgesics and those with known or suspected idiopathic intracranial hypertension or other causes of an increased cerebrospinal fluid pressure. We did not specifically exclude patients if they had had previous lumbar puncture or spinal surgery or if other potential confounding factors were present. Patients received standard information about the procedure and complications. After consenting, the patients were randomised to lumbar puncture with either a 20 gauge atraumatic needle (Sprotte or Pajunk) or a standard needle (Quincke) (fig 1). Randomisation was by a computer generated code stored in opaque envelopes that were serially numbered and sealed.

View larger version (13K): [in this window] [in a new window]   Fig 1.   Atraumatic (top) and standard (bottom) needles for lumbar puncture

Interventions
Seven senior house officers performed the lumbar punctures over the study period. Each was attached to the neurology department for three to six months. Before the study, they received standard training in lumbar puncture techniques, including the manufacturer's video guidelines on the use of atraumatic needles. For at least one month they each performed lumbar punctures with both types of needle. All procedures were performed with the patient in the left lateral position, and 2% lignocaine was used as local anaesthetic. The orientation of the needle bevel during insertion was not stipulated. After withdrawal of cerebrospinal fluid, the needle stylet was reinserted routinely before the needle was withdrawn. Operators were allowed four attempts with the initially allocated needle type, with a maximum of two attempts at any one level. If these were unsuccessful, the operator was allowed two attempts with the alternative needle type before involving a senior colleague or radiological guidance (see figure on BMJ 's website). The use of an introducer for the atraumatic needles was left to the operator's discretion. All patients rested in bed for at least four hours after the procedure, and fluid intake was encouraged.

Follow up
One week after lumbar puncture, the patients were telephoned by a single observer who was blinded to needle allocation. The incidence of both postural headache and backache were recorded and their severity graded as mild, moderate, or severe. The duration of symptoms (hours) and the requirements for analgesia or medical contact were recorded.

End points
Our primary end point was the incidence of moderate or severe headache at one week according to needle type (intention to treat analysis). Our secondary end points were the incidence of moderate or severe headache at one week by successful needle type, incidence of headache at 24 hours, incidence of backache at 24 hours and one week, and ease of use by operator. We undertook additional analyses of the proportion of patients requiring medical interventions within one week of lumbar puncture and the proportion requiring more than one attempt for successful lumbar puncture. For primary and secondary end points we calculated the relative risk, absolute risk reduction, relative risk reduction, and numbers needed to treat for benefit, with 95% confidence intervals. We compared categorical data by ² tests and continuous variables by t tests. We calculated the median and interquartile ranges for the duration of symptoms, and we compared them with Mann-Whitney U tests. Correlations were sought with Pearson's product moment coefficient.

View larger version (31K): [in this window] [in a new window]   Fig 2.   Flow of participants through trial

	Results

Top Abstract Introduction Participants and methods Results Discussion References

Patients' characteristics
We randomised 101 of 116 eligible patients during the study period (fig 2), 99 of whom completed the follow up. Presumptive neurological diagnoses being investigated were multiple sclerosis (73 patients), peripheral polyneuropathy (4), chronic fatigue (2), motor neurone disease (2), myelopathy (2), and other cases of neurological disorders (11). Three patients had headache disorders at entry to the trial, and three other patients gave an incidental history of chronic headache, which was not the reason for investigation.

Ease of use
Operators found the atraumatic needle more difficult to use than the standard needle, although the duration of the procedure did not differ between the two needles. Ease of procedure correlated with body mass index (r=0.23). Atraumatic needles were associated with a non-significant increase in the risk of more than one attempt at lumbar puncture being required (table 4). This risk was related to body mass index: relative risk of multiple attempts with atraumatic needles was non-significantly reduced by 45% (32% reduction to 122% increase) in patients with a body mass index of less than 25 and significantly increased by 277% (118% to 436%) in those with a body mass index of 25 or more. In logistic regression there was a significant interaction between needle type and body mass index regarding the need for multiple attempts at lumbar puncture; neither factor individually was predictive.

Other endpoints
Discomfort during the procedure was graded equally by patients in both groups. Discharge was not delayed by symptoms in any patient. Incidence and severity of backache did not differ between groups at 24 hours or one week.

