EFFECT OF ARTERIAL PCO2 ON LOCAL HBO2 AND RELATIVE HB CONCENTRATION IN THE HUMAN BRAIN - A STUDY WITH THE ERLANGEN MICRO-LIGHTGUIDE SPECTROPHOTOMETER (EMPHO)

Intraoperative investigations of local intracapillary haemoglobin oxyg enation have been performed in 5 patients during neurosurgical interve ntions using the Erlangen micro-lightguide spectrophotometer (EMPHO). As the measurements can be performed in a very short period of time (a pproximately 60 s) the EMPHO enables rapid monitoring of local haemogl obin oxygenation in the brain. All patients received thiopental anaest hesia and were mechanically ventilated. The local measurements were pe rformed during normoventilation (arterial PCO2 - PaCO2 37.8 +/- 0.7 mm Hg) and hyperventilation (PaCO2 31 +/- 0.5 mm Hg). Hyperventilation c aused a decrease in the mean SO2 from 47.8% to 41.1%. The number of SO 2 values < 50% increased from 58% to 77.8%. The possible significance of the low local SO2 values is discussed.