A Randomized Comparison Between Conventional and Waveform-Confirmed Loss of Resistance for Thoracic Epidural Blocks

Pilot epinephrine dose-finding study to counter epidural-related blood pressure reduction

OBJECTIVE

An unwanted side effect associated with epidural analgesia is the reduction in blood pressure (BP) due to the sympathetic blockade. This study evaluated the hemodynamic effects of adding different epinephrine concentrations to epidurally injected local anesthetic solution to counteract sympathectomy. We hypothesized that epinephrine could mitigate the decrease in BP possibly caused by the local anesthetic, specifically decreasing the incidence of hypotension.

METHODS

Sixty-six patients were enrolled in a randomized, controlled, quadruple-blinded prospective study into three groups: epidural ropivacaine 0.2% without epinephrine (control) or with 2 µg/mL or 5 µg/mL epinephrine. Our primary outcome was the assessment of differences in hypotension between groups, defined as a >20% decrease in hypotension from baseline to the end of the intraoperative period.

RESULTS

Forty-seven patients completed the study, and 19 were withdrawn. Fifteen patients were in the control group, while 16 patients received 0.2% ropivacaine +2 µg/mL epinephrine, and 16 received 0.2% ropivacaine +5 µg/mL epinephrine. The overall rate of hypotension was 21.3% (10/47). There were no statistically significant differences in hypotension rates between the control group (33%) and groups receiving either +2 µg/mL (13%, p=0.165) or +5 µg/mL (19%, p=0.353) of epinephrine. In secondary analyses, respiratory rate showed greater decreases in control groups across the perioperative period compared with treatment groups (p=0.016) CONCLUSION: Adding epinephrine to the epidural local anesthetic did not significantly decrease the rate of hypotension. However, epinephrine mitigated decreases in respiratory rate across the perioperative period. Future studies will focus on increasing group size and higher epinephrine concentrations (10 µg/mL).

TRIAL REGISTRATION NUMBER

NCT02722746.

Loss-of-Resistance Versus Dynamic Pressure-Sensing Technology for Successful Placement of Thoracic Epidural Catheters: A Randomized Clinical Trial

BACKGROUND

The traditional loss-of-resistance (LOR) technique for thoracic epidural catheter placement can be associated with a high primary failure rate. In this study, we compared the traditional LOR technique and dynamic pressure-sensing (DPS) technology for primary success rate and secondary outcomes pertinent to identifying the thoracic epidural space.

METHODS

This pragmatic, randomized, patient- and assessor-blinded superiority trial enrolled patients ages 18 to 75 years, scheduled for major thoracic or abdominal surgeries at a tertiary care teaching hospital. Anesthesiology trainees (residents and fellows) placed thoracic epidural catheters under faculty supervision and rescue. The primary outcome was the success rate of thoracic epidural catheter placement, evaluated by the loss of cold sensation in the thoracic dermatomes 20 minutes after injecting the epidural test dose. Secondary outcomes included procedural time, ease of catheter placement, the presence of a positive falling meniscus sign, early hemodynamic changes, and unintended dural punctures. Additionally, we explored outcomes that included number of attempts, needle depth to epidural space, need for faculty to rescue the procedure from the trainee, patient-rated procedural discomfort, pain at the epidural insertion site, postoperative pain scores, and opioid consumption over 48 hours.

RESULTS

Between March 2019 and June 2020, 133 patients were enrolled; 117 were included in the final analysis (n = 57 for the LOR group; n = 60 for the DPS group). The primary success rate of epidural catheter placement was 91.2% (52 of 57) in the LOR group and 96.7% (58 of 60) in the DPS group (95% confidence interval [CI] of difference in proportions: -0.054 [-0.14 to 0.03]; P = .264). No difference was observed in procedural time between the 2 groups (median interquartile range [IQR] in minutes: LOR 5.0 [7.0], DPS 5.5 [7.0]; P = .982). The number of patients with epidural analgesia onset at 10 minutes was 49.1% (28 of 57) in the LOR group compared to 31.7% (19 of 60) in the DPS group ( P = .062). There were 2 cases of unintended dural punctures in each group. Other secondary or exploratory outcomes were not significantly different between the groups.

CONCLUSIONS

Our trial did not establish the superiority of the DPS technique over the traditional LOR method for identifying the thoracic epidural space ( Clinicaltrials.gov identifier: NCT03826186).

