ORIGINAL ARTICLE Original Article Comparison of Pulmonary Gas Exchange in OPCAB Versus Conventional CABG Aitizaz Syed, FRCS, Ed, Consultant Cardiac Surgeon, ∗ Hosam Fawzy, MD, Atef Farag, MD and Arto Nemlander, MD, PhD Cardiac Services Department, North West Armed Forces Hospital, P.O. Box 100, Tabuk, Saudi Arabia Background. Cardiopulmonary bypass has been implicated as a cause of acute lung injury in cardiac surgical patients. This could be avoided with off-pump coronary artery bypass surgery. Aim. To ascertain the possible benefit of OPCAB surgery on pulmonary gas exchange. Methods. We randomized 75 consecutive patients (mean age 57 years) into two groups: Group 1 off-pump coronary artery bypass surgery (OPCAB), n = 37, Group 2 conventional coronary artery bypass grafting (con CABG), n = 38. Alveolar- arterial oxygen difference (A-aO 2 difference) was calculated pre-operatively, then 2 and 4h post-operatively. PaO 2 /FiO 2 ratio and respiratory index (RI) were calculated 2 and 4 h post-operatively. Results. Alveolar-arterial O 2 gradient sharply increased in the immediate post-operative period, from 27 mmHg pre- operatively, to 227mmHg 2h post-operatively, then declined to 152mmHg 4h post-operatively. PaO 2 /FiO 2 ratio and RI also showed severe worsening 2 h post-operatively, with marked improvement at 4 h. The pattern of physiological deterioration of gas exchange was similar in both the groups. Conclusion. In terms of pulmonary gas exchange, similar degree of deterioration is noticed in CABG patients with or without cardiopulmonary bypass. OPCAB seems to provide no physiological benefit of gas exchange at the alveolar capillary membrane when compared to conventional CABG. (Heart Lung and Circulation 2004;13:168–172) © 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved. Keywords. Coronary artery surgery; Off-pump Introduction A cute lung injury manifesting as pulmonary edema and abnormalities of pulmonary gas exchange can occur after cardiac surgery. Pulmonary dysfunction after coronary bypass operations may lead to major morbidity or mortality in such patients. The impact on health care expenditurecanbesubstantialinsuchpatientsduetopro- longed mechanical ventilation requirements and a longer hospital stay. Significant increase in alveolar-arterial (cap- illary) PO 2 gradient has long been known to occur after conventional bypass surgery on mechanical extracorpo- real circulation. 1 Cardiopulmonary bypass (CPB) is also known to produce changes in dynamic and static lung compliance, 2 reduce surfactant activity in children, 3 and reduce the forced vital capacity to one-third (1/3) of the pre-operative value. 4 However, cardiopulmonary bypass itselfmaynotbethemajorcontributortothedevelopment of post-operative pulmonary dysfunction. 5 Avoidance of cardiopulmonary bypass in OPCAB surgery was expected to produce a better outcome in Received 7 November 2003; received in revised form 11 February 2004; accepted 3 March 2004 ∗ Corresponding author. Tel.: +966-4-4411088x85423; fax: +966-4-4411056. E-mail address: aitizaz@hotmail.com (A. Syed). oxygenation and pulmonary gas exchange. Similar stud- ies in Europe and North America have not shown any beneficial effect on pulmonary gas exchange with OPCAB techniques. 18–20 All these studies, however, represented the initial experience with OPCAB techniques where only selected patients were operated as OPCAB. We have tried to validate those findings in our population, with “no exclusion” of the patients based on their clinical demographics. Patients and Methods Patients presenting for myocardial revascularization from June2001toMarch2003atourcenterwereincludedinthis study. Data were available for all 75 consecutive patients who were allocated to Group 1 (OPCAB) or Group 2 (conventional CABG), based on the serial number of their operation. No patients were excluded because of their pre-operative clinical characteristics or risk acuity status. We excluded the patients who had a single graft (both OPCAB and con CABG) and were extubated in the operating room or immediately after transfer to intensive care unit (15 in total). The preoperative demographics are presented in Table 1. Mean age of the two groups was very similar and there was no statistical difference between the two in terms of body mass index or body surface area. The © 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved. 1443-9506/04/$30.00 doi:10.1016/j.hlc.2004.03.015