The effect of low dose (50 KIU/ml) and high dose (200 KIU/ml) aprotini
n on standard thrombelastographic variables (r; K, alpha, MA) was exam
ined in vitro using blood from forty ASA Class I patients. Both concen
trations of aprotinin resulted in minor increases in r time above the
normal range (P < 0.05). Aprotinin did not alter other thrombelastogra
phic variables, The results indicate that aprotinin is a mild direct a
nticoagulant in vitro as assessed by thrombelastography.