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* From the Departments of Anesthesia, and
Research Design and Biostatistics, Sunnybrook & Women’s College Hospital, University of Toronto, Toronto, Ontario, Canada.
Address correspondence to: Dr. Pamela J. Angle, Department of Anesthesia, Women’s College Campus, Sunnybrook and Women’s College Health Sciences Centre, 76 Grenville Street, Toronto, Ontario M5S 1B2, Canada. Phone: 416-323-6008; Fax: 416-323-6307; E-mail: pamela.angle{at}sw.ca
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Abstract |
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Methods: Healthy parturients 
6 cm dilated were recruited. Epidural analgesia was established using a 19 G Tuohy epidural needle, a 23 G single port 40 cm catheter and bupivacaine 0.08% with fentanyl 2 µg·mL–1 (15–20 mL). Breakthrough pain was treated by protocol. There was no formal in-training period for anesthesiologists. The primary outcome was the combined failure rate for initiation (failed needle/catheter placement or failed block 30 min of drug administration). Secondary out-comes included late block failure (> 30 min), recognized dural puncture, PDPH, patient assessment of analgesia within 24 hr of delivery, complications and anesthesiologist satisfaction.
Results: Twenty-seven parturients were recruited. Successful blocks were initiated and maintained in 24/27 who rated overall analgesia from good to excellent (19/24 very good to excellent). Three block failures occurred at the initiation phase only (two unilateral, one absent). There was no evidence of catheter kinking after placement. One patient developed PDPH after unrecognized dural puncture which was self-treated with acetaminophen for four days, followed by complete symptom resolution.
Conclusion: It is feasible to provide high quality labour analgesia using small G epidural needles and catheters. The effect of small G epidural needles on PDPH warrants future study.
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Introduction |
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Preliminary unpublished in vitro work by the authors with 24 G epidural catheters (the largest diameter catheter to pass through a 20 G Tuohy epidural needle) suggested high resistance to flow during hand boluses of the catheter, making it less acceptable for clinical use. This finding prompted a series of studies with a 19 G Tuohy needle and 23 G triple port adult length (90 cm) epidural catheter, the largest catheter able to be easily passed through the 19 G Tuohy needle. The first study conducted, an in vitro study, examined the performance of the Graseby 3300 (Watford, England) patient controlled epidural analgesia (PCEA) pump using an adult length (90 cm) 23 G triple port catheter.8 We found that the PCEA pump apparatus studied was adequate for delivery of epidural solutions via this catheter. A small pilot study was then conducted using the same catheter in labouring women. This study demonstrated that high quality labour analgesia could be achieved using the same catheter inserted via a 19 G Tuohy epidural needle.9 Kinking of the catheter in the lumbar/thoracic region, resulting in occlusion and necessitating cutting of the epidural catheter to restore function in two of five patients, led to discontinuation of the study, a search for a new non-kinking catheter, and the present study. We now report the results of a single arm clinical trial which examined the feasibility of using 19 G Tuohy needles and a single port 40 cm, 23 G catheter for continuous labour analgesia.
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Methods |
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6 cm dilatation were recruited to participate at the Women’s College Campus of Sunnybrook & Women’s College Health Sciences Centre between September 29, 2004 and January 1, 2005. Exclusion criteria included: contraindication to regional anesthesia; multiple gestation, pregnancy-induced hypertension or significant maternal or fetal illness. Morbidly obese patients were excluded since no extra long (6 inch) 19 G Tuohy needle was available for use. No formal in-training period using the study needle or catheter was required before anesthesiologist participation.
