Antihypertensive Medication Effect on Cerebral Blood Flow

Introduction: Data on the cerebral effects of antihypertensive agents are limited but potentially important in patients requiring blood pressure reduction in neurological emergencies. Our objective was to measure the effect of rapid-acting antihypertensive agents on cerebral blood flow (CBF) in patients with acute hypertension. Methods: We conducted a prospective, quasi-experimental study of patients with a SBP \u3e 180 mmHg and planned rapid-acting antihypertensive treatment in the emergency department. Patients \u3c 18 years or pregnant were excluded. Non-invasive hemodynamic and transcranial Doppler measurements of the middle cerebral artery mean flow velocity (MFV) were obtained prior to and post treatment. Analysis included descriptive statistics and generalized linear modeling to test the effect of four categories of antihypertensive agents on MFV. Categories included clonidine, IV labetalol, IV hydralazine and combination therapy. Results: We enrolled 35 patients (37% female) with a mean age of 49 ± 13 years. Eight (23%) patients received clonidine, 6 (17%) IV labetalol, 5 (14%) IV hydralazine and 16 (46%) combined therapy. The mean baseline SBP was 214 ± 24 mmHg and MFV 49 ± 13 cm/sec. The mean percentage fall in SBP by medication was: clonidine -12 ±7%, labetalol -13 ±12%, hydralazine -23 ±11%, and combination -23 ±16%. The overall change in MFV was -9 ±15%, and by medication was: clonidine -10% (95%CI -2 to - 21%), labetalol -11% (95%CI -5 to -27%), hydralazine +1% (95%CI -18 to +21%), and combination -11% (95%CI -2 to -19%). Adjusting for baseline BP, hydralazine caused less change in MFV compared to other medications (difference between means +12%, 95%CI -3 to +26%, p=0.1). Conclusions: In this study with modest BP reductions, rapid-acting antihypertensive medications had comparable effects on cerebral blood flow. These results hint that cerebral blood flow may be more stable with hydralazine administration, but further testing of hydralazine and infusions such as nicardipine is required