Influence of various ventilatory parameters on NIR reflexion spectroscopy based cerebral oxygen measurements. An experimental animal study.

Abstract

Sustained elevation of intracranial pressure (ICP) is commonly found as a sequel to severe head injury and has been demonstrated to adversely affect both cerebral metabolism (Bouma 91, Cruz 90), hemodynamics (Obrist 84) and outcome (Gopinath 94, Marshall 79) in this group of patients. Hyperventilation is in wide use as one of the immediate therapeutic measures in the treatment of head injury to control intracranial hypertension by reduction of cerebral blood volume (CBV) (Cruz 90, Greenberg 78, Owen-Reece 94, Pryds 90, Thoresen 79). However, questions still remain regarding the effects of carbon dioxide tension on cerebral oxydative metabolism in brain injured patients, especially with potential impairment of cerebrovascular reactivity and altered hemodynamics (Cruz 90, Harper 65, Langfitt 65, Muizelaar 91, Obrist 84, Sutton 90). The benefits of lowering raised ICP may sometimes be compromised by adverse effects on cerebral oxygenation (Cruz 90, Muizelaar 91, Sutton 90). The value of NIRS based monitoring of cerebral hemodynamics and oxygenation has already been demonstrated (Höper 94, McCormick 91, Owen-Reece 94, Steinberg 96, Wray 88). However, no conclusive data exist from a controlled experimental study addressing the effects of pCO2 variation on cerebral tissue oxygenation during intracranial hypertension. Quantification of these effects is of importance, since clinical decision making would be greatly facilitated by definition of a therapeutic range, within which pCO2 can be safely varied according to individual requirements without causing cerebral desaturation. We therefore designed this experimental study to elucidate the impact of different ventilatory parameters on cerebral tissue oxygen saturation using a new reflectance spectroscopic system (Multiscan OS 10 (Steinberg 96)) under controlled baseline conditions and during ICP elevation.KeywordsIntracranial HypertensionMean Standard DeviationCerebral Blood VolumeCerebral OxygenationSevere Head InjuryThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.