Rational approach to postoperative transfusion in high-risk patients

An appropriate threshold for transfusion in patients with coronary artery disease has not been defined. Our purpose was to determine: (1) the effects of preoperative volume loading; (2) postoperative function and oxygen delivery (DO₂); (3) an appropriate transfusion threshold based on observed DO₂ in high-risk patients undergoing abdominal aortic aneurysm (AAA) repair, bypass of aortoiliac disease (AOD), distal bypass, or carotid endarterectomy (CEA). Preoperative volume loading increased cardiac output (CO) in all groups by 15% to 22%. Postoperative CO was unchanged from optimal preoperative values except in the CEA group, in which it decreased. Systemic vascular resistance decreased in the AAA and AOD groups. The decrease in postoperative DO₂ in all groups (25% to 31%) was related to a decrease in hemoglobin. Despite marginal (less than 11 mL/kg/min) postoperative DO₂ in more than a third of patients, there was no compensatory increase in CO. Thus, after optimization of function by volume loading, red cell transfusion may be the only way to increase DO₂. Hemoglobin levels of 10 to 12 g/dL may be required for adequate DO₂ when ventricular function is markedly impaired.