Assessment of the lower limit for cerebral perfusion pressure in severe head injuries by bedside monitoring of regional energy metabolism.
BACKGROUND
In patients with severe traumatic brain lesions, the lower limit for cerebral perfusion pressure (CPP) is controversial. The aim of this prospective study was to assess this limit from bedside measurements of cerebral energy metabolism and to clarify whether the penumbra zone surrounding a focal lesion is more sensitive to a decrease in CPP than less-injured areas.


METHODS
Fifty patients with severe head injury were included after evacuation of an intracranial hematoma and/or focal brain contusion. They were treated according to intensive care routine (Lund concept), including continuous monitoring of intracranial pressure. One microdialysis catheter was inserted in less-injured brain tissue ("better" position), and one or two catheters were inserted into the boundary of injured cerebral cortex ("worse" position). Concentrations of glucose, pyruvate, and lactate were analyzed and displayed bedside and were related to CPP (n = 29,495).


RESULTS
Mean interstitial glucose concentration was unaffected by the level of the CPP within the studied ranges. Increases in lactate concentration (P = 0.0008) and lactate-pyruvate ratio (P = 0.01) were obtained in the "worse" but not in the "better" position at CPP less than 50 mmHg compared with the same positions at CPP greater than 50 mmHg.


CONCLUSIONS
The study results support the view that CPP may be reduced to 50 mmHg in patients with severe traumatic brain lesions, provided that the physiologic and pharmacologic principles of the Lund concept are recognized. In the individual patient, preservation of normal concentrations of energy metabolites within cerebral areas at risk can be guaranteed by intracerebral microdialysis and bedside biochemical analyses.
Nordström
Carl-Henrik
CH
Department of Clinical Neuroscience, Lund University Hospital, Lund, Sweden. carl-henrik.nordstrom@skane.se
Reinstrup
Peter
P
Xu
Wangbin
W
Gärdenfors
Anna
A
Ungerstedt
Urban
U
D000293:Adolescent; D000328:Adult; D000368:Aged; D001784:Blood Gas Analysis; D001923:Brain Chemistry / Q000502:physiology; D001930:Brain Injuries / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D006259:Craniocerebral Trauma / Q000503:physiopathology*; D003422:Critical Care; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005947:Glucose / Q000378:metabolism; D006408:Hematoma, Subdural / Q000503:physiopathology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D019095:Point-of-Care Systems; D011187:Posture / Q000502:physiology; D019289:Pyruvic Acid / Q000378:metabolism
D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose