title: Cerebral blood flow (CBF)-directed management of ventilated head-injured patients.
abstract: OBJECTIVE
  Ischaemic brain damage has been shown to be an important contributing factor causing head injury fatality. Maintenance of an adequate cerebral perfusion pressure is difficult in patients with elevated intracranial pressure (ICP) and deranged cerebral vasoreactivity. Thirty-five cases of ventilated moderate-to-severe head-injured patients were prospectively studied, correlating their cerebral haemodynamic abnormalities, neurochemical disturbances (using microdialysis methodology) and clinical outcome.
  
  
  METHODS
  Cerebral haemodynamic abnormalities were defined and classified by transcranial Doppler ultrasonography (TCD) and stable xenon-CT cerebral blood flow measurements (XeCT) into their status of CO2 reactivity, pressure autoregulation, hyperaemia or non-hyperaemia. Two-hour episodes of these abnormalities with and without haemodynamic intervention were followed in their changes in ICP, CPP, intracerebral metabolites and finally their clinical outcome.
  
  
  RESULTS
  Loss of CO2 reactivity was associated with a significantly higher ICP, increasing intracerebral metabolites (lactate, glutamate and glycerol) and invariably a fatal outcome. Impaired pressure autoregulation was also associated with an elevated ICP, but no significant difference in intracerebral metabolites and incidence of favourable clinical outcome. Patients with intact CO2 reactivity and impaired pressure autoregulation were treated with an elevated CPP in 32 episodes, resulting in a significant reduction in ICP, intracerebral glutamate and glycerol and non-survival. In patients with intact CO2 reactivity and impaired pressure autoregulation, eleven episodes of hyperaemia were identified by XeCT. A modest 20%, blood pressure reduction resulted in a trend towards a reduction of ICP, intracerebral glutamate and glycerol and non-survival.
  
  
  CONCLUSIONS
  The need for haemodynamic intervention in this group of ventilated patients with moderate-to-severe head inury can be made logical when these abnormalities are identified daily. The success of management was reflected by a stable or improved ICP, CPP, intracerebral metabolic deranagement and survival.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong. wpoon@surgery.cuhk.edu.hk
authors.forename: W S
authors.initials: WS
authors.lastname: Poon
authors.forename: S C P
authors.initials: SC
authors.lastname: Ng
authors.forename: M T V
authors.initials: MT
authors.lastname: Chan
authors.forename: J M K
authors.initials: JM
authors.lastname: Lam
authors.forename: W W M
authors.initials: WW
authors.lastname: Lam
mesh_terms: D002545:Brain Ischemia / Q000401:mortality* / Q000628:therapy*; D002560:Cerebrovascular Circulation; D015897:Comorbidity; D006259:Craniocerebral Trauma / Q000401:mortality* / Q000628:therapy*; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D019586:Intracranial Hypertension / Q000401:mortality* / Q000628:therapy*; D010477:Perfusion; D011379:Prognosis; D012121:Respiration, Artificial; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome