Beneficial effects of lung recruitment with PEEP after cardiac surgery

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Introduction

Delayed extubation and pulmonary atelectasis increase resource utilization after cardiac surgery. Lung recruitment techniques may help prevent these problems.

Objectives

To study the cardiovascular and respiratory effects of a recruitment maneuver using PEEP in postoperative cardiac surgical patients.

Methods

A prospective, randomized, double-blind study was performed. All patients were stabilized on a standard ventilatory protocol (10 ml/kg at 10/min; with FIO₂ of 0.8 and PEEP=5 cmH₂O). PEEP was either left at 5 cmH₂O (control) or increased (1 cmH₂0/min) until 15 cmH₂O (recruitment), when cardiovascular endpoints were reassessed. PEEP was then returned to baseline at the same rate. Primary endpoints were the proportion of patients achieving predetermined oxygenation criteria for extubation (PaO₂≥ 70 mmHg on ≤ 50% FiO₂) at 1 h, and time to extubation.

Results

100 patients (mean age 63 years; 79% male) were randomized to either recruitment (n=55) or control (n=45). In the recruitment group, at peak PEEP there was a small but statistically significant increase in PAWP and CVP, with a small decrease in mean BP and cardiac index.

Time to extubation was similar in each group. Oxygenation criteria for extubation at 1 h were achieved by 93% of the total recruitment group versus 82% of controls (P=0.13). In the subgroup with an initial PaO₂/FIO₂ ratio <300, 94% achieved oxygenation criteria for extubation at 1 h versus 61% of controls (P<0.01). Chest radiographs taken after completion of the protocol showed significantly less basal pulmonary collapse in the recruitment group (20% versus 53% in controls; P<0.01).

Conclusion

The use of this incremental PEEP maneuver after cardiac surgery improves pulmonary gas exchange, probably via recruitment of otherwise collapsed pulmonary segments. These benefits are more pronounced in those patients with initially poor gas exchange.