Bleeding Complications Associated With Cardiopulmonary Bypass

Reduction in blood loss and blood use after cardiopulmonary bypass with high dose aprotinin (Trasylol).

We audited 540 patients undergoing elective first-time coronary artery bypass grafts at 18 institutions. The purposes of the study were to describe the variability in transfusions among institutions and to determine factors that may account for variability. Mean homologous red blood cell use per patient was 2.9(+/- 0.1) U (institutional range, 0.4 to 6.3 U). One hundred seventy-seven patients (32%) received plasma (institutional range, 0% to 97%), and 119 (22%) received platelets (institutional range, 0% to 80%). After controlling for patient and surgical practice variables, transfusion practice factors still accounted for variation in red blood cell transfusions. Variation in patients receiving plasma and platelet transfusions among institutions was determined in part by prophylactic transfusions. We conclude that blood component usage for coronary artery bypass grafts differs widely among institutions. The variability in use of these components is accounted for in part by unnecessary transfusions in otherwise routine, uncomplicated coronary artery bypass graft procedures.

The variability of transfusion practice in coronary artery bypass surgery. Transfusion Medicine Academic Award Group.

Acute isovolemic hemodilution is used increasingly to avoid the potentially serious side effects of homologous blood transfusions. Cardiovascular physiology during hemodilution is characterized by a marked increase in cardiac output and organ blood flow to compensate for the decrease in arterial oxygen-carrying capacity. During advanced hemodilution an increased oxygen extraction is also observed, such that oxygen consumption generally is maintained even during advanced hemodilution. The increase in cardiac output is related mainly to a decrease in blood viscosity and an enhanced sympathetic tone resulting in stimulation of the heart. The magnitude and the mechanisms involved in the increase depend upon species, state of awareness (awake versus anesthetized), type of anesthesia, type of exchange solution, and condition of the heart prior to hemodilution. Recent laboratory findings, as well as clinical practice in cardiac surgery, suggest that moderate hemodilution to hematocrit values of approximately 25% is well tolerated in single vessel coronary artery disease which should thus not be regarded as an absolute contraindication for moderate hemodilution. An integral concept to minimize homologous blood transfusions consists of preoperative autologous blood donation, preoperative isovolemic hemodilution, meticulous (asanguineous) surgical technique, and acceptance of minimum hemoglobin levels during the entire hospitalization. The incidence of homologous blood transfusions will be reduced using acute isovolemic hemodilution. This incidence will be further reduced once hemoglobin solutions become clinically available for specific indications. At present, research activities are concentrated on defining the critical level of hemodilution in various pathologic conditions and to investigate pharmacology and physiology of the new hemoglobin solutions. Finally, several chemically modified hemoglobin-based oxygen-carrying solutions devoid of renal toxicity will be available in the future. The cardiovascular physiology and pharmacology of these hemoglobin solutions have been studied. Cardiac output is generally constant and oxygen extraction is increased to maintain oxygen consumption during hemodilution with hemoglobin solutions. In most studies, some vasoconstriction was observed also, which might result from interaction of the hemoglobin molecule with the EDRF/NO system. However, with enhanced purification, chemical modification or microencapsulation of the hemoglobin molecule, vasoconstriction can be limited.

Cardiovascular and coronary physiology of acute isovolemic hemodilution: a review of nonoxygen-carrying and oxygen-carrying solutions.

At the recent Tuberous Sclerosis Consensus Conference, a subcommittee proposed recommendations to guide the rational use of diagnostic studies in patients with tuberous sclerosis complex. Recommendations were made for diagnostic evaluation at the time of diagnosis, when testing helps both to establish the diagnosis and to identify potential complications. Additional guidelines were proposed for the ongoing surveillance of established patients to detect later complications of tuberous sclerosis complex. In the absence of comprehensive population studies to govern the use of diagnostic studies in individuals with tuberous sclerosis complex, the panel developed guidelines based on the disorder's natural history, concentrating on complications that are common, clinically significant, and more easily managed when found early. Finally, the group made suggestions for the use of diagnostic tests to identify family members who have tuberous sclerosis complex. Although these recommendations should standardize and improve our use of diagnostic studies in individuals with tuberous sclerosis complex, the clinical approach in a given patient must remain flexible enough to meet the needs of individual patients and families.

William G. Hendren

Papers

Transfusion of predonated autologous blood in elective cardiac surgery.

The effects of calcium and magnesium in hyperkalemic cardioplegic solutions on myocardial preservation.

Calcium-induced ventricular contraction during cardioplegic arrest.

Oxygenation of cardioplegic solutions: Potential for the calcium paradox

Symptomatic bilateral renal angiomyolipomas in a child.