Blood conservation in open heart surgery
Attempts at blood conservation have been made continuously during the entire history of cardiac surgery. In the early days of cardiac surgery with cardiopulmonary bypass, 15 units of whole blood were typed and cross-matched before the procedure, and another 15 set up after induction of anesthesia. Large volume oxygenators were primed with 3 L or more of whole blood, initially heparinized and freshly drawn, and the incidence of reexploration was such that an anesthesia machine was reserved for the reexploration immediately after the patient was brought to the postoperative intensive care unit. The sheer logistical magnitude of obtaining so much blood represented a limit upon the amount of open heart surgery that could be performed. The incidence of hepatitis and other adverse responses to homologous blood transfusion were important factors of morbidity and mortality.
At present, the amount of blood used per case is only a small fraction of that used as recently as a decade ago. Many factors are responsible for this decline, including smaller priming volumes and nonheme blood primes, autologous blood transfusion, more exacting anticoagulation and coagulation reversal protocols, acceptance-of postoperative normovolemic anemia, and recently, retransfusion of intraoperative suction and postoperative shed mediastinal blood. This discussion concentrates on the physiology of acute normovolemic anemia, with emphasis on work performed for many years at the Massachusetts General Hospital, and recent developments in retransfusion of shed blood.
Hemodilution refers to the induction of acute anemia. In most instances, maintenance of normal intravascular volume (normovolemia) is implied. The conditions . . .