Acute normovolemic hemodilution (ANH) in surgery of the thoraco-abdominal aorta - A cohort study to evaluate coagulation parameters and blood products utilization

Objective. To assess whether a modified technique of acute normovolemic hem odilution (ANH) reduces the utilization of blood products and donor exposur es, and/or improves hemostasis in surgery of the thoracoabdominal aorta. Methods. Experimental design: cohort study comparing fifteen control patien ts and seven treated with the adjunct of ANH. Mean follow-up 23 (SD=15.4) m onths. Setting: community hospital acting as a referral centre for vascular diseas es. Patients' selection: Thirty patients between 1990 and 1995 were entered into the study, eight were excluded because of rupture. Interventions: the ANH technique used the withdrawal of up to 3000 mi blood during the time b etween induction of anesthesia and clamping of the thoracic aorta. Colloids were preferentially used for replacement together with up to three units o f packed red blood cells (PRC). The autologous blood was retransfused durin g the final phases of the procedure. Measures: Parameters measured included pre- and postoperative PIT, INR, and platelets; the quantity of stored blo od products and total donor exposures. Results. Blood. losses, PRC transfused, and postoperative hemoglobin concen tration were not statistically different in the two groups. Repeated measur es Analysis of variance on coagulation parameters showed lower PTT values ( F-1,F-20=4.2, p=0.05) and higher platelet concentration (F-1,F-20=8.2, p=0. 01) after surgery in the ANH group. In the latter, the reduction in fresh f rozen plasma (FFP) utilization did not reach statistical significance (T-19 .5=1.79, p=0.08) This group, however, required fewer transfusions of platel ets (T-20=4.27, p=0.0004), and cryoprecipitate (T-20=2.52, p=0.02), and no coagulation adjuncts (dDAVP, epsilon-aminocaproic acid), (Fisher's test=0.0 4). Total donor exposures was also significantly lower in the ANH group (T- 20=3.28, p=0.003). Conclusions. The ANH technique reduces homologous transfusions and donor ex posures, and has a beneficial effect on hemostasis. Moreover, the technique may be useful in the management of cross clamping hypertension.