Ultrasonographic evaluation of incidence of diaphragmatic paralysis following different volumes of supraclavicular brachial plexus block- A prospective randomized double blinded study

BACKGROUND: Ipsilateral diaphragmatic paralysis occurs following supraclavicular blocks such as interscalene blocks, supposedly attributable to the backward diffusion of the local anesthetic (LA) inside the neural sheath. Hence, we have made an attempt to assess diaphragmatic paralysis with ultrasonogram (US) following different volumes of supraclavicular brachial plexus blocks (SCB). AIM: To compare the incidence of diaphragmatic paralysis with different volumes of supraclavicular brachial plexus block using ultrasonogram. METHODS: Sixty patients with American Society of Anesthesiologists (ASA) Physical Status I and II were randomized to receive 20, 25, or 30 mL of 0.375% bupivacaine in a double-blinded fashion, and supraclavicular block was performed using ultrasound guidance in an in-plane technique. Diaphragmatic excursion and velocity were studied using a curvilinear 3.5 MHz transducer before and 20 min after giving the block. RESULTS: The incidence of reduction in diaphragmatic excursion and velocity in the group receiving 30 mL was 45% and 45%, respectively, which was higher, whereas it was 47.5% and 32.5% in the 25 mL group and 40% and 25% in the 20 mL group, respectively, which were still lower. Pre- and post-block data were studied using T-test, Kruskal–Wallis test, and Mann–Whitney U test. The probability of reduction in diaphragmatic excursion and velocity in each group was <0.05, which was statistically significant. CONCLUSION: Our results suggest that there is a greater risk of inadvertent phrenic nerve blockade even in supraclavicular brachial plexus block. The resulting hemidiaphragmatic paralysis is volume dependent, and the overall incidence is higher at greater volumes. Hence, caution is required against compromised perioperative lung function in patients with preexisting cardiorespiratory dysfunction.