Epidural analgesia was established using a 19 G, 90 mm (3
inch) Tuohy epidural needle (Pajunk, Geisengen, Germany) and 23 G single port pediatric length (40 cm) Portex catheter (Portex Ltd, Kent, UK). The technique of epidural needle and catheter placement was left to the discretion of the anesthesiologist performing the procedure. Catheters were threaded from 3 to 5 cm into the epidural space in all patients. Following a test dose using lidocaine 1.5% (3 mL), epidural analgesia was established using a mixture of bupivacaine 0.08% and fentanyl 2 µg·mL–1 (15–20 mL) and maintained using PCEA. Pump settings were as follows: bolus 5 to 9 mL; bolus duration four minutes; lockout ten minutes; and infusion rate 5 to 12 mL·hr–1 The bolus duration of four minutes was based on preliminary work done with the same Graseby 3300 (Watford, SIMS Graseby Ltd, England) PCEA pumps available on our labour ward which showed that this was the minimum time necessary to bolus 9 mL (the maximum bolus allowable in the protocol) without producing a pump occlusion signal. Breakthrough pain was treated via a protocol with bupivacaine 0.125% (10 mL) with fentanyl 100 µg followed by 2% lidocaine (10 mL) for persistent pain after an additional ten to 15 min.
The primary outcome was the combined failure rate of block initiation defined as failure of either needle or catheter placement, or failure of the block itself within the first 30 min of drug administration via the catheter. Secondary outcomes included: mode of delivery; details related to needle placement (patient position, level, loss of resistance technique, type of syringe used, number of attempts required to locate the epidural space; number of recognized dural punctures); catheter placement (ease of passage, paresthesia, intravascular placement); block failure > 30 min; and, anesthesiologist satisfaction with the needle and catheter using a 10-cm non-graduated visual analogue scale (0 = not at all satisfied; and 10 = completely satisfied). Patient assessments were obtained within the first 24 hr of delivery using a structured questionnaire. Outcomes included: pain relief following block initiation during first and second stages of labour (11 point numeric rating scale, 0 = no pain relief at all; 10 = complete pain relief); overall pain relief during labour (six point adjectival scale--no pain relief at all, poor, fair, good, very good, excellent); and, complications of block placement (headache, back pain, nerve symptoms). Patients were instructed to telephone if they developed a postural headache or neck ache at any time following epidural placement. A follow-up telephone interview using a structured questionnaire was conducted between 14 to 21 days postepidural placement to detect evidence of unrecognized dural punctures resulting in PDPH and the methods and success of any treatments administered for it. Postdural puncture headache was defined as the presence of a postural headache or neck ache (with or without cranial nerve symptoms) present at > 24 hr after epidural placement and lasting at least an additional 24 hr, occurring within the first 14 days of epidural placement.
Statistical analysis
An a priori sample size of 25 to 30 participants was deemed necessary in order to assess the feasibility of using small G epidural needles and catheters for labour analgesia. Statistical analysis was performed using SPSS for Windows (version 12.0) by one of the authors (P.A.) and corroborated by Alexander Kiss, PhD, Department of Research Design and Biostatistics, Sunnybrook & Women’s College Health Sciences Centre, Toronto, Canada. Descriptive statistics are reported using means and standard deviations for normally distributed continuous outcomes and median and interquartile ranges for non-normally distributed data. Binomial proportions and their 95% confidence intervals are reported using the equations developed by Fleiss.10
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Results |
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. Successful blocks were established in 24/27 patients. All patients with successful initiation had successful continuation of the epidural block via the 23 G catheter. There were no cases of late (> 30 min) block failure nor was there evidence of catheter occlusion secondary to kinking or catheter migration. There were three episodes of catheter disconnect at the connector site attributed to increased tension secondary to the relatively short (pediatric) length of the catheter. In most cases this shorter length catheter was long enough to reach the shoulder area of the subject. The short length was remedied by insertion of an extension tubing between the catheter connector and the filter. Details related to methods of epidural needle and catheter placement are found in Table II along with anesthesiologist satisfaction ratings.
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In the 24 patients with successful block initiation, assessments of overall labour analgesia ranged from good to excellent (excellent: 50% (12/24); very good: 29% (7/24); good 19% (5/20)). Mean (± standard deviation) visual analogue pain relief scores in these patients were reported as 8.4 ± 1.3 and 5.8 ± 2.9 for first and second stage labour respectively. No difficulties were encountered with the epidural needle (i.e., bending) nor were there any cases of intravascular catheter insertion, later catheter migration or difficulties with catheter removal postdelivery.
