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.

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).

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.

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