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Minimum effective volume 90% for ultrasound-guided selective trunk block: A quantal bioassay
Ranjith Kumar Sivakumar1, Manoj Kumar Karmakar, Rosinni S L Wong
1From the Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong S.A.R, The Peoples' Republic of China (RKS, MKK, RSLW, WS).
This study determined the minimum effective volume 90% (MEV90) of local anesthetic for selective trunk block (SeTB) to achieve surgical anesthesia of the upper extremity. The optimal MEV90 for ultrasound-guided SeTB was found to be 24.7 mL.
Area of Science:
- Anesthesiology
- Regional Anesthesia
- Ultrasound-Guided Procedures
Background:
- Selective trunk block (SeTB) provides anesthesia for the entire upper extremity, but the optimal local anesthetic (LA) volume is unknown.
- Determining the minimum effective volume 90% (MEV90) is crucial for safe and effective SeTB.
Purpose of the Study:
- To evaluate the minimum effective volume 90% (MEV90) of a specific local anesthetic mixture required for ultrasound-guided selective trunk block (USG SeTB).
Main Methods:
- A prospective, single-center study using a quantal bioassay and modified Narayana sequential design.
- 25 patients undergoing upper extremity surgery received USG SeTB with a 1:1 mixture of 2% lidocaine with epinephrine and 0.5% levobupivacaine.
- Success was defined as readiness for surgery (sensory score ≤30, motor score ≤1) within 30 minutes, with MEV90 estimated via isotonic regression.
Main Results:
- The MEV90 for USG SeTB was determined to be 24.7 mL (95% CI, 23.8–28.9 mL).
- Median time to readiness for surgery was 6.6 minutes, and median time to complete anesthesia was 15 minutes.
- The procedure successfully provided surgical anesthesia for the upper extremity, excluding the T2 dermatome.
Conclusions:
- The minimum effective volume 90% (MEV90) of the tested local anesthetic mixture for ultrasound-guided selective trunk block is 24.7 mL.
- This volume ensures surgical anesthesia of the upper extremity, facilitating successful surgical procedures.
- The study provides essential data for optimizing LA dosage in USG SeTB.
