JOIN USGiven the shortage for blood for bypass surgeries, bloodless techniques are the way to go, writes Dr Adarsh S Koppula
Blood wastage during a bypass operation is around 25 to 50 percent of estimated blood volume (EBV) and with aggressive use of multiple blood thinners, most patients require homologous blood transfusion.
In India, there are more than 1800 blood banks and the annual requirement for blood for CABG is around 50,000-90,000 litres. Understandably, there is a tremendous shortage.
Homologous blood transfusion, associated with minimal risk, is considered essentially safe. However, in spite of strict screening tests, there exist real risks of transmission of bacterial, viral and other infections and 40 such documented vectors of infections.
Patients who have had bypass operations and have received four or more blood transfusions have a higher rate of surgical infection, mortality and complication rate as compared with those who did not get a blood transfusion.
Excessive blood loss in a bypass operation is because of several reasons, all of which produce an increased bleeding tendency and alter the coagulation mechanism.
This is mainly due to the contact of blood with artificial surfaces of the cardiopulmonary bypass circuit (artificial heart-lung machine). Present-day beating heart surgery abolishes this factor.
Stress of major surgery results in systemic inflammatory response syndrome, which alters the coagulation and fibrinolytic cascades. Also, hypothermia results in clotting problems, leading to excessive blood loss.
A multimodality approach is used to conserve as much of the red blood cells as possible. Minimal blood investigations are made and cell savers are used, where wasted blood is collected and washed clean and this salvaged red blood cells can then be re-infused following surgery.
Another method is predonation of autologous blood either prior to surgery or intraoperatively. Here, the patient’s own blood in withdrawn in sufficient quantities and the volume is replaced with saline.
This serves the dual purpose of conserving red cells and reduces the red cell loss due to dilution. This stored patient blood is given back to patient at the end of operation.
Blood conservation in perfusion technology includes use of biocompatible circuit material like heparin bonded circuits, maintenance of normal temperatures of body and heart and minimising hemodilution (decreased concentration of cells and solids in the blood resulting from gain of fluid) by using newer low priming oxygenators and circuits, retrograde priming of the cardiopulmonary bypass (CPB) circuit and reinfusing the entire blood prime following the cessation of CPB.
Pharmacological methods include the use of drugs, which help reverse the effect of aspirin on platelet function. Agents such as tranexemic acid, desmopressin, epsilon and amino carpoic acid are known to reduce blood loss in special circumstances. Patients with anaemia preoperative pose another problem, which can be overcome with pretreatment with recombinant human erythropoetin from three weeks prior to surgery.
(The author is associate director, CTVS, Max Super Speciality Hospital, Delhi)