The effect of acute and long-term treatment with propranolol on cerebral blood flow (CBF) and the cerebral metabolic rate of oxygen (CMRO2) has been studied in 8 young healthy volunteers. CBF was measured by 133Xe-inhalation and single photon emission computer tomography, and CMRO2 was calculated from the arterio-venous oxygen difference and CBF. Studies were done before and 1 h after i.v. injection of 5 mg propranolol and after three weeks on oral propranolol 80 mg/d for 1 week and 160 mg/d for 2 weeks. Cerebrovascular CO2 reactivity in terms of the A-V oxygen difference was tested on all three occasions during hypercapnia and hyperventilation. CBF, CMRO2 and cerebrovascular CO2 reactivity remained stable both after acute and after 3 weeks of treatment with propranolol.
The effect of a clinically relevant dose of ketanserin (10 mg as a bolus followed by an infusion of 6 mg/h) on cerebral blood flow (CBF) and CBF autoregulation was examined in 12 healthy volunteers. Changes in CBF were estimated by the cerebral arteriovenous-oxygen saturation difference method, while mean arterial blood pressure (MABP) was increased by norepinephrine and decreased by ganglionic blockade (trimethaphan camphosulphonate) combined with lower body negative pressure one hour after the infusion of ketanserin. During ketanserin infusion, MABP fell insignificantly by 2.5 mmHg (6 to -2), while CBF rose insignificantly by 5 ml/100 g/min. Autoregulation was preserved in all volunteers. CO2-correction factors from 0 to 4.6% CBF/0.1 kPa were used. The lower limit of CBF autoregulation was 82 mmHg (80-86) with an SE of 3 mmHg (1-5) similar to a previous control group of healthy volunteers. Aside from a major decrease in MABP in one subject, no adverse side effects were observed. The present study shows that CBF autoregulation is maintained during ketanserin infusion.
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