Effectiveness of preoperative thoracic epidural testing strategies: a retrospective comparison of three commonly used testing methods

PURPOSE

Thoracic epidural analgesia (TEA) is a well stablished technique for pain management in major thoracic and abdominal surgeries; however, it has considerable failure rates. Local anesthetic (LA) administration and subsequent assessment of sensory block through physical examination (e.g., decreased temperature perception determined via an LA temperature dissociation test [LATDT]) has been the historical standard for evaluation of thoracic epidural placement. Nevertheless, newer methods to objectively evaluate successful placement have recently been developed, e.g., the epidural electrical stimulation test (EEST) and epidural pressure waveform analysis (EWA). The purpose of this study was to evaluate the effectiveness of preoperative TEA catheter testing (LATDT, EEST, and EWA) on reducing TEA failure.

METHODS

After obtaining an institutional research ethics board approval for a retrospective study, we conducted a single-institution retrospective review on all TEAs performed between January 2016 and December 2021. Patients were assigned to one of four groups based on the performed test method to verify the placement of the TEA catheter: no test, LATDT, EEST, and EWA. A TEA was deemed successful if it provided bilateral dermatomal sensory block to ice test in the postoperative period, and was used for patient analgesia for at least 24 hr.

RESULTS

One thousand two hundred and forty-one patients submitted to preoperative TEA were included. Twenty-eight patients were excluded. Tested and untested epidurals had failure rates of 3.8% (95% confidence interval [CI], 1.8 to 6.2) and 11.5% (95% CI, 5.2 to 17.1), respectively (P < 0.001).

CONCLUSION

Objective preoperative testing after placement of thoracic epidurals was associated with a reduction in failure rates.

Primary failure of thoracic epidural analgesia: revisited

Primary failure of thoracic epidural analgesia (TEA) remains an important clinical problem, whose incidence can exceed 20% in teaching centers. Since loss-of-resistance (LOR) constitutes the most popular method to identify the thoracic epidural space, the etiology of primary TEA failure can often be attributed to LOR's low specificity. Interspinous ligamentous cysts, non-fused ligamenta flava, paravertebral muscles, intermuscular planes, and thoracic paravertebral spaces can all result in non-epidural LORs. Fluoroscopy, epidural waveform analysis, electrical stimulation, and ultrasonography have been proposed as confirmatory modalities for LOR.The current evidence derived from randomized trials suggests that fluoroscopy, epidural waveform analysis, and possibly electrical stimulation, could decrease the primary TEA failure to 2%. In contrast, preprocedural ultrasound scanning provides no incremental benefit when compared with conventional LOR. In the hands of experienced operators, real-time ultrasound guidance of the epidural needle has been demonstrated to provide comparable efficacy and efficiency to fluoroscopy.Further research is required to determine the most cost-effective confirmatory modality as well as the best adjuncts for novice operators and for patients with challenging anatomy. Moreover, future trials should elucidate if fluoroscopy and electrical stimulation could potentially decrease the secondary failure rate of TEA, and if a combination of confirmatory modalities could outperform individual ones.

Use of Perioperative Intravenous Lidocaine as Part of an Abdominal Surgery Enhanced Recovery Pathway Does Not Significantly Impact Postoperative Pain

BACKGROUND

The utility of perioperative intravenous lidocaine in improving postoperative pain control remains unclear. We aimed to compare postoperative pain outcomes in ERP abdominal surgery patients who did vs did not receive intravenous lidocaine. We hypothesized that patients receiving lidocaine would have lower postoperative pain scores and consume fewer opioids.

METHODS

We performed a retrospective cohort study of patients undergoing elective abdominal surgery at a single institution via an ERP from 2017 to 2018. Patients who received lidocaine in the 6 months prior to a lidocaine shortage were compared to those who did not receive lidocaine for 6 months following the shortage. The primary outcome measures were pain scores as measured on the visual analogue scale and opioid consumption as measured by oral morphine equivalents (OME).

RESULTS

We identified 1227 consecutive ERP abdominal surgery patients for inclusion (519 patients receiving lidocaine and 708 patients not receiving lidocaine). Demographics between the two cohorts were similar, with the following exceptions: more females, and more patients with a history of psychiatric diagnoses in the group that did not receive lidocaine. Adjusted, mixed linear models for both OME (P = .23) and pain scores (P = .51) found no difference between the lidocaine and no lidocaine groups.

DISCUSSION

In our study of ERP abdominal surgery patients, perioperative intravenous lidocaine did not offer improvement in postoperative pain scores or OME consumed. We therefore do not recommend the use of intravenous lidocaine as part of an ERP multimodal pain management strategy in abdominal surgery patients.

