A comparison of ultrasound-guided supraclavicular and infraclavicular blocks for upper extremity surgery.

BACKGROUND: Ultrasound (US)-guided supraclavicular or infraclavicular blocks are commonly used for upper extremity surgery. The aims of this randomized study were to compare the block performance and onset times, effectiveness, incidence of adverse events and patient's acceptance of US-guided supraclavicular or infraclavicular blocks. We hypothesized that the supraclavicular approach, being more superficial and easier to visualize using a 10 MHz transducer, will produce a faster and a more extensive sensory block.

METHODS: One hundred and twenty patients were randomized to two equal groups: supraclavicular (S) and infraclavicular (I). Each patient received a mixture containing equal volumes of ropivacaine 7.5 mg/ml and mepivacaine 20 mg/ml with adrenaline 5 microg/ml, 0.5 ml/kg body weight (minimum 30 ml, maximum 50 ml). The sensory score (anaesthesia--2 points, analgesia--1 point and pain--0 point) of the seven terminal nerves was assessed every 10 min. Patients were declared ready for surgery when they had an effective surgical block--anaesthesia or analgesia of the five nerves below the elbow. Thirty minutes after the block, the unblocked nerves were supplemented. The block performance and latency times, surgical effectiveness, adverse events and patient's acceptance were recorded.

RESULTS: Significantly more patients in the I group were ready for surgery 20 and 30 min after the block. The mean block performance time was 5.7 min in the S group and 5.0 min in the I group (NS). Block effectiveness was superior in the I group: 93% vs. 78% in the S group (P=0.017). The S group patients had a significantly poorer block of the median and ulnar nerves, but a better block of the axillary nerve. Sensory scores at 10, 20 and 30 min were not significantly different. Thirty-two patients in the S group vs. nine patients in the I group experienced transient adverse events (P<0.0001). Patients' acceptance of the block was similar in both groups.

CONCLUSIONS: Infraclavicular block had a faster onset, better surgical effectiveness and fewer adverse events. Block performance time and patients' acceptance of the procedure were similar in both groups.