SPECIAL FEATURE

Managing Hypertension in the Pregnant Patient

By James E. McFeely, MD

Medical Director, Critical Care Units, Alta Bates Summit Medical Center, Berkeley, CA

Dr. McFeely reports no financial relationships relevant to this field of study.

The American College of Obstetrics and Gynecology recently published updated evidence-based recommendations for the management of hypertension and its complications during pregnancy.¹ Despite substantial advances in the diagnosis and management of preeclampsia since the previous report 10 years ago, hypertensive disorders during pregnancy remain a major health issue for women and their infants.

Hypertension during pregnancy falls into one of four categories: gestational hypertension (hypertension after 20 weeks gestation without proteinuria), chronic hypertension (pre-existing the pregnancy), chronic hypertension with superimposed preeclampsia, and preeclampsia-eclampsia. Hypertension during pregnancy is defined as systolic pressure > 140 mmHg or diastolic pressure > than 90 mmHg. Preeclampsia is defined as hypertension plus new-onset proteinuria; it can also occur without proteinuria if any of the severe multisystem complications are present (see Table 1).² Preeclampsia without severe features can evolve rapidly and cause severe morbidity and mortality and should not be underestimated. Elevations in BP of 15 mmHg diastolic and 30 mmHg systolic are common in uncomplicated pregnancy and do not define preeclampsia but warrant close observation. Rapid weight gain and/or development of edema are not diagnostic criteria or sensitive or specific signs of preeclampsia. Eclampsia is the presence of new-onset grand mal seizures in a woman with preeclampsia. HELLP syndrome is the development of hemolysis, elevated liver function tests, and low platelets. These illnesses may occur before, during, or after labor.

Some clinical circumstances increase the risk of preeclampsia. These include previous preeclampsia, a family history of preeclampsia, age > 40 years, diabetes, obesity, and preexisting hypertension. Most cases, however, occur in healthy nulliparous women.³ Currently, there is no single laboratory test that predicts development of preeclampsia. Although strategies to prevent preeclampsia have been studied, no intervention has been found to be unequivocally effective. Low-dose aspirin started late in the first trimester for high-risk women provides some benefit. However, salt restriction, bed rest, and restriction in physical activity are not beneficial.⁴

Chronic hypertension is managed differently during pregnancy than at other times. Angiotensin-converting enzyme inhibitors and angiotensin reuptake blockers should be avoided during pregnancy due to harmful effects on the fetus seen in all three trimesters of pregnancy. Treatment should be initiated for blood pressures > 160 mmHg systolic or > 105 mmHg diastolic. Goals of therapy are systolic blood pressure between 160-120 mmHg and diastolic blood pressure 105-80 mmHg. Treatment to lower pressures than these does not improve outcomes and may lead to adverse fetal outcomes. Weight loss, low-sodium diets, and reduced amounts of exercise are not recommended treatment. Recommended drugs include labetolol, hydralazine, and nifedipine (see Table 2).⁵ Diuretics are considered second-line therapy.

Management of preeclampsia and HELLP syndrome varies depending on the stability of the mother and the gestational age of the fetus. In women with mild gestational hypertension, the progression to severe hypertension or preeclampsia often develops within 1-3 weeks after diagnosis, whereas in women with preeclampsia without any severe features, the progression to severe disease may occur within days. The clinical course of severe preeclampsia is often characterized by progressive deterioration of maternal and fetal conditions if delivery is not pursued. Hospitalization, stabilization, and delivery of the fetus are appropriate after 37 weeks, or after 34 weeks with any of the following: rupture of membranes, progressive labor, oligohydramnios, fetal weight less than 5th percentile or abnormal biophysical fetal profile, or laboratory values consistent with HELLP syndrome.

Severe preeclampsia at < 34 weeks should be managed only at facilities with high-risk obstetric services and neonatal critical care units. Close maternal and fetal monitoring are needed, including frequent laboratory assessments (complete blood count, liver function tests, creatinine) and biophysical profiles. For women with stable severe preeclampsia at less than 34 weeks gestation, corticosteroids should be administered for fetal lung maturity.⁶ Progressive proteinuria alone should not affect the decision to continue expectant management. Indications for delivery during expectant management are listed in Table 3. Severe preeclampsia before fetal viability should result in a prompt delivery after maternal stabilization.

For women with blood pressures below 160/110 mmHg and no maternal symptoms, magnesium sulfate is not recommended to prevent eclampsia. Development of maternal symptoms (such as occipital or frontal headache, blurred vision, photophobia, epigastric or right upper quadrant abdominal pain, or altered mental status) or development of severe preeclampsia should prompt use of intravenous magnesium, with initial loading doses of 4-6 g followed by maintenance doses of 1-2 g per hour. If an eclamptic seizure occurs, magnesium will need to be continued for at least 24 hours after the last seizure. Magnesium has been shown to be superior to phenytoin and diazepam for eclampsia. Labetolol, nifedipine, and hydralazine may be used intravenously for urgent blood pressure control (see Table 2).5 Eclampsia is an indication for delivery following maternal stabilization. Routine use of hemodynamic monitoring is not recommended.

Magnesium should be continued while in the operating room and in the recovery room. Induction of anesthesia for a cesarean section and the stress of delivery may reduce the seizure threshold. In addition, because magnesium has a 5-hour half-life, stopping magnesium for surgery does not abate potential interaction with anesthetic agents (it prolongs the duration of nondepolarizing muscle relaxants), but puts the patient at risk for subtherapeutic magnesium levels in the recovery room or postpartum.

Blood pressure usually decreases within 48 hours after delivery, but may increase again 3-6 days postpartum.⁷ Preeclampsia and eclampsia may occur up to 4 weeks postpartum. Use of nonsteroidal anti-inflammatory agents may contribute to this. Women with hypertension during pregnancy should have close blood pressure monitoring for 72 hours after delivery and again 7-10 days postpartum or sooner if symptoms develop. Women who develop postpartum symptoms (headache, blurred vision) or findings consistent with severe preeclampsia should be hospitalized and treated with magnesium and antihypertensives as needed.

Prompt recognition and treatment of hypertension and its complications in pregnancy can avoid major maternal and fetal morbidity and mortality. Treating these cases can be one of the most rewarding things an intensivist can do.

REFERENCES

1. American College of Obstetricians and Gynecologists; Task Force on Hypertension in Pregnancy. Hypertension in pregnancy. Report of the American College of Obstetricians and Gynecologists’ Task Force on Hypertension in Pregnancy. Obstet Gynecol 2013;122: 1122-1131.

2. Homer CS, et al. Non-proteinuric pre-eclampsia: A novel risk indicator in women with gestational hypertension. J Hypertens 2008;26:295-302.

3. Poon LC, et al. Maternal risk factors for hypertensive disorders in pregnancy: A multivariate approach. J Hum Hypertens 2010;24: 104-110.

4. Meher S, et al. Bed rest with or without hospitalisation for hypertension during pregnancy. Cochrane Database Syst Rev 2005;(4):CD003514.

5. Duley L, et al. Drugs for treatment of very high blood pressure during pregnancy. Cochrane Database Syst Rev 2013;7:CD001449.

6. Woudstra DM, et al. Corticosteroids for HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome in pregnancy. Cochrane Database Syst Rev 2010;(9):CD008148.

7. Sibai BM. Etiology and management of postpartum hypertension-preeclampsia. Am J Obstet Gynecol 2012;206:
470-475.