Hypothermia has a considerable protective effect during brain ischemia. On the other hand small increases of brain temperature have a remarkable effect on the exacerbation of neurological damage following an ischemic event. Hyperthermia of the brain tissue after severe head injury is described. The effect of acutely increased intracranial pressure on cerebrovenous blood temperature is not described yet. The aim of this study was to investigate the relationship between temperature in the cerebrovenous compartment (Tcv) and changes of the CPP in an animal model of raised intracranial pressure.
Methods: A thermocouple was inserted in the sagittal sinus in 9 pigs under general anesthesia. By stepwise inflating a supracerebral and infratentorial placed balloon catheter intracranial pressure (ICP) was increased and CPP concomitantly decreased. The central body temperature was measured simultaneously in the abdominal aorta (Ta) with a second thermocouple.
Results: In our model th Tcv was lower than Ta at the beginning of the ICP increase. The mean difference between Ta and Tcv, (delta Ta-cv) was 0.86 degree C (+/- 0.44) prior to ICP increase and 1.19 degrees C (0.58) at the maximum ICP increase. Thus, delta Tav increased during CPP reduction. This relation was represented by an adjusted R(square) of r2 = 0.89 (p < 0.001).
Conclusions: The CPP decrease, caused by an increasing ICP, results in changes of the cerebrovenous blood temperature. Interpreting the present results the experimental situation of a relative colder cerebral compartment in comparison to the central body temperature has to be considered. However, the results imply, that simultaneous temperature monitoring of the central body temperature and the cerebrovenous blood temperature is an additional source of information about relative changes of the CBF.