effectiveness of oral n-acetyl-cystein in reduction of pulmonary complications in smokers undergoing coronary artery bypass surgery

introduction: up to 12% of patients undergoing coronary artery bypass graft have pulmonary complications. smoking can cause a six-time increase in pulmonary complication after major surgery. the most common pulmonary changes after cabg are decrease in frc, vc and atelectasis. in this study, the effect of oral n-acetyl-cystein in reduction of severity of hypoxemia and atelectasis in current smokers who smoked more than 10 packs/year and had undergone cabg was evaluated. methods: in the study, 54 current smoker patients were selected randomly and allocated to two drug and placebo groups. in the study group, 300mg n-acetyl-cystein (acc long) containing vitamin c was prescribed two times a day from 4 days before operation up to 3 days after surgery and in control group, effervescent vitamin c tablet was prescribed as placebo. patients with body mass index more than 35, nyha class iv, those who needed intra aortic balloon pump and those who needed reoperation due to bleeding were excluded from the study. in all patients, spirometry was done in the preoperative visit and fev1/fvc was determined. induction and maintenance of anesthesia was similar in all patients. arterial blood gas samples were obtained immediately after anesthesia induction and 4 to 6 hours after extubation. chest x ray was taken before, 6 to 10 hours after extubation and 3rd postoperative day. severity of atelectasis was also measured. quantitative & qualitative data was analyzed by anova and chi-square tests, respectively. pvalue<0.05 was considered as statistically significant. results: both groups were similar with respect to demographic data including ejection fraction, nyha class, fev1/fvc, cigarette smoking and lima harvesting. the ratio of arterial oxygen pressure to fraction of inspiratory oxygen pao2/fio2 was not significantly different after induction but this difference was strongly significant (pvalue<0.005) after extubation. duration of mechanical ventilation was significantly shorter in patients who had n-acetyl-cystein, but duration of icu stay was similar. linear and segmental atelectasis was significantly less in the study group. conclusion: n-acetyl-cystein can improve oxygenation and ventilatory parameters in pathological lungs, but further studies with different doses and different situations are needed .