Labetalol is not teratogenic and may preserve uteroplacental blood flow better than other antihypertensive drugs.

Nifedipine, methyldopa, and hydrochlorothiazide have been used safely in pregnancy, but have been studied less than hydralazine and labetalol and should be considered second- or third-line treatments.⁶

Diazoxide (potassium channel blocker) was shown to be beneficial and safe in treating hypertension when used in small doses (15 mg) with hydralazine.⁷ Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are contraindicated in pregnancy because of adverse fetal outcomes.⁵ Nitroprusside is known to cause fetal cyanide poisoning if used for more than 4 hours and should be avoided during pregnancy.

Betamethasone for fetal lung maturity should be administered to women of less than 34 weeks gestation in case of emergent preterm delivery. The decision to use steroids should be made in consultation with the high-risk obstetrician.

Once stabilized, patients should be continued on oral antihypertensive therapy until delivery. There is no well-established target blood pressure for the pregnant patient.

Although severe preeclamptic patients are in total body fluid overload, they are often intravascularly depleted and very sensitive to changes in volume status. Uterine contractions are also increased because of dehydration; therefore, improving volume status is essential in management.

Intravenous hydration, however, must be carefully administered, because studies have shown that excessive fluid use leads to an increase in extravascular fluid stores and greatly increases the risk of pulmonary edema.

Summary

Pregnancy-induced hypertension, preeclampsia, and eclampsia are on a continuum of a disease process that emergency physicians must be able to handle adeptly in the emergency department. Preventing progression of preeclampsia to seizures or other end-organ damage is accomplished through a variety of methods, both nonpharmacologic (bed rest, hydration) and pharmacologic (magnesium, labetalol, hydralazine, etc.).

Although controversy persists, magnesium remains the mainstay of therapy because of its familiarity, wide safety margin, and physiologic advantages to the fetus.

References

1. Pearlman M, Tintinalli JE, Dye P, et al: Preeclampsia and Hypertensive Disorders in Pregnancy, in Obstetric and Gynecologic Emergencies: Diagnosis and Management. McGraw-Hill Professional, 2003. pp. 96-103.
2. Coetzee EJ, Dommisse J, Anthony J. A randomized controlled trial of intravenous magnesium sulphate versus placebo in the management of women with severe preeclampsia. Br J Obstet Gynaecol 1998;105:300.
3. Lucas MJ, Leveno KJ, Cunningham FG. A comparison of magnesium sulfate with Phenytoin for the prevention of eclampsia. N England J Med 1995;333:201.
4. Martin JN Jr, Thigpen BD, Moore RC, et al. Stroke and severe preeclampsia and eclampsia: a paradigm shift focusing on systolic blood pressure. Obstet Gynecol 2005;105:246.
5. Podymow T, August P. Hypertension in pregnancy. Adv Chronic Kidney Disease. 2007 Apr; 14(2):178-90.
6. McCoy S, Baldwin K. Pharmacotherapeutic options for the treatment of preeclampsia. Am J Health Syst Pharm. 2009 Feb 15; 66(4):337-44.
7. Hennessy A, Thornton CE, Makris A, et al. A randomized comparison of hydralazine and mini-bolus diazoxide for hypertensive emergencies in pregnancy: The PIVOT trial. Aust N Z J Obstet Gynaecol 2007;47:279.