Drugs given during surgery to reduce blood loss and so lessen the need for transfusion may be largely ineffective and actually do harm.
The two drugs generally seen as most appropriate are the lysine analogues tranexamic acid and eaminocaproic acid, and the serine protease inhibitors (SERPINS) aprotinin, nefamostat and gabexate.
However, although these drugs may reduce bleeding during operations, they don't reduce the need for donated blood with all the dangers that entails (see WDDTY, vol 3, no 2). "With the exception of aprotinin, none of the agents has been shown to influence the requirements for blood or blood product transfusion consistently or substantially, particularly in the high risk categories of surgical, and especially cardiac surgical patients," writes David Royston in The Lancet. SERPINS also inhibit the activation of white cells and platelets which are needed for blood clotting, which has major drawbacks during cardiac surgery, especially when the drug heparin is given.
Blood clots on the brain are a reported side effect when tranexamic acid is given over several days, but not when its use is restricted to the heart operation itself. "We need more information about which agent and dose is appropriate for all these compounds, and we also need to know more about their efficacy in reducing the need for donor blood and their safety profile in high risk procedures," Royston concludes. The Lancet, 26 June 1993.
Meanwhile, the safety of the Canadian blood supply system is to be the subject of a public inquiry following a call by a parliamentary committee. Announcing the inquiry, health minister Benoit Bouchard admitted that confidence in the system has been "profoundly shaken" following transfusion associated HIV infection in 1000 patients. Earlier, the government had insisted that an inquiry into HIV infection would be unnecessary.