	Discussion

Top Abstract Introduction Participants and methods Results Discussion References

Our study confirms a reduced incidence of moderate to severe headache after diagnostic lumbar puncture with atraumatic needles in a patient group typical of neurological practice. We found a higher incidence of dural puncture headache than some reportsfor example, 25% with moderate to severe headache over seven days after lumbar puncture with standard 20 gauge needles compared with 16% after lumbar puncture with atraumatic needles in similar neurological populations. ^{2 3} Others have reported incidences as high as 54%, comparable to our results.¹⁰ Operator experience may be a factor, with specifically trained staff or experienced neurologists in previous studies contrasting with our less experienced operators, who are typical of those likely to perform lumbar puncture in UK hospitals. ^{2 3} Our patients were also younger than those in some series, and younger age has been associated with a higher incidence of dural puncture headache. ^{2 11}

Point estimates of the number needed to treat for benefit indicate that one moderate to severe headache is avoided for every four patients tapped with atraumatic rather than standard needles: this was at the potential expense of one additional patient requiring more than one lumbar puncture attempt for every seven patients treated. Taking into account the higher failure rate with atraumatic needles in "successful needle" rather than intention to treat analysis, the absolute benefit in terms of headaches and subsequent medical interventions avoided persisted, with a number needed to treat of 5 for each end point, but much wider confidence intervals. Reducing the failure rate in practice is therefore crucial if patients are to benefit from lumbar punctures with atraumatic needles. The failure rate in our study (16%) was high, consistent with operators' grading of atraumatic needles as significantly more difficult to use than standard needles, notably so in patients with a high body mass index. The number needed to treat for benefit would be greater if baseline incidence was closer to rates suggested in the literature.

On the basis of these data it would be appropriate to introduce atraumatic needles into standard neurological practice for diagnostic lumbar puncture, provided that failure rates are reviewed. Standard needles will continue to be required, particularly in patients with a high body mass index, in whom failure was most often observed. Standard needles will also continue to be used for therapeutic lumbar punctures for idiopathic intracranial hypertension or hydrocephalus. If these results are borne out in practice, the sevenfold higher cost of atraumatic needles compared with standard needles (£5.30 versus £0.78 at local health board prices) should be offset by the reduced need for medical intervention.

	Acknowledgments

We thank the senior house officers who contributed to the study and the medical illustration department of Southern General Hospital for figure 1.

Contributors: DRSJ conceived the study, undertook collection of the pilot data, and reviewed the manuscript. SRT undertook data collection, supervised staff training, performed all follow ups and data entry, and drafted the manuscript. KWM designed the study, performed the analyses, and jointly wrote the manuscript; he will act as guarantor for the paper.

	Footnotes

Funding: Glasgow Neurosciences Foundation.

Competing interests: None declared.

The procedure for the operators appears on the BMJ's website

	References

Top Abstract Introduction Participants and methods Results Discussion References

1.	Grant R, Condon B, Hart I, Teasdale GM. Changes in intracranial CSF volume after lumbar puncture and their relationship to post-LP headache. J Neurol Neurosurg Psychiatry 1991; 54: 440-442[Abstract].
2.	Kuntz KM, Kokmen E, Stevens JC, Miller P, Offord KP, Ho MM. Post lumbar puncture headaches: experience in 501 consecutive procedures. Neurology 1992; 42: 1884-1887[Abstract/Free Full Text].
3.	Strupp M, Brandt T, Muller A. Incidence of post-lumbar puncture syndrome reduced by reinserting the stylet: a randomised prospective study of 600 patients. J Neurol 1998; 245: 589-592[CrossRef][Medline].
4.	Greene HM. Lumbar puncture and the prevention of post puncture headache. JAMA 1926; 86: 391-392.
5.	Evans RW. Complications of lumbar puncture. Neurol Clin North Am 1998; 16: 83-105.
6.	Carson D, Serpell M. Choosing the best needle for diagnostic lumbar puncture. Neurology 1996; 47: 33-37[Abstract/Free Full Text].
7.	Muller B, Adelt K, Reichmann H, Toyka K. Atraumatic needle reduces the incidence of post-lumbar puncture syndrome. J Neurol 1994; 241: 376-380[CrossRef][Medline].
8.	Kleyweg RP, Hertzberger LI, Carbaat PAT. Significant reduction in post-lumbar puncture headache using an atraumatic needle. A double-blind, controlled clinical trial. Cephalalgia 1998; 18: 635-637[CrossRef][Medline].
9.	Braune HJ, Huffman G. A prospective double-blind clinical trial, comparing the sharp Quincke needle (22G) with an "atraumatic" needle (22G) in the induction of post-lumbar puncture. Acta Neurol Scand 1992; 86: 50-54[Medline].
10.	Flaatten H, Krakenes J, Vedeler C. Post-dural puncture related complications after diagnostic lumbar puncture, myelography and spinal anaesthesia. Acta Neurol Scand 1998; 98: 445-451[Medline].
11.	Lybecker H, Moller JT, May O, Nielsen HK. Incidence and prediction of postdural puncture headache. A prospective study of 1021 spinal anesthesias. Anesth Analg 1990; 70: 389-394[Abstract/Free Full Text].

(Accepted 17 July 2000)