General Papers 18

To assess the effects of surgery and ANH on coagulation. A total of 33 patients randomized to ANH (n = 17)/no ANH (n = 16), undergoing major gastrointestinal surgery, were prospectively studied. Coagulation tests included aPTTR, INR, platelets, fibrinogen and thromboelastography (TEG). There was no significant difference between groups at entry. In ‘no ANH’, as operation progressed, there was a decrease in platelet count (P < 0.001) and fibrinogen (P = 0.001), and increase in aPTTR (P = 0.002) and INR (P = 0.001). The TEG confirmed this; decrease in alpha angle (P = 0.006), MA (P = 0.003) and G (P = 0.001), increase in K (P = 0.008). Prior to knife to skin, ANH reduced platelet count (P = 0.003) and fibrinogen (P = 0.001), and increased aPTTR (0.003) and INR (P = 0.001). R time was shortened (P = 0.001) but MA (P = 0.001) and G (P < 0.001) decreased. Re-transfusion of autologous blood increased platelet count (P = 0.03) and fibrinogen (P = 0.004), decreased aPTTR (P = 0.017) and INR (P = 0.002), without affecting the TEG. Between the groups, at the time of knife to skin, the ANH group had a lower platelet count (P < 0.001), increased INR (P = 0.006), reduced MA (P = 0.010) and G (P = 0.011), but shortened R time (P = 0.004). At 1 h into operation, the platelet count remained lower (P = 0.002), the INR (P = 0.005) and aPTTR (P = 0.008) significantly prolonged. Immediately prior to re-transfusion the only difference was a prolonged INR (P = 0.023). By the end of the operation there was no difference between groups. In addition there was no difference in estimated blood loss. Coagulation is significantly impaired as operation progresses. Acute normovolaemic haemodilution impairs coagulation; this remains significantly impaired throughout operation.