Impaired pulmonary oxygenation of diabetic origin in patients undergoing coronary artery bypass grafting

The effect of a disposition to diabetes mellitus on pulmonary function was determined by dividing 70 consecutive patients who underwent coronary artery bypass grafting (CABG) into a group of 41 patients with such a disposition and a group of 29 without. Indices of pulmonary function studied were the ratio of the arterial partial pressure of oxygen to the inspired oxygen fraction (PaO2/FiO2), the alveolar-arterial oxygen gradient (A-aDO2) and the respiratory index (A-aDO2/PaO2). These were determined before CABG, at the maximum level of blood glucose and when FiO2 was in the range 0.4-0.7 within 6 h after CABG. Even before bypass, all indices were significantly worse in the group with a disposition to diabetes mellitus than in that without. After surgery, these dysfunctions were more severely exacerbated in the former group. FiO2 was the best predictor of the current state of pulmonary function in both groups. Variables that strongly affected pulmonary function were pulmonary arterial wedge pressure in the group with no diabetic disposition and central venous pressure in those with such a disposition. Thus, pulmonary dysfunction of diabetic origin exists not only before CABG, but also after the procedure. Attending physicians must be careful not to increase wedge pressure and central venous pressure.