Evaluation of a modified ultrasound-assisted technique for mid-thoracic epidural placement: a prospective observational study

BACKGROUND

Although mid-thoracic epidural analgesia benefits patients undergoing major surgery, technical difficulties often discourage its use. Improvements in technology are warranted to improve the success rate on first pass and patient comfort. The previously reported ultrasound-assisted technique using a generic needle insertion site failed to demonstrate superiority over conventional landmark techniques. A stratified needle insertion site based on sonoanatomic features may improve the technique.

METHODS

Patients who presented for elective abdominal or thoracic surgery requesting thoracic epidural analgesia for postoperative pain control were included in this observational study. A modified ultrasound-assisted technique using a stratified needle insertion site based on ultrasound images was adopted. The number of needle passes, needle skin punctures, procedure time, overall success rate, and incidence of procedure complications were recorded.

RESULTS

One hundred and twenty-eight subjects were included. The first-pass success and overall success rates were 75% (96/128) and 98% (126/128), respectively. In 95% (122/128) of patients, only one needle skin puncture was needed to access the epidural space. The median [IQR] time needed from needle insertion to access the epidural space was 59 [47-122] seconds. No complications were observed during the procedure.

CONCLUSIONS

This modified ultrasound-assisted mid-thoracic epidural technique has the potential to improve success rates and reduce the needling time. The data shown in our study may be a feasible basis for a prospective study comparing our ultrasound-assisted epidural placements to conventional landmark-based techniques.

Confirming identification of the epidural space: a systematic review of electric stimulation, pressure waveform analysis, and ultrasound and a meta-analysis of diagnostic accuracy in acute pain

To review the use of epidural electric stimulation test, pressure waveform analysis, and ultrasound assessment of injection as bedside methods for confirming identification of the epidural space in adults with acute pain, the PubMed database was searched for relevant reports between May and August 2022. Studies reporting diagnostic accuracy with conventional Touhy needles and epidural catheters were further selected for meta-analysis. Sensitivity and specificity were estimated using univariate logistic regression for electric stimulation and pressure analysis, and pooling of similar studies for ultrasound. Risk of bias and applicability was assessed using QUADAS-2. For electric stimulation, pressure waveform analysis, and ultrasound, respectively 35, 22, and 28 reports were included in the review and 9, 9, and 7 studies in the meta-analysis. Electric stimulation requires wire-reinforced catheters and an adequate nerve stimulator, does not reliably identify intravascular placement, and is affected by local anaesthetics. Sensitivity was 95% (95% CI 93-96%, N = 550) and specificity unknown (95% CI 33-94%, N = 44). Pressure waveform analysis is unaffected by local anaesthetics, but does not identify intravascular nor intrathecal catheters. Sensitivity was 90% (95% CI 72-97%, N = 694) and specificity 88% (95% CI 78-94%, N = 67). B-mode, M-mode and doppler ultrasound may be challenging, and data is still limited. Risk of bias was significant and accuracy estimates must be interpreted with caution. Electric stimulation and pressure waveform analysis seem clinically useful, although they must be interpreted cautiously. In the future, clinical trials in patients with difficult anatomy will likely be most useful. Ultrasound requires further investigation.

The Quality of Preoperative Glycemic Control Predicts Insulin Sensitivity During Major Upper Abdominal Surgery: A Case-Control Study

Objective

To examine the association of the quality of preoperative glycemic control and insulin sensitivity during major upper abdominal surgery.

Background

In cardiac surgery, glycated hemoglobin A1c (HbA1c), an indicator of glycemic control during the preceding 3 months, correlated with intraoperative insulin sensitivity. Furthermore, insulin resistance showed a significant association with adverse clinical outcomes.

Methods

This study is a post hoc exploratory analysis of a randomized controlled trial in patients undergoing elective hepatectomy and receiving the hyperinsulinemic-normoglycemic clamp (HNC) as a potential intervention to reduce surgical site infections (ClinicalTrials.gov NCT01528189). Immediately before skin incision, the HNC was initiated by infusing insulin at the rate of 2 mU/kg/min. Dextrose was administered at rates titrated to maintain normoglycemia (4.0-6.0 mmol/L). The average of 3 consecutive dextrose infusion rates during steady state was used as a measure of insulin sensitivity. Primary outcome was the relationship between preoperative HbA1c and insulin sensitivity during surgery. Secondary outcomes were the associations of insulin sensitivity with the patient's body mass index (BMI) and postoperative morbidity.

