Comparative studies of hydralazine versus labetalol show equivalent results (Umans, 2015). In one trial, labetalol lowered blood pressure more rapidly, and associated tachycardia was minimal. But, hydralazine lowered mean arterial pressures to safe levels more efectively (Mabie, 1987). In another trial, maternal and neonatal outcomes were similar (Vigil-De Gracia, 2007). Hydralazine causes significantly more maternal tachycardia and palpitations, whereas labetalol more frequently leads to maternal hypotension and bradycardia. Both drugs have been associated with a reduced frequency of fetal heart rate accelerations (Cahill, 2013). Labetalol is not given to asthmatic women.
FIGURE 40-20 Hydralazine was given at 5-minute intervals instead of 15-minute intervals. The there is a tendency to give a larger initial dose of hydralazine. But, this must be avoided. The response 100 not be predicted by hypertension severity. Thus, our protocol is to o 15 30 45 15 always administer 5 mg as the ini-Time (hours) tial dose. n adverse response to exceeding this initial dose is shown mean arterial pressure dropped from 180 to 90 mm Hg within 1 hour and was associated with in Figure 40-20. This woman had fetal bradycardia. Rapid crystalloid infusion raised the mean pressure to 115 mm Hg, and the fetus chronic hypertension complicated recovered.
his orally administered calcium-channel blocking agent has become popular because of its eicacy to control acute pregnancy-related hypertension. he American College of Obstetricians and Gynecologists (2017a), the NHBPEP Working Group (2000), and the Royal College of Obstetricians and Gynaecologists (2006) recommend a 10-mg initial immediate-release oral dose to be followed in 20 to 30 minutes with 10 to 20 mg if necessary. If not satisfactory, this is followed by labetalol. Nedipine given sublingualy is no longer recommended. his route is associated with dangerously rapid and extensive efects. Randomized trials that compared nifedipine with labetalol found neither drug definitively superior, but nifedipine lowered blood pressure more quickly (Scardo, 1999; Shekhar, 2016; Vermillion, 1999). Finally, nifedipine does not potentiate magnesium-related efects (Magee, 2015).
A few other generally available antihypertensive agents have been tested in clinical trials but are not widely used (Umans, 2015). These include verapamil, nitroglycerin, nitroprusside, ketanserin, nicardipine, and nimodipine (Belfort, 1990, 2003; Bolte, 2001; Cornette, 2016). There are also experimental antihypertensive drugs that may become useful for preeclampsia treatment (Lam, 2013).
Potent loop diuretics can further compromise placental perfusion. Immediate efects include redistribution of the intravascular volume, which most oten is already reduced in severe preeclampsia (p. 718). herefore, before delivery, diuretics are not used to lower blood pressure (Zeeman, 2009; Zondervan, 1988). We use antepartum furosemide or similar drugs solely to treat pulmonary edema.