Background and Objectives. Continuous interscalene brachial plexus block with 0.25% bupivacaine decreases diaphragmatic motility and ventilatory function. The author studied the effects of 0.125% bupivacaine with and without fentanyl.

Methods. Forty patients who were to undergo shoulder surgery were given an interscalene brachial plexus block using 20-28 ml 0.75% bupivacaine plus epinephrine. In random order, 10 patients then had a 24-hour continuous block with 0.125% bupivacaine (BUPI) (5-9 ml/h). Nine patients had an additional s.c. infusion of fentanyl (F-SC) (15-27 μg/h) and 10 the same dose of fentanyl with the bupivacaine infusion (F-PLX). Ten patients had a single block (PLX) for minor surgery. Spirometry, double-exposure chest radiography, pulse oximetric hemoglobin saturation and maximal airway pressures were measured.

Results. Postoperatively, BUPI patients were given, on average, 1.2, F-SC patients 0.7, and F-PLX patients 0.4 doses of oxycodone in 24 hours (not significant). Average ipsilateral diaphragmatic motility was reduced to 8% in F-PLX group ( p < 0.01) and to 19-30% in the other groups ( p < 0.05). At 24 hours, average motility in BUPI, F-SC, F-PLX and PLX groups was 54, 48, 31 and 91%, respectively. In all groups FVC, FEV₁ and PEF were reduced by 20-40% at 3 hours ( p < 0.001). At 8 and 24 hours, FVC and FEV₁ were in F-SC and F-PLX groups significantly lower ( p < 0.05) than in PLX group.

Conclusions. Use of 0.125% bupivacaine for continuous interscalene block did not prevent a deterioration of diaphragmatic motility and ventilatory function. Coinfusion of fentanyl did not significantly potentiate the block.