MINIMUM EFFECTIVE ANESTHETIC CONCENTRATION (MEAC90) OF ROPIVACAINE IN ULTRASOUND GUIDED POPLITEAL SCIATIC NERVE BLOCK: A DOSE FINDING STUDY.
Journal Title: PARIPEX-Indian Journal of Research - Year 2017, Vol 6, Issue 12
Abstract
Background: Peripheral nerve blocks provide excellent regional anaesthesia for limb surgeries. Ultrasound guidance improves the precision and success of the peripheral nerve blocks; and appears to reduce both the concentration and volume of the local anaesthetics required for successful blocks. Objectives: This study was aimed at estimating the minimum effective anesthetic concentration of ropivacaine for ultrasound guided popliteal sciatic nerve block, successful in 90% of patients (MEAC ). 90 Materials and Methods: Design: Prospective, Interventional, Single Group, Double blind (subject and outcome assessor) study. Setting: The study was carried out in the Pre anesthesia procedure room of a tertiary care hospital in India. Patients: 47 ASA functional status 1 2 adult patients aged 18years and above, scheduled to undergo unilateral leg procedures of less than 90 minutes duration were included. Intervention: 47 patients scheduled to undergo lower leg surgeries received popliteal sciatic nerve block using 15 ml of ropivacaine in sub-paraneural plane starting with 0.2% w/v. The concentration of ropivacaine administered to the subsequent patient was determined by the effectiveness of nerve block in the previous patient, using the biased-coin design sequential updown method. If the nerve block was effective in a patient, then the next patient was randomized to receive either the same concentration as the previous patient(probability of 0.89) or a concentration 0.02% w/v less than the previous patient(probability of 0.11). If the nerve block was not effective in a patient, then ropivacaine concentration was increased by 0.02% w/v in the next patient. The block efficacy was assessed by an independent observer every 5 minutes for 30 minutes following the block. Measurements: Time to onset of block, Duration of procedure, Time to first rescue analgesic and complications of procedure were recorded. Results and Conclusion: Out of the 47 patients, 45 had successful blockade. Minimum Effective Anesthetic Concentration in 90% of subjects (MEAC ) was estimated to be 0.139%w/v (95% confidence interval, 0.129% - 0.158%). 90 Ultrasound guided sub-paraneural popliteal sciatic nerve block with 15 ml of 0.139% w/v ropivacaine can produce successful blockade in 90% of patients.
Authors and Affiliations
Davies Cherayath Vergheese, Mariam Koshy Thomas, Sahir Aftab
Keywords
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