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Randomized comparison between epidural waveform analysis through the needle versus the catheter for thoracic epidural blocks
  1. Amornrat Tangjitbampenbun1,
  2. Sebastián Layera2,
  3. Vanlapa Arnuntasupakul1,
  4. Worapot Apinyachon1,
  5. Karen Venegas2,
  6. Jaime Godoy2,
  7. Julián Aliste2,
  8. Daniela Bravo2,
  9. Alonso Blanch2,
  10. Javier Webar3,
  11. Mohammed Saadawi3,
  12. Andrew Owen3,
  13. Roderick J Finlayson3 and
  14. De Q Tran4
  1. 1 Anesthesia, Mahidol University Faculty of Medicine Ramathibodi Hospital, Bangkok, Thailand
  2. 2 Anesthesia, University of Chile, Santiago, Metropolitan, Chile
  3. 3 Anesthesia, McGill University, Montreal, Quebec, Canada
  4. 4 Anesthesia, St Mary's Hospital, Montreal, Quebec, Canada
  1. Correspondence to Dr De Q Tran, Anesthesia, St Mary's Hospital, Montreal, Quebec H3T-1M5, Canada; de_tran{at}


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.

  • neuraxial blocks: epidural
  • postoperative pain
  • spinal/epidural injection

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  • Contributors All authors have participated in the conceptualization of the protocol and/or in the recruitment of study patients and/or the data analysis and/or the writing of the manuscript. All authors have seen and approved the final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval Ethics committees of McGill University Health Centre, Montreal, Canada; Ramathibodi Hospital, Bangkok, Thailand; and Hospital Clínico Universidad de Chile, Santiago, Chile.

  • Provenance and peer review Not commissioned; externally peer reviewed.