Ultrasound-guided Assessment of Phrenic Nerve Involvement after Interscalene Brachial Plexus Block

Phrenic nerve is usually involved while administering intersalene brachial plexus block (ISBPB), resulting in partial/total hemidiaphragmatic paresis (Hdp) that can affect respiratory mechanics. The aim was to determine the incidence of diaphragm excursion before and after administration of ISBPB using ultrasonography.

Sixty-two patients received ISBPB for anesthesia in the shoulder region who consented to be a part of a prospective observational study. Pre- and postblock values for diaphragmatic excursions were recorded for quiet and deep breathing (DB) using a 3-5 MHz ultrasound (USG) probe to calculate the percentage change. The volume of local anesthesia (LA) was in the range of 10-40 ml. Categorical data were analyzed using the Chi-square test and correlated with continuous data using c. The level of significance was P < 0.05.

In the group of patients who received 10-20 mL of local anesthetic, 30% of patients had total Hdp, whereas 66.7% had total Hdp upon receiving 20-30 mL of local anesthetic ( P = 0.015, Chi-square test) during quiet breathing (QB). Similarly, during DB, total Hdp was observed in 20% of patients who received 10-20 mL local anesthetic, whereas it was significantly higher in 47.6% of patients who received 20-30 mL of local anesthetic ( P = 0.018, Chi-square test). A significant positive moderate correlation was observed between volume of LA and diaphragmatic excursions during QB (Spearman's correlation coefficient = 0.571, P = 0.001) as well as during DB (Spearman's correlation coefficient = 0.556, P = 0.001) were the additional outcome measures. Only two patients developed complications and paradoxical movement was seen in 77.4% of patients.

An increase in the volume of LA increased the incidence of Hdp and total diaphragmatic paralysis.