CORRELATION OF JUGULAR VENOUS OXYGEN-SATURATION TO SPONTANEOUS FLUCTUATIONS OF CEREBRAL PERFUSION-PRESSURE IN PATIENTS WITH SEVERE HEAD-INJURY

Continuous measurements of mean arterial pressure (MAP), ICP, and jugular venous oxygen saturation (SjO(2)) were performed in 11 patients with severe head injury (GCS 3-7) to assess the dependence of SjO(2) from the cerebral perfusion pressure (CPP) trying to establish an indirect measure of cerebrovascular autoregulation. Changes in CPP resulting from spontaneous fluctuations in MAP or ICP induced highly significant alterations in SjO(2) in the range of 0.14-0.56% SjO(2) mmHg(-1) CPP in all patients and all periods after trauma. The analysis of the distribution of the SjO(2):CPP-ratios showed the highest frequency of values in the range of 0.0-0.25% SjO(2) mmHg(-1) CPP in 9 of the 11 patients. Within the first 2 days after trauma, a more pronounced dependency of SjO(2) from changes in CPP was found, but this was not statistically significant. No predictable relationship of the SjO(2):CPP-ratio to the level of ICP could be demonstrated in the patients. Because changes in SjO(2) induced by alterations in CPP were found in all patients and throughout the acute phase of severe head injury, these changes more probably reflect physiological alterations in CBF with varying perfusion pressure rather than impaired autoregulation after head trauma. Although assessment of cerebral autoregulation by estimation of the SjO(2):CPP-ratio offers new possibilities for monitoring of these patients, the high frequency of erroneous readings or irregular fluctuations of the SjO(2)-signal from the fibreoptic catheter limits the usefulness of the SjO(2)-dependency from CPP for practical use in the intensive care unit.