Early Detection and Temporal Progression of Hemidiaphragmatic Paralysis After Supraclavicular Brachial Plexus Block with 20 mL vs 30 mL Ropivacaine: A Randomized Controlled Trial.

OBJECTIVE

Hemidiaphragmatic paralysis (HDP) is a recognized complication of supraclavicular brachial plexus block (SCBPB). This study aimed to compare the incidence and temporal progression of HDP following ultrasound-guided SCBPB with 20 mL versus 30 mL of 0.375% ropivacaine.

METHODS

Eighty-two patients undergoing removal of internal fixation devices in the upper extremities were randomly allocated to receive 20 mL (Group A) or 30 mL (Group B) of 0.375% ropivacaine for ultrasound-guided SCBPB. The diaphragmatic compound muscle action potential amplitude (Dia CMAP Amp) was measured before (T0) and 5 min (T1), 10 min (T2), 20 min (T3), and 30 min (T4) after SCBPB. The primary outcome was the incidence of HDP, defined as a ≥50% decrease in the Dia CMAP Amp from baseline. The secondary outcome was the Dia CMAP Amp at different times.

RESULTS

The risk of HDP was significantly greater in Group B than in Group A (RR=1.972, P=0.011). There was a significant time effect on the incidence of HDP (Wald's χ2=15.547, P=0.001); HDP could occur within 5 minutes, and the incidence of HDP at T2, T3 and T4 was 1.222 (P=0.046), 1.889 (P<0.001) and 1.944 P<0.001) times greater than that at T1, respectively. The Dia CMAP Amp following SCBPB was significantly different between the ropivacaine groups (Wald's χ2=5.517, p=0.019).

CONCLUSION

HDP can be detected as early as 5 minutes after SCBPB, with incidence plateauing by 20 minutes while CMAP amplitude continues declining. Higher volume (30 mL) nearly doubles HDP risk (RR=1.972). Respiratory monitoring should begin within 5 minutes of block placement.