Mild dehydration modifies the cerebrovascular response to the cold pressor test

Area of Science:

• Physiology
• Neuroscience
• Cardiovascular Research

Background:

• The cold pressor test (CPT) is a standard physiological stressor.
• Autonomic responses to CPT include increased heart rate (HR) and mean arterial pressure (MAP).
• Cerebrovascular reactivity, measured by middle cerebral artery blood flow velocity (MCAv), is also affected by CPT, but hydration status is often overlooked.

Purpose of the Study:

• To investigate the impact of mild dehydration on the physiological and cerebrovascular responses to the CPT.
• To determine if hydration status influences MCAv changes during cold stress.

Main Methods:

• Ten healthy males underwent two CPTs: one in a euhydrated state and one in a mildly dehydrated state.
• Continuous beat-to-beat measurements of MCAv, MAP, HR, and partial pressure of end-tidal CO2 (P(ET,CO2)) were recorded.
• Pain perception was assessed using a visual analog scale during the CPT.

Main Results:

• Mild dehydration was confirmed by increased plasma osmolality and reduced body mass.
• While MAP and HR responses were similar between conditions, MCAv(mean) and P(ET,CO2) changes were significantly lower during dehydration.
• Participants reported greater pain perception during the CPT when mildly dehydrated.

Conclusions:

• Mild dehydration significantly alters the cerebrovascular response to the CPT.
• Dehydration blunts the increase in MCAv(mean) and lowers P(ET,CO2) during cold exposure.
• Hydration status should be considered and reported in studies utilizing the CPT.