CONTINUOUS MONITORING OF THE PARTIAL-PRESSURE OF OXYGEN IN CEREBRAL VENOUS-BLOOD

OBJECTIVE: Clinical oxygen monitoring in the injured brain is somewhat difficult. However, ischemia is one of the major factors responsible for secondary tissue damage after head injury or subarachnoid hemorrha ge. Therefore, the aim of the present study was to investigate the val ue of continuously monitoring the partial pressure of oxygen in cerebr al venous blood (PcvO2) during changes in intracranial pressure (ICP). METHODS: In eight domestic pigs with Clark type probes placed in the posterior third of the superior sagittal sinus, PcvO2 was continuously registered while ICP was stepwise elevated by an inflatable balloon p laced below the tentorium. Arterial blood pressure was continuously mo nitored, cerebral perfusion pressure (CPP) was calculated, and arteria l partial carbon dioxide pressure and partial pressure of oxygen were registered intermittently. RESULTS: The mean intraparenchymal ICP befo re the start of balloon inflation was 5 +/- 1 mm Hg, the mean CPP was 80 +/- 15 mm Hg, and the mean PcvO2 was 36 +/- 3 mm Hg. At maximum ICP elevation, CPP decreased to 20 +/- 12 mm Hg, PcvO2 decreased to 10 +/ - 6 mm Hg, and ICP increased to 90 +/- 10 mm Hg. Strong linear correla tions between ICP and PcvO2 and between CPP and PcvO2 were revealed, a nd mean correlation coefficients of 0.89 for ICP/PcvO2 and 0.73 for CP P/PcvO2 were calculated. CONCLUSION: The present study demonstrates th at polarographic PcvO2 monitoring in the superior sagittal sinus is a reliable method for the early detection of reduced CPP during ICP elev ation. This technique is capable of registering the global oxygen supp ly and oxygen consumption of the brain. It seems superior to jugular v enous oxymetry and is better suited for clinical use because of a some what low artifact susceptibility.