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Safety and Efficacy of Perioperative Cell Salvage and Autotransfusion After Coronary Artery Bypass Grafting: A Randomized TrialMurphy, MD, Allen SM, et al. Ann Thorac Surg 2004; 77 :1553-9Reviewer: Feroze Mahmood, MD
Background: Reinfusion of shed, unprocessed salvaged mediastinal blood in cardiac surgery has been associated with fibrinolysis, coagulopathy, excessive bleeding and a paradoxical increase in the utilization of homologous blood. However, recent trials of autotransfusion of washed red blood cells have shown a significant reduction in homologous blood use. This study was undertaken to establish the safety and efficacy of the mechanical means of perioperative blood conservation during cardiac surgery. Patients and Methods: Between March 2002 and January 2003, 200 patients aged 18 years or over undergoing primary coronary artery bypass (CAB) grafting utilizing cardiopulmonary bypass (CPB) were enrolled in this study. Jehovah's witnesses; patients on heparin and other systemic anticoagulants, patients with congenital or acquired platelet, red cell or clotting disorders and patients with ongoing sepsis were excluded from the study. Patients were randomized into autotransfusion (AT) group and a control group. In the autotransfusion group, all blood loss from skin incision to the commencement of CPB and then after protamine administration until skin closure was salvaged and washed with heparinized .9% saline and then retransfused as a first line of therapy. All blood remaining in the CPB circuit was transfused back to the patient via the aortic cannula prior to decannulation and was not transferred to the autotransfuser. After the surgery, blood was collected and salvaged to the same collection chamber via mediastinal tubes in the intensive care unit (ICU). After twelve hours all autotransfuser disposables were discarded per the hospital policy. In the control group (CG), banked homologous leucodepleted packed red cells were used as blood replacement therapy. All blood collected during the surgery and afterwards in the ICU was discarded. The threshold for transfusion of homologous blood in the CG was hemoglobin (Hb) less than 7, packed cell volume (PCV) less than .2 and hemodynamic instability and discretion of the ICU staff. The indications for transfusion of homologous blood in the AT group were the same after autotransfusion. Platelet count, prothrombin time (expressed as international normalized ratio- PT ratio), activated partial thromboplastin time (APTT, expressed as APTT ratio to normalized control), fibrinogen concentration, D-dimer concentration and thromboelastography (TEG) measurements were drawn on start and at the end of surgery and immediately before and 20 minutes after the infusion of first autologous or homologous transfusion postoperatively. Results: There were 97 patients in CG and 99 in the AT group. Three patients in the CG were excluded from the study as the grafts were done off pump. A total of 13 patients in the AT group were excluded from the study, one had the grafts done off pump, two were withdrawn because of deviation from protocol, two had post-CPB coagulopathy, and remaining eight had excessive post operative bleeding and hemodynamic instability. Both groups were matched for age, gender, and co-morbidities and clinicopathological conditions. The operative details of both groups were also similar. Patients in the AT group received a mean of 383 +/- 129 ml of autotransfused red cells postoperatively. Patients in the AT group were significantly less likely to receive homologous blood transfusion (odds ratio 0.40, 95% confidence interval), Figure 1.
There was no significant difference in adverse events, specifically septic or bleeding complications between the two groups and also in the utilization of platelets or clotting factors. It was also shown that the transfusion of any kind of blood products was associated with reduction in PT ratio and an increase in the APTT ratio and fibrinogen concentration. There was also no change in the TEG parameters in either of the two groups. Discussion and Comments: This study concluded that the intraoperative and postoperative cell salvage and autotransfusion is a safe procedure and is associated with reduction in exposure to allogenic blood products in elective coronary artery bypass graft surgery. There was also no derangement of the clotting pathway or platelet function as well. AT group showed more attrition, and patients were converted to CG due to excessive bleeding or hemodynamic instability and there was also more significant derangement of APTT ratio than the CG, but it was not associated with any clinical sequelae. Patients withdrawn from the AT group because of excessive bleeding and coagulopathy could have made a difference in terms of clotting pathway between the two groups if they had been included. Both groups had very few patients on antifibirinolytics, CG-9 and AT-6. Having more patients on antifibirinolytics, could have further reduced the exposure to the allogenic blood products, and also reduced the yield in the AT group. The quality of the autotransfused red cells is at least as good as the banked cells.1 However, the extent to which the salvaged blood is contaminated with activated leukocytes, platelets, or other plasma elements, such as fat particles is unclear.2 Platelets in the salvaged blood have been implicated in the development of DIC and ARDS.3 But in a review of 36,000 cases of cell salvage, Tawes and Duvall4 concluded that the development of DIC and ARDS was a result of complex interaction of shock, hypothermia and multiple organ failure and not as a result of autotransfusion of salvaged red cells. Cell washing effectively removes almost 93% of the water-soluble cytokines and complement,2 but these factors may assume significance when a large amount of blood is autotransfused. The use of leukocyte depletion filters is associated with an effective removal of leukocytes and fat particles,2, 5 but the removal of tumor cells via these filters is not as complete6 and hence autotransfusion is contraindicated in oncologic surgery.2 Cell salvage remains to be a valuable adjunct in the clinical management of patients requiring intraoperative blood transfusions, and despite many concerns has been shown to reduce the exposure of patients to allogenic blood products. References
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