Tranfusion techniques in cardiac surgery

AORN Journal,  April, 2007  by George Allen

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European Journal of Cardio-thoracic Surgery

August 2006

Blood frequently is administered to patients during cardiac surgical procedures, with approximately three out of four cardiac surgical patients requiring transfusion of at least one unit of homologous (ie, allogeneic) blood. Given the declining rate of blood donations and the increasing cost of blood and blood products, finding alternatives to or ways to reduce the need for homologous blood transfusions has become increasingly urgent.

The use of cardiopulmonary bypass (CPB) during coronary artery bypass graft (CABG) surgery has been associated with increased coagulation abnormalities; inflammatory responses; and consequently, a greater need for blood transfusion. Off-pump CABG surgery, on the other hand, is potentially associated with reduced intraoperative blood loss and is now a well-established alternative. Additionally, cell saver autologous blood transfusion (ie, autotransfusion) and predonated autologous blood are being used more frequently as alternatives to homologous transfusions. Cell saver autologous blood transfusion is the collection of a patient's own blood during the surgical procedure or from the surgical wound and subsequent reinfusion of this blood into the patient. The objectives of this prospective, randomized study were to investigate the potential additive effects of cell saver autologous blood transfusion and CPB on blood loss, homologous blood transfusion requirements, and clotting parameters in patients undergoing CABG for the first time. These effects were compared among patients undergoing CABG both with and without CPB and with and without cell saver blood transfusion. (1)

Eighty patients undergoing first-time CABG at a hospital in the United Kingdom were randomly assigned to one of four groups, with 20 patients in each group. The four groups included

* group A: procedures were on-CPB with cell saver blood transfusion,

* group B: procedures were on-CPB without cell saver blood transfusion,

* group C: procedures were off-CPB with cell saver blood transfusion, and

* group D: procedures were off-CPB without cell saver blood transfusion.

Patients were excluded if they

* had known inflammatory diseases or existing infections,

* needed emergent surgery,

* were using long-term corticosteroids and nonsteroidal anti-inflammatory medications,

* had used antiplatelet agents in the week before surgery,

* had known coagulopathy with warfarin or heparin, or

* had severe pre-existing renal dysfunction or lung dysfunction.

The anesthesia and surgical techniques were standardized for all patients. For patients in the on-CPB groups (ie, groups A and B), the procedures were performed through a median sternotomy, and heparin was used to achieve an activated clotting time of more than 480 seconds before aortic and venous cannulation. In addition, nonpulsatile extracorporeal circulation at moderate hypothermia of 32[degrees]C (89.6[degrees]F) was performed, and cold blood antegrade cardioplegia for myocardial protection was administered. Protamine sulphate was used at the end of the procedure to reverse heparinization and to achieve the preoperative activated clotting time. In the off-CPB groups (ie, groups C and D), anticoagulation was achieved using heparin to achieve an activated clotting time of more than 300 seconds, the mean arterial blood pressure was maintained between 50 mm Hg and 70 mm Hg, and protamine sulphate was used at the end of the procedure to reverse heparinization.

Patients in the cell saver groups (ie, groups A and C) underwent intraoperative cell salvage, with autotransfusion of washed, salvaged red blood cells occurring at the conclusion of the procedure. In the groups without cell saver transfusion (ie, groups B and D), all blood lost during the procedure was aspirated and discarded.

Preoperatively and on the first and fifth postoperative day, all patients had a full blood count, which included hemoglobin, hematocrit, and prothrombin time. Intraoperatively, routine cardiovascular and pulmonary monitoring was conducted. Postoperatively, the amount of chest tube drainage and the total amount of homologous blood transfusion during the first 24 hours were recorded. Homologous blood was only transfused if the hemoglobin concentration was less than 8 g/dL. Postoperative complications including atrial fibrillation, renal complications, pulmonary problems, and cerebrovascular accidents were documented. Additionally, data were collected on the length of intubation, the length of intensive care unit stay, and the total length of hospital stay. Common statistical procedures, including mean, standard deviation, and Student's t test, were used to analyze the data.

Findings. There were no significant differences in patient demographics, postoperative morbidity, or clotting test results between the groups. The total hospital stay, however, was significantly shorter in the off-CPB groups (ie, groups C and D) than the on-CPB groups (ie, groups A and B).