Coagulation and platelet laboratory testing in cardiac surgery

Blood transfusion is a lifesaving treatment for excessive bleeding that is used commonly in patients having major surgery. However, blood transfusion is also expensive and has harmful effects on the immune system and circulation of recipients. As a consequence, the need to improve how blood is used was recognised as an NHS strategic priority in 2007. Heart surgery often causes excessive bleeding and accounts for over 6% of all blood transfused in the UK. One important reason for this statistic is that heart surgery patients often have abnormal blood clotting. This can be because of tablet medication for heart disease taken before surgery or as an effect of the techniques used to perform heart surgery.

We investigated whether it is useful to perform blood tests either just before, or just at the end of heart surgery to identify exactly how the blood clotting system is abnormal in each patient. The results of these tests could potentially lead to recommendations to give specific treatments to patients to improve blood clotting and reduce bleeding and blood transfusion. We performed this research over 24 months by taking two blood tests from 2400 consecutive patients having heart surgery at the University Hospitals Bristol. The blood was analysed using specialist blood clotting tests so that we could identify exactly what abnormalities were present. We tested the blood using blood clotting analysers that are designed to be used in the operating theatre to find out how often these analysers correctly identify a clotting abnormalities and what additional test information is required to give the correct diagnosis when they do not. We also investigated how our laboratory test results relate to the amount of bleeding and other complications in our patients. This information showed the benefits of performing different kinds of tests so that we could recommend the best tests to perform in future.