Ultrasonographic guidance reduces the amount of local anesthetic for 3-in-1 blocks*1

BACKGROUND AND OBJECTIVES: Recently it has been demonstrated that the use of ultrasound (US) improves the onset time and the quality of sensory block for 3-in-1 blocks compared with conventional nerve stimulator (NS) techniques. The present study was designed to evaluate if US guidance for 3-in-1 blocks reduces the amount of local anesthetic compared to NS guidance. METHODS: After institutional approval and informed consent, 60 patients undergoing hip surgery following trauma were randomly assigned to three groups of 20 patients each. In group A, the 3-in-1 block was performed using US guidance with 20 mL 0.5% bupivacaine. Group B received 20 mL 0.5% bupivacaine, and group C received 30 mL 0.5% bupivacaine during NS guidance. The quality and the onset time was assessed by pinprick test in the central sensory region of each of the three targeted nerves and compared with the contralateral leg every 10 minutes for 1 hour by a blinded observer. The rating was undertaken using a scale from 100% (uncompromised sensibility) to 0% (no sensation). RESULTS: Overall success for the 3-in-1 block in group A was 95% and in groups B and C 80%. Onset time was significantly shorter in the US-guided group compared with both NS-guided groups (group A 13+/-6 minutes; group B 27+/-12 minutes; and group C 26+/-13 minutes; P < .01 to groups B and C). Quality of sensory block was significantly better in group A (4%+/-5% of initial value) compared with groups B and C (group B 21%+/-11% of initial value, P < .01 to group A; group C 22%+/-19%, P < .01 to group A). CONCLUSION: The amount of local anesthetic for 3-in-1 blocks can be reduced by using US guidance compared with the conventional NS-guided technique.