HIGH SALT DIET EFFECTS ON CEREBRAL AND SYSTEM HEMODYNAMICS IN RESPONSE TO BREATH HOLDING TEST AND HYPERVENTILATION

Abstract

Objective: High salt (HS) diet impairs endothelium-dependent vasodilation in many vascular beds, including cerebral microcirculation, and may affect vascular resistance. The aim of present study was to determine if 7-day HS diet affected cerebral and system hemodynamics in response to breath holding test (BHT) and hyperventilation in healthy young persons. Design and method: In this controlled intervention study 27 persons participated (F:21, M:6, age range 19-24). Participants consumed 7-day low salt (LS) diet (<2.3g NaCl/day) and afterwards 7-day of HS diet (>11.2g NaCl/day). Blood and urine analysis and anthropometric measurements were performed after each diet. Arterial blood pressure, heart rate and heart rate variability (HRV), cerebral and systemic hemodynamic parameters were recorded simultaneously with transcranial Doppler ultrasound and the Task Force® Monitor in response to BHT and hyperventilation. Results: The subjects remained normotensive during both protocols. After hyperventilation test, HS diet did not affect parameters of cerebral or systemic hemodynamics. HRV was more decreased after HS diet, while baroreceptor sensitivity (BRS) decreased in both LS and HS diet. Similar lack of effects of HS diet on cerebral and system hemodynamics was observed in BHT. Urine concentration of noradrenaline and vanillylmandelic acid was significantly decreased by HS diet. Conclusions: Results suggest that HS diet suppresses sympathetic activity. However, physiological hemodynamic responses to BHT and hyperventilation are preserved, which could be contributed to salt-resistant phenotype of participants and some, still unexplained (chemoreceptors-mediated) compensatory mechanisms preserving cerebral and systemic blood flow.