Postoperative Pulmonary Edema in Postcoronary Artery Bypass Graft Patients: Relationship of Total Serum Protein and Colloid Oncotic Pressures

Abstract

A blinded, prospective study of 52 consecutive male patients undergoing coronary artery bypass grafting was designed to determine which factors were associated with pulmonary edema (PE) in the postoperative period. PE was demonstrated in 18 patients, but not in the remaining 34 patients. PE correlated with the maximum left atrial pressure (p <.001), but not with the degree of preoperative left ventricular dysfunction as manifested by ejection fraction. PE developed in nine of 18 patients at pulmonary capillary hydrostatic pressures (PCHP) ≤15 mm Hg, defining a population with noncardiogenic PE. Postoperative PE was associated with the degree of intraoperative dilutional hypoproteinemia which occurred to a varying degree in every patient. When the immediate postoperative total serum protein (TSP) was ≤4.0 g/dl, PE developed in 72 percent (13 of 18 patients), but occurred in only 15 percent (five of 34 patients) with levels above 4.0 g/dl. The calculated filtration gradient, reflecting the difference between the colloid oncotic pressure and the PCHP was The best univariate predictor of PE. When this fell to ≤2,100 percent (eight of eight patients) developed PE as compared to 12.5 percent (three of 24) above this value (p <.001). The magnitude of pump-induced, hemodilutional hypoproteinemia is the major cause of PE in patients with normal PCHP.