General Papers 18

Aims: To assess the effects of surgery and ANH on coagulation. Methods: 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). Results: 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. Conclusions: Coagulation is significantly impaired as operation progresses. Acute normovolaemic haemodilution impairs coagulation; this remains significantly impaired throughout operation.