THE EFFECT OF MAGNESIUM-SULFATE ON BLEEDING-TIME IN PREGNANCY

OBJECTIVE: The bleeding time is one of the most commonly used diagnost ic tests to evaluate platelet-related hemorrhagic disorders. Magnesium has been shown in vitro to be a platelet antiaggregant. This study wa s conducted to evaluate the hypothesis that magnesium sulfate has no e ffect on the template bleeding time. STUDY DESIGN: The study group con sisted of 24 women who required magnesium sulfate in pregnancy. A bloo d cell count, platelet count, magnesium level, bleeding time, and mean arterial pressure were obtained before and 2 hours after magnesium su lfate infusion. Magnesium sulfate was infused beginning with a 6 gm in travenous bolus followed by 2 gm/hr. A template bleeding time was perf ormed with a Simplate-II (Organon Teknika, Durham, N.C.) device. Two o f the authors performed all the bleeding times. Data were analyzed wit h a paired t test and Wilcoxon rank test. RESULTS: Fifteen (63%) patie nts received magnesium sulfate for tocolysis or before external cephal ic version and nine (37%) for preeclampsia prophylaxis, No differences were found between the normotensive and hypertensive groups regarding maternal age, gestational age, initial bleeding time, or platelet cou nt. Analysis of the entire study group revealed a prolongation of the bleeding time after magnesium sulfate (5.7 +/- 1.8 vs 6.6 +/- 1.9 minu tes, p < 0.05); a lowering of the mean arterial pressure (p < 0.05), a nd a rise in the magnesium level (p < 0.05). Four patients (16.7%) had a postmagnesium bleeding time > 9 minutes. CONCLUSION: Magnesium sulf ate appears to prolong tile bleeding time in pregnancy. The clinical s ignificance remains to be determined.