Results

Thirty-four patients were studied. HbA1c (Y = -0.52X + 4.8, P < 0.001, R2 = 0.29), BMI (Y = -0.12X + 5.0, P < 0.001, R2 = 0.43) showed negative correlations with insulin sensitivity. The odds ratio of postoperative complications within 30 days of surgery for every increase in insulin sensitivity by 1 mg/kg/min was 0.22 (95% confidential interval, 0.06-0.59; P = 0.009).

Conclusions

We demonstrate significant associations of the quality of preoperative glycemic control and body mass index with insulin sensitivity during hepatectomy. The degree of insulin resistance correlated with postoperative morbidity.

A randomized comparison of loss of resistance versus loss of resistance plus electrical stimulation: effect on success of thoracic epidural placement

Background

Loss of resistance (LOR) for epidural catheter placement has been utilized for almost a century. LOR is a subjective endpoint associated with a high failure rate. Nerve stimulation (NS) has been described as an objective method for confirming placement of an epidural catheter. We hypothesized that the addition of NS to LOR would improve the success of epidural catheter placement.

Methods

One-hundred patients were randomized to thoracic epidural analgesia (TEA) utilizing LOR-alone or loss of resistance plus nerve stimulation (LOR + NS). The primary endpoint was rate of success, defined as loss of sensation following test dose. Secondary endpoints included performance time. An intention-to-treat analysis was planned, but a per-protocol analysis was performed to investigate the success rate when stimulation was achieved.

Results

In the intention-to-treat analysis there was no difference in success rates (90% vs 82% [LOR + NS vs LOR-alone]; P = 0.39). The procedural time increased in the LOR + NS group (33.9 ± 12.8 vs 24.0 ± 8.0 min; P < 0.001). The per-protocol analysis found a statistically higher success rate for the LOR + NS group compared to the LOR-alone group (98% vs. 82%; P = 0.017) when only patients in whom stimulation was achieved were included.

Conclusions

Addition of NS technique did not statistically improve the success rate for epidural placement when analyzed in an intention-to-treat format and was associated with a longer procedural time. In a per-protocol analysis a statistically higher success rate for patients in whom stimulation was obtained highlights the potential benefit of adding NS to LOR.

Trial registration

ClinicalTrials.gov identifier NCT03087604 on 3/22/2017; Institutional Review Board Wake Forest School of Medicine IRB00039522, Food and Drug Administration Investigational Device Exemption: G160273.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01584-x.

Sensitivity and specificity of waveform analysis for assessing postoperative epidural function

STUDY OBJECTIVES

To characterize the accuracy of epidural waveform analysis (EWA) in assessing the functionality of thoracic epidural catheters in the immediate postoperative period (primary objective), and to determine the inter-rater reliability between EWA waveform observers (secondary outcome).

DESIGN

Single center, prospective diagnostic accuracy cohort study.

SETTING

Post-anesthetic care unit of a university teaching hospital.

PATIENTS

84 adult patients undergoing elective thoracic, gynecologic, vascular, urologic, or general surgery with preoperative placement of a thoracic epidural catheter for perioperative analgesia.

INTERVENTIONS

EWA tracings were video recorded in the immediate postoperative period through the epidural catheter in the post-anesthetic care unit.

MEASUREMENTS

Postoperative EWA tracings were compared with clinical assessments of the sensory block to ice produced by epidural local anesthetic in the immediate postoperative period. Additionally, intra-class correlation analysis of agreement between 3 independent (and blinded) EWA waveform observers was carried out.

RESULTS

Among 80 patients with thoracic epidurals who completed the study protocol, 73 demonstrated postoperative functional epidurals with sensory block to ice and 7 demonstrated non-functional epidurals. EWA yielded 65 true positives, 6 true negatives, 8 false negatives, and 1 false positive. Postoperative EWA sensitivity, specificity, positive predictive value and negative predictive value, along with the 95% confidence intervals (CI) were 89% (79-95%), 86% (42-100%), 98% (92-100%), and 43% (18-71%) respectively. Intra-class correlation between waveform assessors was 0.870 (95% CI 0.818-0.910, p < 0.001).

CONCLUSIONS

EWA is useful in assessing the position of thoracic epidural catheters in the immediate postoperative period, demonstrating high sensitivity and specificity as well as robust inter-rater reliability. For patients in whom sensory block to ice cannot be reliably assessed postoperatively, EWA may provide a useful adjunct for assessing epidural functionality.

