Mechanical ventilation strategies and inflammatory responses to cardiac surgery: A prospective randomized clinical trial

Objective: To examine whether postoperative mechanical ventilation with lower tidal volumes (V_T) has protective effects on inflammatory responses induced by cardiopulmonary bypass (CPB) surgery in smokers and nonsmokers. Design and setting: Prospective, randomized, controlled clinical trial in the intensive care unit of a university hospital. Patients and participants: We examined 44 patients (22 smokers, 22 nonsmokers) immediately after uncomplicated CPB surgery. Interventions: Ventilation was applied for 6 h with either V_T of either 6 or 12 ml/kg ideal body weight. Measurements and results: The time course of serum tumor necrosis factor (TNF) α, interleukin (IL) 6, and IL-8 determined 0, 2, 4, and 6 h after randomization did not differ significantly between the ventilatory strategies. By contrast, in bronchoalveolar lavage fluids sampled after 6 h only TNF-α levels were significantly higher in the high V_T group than the low V_T group (50±111 pg/ml vs. 1±7 pg/ml). IL-6 and IL-8 concentrations did not differ between groups. Subgroup analysis of patients with serum TNF-α level higher than 0 pg/ml after surgery revealed lower TNF-α serum levels during lower V_T ventilation. All observed effects were small, independent of patients' history of smoking, and were not correlated with duration of ventilation and ICU stay. Conclusions: Ventilation with lower V_T had no or only minor effect on systemic and pulmonary inflammatory responses in patients with healthy lungs after uncomplicated CPB surgery. Our data do not suggest a clinical benefit of using low V_T ventilation in these selected patients.