Reply to von Heymann et al.

Heparin, ACT, Cardiopulmonary bypass, Blood loss, Activation, Coagulation

I would like to thank Dr von Heymann [1] and colleagues for this interesting interaction.

Let me start by confirming to Dr von Heymann the following

1. Pre operative coagulation assessment were done and patients on anticoagulation or abnormal results were excluded from the study.

2. We did take into consideration Gibbs [2] paper. This is one of the reasons why we continue with aspirin till the day of the operation in all patients. Gibbs paper confirms the universal inhibition of platelet function by aspirin. And since Aspirin inhibition to platelet function is irreversible, the individual variability in platelet function reflects the rate of regaining function by producing new platelets.

3. The other aim of inhibiting platelet is to cancel out their contribution to the activation of neutrophils and hence a beneficial effect on the inflammatory response.

4. There is no strong evidence [3] today to suggest that a decrease in anti thrombin III levels will translate into a decrease in soluble Fibrin level which is the end point of the clotting cascade and have the real effect in haemostasis.

5. The results from Despotis [4] paper can not be compared with ours, his population is smaller and different (re-operations vs. primary CABG).

All in all this is a large study which we set out to exclude most of the confounding variables rather than trying to give plausible explanations. Activated Clotting Time measurement is still in use by the majority despite its critics. The clotting cascade remains a complex multi-factorial system that we have yet to elucidate comprehensively. ACT is a simple test and a good indicator of the haemostatic system. What we tried to say was simple, can we use less heparin to achieve the same target ACT. We proved that we can. Whether our observation; of less post operative blood loss; is only due to less heparin. That has to be teased out further.