Measurement of bupivacaine induced myotoxicity in interfascial plane blocks: A randomised controlled trial

Recent reports of local-anaesthetic induced myotoxicity after peripheral nerve blocks have increased interest in this less commonly known complication. Although the morphological, physiological and biochemical changes in muscle after injection of clinically used concentration of bupivacaine have been studied in animals, little research has been conducted on human subjects, especially in relation to fascial plane blocks. We conducted a study to examine the changes in circulating creatine phosphokinase (CPK) levels in patients undergoing modified radical mastectomy (MRM) or mesh hernioplasty (MH) with or without peripheral nerve blocks. The study explored local anaesthetic (bupivacaine) induced myotoxicity by measuring changes in serum CPK levels following transversus abdominis plane block (TAP) or pectoral nerve block-II (PEC- II) in patients undergoing MH or MRM, respectively.

The study was a randomised, controlled open-label trial. Patients undergoing MH who were randomised to the intervention group received TAP block whereas those undergoing MRM received PEC-II block. Blood samples were drawn at baseline, 6 and 24 hours after surgery for serum CPK measurements. Changes in serum CPK levels between the control and intervention groups were compared using repeated-measures analysis of variance.

Baseline serum CPK levels were similar between the groups. There was a significant difference in the change in serum CPK levels between the groups. It significantly rose in the intervention group as compared to the control group (p < 0.001).

The study shows that serum CPK levels significantly increase at 24 hours after interfascial plane block thereby indirectly indicating myotoxicity. Further research is needed to ascertain its clinical impact.