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) , 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- 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- level higher than 0 pg/ml after surgery revealed lower TNF- 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.This study was supported by grants from the BONFOR Forschungsförderung (project O-117.0006), University of Bonn, Germany, and from the Deutsche Forschungsgemeinschaft (Pu 219/1-1, and Uh 88/4-1), Bonn, Germany, and by departmental funding.