Effect of N-acetylcystein on pulmonary function in patients undergoing off-pump coronary artery bypass surgery

Background: Pulmonary dysfunction related to inflammatory response and radical oxygen species remains a problem in off-pump coronary bypass graft surgery (OPCAB), especially in patients with reduced left ventricular (LV) function. The aim of this study was to evaluate the effect of N-acetylcystein (NAC) on pulmonary function following OPCAB. Methods: Patients with LV ejection fraction ≤ 40% were randomly assigned to receive either a bolus of 100mg/kg of intravenous NAC over a 15-min period immediately after anesthetic induction, followed by an intravenous infusion at 40mg/kg/day for 24h (NAC group, n = 24), or a placebo (control group, n = 24). Hemodynamic and pulmonary parameters, and the incidence of acute lung injury (PaO₂/ FiO₂<300mmHg) were assessed and compared. Results: The pulmonary vascular resistance index (PVRI) did not change during mechanical heart displacement compared with the baseline value in the NAC group while it was significantly increased in the control group. Significantly less number of patients developed acute lung injury at 2 h after the surgery in the NAC group. The other pulmonary parameters and the duration of ventilator care were all similar. Conclusions: NAC demonstrated promising results in terms of mitigating the increase in PVRI during mechanical heart displacement and attenuating the development of acute lung injury in the immediate post-operative period. However, NAC could not induce a definite improvement in the other important pulmonary variables including PaO ₂/FiO₂ and Q_s/Q_t, and did not lead to a decreased duration of ventilatory care or length of stay in the intensive care unit.