Brain metabolism during a decrease in cerebral perfusion pressure caused by an elevated intracranial pressure in the porcine neocortex.
BACKGROUND
Cranial hypertension coincides with a reduction in cerebral blood flow as well as in oxygen delivery and influences outcome. In this study, we monitored changes in energy-related metabolites in the porcine cortex during an increase of intracranial pressure (ICP) and to determine the level at which damage occurs.


METHODS
Male domestic pigs (32-40 kg) were anesthetized, mechanically ventilated, and randomly assigned to either the experimental (n = 6) or control groups (n = 5). A microdialysis probe (CMA 70) was inserted into the cortex to measure extracellular dialysate concentrations of lactate, pyruvate, glucose, glutamate, and glycerol. Every hour an increase of 10 mm Hg in ICP was preformed in the experimental group by infusion of artificial cerebrospinal fluid into the ventricular system of the brain until a maximum ICP of 50 mm Hg was reached.


RESULTS
We demonstrated a significant increase of lactate and glycerol compared with control at ICP values > or =30 mm Hg and cerebral perfusion pressure (CPP) below 50 mm Hg. The increase of ICP to > or =40 mm Hg in conjunction with a reduction in CPP below 40 mm Hg led to a significant increase in the lactate/pyruvate-ratio and glutamate, as well as a decrease of glucose in relation to control.


CONCLUSIONS
Our data strongly suggest that, during a defined ICP increase, lower CPP values may be tolerable until severe damage occurs. Borderline ICP and CPP values of 30 and 40 mm Hg, respectively, could be advised.
Zoremba
Norbert
N
Department of Anesthesiology, University Hospital RWTH Aachen, Aachen, Germany. nzoremba@ukaachen.de
Schnoor
Joerg
J
Berens
Michael
M
Kuhlen
Ralf
R
Rossaint
Rolf
R
D000818:Animals; D002545:Brain Ischemia / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D019586:Intracranial Hypertension / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D007427:Intracranial Pressure; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D019579:Neocortex / Q000098:blood supply / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D034421:Sus scrofa; D013997:Time Factors
D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005947:Glucose; D005990:Glycerol