title: Higher systemic arterial pressures are rarely associated with cerebral perfusion pressure deterioration in brain injury.
abstract: BACKGROUND
  A computerized monitoring system was developed and utilized to evaluate the relationship between mean arterial pressure and intracranial pressure and its effect on cerebral perfusion pressure to determine how best to maximize cerebral perfusion pressure.
  
  
  METHODS
  The monitoring system recorded mean arterial pressure and intracranial pressure, the values of which were used to calculate cerebral perfusion pressure. We developed the program for and utilized a "moving window" regression analysis to divide the total monitoring period into 2-hour overlapping epochs. The relationship between mean arterial pressure and intracranial pressure was then analyzed in each 2-hour epoch and classified into Types A, B, C, and D epochs, each with clinical significance. Type A epochs involved intracranial pressure increasing more than mean arterial pressure and resulted in deterioration of cerebral perfusion pressure. Type B epochs involved mean arterial pressure increasing more than intracranial pressure and resulted in an increase of perfusion pressure. Type C epochs involved mean arterial pressure increasing and intracranial pressure decreasing and also resulted in an increase in perfusion pressure. Type D epochs had no statistically significant relationship between mean arterial pressure and intracranial pressure.
  
  
  RESULTS
  Forty-five patients with various pathologies were studied. The majority (n = 35) were patients with severe brain injury. Of 5,694 total hours monitored and 22,776 total epochs analyzed, 1.5% epochs were Type A, 5.9% were Type B, 2.1% were Type C, and 90.5% were Type D.
  
  
  CONCLUSIONS
  In most patients, most of the time, increasing mean arterial pressure did not worsen cerebral perfusion pressure.
authors.affiliation: Division of Neurosurgery, St. Luke's Hospital, Bethlehem, Pennsylvania, USA.
authors.forename: George I
authors.initials: GI
authors.lastname: Chovanes
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Richards
authors.forename: Robert A
authors.initials: RA
authors.lastname: Morrow
authors.forename: Michael
authors.initials: M
authors.lastname: Rhodes
mesh_terms: D000368:Aged; D001794:Blood Pressure; D001930:Brain Injuries / Q000503:physiopathology* / Q000628:therapy; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007427:Intracranial Pressure; D008297:Male; D008991:Monitoring, Physiologic; D013997:Time Factors; D014696:Ventriculostomy