Continuous interscalene brachial plexus nerve block prolongs unilateral diaphragmatic dysfunction.

BACKGROUND AND OBJECTIVES: Single interscalene blocks (ISB) impair pulmonary function (<24h). We hypothesized that continuous ISBs would prolong pulmonary dysfunction until h48 compared with a single ISB. We compared the time course of spirometric and diaphragmatic dysfunction following single or continuous ISBs.

METHODS: We prospectively included consecutive adult patients scheduled to undergo shoulder surgery under standard general anaesthesia with single (n=30) or continuous (n=31) ISB. Before ISB (baseline), spirometric tests were recorded and the diaphragm course was evaluated with a B-mode ultrasound technique every 12h until h48. ISBs were performed with 15mL 0.5% ropivacaine using an ultrasound technique approach. The continuous group received the same bolus followed by 0.2% ropivacaine 5mL·h-1 (48h). The primary end point was the reduction (> 25% from baseline) of forced vital capacity (FVC) over the study period (48h).

RESULTS: Patient characteristics were similar in both groups. Thirty minutes after blocks in the PACU, all patients demonstrated a similar and significant unilateral diaphragm paralysis (< 25% from baseline). For the primary end point (FVC), no significant difference was observed between groups over the study period. A difference between single and continuous groups was observed at h24 for: FVC (-25%, P=0.038), FEV1s (-24%, P=0.036), diaphragmatic course (-26%, P=0.02), while no differences for other time points (h0-h48) were noted. Clinical respiratory evaluations (respiratory rate, SpO2, supplementary nasal O2), postoperative pain scores and additional opioid consumption were similar between groups.

CONCLUSION: Over infusion, continuous ISB did not significantly prolong unilateral phrenic paresis and demonstrated a limited pulmonary impact.