First-dose effects of enalapril and atenolol upon blood pressure and cerebral blood flow in patients with mild hypertension on diuretic therapy.
Level 2 - randomized trial
Individual randomized crossover trial
What was done
In a single-blind, randomized, placebo-controlled crossover study, 10 patients with mild hypertension already receiving a thiazide diuretic were administered a single oral dose of atenolol 50 mg and enalapril 5 mg. Blood pressure and cerebral blood flow (measured by Xenon inhalation) were evaluated following the initial dose.
What was found
The abstract does not provide group-level numerical values for blood pressure or cerebral blood flow changes. The timing and degree of blood pressure reduction were reported to be similar between atenolol and enalapril, generally occurring without symptoms or reductions in cerebral blood flow. In an individual case, dizziness occurred alongside a 43% reduction in cerebral blood flow without a marked drop in systolic blood pressure.
Why it matters
It indicates that initial doses of ACE inhibitors or beta-blockers combined with diuretics generally maintain cerebral perfusion, although isolated symptomatic cerebral blood flow drops can occur without pronounced systemic systolic hypotension.
Limits
The study is limited by an extremely small sample size (n = 10) and a single-blind design. The abstract lacks aggregate numerical data, confidence intervals, and statistical test values for blood pressure and flow outcomes, and only examines acute first-dose effects.
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