Randomized comparison between epidural waveform analysis through the needle versus the catheter for thoracic epidural blocks

BACKGROUND

Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for loss of resistance (LOR): when the needle/catheter tip is correctly positioned inside the epidural space, pressure measurement results in a pulsatile waveform. Epidural waveform analysis can be carried out through the tip of the needle (EWA-N) or the catheter (EWA-C). In this randomized trial, we compared the two methods. We hypothesized that, compared with EWA-C, EWA-N would result in a shorter performance time.

METHODS

One hundred and twenty patients undergoing thoracic epidural blocks for thoracic or abdominal surgery were randomized to EWA-N or EWA-C. In the EWA-N group, LOR was confirmed by connecting the epidural needle to a pressure transducer. After obtaining a satisfactory waveform, the epidural catheter was advanced 5 cm beyond the needle tip. In the EWA-C group, the epidural catheter was first advanced 5 cm beyond the needle tip after the occurrence of LOR. Subsequently, the catheter was connected to the pressure transducer to detect the presence of waveforms. In both study groups, the block procedure was repeated at different intervertebral levels until positive waveforms could be obtained (through the needle or catheter as per the allocation) or until a predefined maximum of three intervertebral levels had been reached. Subsequently, the operator administered a 4 mL test dose of lidocaine 2% with epinephrine 5 µg/mL through the catheter. An investigator present during the performance of the block recorded the performance time (defined as the temporal interval between skin infiltration and local anesthetic administration through the epidural catheter). Fifteen minutes after the test dose, a blinded investigator assessed the patient for sensory block to ice. Success was defined as a bilateral block in at least two dermatomes. Furthermore, postoperative pain scores, local anesthetic consumption, and breakthrough analgesic consumption were recorded.

RESULTS

No intergroup differences were found in terms of performance time, success rate, postoperative pain, local anesthetic requirement, and breakthrough analgesic consumption.

CONCLUSION

EWA can be carried out through the needle or through the catheter with similar efficiency (performance time) and efficacy (success rate, postoperative analgesia).

TRIAL REGISTRATION NUMBER

NCT03603574.

Guidelines for Perioperative Care in Elective Colorectal Surgery: Enhanced Recovery After Surgery (ERAS®) Society Recommendations: 2018

BACKGROUND

This is the fourth updated Enhanced Recovery After Surgery (ERAS®) Society guideline presenting a consensus for optimal perioperative care in colorectal surgery and providing graded recommendations for each ERAS item within the ERAS® protocol.

METHODS

A wide database search on English literature publications was performed. Studies on each item within the protocol were selected with particular attention paid to meta-analyses, randomised controlled trials and large prospective cohorts and examined, reviewed and graded according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

RESULTS

All recommendations on ERAS® protocol items are based on best available evidence; good-quality trials; meta-analyses of good-quality trials; or large cohort studies. The level of evidence for the use of each item is presented accordingly.

CONCLUSIONS

The evidence base and recommendation for items within the multimodal perioperative care pathway are presented by the ERAS® Society in this comprehensive consensus review.

The impact of fluoroscopic confirmation of thoracic imaging on accuracy of thoracic epidural catheter placement on postoperative pain control

Background

Thoracic epidural analgesia (TEA) provides superior postoperative pain control compared to parenteral opioids after major thoracic and abdominal surgeries. However, some studies with respect to benefits of continuous TEA have shown mixed results. The purpose of this study was to determine the rate of successful TEA catheter insertion into the epidural space using contrast fluoroscopy and the impact of placement location on postoperative analgesia and opioid use.

Patients and methods

After Advocate health care institutional review board approval, we conducted a prospective, open-label, single intervention study on patients undergoing thoracic or upper abdominal surgery. A thoracic paramedian epidural approach and a loss of resistance to saline technique were used to place an epidural catheter above the T11 level and fluoroscopic images with injected contrast were taken to locate the catheter tip in the epidural space.

Results

Twenty-five subjects were included in the study, of which 3 catheters (12%) were not identified as being in the epidural space. We found an average difference of 1.5 vertebral levels between clinical and radiological assessments of catheter tips. Thirteen catheters (52%) were more than 1 vertebral level away from the clinically assessed level. No significant difference was found in the pain scores at 1, 24, and 48 hours after surgery between patients with correct versus incorrect catheter placement. Less opioids were used in the correct catheter placement group at 24 hours (256 morphine milligram equivalent [MME] vs 201 MME) and at 48 hours after surgery (250 MME vs 173 MME), but it was not statistically significant (p=0.149 and p=0.068, respectively).

