(128) Use of Hydralazine as an Acute Antihypertensive in Pregnancy

In 2020, ACOG published algorithms for acute antihypertensive management, which recommend no more than 20 mg of hydralazine before switching to labetalol or seeking expert consultation. Our hospital has historically used a protocol with no upper limit for intravenous hydralazine. We sought to study the effect of the ACOG algorithm before (2017) and after (2021) the algorithm’s publication.

Study Design:

We obtained pharmacy data for acute antihypertensive therapy (intravenous hydralazine and labetalol, as well as oral immediate release nifedipine) for delivery admissions in 2017 and 2021. If a patient was readmitted in relation to the delivery admission, doses of acute antihypertensive therapy were included. Charts were retrospectively reviewed for timing of doses in relation to delivery and maternal and neonatal outcomes, as well as with respect to oral antihypertensive therapy.

Results:

In 2017 there were 12,270 deliveries, and in 2021 there were 11,410 deliveries. A total of 572 (4.7%) and 623 (5.5%) of these patients for 2017 and 2021, respectively, received acute antihypertensive therapy associated with delivery admissions. The maximum individual doses of such intravenous hydralazine in 2017 and 2021 were 265 mg and 195 mg for delivery admissions and readmissions.  Given that delivery admissions varied in length, we compared maximum doses of intravenous hydralazine in any 24-hour period, which were 65 mg and 70 mg in 2017 and 2021, respectively (Table). No cardiopulmonary events or maternal ICU admissions were attributed to antihypertensive therapy.

Conclusion:

The increased national attention to acute treatment of hypertension was associated with a higher proportion of patients acutely treated in 2021, with most patients requiring 20 mg or less of hydralazine in any 24-hour period. Importantly, about 1-in-5 patients required doses exceeding 20 mg in any 24-hour period. This study provides additional guidance for the use of hydralazine exceeding 20 mg per 24 hours, which is safe when indicated and used as part of a defined algorithm.