[Continuous fiberoptic monitoring of oxygen saturation in cerebral veins in severe craniocerebral trauma--experiences and results].

AIM

Monitoring of jugular-venous O2-saturation (SjO2) enables the assessment of cerebral oxygen supply and the rapid detection of cerebral desaturation in patients with severe head injury. Furthermore, it may help to optimize circulation, ventilation, and intracranial hypertension therapy in these patients. This study was performed to evaluate the reliability of SjO2-monitoring as well as to measure cerebral O2-extraction and the frequency of episodes of cerebral desaturation after traumatic brain injury.

METHODS

In 16 patients with severe head injury (GCS 3-8), SjO2 (fibreoptic system), arterial blood pressure, and intracranial pressure were continuously recorded after admission of the patients to the intensive care unit. Fluctuations of SjO2 (> 10% within 30 min), which were not included by therapeutic measures, were classified by off-line analysis as irregular-isolated or irregular-combined, if accompanied by similar fluctuations of ICP and arterial blood pressure. Recordings which were unreliable due to technical reasons, mainly because of wall adherence of the tip of the fibreoptic catheter, were evaluated separately. Episodes of cerebral desaturations (SjO2 < 50%) were assessed with regard to their frequency, duration (5-10/> 10 min) and underlying mechanisms. Cerebral O2-extraction was calculated as the difference between arterial and cerebrovenous O2-saturation and averaged for each day after trauma.

RESULTS

Mean time of measurement for each patient was 194 hrs, a total of 3106 hrs were recorded. The correlation coefficient between in-vivo and in-vitro measured SjO2 was r = 0.62 (n = 367, p < 0.001). Reliable and artifact-free measurements of SjO2 were obtained only during 58.3% of all hours. Irregular-isolated fluctuations of the SjO2 occurred in 22.2% of the hours, and technical problems in 14.5%. Erroneous readings due to irregular-combined fluctuations of the jugular-venous O2-saturation were detected in 5.0% of the time periods. A total number of 66 episodes of cerebral desaturation (SjO2 < 50%) were found in all 16 patients, 41 of them had a duration of more than 10 minutes. Cerebral hypoxia was attributed to low cerebral perfusion pressure in 35% and hypocapnia in 17%. Global cerebral O2-extraction was significantly elevated at the day of injury compared to days 1-5 after trauma (37.4% vs. 28.9%-31.9%, p < 0.05).

CONCLUSIONS

Monitoring of SjO2 in severe head injury provides an estimate of cerebral oxygen supply and may improve the assessment of therapeutic measures in these patients. The high incidence of erroneous readings of the SjO2 is a major drawback of this method. Initially after trauma, a high extraction of oxygen was found, followed by a marked decrease in the subsequent days, presumably reflecting an early, decreased cerebral blood flow and a hyperaemic flow pattern thereafter. Continuous measurements of SjO2 may contribute to advanced, organ-specific cerebral monitoring in severe craniocerebral trauma. The reliability of data, however, should be considerably improved for common clinical use.