There were no recognized dural punctures in any of the 27 patients recruited. One patient developed a postural headache (continuous loss of resistance to saline technique used during insertion) lasting four days that resolved without any treatment other than acetaminophen. This outcome was noted at the follow-up interview on day 14 (after symptoms had been long resolved). No other complications of epidural placement were observed in any patient.
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Discussion |
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Our previous pilot work8,9 suggested that use of 23 G epidural catheters could be used to provide continuous analgesia for labour using an older PCEA pump. While 24 G catheters can be passed through 20 G needles, we chose to study 23 G catheters since these were: 1) thought more likely to function appropriately with current pump technology; 2) would be more acceptable clinically for dosing epidural top ups by hand; and 3) less likely to kink than the smaller catheter.
In the current study we established successful epidural analgesia for labour in 24/27 parturients. Block failures (two unilateral, one absent) occurred in three patients during the initiation phase of epidural analgesia only. While this rate may seem high, these failures represent one failure for each of three anesthesiologists and occurred very early during study onset, likely reflecting the lack of an in-training period. Given these circumstances, this failure rate would appear acceptable. Of note, continuous epidural analgesia was established throughout the duration of labour in all women with successful epidural initiation suggesting that the catheter, PCEA pump and method of pump programming (increased bolus duration) were adequate. These women (24/24) rated overall analgesia as good to excellent with 19/24 rating it as very good to excellent. There were no episodes of catheter kinking resulting in occlusion following placement, although there were two episodes where catheter kinking at the needle hub during placement required use of a second 23 G catheter at the time of insertion.
Most of the epidural blocks in our study were initiated using a continuous loss of resistance to saline technique. This technique is also reported in a study examining use of small diameter epidural needles for lumbar pediatric epidural catheter placement.14 The authors of this retrospective study reviewed epidural placement in children weighing between 4.5 and 10 kg over a five-year period. Patients were divided into those receiving a 19 G epidural needle and 23 G catheter vs an 18 G needle and 21 G catheter. Difficulties encountered in children included catheter kinking leading to catheter occlusion (similar to what was found in our previous pilot work with a triple port adult length 23 G catheter, but not in the current study using the 40 cm Portex single port catheter). Backflow of epidural solution from the epidural space secondary to the short distance of catheter insertion was also a noted difficulty in pediatric patients. This problem was not encountered in our previous pilot work, nor in the present study with parturients. Two of three patients experiencing paresthesia during catheter insertion received a loss of resistance to air technique.
Overall our findings suggest that use of 19 G Tuohy epidural needles and 23 G catheters may represent a viable option for those providing labour analgesia. Further study is warranted to determine the effect of using small G epidural needles on the incidence and severity of PDPH as well as the generalizability of these findings to other centres before they are introduced into widespread clinical practice. A randomized trial is now planned using an adult length (90 cm) catheter made of the same material used in the present study.
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Footnotes |
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Accepted for publication August 9, 2005. Revision accepted September 15, 2005.
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References |
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2 Aida S, Taga K, Yamakura T, Endoh H, Shimoji K. Headache after attempted epidural block: the role of intrathecal air. Anesthesiology 1998; 88: 76–81.[Medline]
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7 Safa-Tisseront V, Thormann F, Malassine P, et al. Effectiveness of epidural blood patch in the management of postdural puncture headache. Anesthesiology 2001; 95: 334–9.[Medline]
8 Purdie NL, Angle PJ. In vitro validation of 23G epidural catheter performance using standard infusion pump apparatus. Anesthesiology 2004; 101: A36 (abstract).
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10 Fleiss JL. Statistical Methods for Rates and Proportions, 2nd ed. New York: Wiley and Sons Publishers; 1981: 14–5.
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13 Rasmussen BS, Blom L, Hansen P, Mikkelsen SS. Postspinal headache in young and elderly patients. Two randomised, double-blind studies that compared 20- and 25-gauge spinal needles. Anaesthesia 1989; 44: 571–3.[Medline]
14 Sage F, Thomas AR, Howard RF. Paediatric lumbar epidurals: a comparison of 21-G and 23-G catheters in patients weighing less than 10 kg. Paediatr Anaesth 2000; 10: 279–82.[Medline]
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