Monitoring of cerebral perfusion pressure during intracranial hypertension: a sufficient parameter of adequate cerebral perfusion and oxygenation?
OBJECTIVE
A cerebral perfusion pressure (CPP) oriented treatment is a widely accepted standard for patients with intracranial hypertension. In an animal model of controlled intracranial hypertension we investigated whether CPP is a reliable parameter of sufficient cerebral perfusion and oxygenation. Using near-infrared reflexion spectroscopy the effect of decreasing CPP due to increasing intracranial pressure (ICP) on cerebral tissue oxygenation was studied.


METHODS
Ten rabbits were subjected to artificially elevated ICP using the cisterna-magna infusion technique. Regional cerebral O(2) saturation of hemoglobin (tiSO(2)), regional tissue concentration of hemoglobin (tiHb), and CPP were recorded continuously. CPP was investigated with respect to tiSO(2). Electrocortical activity was simultaneously recorded by two-channel EEG to determine the onset of ischemia.


RESULTS
Reduced CPP due to increased ICP led to a continuous decrease in tiSO(2.) There was progressive suppression of EEG frequency and amplitude with decreasing CPP in all animals. Onset of EEG-silence due to elevated ICP was observed in a wide range of CPP-values between 9 and 42 mmHg. At the same time tiSO(2) varied merely between 0 and 5%.


CONCLUSIONS
Regarding the EEG effects due to increased ICP (EEG silence), CPP values showed a wide interindividual variability, in contrast to tiSO(2). In our animal model the sole calculation of CPP did not reflect adequate cerebral perfusion.
Thees
Christof
C
Department of Anesthesia and Intensive Care Medicine, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany. christof.thees@ukb.uni-bonn.de
Scheufler
Kai-Michael
KM
Nadstawek
Joachim
J
Zentner
Josef
J
Lehnert
Ariane
A
Hoeft
Andreas
A
D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D019586:Intracranial Hypertension / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology*; D011817:Rabbits; D019265:Spectroscopy, Near-Infrared; D018709:Statistics, Nonparametric