Background: High tidal volumes in patients with acute respiratory distress syndrome and acute lung injury lead to ventilator-induced lung injury and increased mortality. We evaluated the impact of tidal volumes on cardiac surgery outcomes.
Methods: We examined prospectively recorded data from 3,434 consecutive adult patients who underwent cardiac surgery. Three groups of patients were defined based on the tidal volume delivered on arrival at the intensive care unit: (1) low: below 10, (2) traditional: 10-12, and (3) high: more than 12 ml/kg of predicted body weight. We assessed risk factors for three types of organ failure (prolonged mechanical ventilation, hemodynamic instability, and renal failure) and a prolonged stay in the intensive care unit.
Results: The mean tidal volume/actual weight was 9.2 ml/kg, and the tidal volume/predicted body weight was 11.5 ml/kg. Low, traditional, and high tidal volumes were used in 724 (21.1%), 1567 (45.6%), and 1,143 patients (33.3%), respectively. Independent risks factors for high tidal volumes were body mass index of 30 or more (odds ratio [OR] 6.25; CI: 5.26-7.42; P < 0.001) and female sex (OR 4.33; CI: 3.64-5.15; P < 0.001). In the multivariate analysis, high and traditional tidal volumes were independent risk factors for organ failure, multiple organ failure, and prolonged stay in the intensive care unit. Organ failures were associated with increased intensive care unit stay, hospital mortality, and long-term mortality.
Conclusion: Tidal volumes of more than 10 ml/kg are risk factors for organ failure and prolonged intensive care unit stay after cardiac surgery. Women and obese patients are particularly at risk of being ventilated with injurious tidal volumes.