The effect of temperature and hemodilution on activated clotting time during coronary artery bypass grafting

Activated clotting time (ACT) is an important test to measure the anticoagulation in cardiac surgeries. In this study different factors were examined which affect ACT during Coronary Artery Bypass Grafting (CABG). Blood Samples from 21 patients were taken and examined by using ACTALYKE MINI II. Once CPB initiated, the effect of hemodilution was measured on pre-CPB ACT value (P<0.05). Hemodilution occurred at the start of CPB caused a prolongation of ACT. After aorta was cross clamped, patient was cooled moderately to 32±2°C. The ACT value increased in the result (P<0.05) which proved significant. This change was due to low metabolic rate and decreased function of enzymes. Before termination patient was rewarmed to normothermia 36±1°C. This increase in temperature caused a decrease in ACT value (P<0.05). This change occurred due to an increase in metabolic rate and functioning of clotting enzymes, also there was a decrease in the blood volume due to urination. These findings can be used for better management of anticoagulation during CPB. So, ACT value has a direct relationship with hemodilution and inverse relationship with temperature.