Monitoring of brain tissue oxygenation following severe subarachnoid hemorrhage

The purpose of this prospective observational study was to investigate the relation between the frequency of critical neuromonitoring parameters (brain tissue pO(2), (PtiO2) less than or equal to 10 mmHg, intracranial pressure (ICP) > 20 mmHg, cerebral perfusion pressure (CPP) less than or equal to70 mmHg) and outcome after severe aneurysmal subarachnoid hemorrhage (SAH). In a prospective study on 42 patients monitoring of ICP, CPP, and PtiO2 (in the area at risk for vasospasm) was performed. All patients were primarily classified as Hunt and Hess grade 4 or with secondary deterioration to this grade. Relative proportions of PtiO2 less than or equal to 10 mmHg (n = 42), ICP > 20 mmHg (n = 25) and CPP less than or equal to70 mmHg (n = 23) were derived from multimodal neuromonitoring data sets for different time intervals, i.e. 1. the total monitoring time, 2. the total monitoring time without the last two monitoring days; 3. the second last monitoring day; and 4. the last monitoring day. Patients were divided into nonsurvivors (GOS= 1) and survivors (GOS= 3-5). For the total monitoring time, significant differences in the relative proportion of critical values were found for all neuromonitoring parameters (p < 0.05). The detailed analysis of consecutive time intervals revealed significantly increased proportions of critical values in nonsurvivors for all neuromonitoring parameters during the last day only. Additionally, ICP > 20 mmHg was significantly more frequent during the second last day (p < 0.01). For other time periods no differences were observed. We conclude, that critical neuromonitoring values are not early predictors of nonsurvival in patients suffering from severe SAH.