Continuous monitoring of brain tissue PO2: a new tool to minimize the risk of ischemia caused by hyperventilation therapy.
Secondary ischemic events worsen the outcome of patients with severe head injury. Such a secondary ischemic event may be caused by a forced hyperventilation. A consequence of the induced vasoconstriction is the risk of ischemia with an adverse effect on outcome. As a reliable and on-line technique, brain tissue pO2 (p(ti)O2) is used for monitoring regional microcirculation, to detect critical hypoperfusion. On 22 patients with a severe head injury 70 hyperventilation tests were performed from day 0-9 after trauma, calculating TCD-CO2-reactivity (% change of mean flow velocity per mm Hg paCO2 change). Additionally brain p(ti)O2-CO2-reactivity (% change of brain p(ti)O2 per mm Hg paCO2 change) was calculated and introduced. Group A +2 (p(ti)O2 < or = 15 mm Hg, TCD-CO2-reactivity > or = 2.5%, p(ti)O2-CO2-reactivity > 0%) and group B +2 (p(ti)O2 > 15 mm Hg, TCD-CO2-reactivity > or = 2.5%. p(ti)O2-CO2-reactivity > 0%) was formed. P(ti)O2 values in group A+2 decreased to an ischemic level or ischemia aggravated during hyperventilation. In group B+2 no ischemic events occurred. TCD-CO2-reactivity, p(ti)O2-CO2-reactivity and decrease of paCO2 were not significantly different in both groups. 6 out of 22 patients showed, from day 0-9, at least once a risk of (aggravating) ischemia by hyperventilation therapy.
Dings
J
J
Department of Neurosurgery, University of Würzburg, Germany.
Meixensberger
J
J
Amschler
J
J
Roosen
K
K
D001921:Brain / Q000098:blood supply*; D001930:Brain Injuries / Q000503:physiopathology / Q000628:therapy*; D002545:Brain Ischemia / Q000503:physiopathology / Q000517:prevention & control*; D002245:Carbon Dioxide / Q000502:physiology; D003422:Critical Care; D015600:Glasgow Coma Scale; D006801:Humans; D008833:Microcirculation / Q000503:physiopathology; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009862:Online Systems / Q000295:instrumentation*; D010101:Oxygen Consumption / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012121:Respiration, Artificial; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*
D002245:Carbon Dioxide