Date of Award

10-1-2021

Publication Type

Thesis

Degree Name

M.H.K.

Department

Kinesiology

Keywords

Blood-brain barrier, Heat stress, Hyperthermia, Neuronal Damage, Neurovascular unit

Supervisor

A. Bain

Supervisor

C. MacGowan

Rights

info:eu-repo/semantics/openAccess

Abstract

With growing use for hyperthermia as a cardiovascular therapeutic, there is surprisingly little information regarding the acute effects it may have on the integrity of the neurovascular unit (NVU). Indeed, relying on animal data would suggest hyperthermia comparable to levels attained in thermal therapy will disrupt the blood- brain barrier (BBB) and damage the cerebral parenchymal cells. We sought to address the hypothesis that controlled passive hyperthermia is not sufficient to damage the NVU in healthy adults. Eleven young men (age 23 ± 3 years) underwent acute passive heating until +2°C or absolute esophageal temperature of 39.5°C. The presence of BBB opening was determined by trans-cerebral exchange kinetics (radial-arterial and jugular venous cannulation) of S100B. Neuronal parenchymal damage was determined by the trans- cerebral exchange of tau protein, neuron specific enolase (NSE) and neurofilament-light protein (NF-L). Cerebral blood flow to calculate exchange kinetics was measured by duplex ultrasound of the right internal carotid and left vertebral artery. Passive heating was performed via warm-water perfused suit. In hyperthermia, there was no increase in the cerebral exchange of S100B (p=0.327), tau protein (p=0.626), NF-L (p=0.447) or NSE (p=0.908) suggesting +2°C core temperature is not sufficient to acutely stress the NVU in healthy men. However, there was a significant condition effect (p=0.028) of NSE, corresponding to a significant increase in arterial (p=0.023) but not venous (p=0.173) concentrations in hyperthermia, potentially indicating extra- cerebral release of NSE. Collectively, results from the present study support the notion that in young men there is little concern for NVU damage with acute hyperthermia of +2°C.

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