Local-Anaesthetic-Induced Myotoxicity in Interfascial Plane Blocks: A Comparative Study between Bupivacaine and Ropivacaine

Objective: Local-anaesthetic (LA)-induced myotoxicity in the use of peripheral nerve blocks has emerged as a topic of interest recently. Very few studies on human subjects have been done in this field, though the technique of nerve blocks is being widely practiced both for anaesthesia and analgesia. Studies have shown that bupivacaine induces reproducible skeletal muscle degeneration. The present study is thus aimed at comparing the myotoxicity induced by bupivacaine and ropivacaine in interfascial plane blocks.Material and Methods: The study was a randomized comparative study done at a tertiary care hospital. The subjects were randomly assigned into 3 groups of 50 patients each:- Group B, with patients in whom bupivacaine was used; Group R, comprised of patients in which ropivacaine was used, Group N, who received no fascial plane block during their procedures. An erector spinae block (ESP block) was performed for patients undergoing unilateral lung decortication or lobectomy. Creatine phosphokinase (CPK) levels at 6 and 24 hours after completion of surgery were taken in all 3 groups and compared with baseline values using Repeated Measures Analysis of Variance.Results: Baseline serum CPK levels were similar in all 3 study groups. Significant increases in serum CPK levels were noticed in group B compared to group R at 6 hours and 24 hours, with no increase in group N.Conclusion: The study showed that serum CPK, a marker of skeletal muscle injury and local-anaesthetic-induced myotoxicity, significantly rose at 24 hours after an ESP block and this increase was considerably higher in group B (bupivacaine) compared to group R (ropivacaine), indicating significantly higher myotoxicity with bupivacaine.