Central versus peripheral blood pressure in malignant hypertension; effects of antihypertensive treatment

Sodium nitroprusside (SNP) and labetalol are recommended for the immediate treatment of malignant hypertension. Both are intravenous agents but have different effects on systemic hemodynamics, and may have differential effects on pulse-wave reflection and pulse-pressure amplification, with consequences for peripheral versus central blood pressures (BPs).

We conducted a nonrandomized, open-label study of 8 patients treated with sodium nitroprusside (mean age (±SD), 44±14 years; 6 males; diastolic/systolic BP, 225±22/135±8mm Hg) and 6 patients treated with intravenous labetalol (mean age, 39±15 years; 4 males; systolic/diastolic BP, 232±22/138±17mm Hg) before and after treatment for malignant hypertension, aiming at a 25% reduction in mean arterial pressure. We measured peripheral pressures with an intra-arterial catheter in the radial artery and derived central pressures with a generalized transfer filter.

Mean arterial pressure was similarly reduced with sodium nitroprusside and labetalol (by 27% and 30%, respectively; P = 0.76). There was a nonsignificantly greater reduction in peripheral systolic blood pressure (SBP) with labetalol than with sodium nitroprusside (29±11% vs. 18±7%, P = 0.08). The decline in peripheral diastolic blood pressure (DBP) with the two agents was comparable, whereas the reduction in peripheral pulse pressure was 8±16% with SNP and 33±17% with labetalol (P = 0.01). The decline in reflection magnitude was greater with SNP than with labetalol. There were no significant differences in the reduction of central BP with SNP and labetalol. The amplification of PP increased with SNP but did not change with labetalol.

We found no difference in central SBP or PP in subjects treated with SNP and labetalol, but labetalol produced a greater reduction in peripheral SBP and PP in the immediate treatment of malignant hypertension.