Background and Objectives The comparative incidences of hemidiaphragmatic paralysis associated with contemporary ultrasound-guided supraclavicular versus infraclavicular blockade have not received extensive study. We tested the hypothesis that the infraclavicular approach results in a lower incidence of hemidiaphragmatic paralysis compared with supraclavicular blockade when a standard local anesthetic volume and concentration are used.

Methods With institutional human ethics board approval, we enrolled 64 patients undergoing right-sided upper extremity surgery in a randomized, blinded, parallel-group trial. Patients were assigned to ultrasound-guided supraclavicular or infraclavicular blockade with 30 mL of 0.5% ropivacaine. The primary end point was complete hemidiaphragmatic paralysis at 30 minutes, defined as a greater than 75% reduction in diaphragmatic excursion measured with the voluntary sniff test using M-mode ultrasonography. Partial paralysis was defined as a 25% to 75% reduction.

Results Eleven (34%) of 32 patients in the supraclavicular group versus 1 (3%) of 32 in the infraclavicular group had complete hemidiaphragmatic paralysis (P = 0.001 [1-tailed]; relative risk, 11.0 [95% confidence interval, 1.5–80.3]); 44% versus 13% had any (complete or partial) paralysis (P = 0.006; relative risk, 3.5 [95% confidence interval, 1.3–9.5]). Eight (25%) of 32 patients in the supraclavicular group versus 5 (16%) of 32 in the infraclavicular group reported dyspnea (P = 0.54).

Conclusions Ultrasound-guided supraclavicular blockade with 30 mL of 0.5% ropivacaine produced complete hemidiaphragmatic paralysis in approximately one-third of patients. The infraclavicular approach greatly reduced this risk but did not eliminate it. These data may aid in the selection of the approach to brachial plexus blockade, particularly in ambulatory patients and/or those with respiratory comorbidities.