Nocturnal cerebral oxygenation in relation to vital parameters in acute stroke.

Background: Stroke is the third leading cause of death in the world. Admittance to a specialized hospital ward (so called Stroke Unit) is proven beneficial for outcome after acute stroke. So far it is unclear what exactly the rationale behind this specialized care is. Damaged brain tissue and vessels cannot compensate for drops in blood pressure and oxygenation (so called impaired cerebral autoregulation). Vital parameters are frequently measured and corrected on the Stroke Unit to optimize brain perfusion and oxygenation. Near-infrared spectroscopy (NIRS) provides a non invasive method of continuously monitoring cerebral oxygenation. The aim was to measure nocturnal vital parameters and cerebral oxygenation in the frontal areas in acute stroke patients to see whether nocturnal fluctuations of NIRS (rSO2) occur and differ between hemispheres. Furthermore we investigated whether fluctuations are related to variations in vital parameters. Method: Observational ‘pilot’ study. 8 acute anterior stroke patients were monitored within 24 hours after onset overnight. The NIRS optodes were attached bifrontally. Saturation and mean arterial pressure (Map) were measured continuously, Map was recorded with an ambulatory blood pressure device (Portapres). Statistics: Pearson or Spearman correlations are applied to evaluate the degree of association (NIRS L and R with Map (Mx) and SpO2 (Sx)). The Wilcoxon signed rank test is used to compare vital parameters (Mx and Sx analysis) with NIRS to see if there are hemispherical differences (non affected versus affected hemisphere, non-lacunar versus lacunar infarction). Results: In our patients Mx was slightly higher in the affected hemispheres, however the difference was not significant. The Sx was non-significantly higher in the non affected hemispheres. Subgroup analysis showed a slight higher trend for type of infarction, atrium fibrillation and hypertension in the non affected hemisphere. Creating subgroups with or without hypertension, diabetes and atrium fibrillation did not provide any new insights. Patients with a higher NIHSS displayed a wider difference between affected and non affected hemisphere in the Mx. In older patients a lower Mx was observed. The Sx analysis follows in opposite direction of Mx, especially in non lacunar infarctions (Mx high, Sx low). Studying the Mx and Sx of each patient separate, it seems that with lacunar infarctions both correlation indices follow one another with a narrow range. For the non lacunar infarctions this was less clear. Conclusions: NIRS offers a continuous, non invasive monitoring measurement of cerebral oxygenation in real time at bedside in acute stroke patients. Combining NIRS with other vital parameters offers new insights in cerebral autoregulation after acute stroke. In this pilot correlation study with a diversity of patients, we found small differences between affected and non affected hemispheres, infarct type and stroke severity, which needs further inclusion of patients. The correlation indices Mx and Sx seem promising ways to evaluate the state of cerebral autoregulation in two hemispheres in acute stroke patients over time.