Many animal species are able to keep the brain temperature some degrees centigrade lower than the deep body temperature when exposed to environmental heat stress. The lower temperature is based on cooling of the nasal venous blood through the respiratory airflow and local counter-current transfer of heat between venous and arterial blood in the cavernous sinus-carotid artery complex. Anaesthetized, intubated animals do not have any air flow through the nasal cavities. However, when the nasal cavities were flushed with oxygen, the deep brain temperature dropped within minutes and returned to previous values when the oxygen flushing was stopped. Cooling was found in animals with a rete a similar cooling mechanism is present in man (no rete) under mirabile (pigs), and in animals without a rete (rats). intensive care, a simple flushing of the nasal cavities with gas will protect the brain against hyperthermal damage. 2002, Elsevier Science Ltd. All rights reserved.