Reducing allogeneic transfusion in cardiac surgery

E-mail: tempedeepak{at}hotmail.com

Editor—I welcome the study by Diprose and colleagues1 comparing aprotinin and tranexamic acid in patients undergoing first time cardiac surgery. The authors have nicely demonstrated that aprotinin used in addition to intraoperative cell salvage is the most efficacious pharmacological therapy for reducing patient exposure to allogeneic transfusion. One of the most important factors in making blood conservation a reality during cardiac surgery, is the acceptance of normovolaemic haemodilution. However, the transfusion trigger during cardiac surgery continues to remain controversial.2 We have earlier shown that cell saver in combination with intraoperative autologous blood donation decreased transfusion requirements in a group of patients with a mean body weight of 45 kg.3 Seventy-eight per cent of these patients undergoing valve surgery did not require any blood transfusion. This was possibly attributable to acceptance of a haematocrit of 15% on bypass and 25% after bypass. We have also compared cell saver and low dose aprotinin in patients undergoing valve surgery and found them to be comparable in terms of reducing blood transfusion requirement.4 Aprotinin helps by decreasing the postoperative bleeding, whereas the cell saver helps by making the patient's own blood available for transfusion.

While these blood conservation strategies can substantially decrease the transfusion of allogeneic red blood cells and coagulation products, the clinical application of these reports should be carefully chosen. The important concerns related to the use of aprotinin include graft occlusion in patients undergoing coronary artery bypass grafting (CABG), anaphylactic reaction, and risk of impaired renal function. The risk of graft thrombosis is real and well documented.5 6 As regards cell saver, there is some concern about transfusion of cytokines through autologous shed blood.7 In addition, these are expensive techniques and the use of cell saver also requires services of a trained technician. It seems that preoperative risk stratification is essential to allow for more rational resource allocation of costly blood conservation strategies and blood bank resources. One such model has been recently developed.8 According to this model, independent predictors of blood product usage in CABG patients were preoperative haemoglobin 12.0 g or less, emergent operation, renal failure, female sex, age 70 yr or older, left ventricular ejection fraction 0.40 or less, redo procedure and low body surface area. Since with careful surgery homologous blood transfusion can be avoided in most patients undergoing primary CABG, we prefer to use aprotinin only in patients who have increased risk of bleeding such as those on aspirin or thrombolytic therapy, redo surgery or those having rare blood type. A combined approach, as described by Diprose and colleagues can also be considered in these patients.

D. K. Tempe

New Delhi, India

References

1 Diprose P, Herbertson MJ, O'Shaughnessy D, Deakin CD, Gill RS. Reducing allogeneic transfusion in cardiac surgery: a randomized double-blind placebo-controlled trial of antifibrinolytic therapies used in addition to intra-operative cell salvage. Br J Anaesth 2005; 94: 271–8[Abstract/Free Full Text]

2 Hebert PC, Fergusson D. Do transfusions get to the heart of the matter? JAMA 2004; 292: 1610–12[Free Full Text]

3 Tempe D, Bajwa R, Cooper A, et al. Blood conservation in small adults undergoing valve surgery. J Cardiothorac Vasc Anesth 1996; 10: 502–6[ISI][Medline]

4 Tempe DK, Banerjee A, Virmani S, et al. Comparison of the effects of a cell saver and low-dose aprotinin on blood loss and homologous blood usage in patients undergoing valve surgery. J Cardiothorac Vasc Anesth 2001; 15: 326–30[CrossRef][ISI][Medline]

5 Alvarez JM, Chandraratna H, Newman MA, et al. Intraoperative coronary thrombosis in association with low dose aprotinin therapy. J Cardiothorac Vasc Anesth 1999; 13: 623–8[CrossRef][ISI][Medline]

6 Alderman EL, Levy JH, Rich JB, et al. Analyses of coronary graft patency after aprotinin use: results from the International Multicenter Aprotinin Graft Patency Experience (IMAGE) trial. J Thorac Cardiovasc Surg 1998; 116: 716–30[Abstract/Free Full Text]

7 Arnestad JP, Bengtsson A, Bengtson JP, Tylman M, Redl H, Schlag G. Formation of cytokines by retransfusion of shed whole blood. Br J Anaesth 1994; 72: 422–5[Abstract]

8 Arora RC, Legare JF, Buth KJ, Sullivan JA, Hirsch GM. Identifying patients at risk of intraoperative and postoperative transfusion in isolated CABG: toward selective conservation strategies. Ann Thorac Surg 2004; 78: 1537–54