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. 2021 Jul-Sep;37(3):402-405.
doi: 10.4103/joacp.JOACP_34_19. Epub 2021 Oct 12.

What is the minimum effective anesthetic volume (MEAV90) of 0.2% ropivacaine required for ultrasound-guided popliteal-sciatic nerve block?

Sandeep N David  1 , Davies C Varghese  1 , Sebastian Valiaveedan  1
Affiliations

What is the minimum effective anesthetic volume (MEAV90) of 0.2% ropivacaine required for ultrasound-guided popliteal-sciatic nerve block?

Sandeep N David et al. J Anaesthesiol Clin Pharmacol. 2021 Jul-Sep.

Abstract

Background and aims: Popliteal-Sciatic nerve block under Ultrasound Guidance (USG) using a local anesthetic agent like Ropivacaine is an established technique for providing analgesia and muscle relaxation for lower limb surgeries with minimal untoward events. Establishing the minimal volume of 0.2% ropivacaine required to provide intraoperative and postoperative analgesia will further reduce the drug requirements and adverse effects toward the patient.

Material and methods: This randomized prospective observational blinded study was done in a tertiary care referral hospital in South India over 9 months from August 2017 till April 2018. The block was performed on all recruited patients under ultrasound guidance with a starting volume of 16 ml 0.2% ropivacaine. Duration of time for loss of pin-prick sensation around the sole of the foot (tibial nerve) and the lateral malleolus (common peroneal nerve) was noted. If successful, the volume of the drug for subsequent patients was randomized by lottery method to either be kept the same or reduced. If the block failed, the subsequent patient recruited would have an increased volume of drug injected.

Results: By Probit regression analysis using the biased coin up-and-down method we found that 9.3 ml (MEAV90) of 0.2% ropivacaine was sufficient for providing adequate analgesia. Factors such as patient age or weight had no role in efficacy of the block. There were no adverse effects such as allergy to the drug or systemic toxicity noted in the studied patients.

Conclusion: 9.3 ml of 0.2% ropivacaine is sufficient to provide analgesia (assessed by pin-prick) in 90% of patients undergoing popliteal-sciatic block for lower limb surgeries.

Keywords: Minimum effective anesthetic volume; popliteal-sciatic; ropivacaine; ultrasound.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
USG Pop-sciatic block with 0.2% ropivacaine while visualizing the needle tip
Figure 2
Figure 2
Adequate spread of LA around the tibial and common peroneal nerves
Graph 1
Graph 1
Volume of 0.2% ropivacaine given
Graph 2
Graph 2
Up-and Down graph showing the volume of 0.2% Ropivacaine given per patient
Graph 3
Graph 3
Distribution of subjects based on the outcome of intervention
See this image and copyright information in PMC

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