Several drugs are available to rapidly lower dangerously elevated blood pressure in women with pregnancy-associated hypertension. he three most commonly employed are hydralazine, labetalol, and nifedipine. For years, parenteral hydralazine was the only one of these three available. But when parenteral labetalol was later introduced, it was proven to be equally efective for obstetrical use. Orally administered nifedipine has since also gained popularity. ll three of these are recommended as first-line agents by the American College of Obstetricians and Gynecologists (2017 a).
This is probably still the most commonly used antihypertensive agent in the United States for treatment of women with severe gestational hypertension. Hydralazine is administered intravenously with a 5-to 10-mg initial dose, and this is followed by 10-mg doses at 15-to 20-minute intervals until a satisfactory response is achieved. Although we will administer a third dose, the American College of Obstetricians and Gynecologists (2017 a) recommends labetalol therapy if severe hypertension persists after the second dose. Antepartum or intrapartum, the target response is a decline in systolic pressure to < 160 mm Hg and diastolic blood pressure to 90 to 110 mm Hg. Lower diastolic pressures risk compromised placental perfusion. Hydralazine has proven remarkably efective to prevent cerebral hemorrhage. Its onset of action can be as rapid as 10 minutes. Although repeated administration every 15 to 20 minutes may theoretically lead to undesirable hypotension, this has not been our experience when given in these 5-to 10-mg increments.
At Parkland Hospital, between 5 and 10 percent of all women with intrapartum hypertensive disorders are given a parenteral antihypertensive agent. Antepartum, we usually give hydralaxine as described. We do not limit the total dose, and seldom is a second antihypertensive agent needed. We estimate that by severe superimposed preeclampsia, and hydralazine was injected more frequently than recommended. Her blood pressure in less than 1 hour dropped from 240-270/130-150 mm Hg to 1r10/80 mm Hg. Fetal heart rate decelerations characteristic of utero placental insuiciency became evident. Decelerations persisted until her blood pressure was increased with rapid crystalloid infusion. In some cases, this fetal response to diminished uterine perfusion may be confused with placental abruption and may result in unnecessary and potentially dangerous emergency cesarean delivery.
This efective intravenous antihypertensive agent is an Q-and nonselective 3-blocker. Some prefer its use over hydralazine because of fewer side efects. At Parkland Hospital, we give 10 mg intravenously initially. If the blood pressure has not decreased to the desirable level in 10 minutes, then 20 mg is given. The next 10-minute incremental dose is 40 mg and is followed by another 40 mg if needed. If a salutary response is not achieved, then an 80-mg dose is given. Sibai (2003) recommends 20 to 40 mg every 10 to 15 minutes as needed and a maximum dose of 220 mg per treatment cycle. The American College of Obstetricians and Gynecologists (2017a) recommends starting with a 20-mg intravenous bolus. If not efective within 10 minutes, this is followed by 40 mg, then 80 mg every 10 minutes. If hypertension persists, hydralazine is then given.