Resuscitation from experimental heatstroke by brain cooling therapy

Area of Science:

• Physiology
• Neuroscience
• Toxicology

Background:

• Heatstroke is a life-threatening condition characterized by hyperthermia and central nervous system dysfunction.
• Previous studies suggest hypothermic retrograde jugular venous flush can cool the brain and improve resuscitation in heatstroke models.
• The impact of brain cooling on specific inflammatory mediators and oxidative stress markers during heatstroke requires further investigation.

Purpose of the Study:

• To assess the effects of brain cooling on reactive nitrogen species (RNS), reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-α), and interleukin-10 (IL-10) in serum and brain during heatstroke.
• To compare the efficacy of direct brain cooling versus peripheral saline infusion for heatstroke resuscitation in rats.
• To investigate the potential of brain cooling to mitigate cerebrovascular dysfunction during heatstroke.

Main Methods:

• Rats were induced into heatstroke by exposure to 43°C for 70 minutes under general anesthesia.
• Groups received either 36°C or 4°C saline infusion via the external jugular vein immediately after heatstroke onset.
• Measurements included survival time, brain temperature, intracranial pressure, mean arterial pressure, cerebral perfusion pressure, serum and brain levels of nitric oxide metabolites, TNF-α, dihydroxybenzoic acid, IL-10, and hypothalamic inducible nitric oxide synthase (iNOS) immunoreactivity.

Main Results:

• Rats receiving 4°C saline infusion (brain cooling) showed significantly improved survival (226-268 min) compared to 36°C saline (21-25 min) and normothermic controls.
• Brain cooling suppressed elevated brain temperature, intracranial pressure, RNS, ROS, TNF-α, and iNOS, while improving cerebrovascular function (mean arterial pressure, cerebral perfusion pressure, local blood flow, oxygen partial pressure).
• Serum and hypothalamic IL-10 levels, initially negligible, were significantly elevated by brain cooling during heatstroke.

Conclusions:

• Hypothermic brain cooling is a highly effective resuscitation strategy for heatstroke, significantly improving survival rates in a rat model.
• Brain cooling mitigates heatstroke-induced pathology by reducing the overproduction of RNS, ROS, and TNF-α, and ameliorating cerebrovascular dysfunction.
• The increase in IL-10 production induced by brain cooling may play a protective role in heatstroke recovery.