An In Vitro Investigation of the Coagulation Effects of Exogenous Oxytocin Using Thromboelastography in Healthy Parturients

BACKGROUND: We investigated the coagulation effects in vitro of exogenous oxytocin in whole blood of healthy term parturients. METHODS: Thromboelastography (TEG (R)) was performed on kaolin-activated citrated blood samples from 25 healthy, term, nonlaboring parturients. We compared the in vitro effects on the maternal thromboelastographic profile of 3 different exogenous oxytocin concentrations (22.5, 30.1, and 32.9 mu U/mL) and a control (0 mu U/mL). These exogenous oxytocin concentrations were chosen to approximate maternal plasma oxytocin concentrations during elective cesarean delivery, vaginal delivery, and nonelective cesarean delivery, respectively. RESULTS: Increasing the oxytocin concentration was significantly associated with hypercoagulable effects as observed with TEG (R) (decreasing reaction time, clot formation time, and Tmax; increasing alpha angle and maximum rate of thrombus generation). Compared with control samples, the median percentage change (interquartile range) in TEG (R) values for samples with the highest exogenous oxytocin concentration (32.9 mu U/mL) was largest for reaction time: -40.3% (-45.8%, -22.2%); and Tmax: -39.2% (-42.9%, -28.5%). CONCLUSION: The results of this in vitro investigation suggest that exogenous oxytocin is associated with modest hypercoagulable effects in the maternal blood of healthy term parturients. (Anesth Analg 2011;113:323-6)