Conclusion

Improvement in assuring success in the technique for TEA catheter placement following major thoracic or upper abdominal surgery exists, for which contrast-enhanced fluoroscopy might be a promising solution.

Analysis of epidural waveform for cervical epidural steroid injections confirmed with fluoroscopy

The identification of epidural space with loss of resistance (LOR) is commonly performed. But it lacks specificity. Epidural pressure waveform analysis (EPWA) provides a simple confirmative adjunct for LOR. If the needle is located within the epidural space, measurement of the pressure at its tips shows a pulsatile waveform. Previous studies demonstrated satisfactory sensitivity and specificity of EPWA. However, success or failure of epidural injection was confirmed by the pinprick test, which is limited for patients in the setting of the pain clinic. In this study, we evaluated the sensitivity, specificity, as well as positive and negative predictive values of EPWA for cervical epidural steroid injection (CESI) confirmed by fluoroscopy.One hundred and five CESIs of 75 patients suffering from neck and radicular arm pain of over 3 months duration were enrolled. The physician injected 5 mL of normal saline after a feeling of satisfactory LOR. Saline filled extension tubing, connected to a pressure transducer, was attached to the needle. A 3 mL bolus of contrast medium was injected to confirm the success of CESI.The incorrect identification of epidural space with LOR (false LOR) was 29.5%. Of these 31 failed CESIs, 2 showed epidural waveform and 29 did not. The sensitivity, specificity, positive and negative predictive value of EPWA was 94.5%, 93.5%, 97.2%, and 87.7%, respectively.EPWA shows satisfactory reliability and is a simple adjunct to decrease false LOR for CESI. Further confirmative studies are required before its routine use in clinical practice.

Thermographic skin temperature measurement compared with cold sensation in predicting the efficacy and distribution of epidural anesthesia

Due to the high rates of epidural failure (3-32%), novel techniques are required to objectively assess the successfulness of an epidural block. In this study we therefore investigated whether thermographic temperature measurements have a higher predictive value for a successful epidural block when compared to the cold sensation test as gold standard. Epidural anesthesia was induced in 61 patients undergoing elective abdominal, thoracic or orthopedic surgery. A thermographic picture was recorded at 5, 10 and 15 min following epidural anesthesia induction. After 15 min a cold sensation test was performed. Epidural anesthesia is associated with a decrease in skin temperature. Thermography predicts a successful epidural block with a sensitivity of 54% and a PPV of 92% and a specificity of 67% and a NPV of 17%. The cold sensation test shows a higher sensitivity and PPV than thermography (97 and 93%), but a lower specificity and NPV than thermography (25 and 50%). Thermographic temperature measurements can be used as an additional and objective method for the assessment of the effectiveness of an epidural block next to the cold sensation test, but have a low sensitivity and negative predictive value. The local decrease in temperature as observed in our study during epidural anesthesia is mainly attributed to a core-to-peripheral redistribution of body heat and vasodilation.

Reliability of pressure waveform analysis to determine correct epidural needle placement in labouring women

Pressure waveform analysis provides a reliable confirmatory adjunct to the loss-of-resistance technique to identify the epidural space during thoracic epidural anaesthesia, but its role remains controversial in lumbar epidural analgesia during labour. We performed an observational study in 100 labouring women of the sensitivity and specificity of waveform analysis to determine the correct location of the epidural needle. After obtaining loss-of-resistance, the anaesthetist injected 5 ml saline through the epidural needle (accounting for the volume already used in the loss-of-resistance). Sterile extension tubing, connected to a pressure transducer, was attached to the needle. An investigator determined the presence or absence of a pulsatile waveform, synchronised with the heart rate, on a monitor screen that was not in the view of the anaesthetist or the parturient. A bolus of 4 ml lidocaine 2% with adrenaline 5 μg.ml^-1 was administered, and the epidural block was assessed after 15 min. Three women displayed no sensory block at 15 min. The results showed: epidural block present, epidural waveform present 93; epidural block absent, epidural waveform absent 2; epidural block present, epidural waveform absent 4; epidural block absent, epidural waveform present 1. Compared with the use of a local anaesthetic bolus to ascertain the epidural space, the sensitivity, specificity, positive and negative predictive values of waveform analysis were 95.9%, 66.7%, 98.9% and 33.3%, respectively. Epidural waveform analysis provides a simple adjunct to loss-of-resistance for confirming needle placement during performance of obstetric epidurals, however, further studies are required before its routine implementation in clinical practice.