CO2 Reactivity and Autoregulation in Severe Head Injury: Bedside Assessment by Relative Changes in Arteriojugular Differences of Oxygen
It has been demonstrated both clinically and in experimental models that autoregulation and CO2 reactivity can be impaired independently of each other in many brain insults, the so-called dissociated vasoparalysis . The theoretical combination of preserved CO2 reactivity and impaired or absent autoregulation can have many clinical implications in the overall daily management of brain-injured patients. To optimize their treatment, a bedside assessment of autoregulation and CO2 reactivity is desirable. In spite of some unresolved and controversial methodological problems, monitoring hemodynamic parameters through a reverse catheter with its tip in the jugular bulb is an easy way of monitoring brain metabolism and cerebral blood flow (CBF) coupling and in some cases of estimating CBF [2-4]. When the cerebral metabolic rate of oxygen (CMRO2) is constant, changes in arteriojugular differences of oxygen (AVDO2) reflect changes in CBF . In this situation, relative changes in AVDO2 can be viewed as inverse changes in CBF and used as an evaluation method of CO2 reactivity and autoregulation. Our aims in this chapter are to use relative changes in AVDO2 after manipulations of mean arterial blood pressure and arterial pCO2 to assess CO2 reactivity and autoregulation in severe head injury patients.
KeywordsCerebral Blood Flow Cerebral Perfusion Pressure Mean Arterial Blood Pressure Cerebral Blood Volume Jugular Bulb
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