(846) Furosemide to lower antenatal severe hypertension (FLASH): a randomized placebo-controlled trial

In high cardiac output hypertension, reducing volume may be an effective strategy in lowering blood pressure (BP). We evaluated whether the addition of IV furosemide to first-line antihypertensive agents reduces systolic BP (SBP) for the management of acute-onset, severe (SBP ≥160 mmHg and/or diastolic BP (DBP) ≥110 mmHg) antenatal hypertension with wide (≥60 mmHg) pulse pressure (PP), a proxy for stroke volume.

Study Design:

We conducted a double-blinded RCT allocating participants to 40 mg of IV furosemide or placebo in addition to a first-line antihypertensive agent. The primary outcome was mean SBP during the first hour after intervention. Secondary outcomes included mean DBP during the hour after intervention; SBP, DBP, and PP at 2 hours, duration of BP control, need for additional antihypertensive agents, and maternal electrolyte and 6-hour urine output responses.

Results:

Between January 2021 to March 2022, 33 individuals were randomized to furosemide and 32 to placebo. Baseline characteristics were similar between groups. We found no difference in the primary outcome of mean [SD] SBP (147 [14.8] vs 152 mmHg [13.8], P=.200) 1 hour after intervention. At 2 hours, we noted significantly lower mean SBP in the furosemide group (139 [18.5] vs 154 mmHg [18.4], P=.007) and significantly lower mean PP in the furosemide group (55 [12.5] vs 67 mmHg [15.1], P=.003). Electrolytes before and after allocation and urine output were similar between groups. Subgroup analysis showed a significant reduction in the primary outcome, 2-hour SBP, and 2-hour PP among patients with new-onset but not pre-existing hypertension. 

Conclusion:

IV furosemide in conjunction with a first-line antihypertensive agent did not significantly reduce SBP in the hour after administration. However, both SBP and PP at 2 hours were lower in the furosemide group. SBP at 1 and 2 hours and PP were significantly lower in the new-onset hypertension subgroup. Our findings suggest that a one-time dose of IV furosemide may decrease SBP by reducing volume without causing major electrolyte disturbances, though the effect is not immediate.