Association between nocturnal oxygen desaturation and ischaemic stroke outcomes

CLINICAL RATIONALE FOR THE STUDY: This study aimed to assess the association between nocturnal hypoxemia and early acute ischaemic stroke (AIS) outcomes in patients without oxygen supplementation. MATERIAL AND METHODS: One hundred and six AIS patients consecutively admitted to the stroke unit were included in this study. Baseline demographic and medical data and arterial blood saturation (SpO2) measurements during night-sleep (from 10pm to 6am) were examined for their association with stroke outcomes, including the National Institutes of Health Stroke Scale (NIHSS) score on the 7th day or differences between the NIHSS score on the 1st day and the 7th day after stroke onset. Measurements of SpO2 were made using a pulse oximeter of the Spacelabs Medical Inc. (USA) monitoring system, and the number of apnoea episodes and their duration were recorded by ECG Holter with respiration monitoring (CardioMem®, Getamed, GE). RESULTS: The study showed that age (Spearman's r = 0.207, p = 0.033) and parameters attributable to anaemia (RBC r = -0.205, p = 0.035, Hb r = -0.225, p = 0.02 and HCT r = -0.196, p = 0.044), atrial fibrillation and ischaemic changes in both brain hemispheres (p = 0.023 and 0.01, respectively) were correlated with the study outcomes. In terms of saturation parameters, we demonstrated that the 'total desaturation burden' (i.e. 100% minus actual measured SpO2% x apnoea duration) and multiple apnoeas of longer than 20 seconds were correlated with worse functional outcomes. Measures of shorter desaturation episodes (i.e. SpO2 oxygen desaturation index (ODI) at 3% and 4%, and time-weighted desaturations below the determined thresholds (SpO2 from 95% to 85%) demonstrated non-significant associations with the study outcomes. CONCLUSIONS AND CLINICAL IMPLICATIONS: This study demonstrated that long-lasting desaturation episodes during the night, depicted by the 'total desaturation burden', were correlated with worse functional outcomes in AIS, while measures of shorter desaturation episodes were not correlated. In future clinical trials, indications for oxygen supplementation should include the methodology of personalised medicine and introduce individual approaches based on specially formulated, novel multifactorial algorithms.