Biomedical subjects
Publications and source records attributed to T Lysoń.
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Mild hypothermia may occur spontaneously or, because of its putative neuroprotective effect, may be induced purposefully during neurosurgical procedures. Though the brain is the organ targeted for the purpose of neuroprotection, little is known about its temperature during general anaesthesia and craniotomy. The purpose of this study was to define the relations between core, skin and brain temperature during craniotomy and to compare two modes of inducing thermal insulation in patients during operative procedures. To achieve this we recorded core: rectal (Tre), oesophageal (Tes) and tympanic (Try) temperature, brain temperature in the subdural space (Tsd), and skin temperature on the thigh (Tfe), forehead (Tfr) and sternum (Tst) in 15 patients undergoing standard procedure for aneurysm clipping. In 13 patients the core temperature decreased, whereas skin temperature increased, after induction of general anaesthesia with isofluran. Nevertheless the mean body temperature remained unchanged, thus supporting the view that the cause of the resultant core hypothermia was heat redistribution between the thermal core and the periphery. Special thermofoil proved to be only as effective as a plain cotton blanket in preventing further heat loss during the later phases of the operation. Brain temperature was found to be the lowest core temperature throughout the procedure. It differed by as much as 0.1-1.2 degrees C from rectal temperature (mean 0.75 +/- 0.41 degree C) and reached the level of mild hypothermia (below 35 degrees C) even in those patients in whom rectal temperature indicated the state of normothermia. Furthermore tympanic and oesophageal temperature was on average 0.5 degree C higher than brain temperature. In conclusion, temperature measurements obtained in standard sites do not reflect brain temperature reliably during craniotomy and general anaesthesia. This indicates that the direct measurement of intracranial temperature is necessary for correct estimation of brain hypothermia.
The knowledge of human brain temperature is still very limited. In this report we investigated the relationship between brain and trunk temperature in neurosurgical patients during normothermia and fever. Another problem addressed was that of possible gradients of temperature within the brain. We carried out direct recordings of temperature in 63 operated, neurosurgical patients with a variety of intracranial pathologies. Flexible, teflon-coated thermocouples were placed intracranially during neurosurgical procedures. Oesophageal, rectal and tympanic temperatures were also monitored. An error of up to 1.3 degrees C is to be expected in single cases if brain temperature is deduced from the rectal or oesophageal temperature. Mean differences between brain temperature and core body temperature measured in the rectum or in the oesophagus, were between 0 to 0.3 degree C. Tympanic temperature (Tty) improved the approximation of brain temperature (Tbr) to within the mean difference between Tbr-Tty close to 0 degree C. Nevertheless Tty also differed from Tbr by as much as 1 degree C in single cases. Brain temperature was the highest body temperature measured, either in normothermia or in fever. Temperature gradients were proved to exist between the warmer brain interior and cooler surface, with maximal differences in temperature reaching 0.6 degree C. This temperature gradient tended to increase along with the rise in intracranial pressure and deterioration of the level of consciousness. Our results suggest that conclusions regarding brain temperature drawn on the basis of other core temperatures, may lead to significant errors, and intracranial temperature measurement is desirable in neurosurgical intensive care. Temperature gradients within the brain may exacerbate its biochemical injury during ischaemia and fever--a combination seen frequently in neurosurgical patients. This may be particularly so, since brain temperature in fever is the highest body temperature in a high proportion of these patients.