Effect of neuromuscular blocking agents on gas exchange in patients presenting with acute respiratory distress syndrome

Objective: To evaluate the effects of a 48-hr neuromuscular blocking agents (NMBA) infusion on gas exchange over a 120-hr time period in patients with acute respiratory distress syndrome. Design: Multiple center, prospective, controlled, and randomized trial. Setting: Four adult medical or mixed medical-surgical intensive care units. Patients: A total of 56 patients with acute respiratory distress syndrome with a Pao(2)/FIo(2) ratio of < 150 at a positive end-expiratory pressure of greater than or equal to 5 cm H2O. Interventions: After randomization, patients received either conventional therapy without NMBA (control group) or conventional therapy plus NMBA for the next 48 hrs. The initial ventilator mode was volume-assist/control. The ventilator remained on assist-control mode throughout the initial 48-hr period in both groups. Tidal volume was 6-8 mL/kg ideal body weight. Measurements and Main Results: When analyzed for the entire 120 hrs, there was a significant effect of the NMBA on the course of Pao(2)/FIo(2) ratio (p = .021). Separate comparisons at each time point indicated that patients randomized to the NMBA group had a higher Pao(2)/FIo(2) at 48, 96, and 120 hrs after randomization. Moreover, a decrease of positive end-expiratory pressure (p = .036) was only found in the NMBA group. Two-way repeated-measures analysis of variance exhibited a decrease in positive end-expiratory pressure over time (p = .036). Concerning short-term effects, there was no modification of Pao(2)/FIo(2) ratio 1 hr after randomization in either group. Only one patient (from the control group) developed pneumothorax. Conclusions: Use of NMBA during a 48-hr period in patients with acute respiratory distress syndrome is associated with a sustained improvement in oxygenation.