January 1, 2012Open Access

Melatonin does not attenuate dynamic cardiovascular and cerebrovascular reflex responses to acute hypotension in healthy men

Structured PICO

Does oral melatonin premedication alter dynamic cardiovascular and cerebrovascular reflex responses to acute hypotension in healthy men?

Population

12 healthy men, mean age 26 ± 3 years, free of any known cardiovascular or cerebrovascular diseases and not taking any medications.

Intervention

Oral melatonin 0.2 mg/kg (mean 13.1 ± 0.9 mg) administered 60 minutes prior to testing.

Comparator

Baseline measurements taken before melatonin ingestion (each subject served as their own control).

Outcome

Dynamic cardiovascular and cerebrovascular reflex responses to acute hypotension induced by thigh cuff release (including changes in systolic arterial pressure, heart rate, cardiac output, total peripheral resistance, and cerebral blood flow velocity).surrogate

Melatonin premedication at 0.2 mg/kg does not impair the body's compensatory cardiovascular and cerebrovascular responses to acute hypotension, suggesting it is safe regarding hemodynamic stability during postural changes or hemorrhage.

Abstract

BACKGROUND: Melatonin has been shown to attenuate the reflex sympathetic increases that arise in response to orthostatic challenges. We tested the hypothesis that the attenuated sympathetic increase induced by melatonin premedication may weaken the arterial blood pressure (ABP) preserving the capability during acute hypotension, thereby altering dynamic cerebral autoregulation and causing a further decrease in cerebral blood flow (CBF). METHODS: Acute hypotension was induced in 12 healthy subjects by releasing bilateral thigh cuffs before and after an oral dose of melatonin (0.2 mg/kg). Heart rate (HR), arterial blood pressure (ABP), Modelflow estimate of cardiac output (CO), total peripheral resistance (TPR) and cerebral blood flow velocity (CBFV) by transcranial Doppler were measured. RESULTS: Steady state HR, the mean arterial pressure and CBFV were not altered 60 minutes after melatonin ingestion. Reduced systolic arterial pressure (ΔSAP), changes in HR (ΔHR), CO (ΔCO), and TPR (ΔTPR), ΔHR/ΔSAP and percentage restoration of SAP were not affected after a temporal decrease in ABP induced by thigh cuff release. In the cerebral circulation, melatonin did not affect changes in CBFV, cerebrovascular resistance index, the rate of regulation and percentage restoration of CBFV following a sudden decrease in ABP. CONCLUSIONS: Contrary to our hypothesis, melatonin did not affect the rapid vasodilatory and recovery responses of cardiovascular and dynamic cerebral autoregulation. These results suggest that melatonin premedication may not impair ABP and CBF preserving capability induced by sudden postural changes or hemorrhage.

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