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OBSTETRIC ANESTHESIA

Hemostatic Function in Healthy Pregnant and Preeclamptic Women: An Assessment Using the Platelet Function Analyzer (PFA-100®) and Thromboelastograph®

From the Department of Anesthetics, Royal Free Hospital, London, United Kingdom.

Address correspondence and reprint requests to Dr. Roshan Fernando, Department of Anesthesia, Royal Free Hospital, Pond St., London NW3 2QG, UK. Address e-mail to r.fernando{at}btinternet.com.

BACKGROUND: The PFA-100® is a point-of-care platelet function analyzer which measures the speed of formation of a platelet plug in vitro, expressed as closure time (CT) in seconds. This device could potentially be used to assess primary hemostasis prior to regional anesthesia. In this prospective, observational study we sought to establish 95% reference intervals for PFA-100 and Thromboelastograph® (TEG®) values for our normal pregnant population, before comparing the PFA and TEG in measuring platelet function in preeclamptic and healthy pregnant women at term, using confidence interval analysis and analysis of variance.

METHODS: Routine hematologic and coagulation tests were performed along with von Willebrand Factor, CT, and TEG measurements. Results are expressed as mean (sd).

RESULTS: Increased severity of preeclampsia was associated with increasing prolongation of CT, even in the presence of normal platelet counts. In severe preeclampsia, the PFA-100 CT (mean (sd): 155 (65) s) exceeded the 95% reference interval of the control group (70–139 s). In contrast, TEG maximum amplitude (MA) in severe preeclampsia (mean (sd): 71 (8) mm) remained within the 95% reference interval for MA in normal pregnancy (64–82 mm).

CONCLUSION: We conclude that impairment of primary hemostatic function with increasing severity of preeclampsia was recorded by the PFA-100 but not the TEG.

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