Cerebrovenous blood temperature-influence of cerebral perfusion pressure changes and hyperventilation: evaluation in a porcine study and in man.

The objective of the first part of this study was to use an animal model to investigate the relationship between temperature in the cerebrovenous compartment and cerebral perfusion pressure. In the second part of the study, the objective was to examine the influence of hyperventilation and hypothermia on jugular bulb temperature and body temperature in patients undergoing elective neurosurgery. Intracranial pressure was increased artificially by inflating an infratentorial supracerebellar placed balloon catheter in nine pigs under general anesthesia. Temperature was monitored by thermocouples inserted in the sagittal sinus, white matter of the left lobe and abdominal aorta during the ensuing decrease in cerebral profusion pressure (CPP). Cerebrovenous blood temperature (jugular bulb) and body temperature (urinary bladder) were simultaneously monitored in 24 patients undergoing craniotomy. Moderate hyperventilation was performed in all patients. Cerebrovenous blood and core body temperature were recorded and differences between these two temperatures calculated at the beginning and the end of hyperventilation. At the beginning of the intracranial pressure (ICP), increase mean temperatures of cerebrovenous blood and cerebral tissue (left lobe) were lower than core body temperature. During CPP reduction the difference between core body temperature and cerebrovenous blood temperature increased significantly from 0.86+/-0.44 degrees C prior to ICP rise to 1.19+/-0.58 degrees C at maximum ICP. Before hyperventilation, cerebrovenous blood temperature was higher in 19 patients (+/- difference: 0.34 degrees C +/- 0.27) and equal or lower in five patients (difference: -0.08 degrees C +/- 0.11), than core body temperature. At the end of hyperventilation, the difference between cerebrovenous blood temperature and core body temperature increased (+0.42 degrees C +/- 0.24) in those 19 patients who had started with a higher cerebrovenous blood temperature and decreased (-0.10 degrees C +/- 0. 18) in the other five patients. Both studies demonstrated that the temperature of cerebrovenous blood is influenced by maneuvers which are supposed to decrease cerebral blood flow.