Ictal hypoxemia: A systematic review and meta-analysis

Purpose: To estimate the incidence of ictal hypoxemia (IH) and to identify clinical and study-related factors modulating the estimate. Methods: We searched articles recording concurrent peri-ictal and ictal EEG and SpO2 in adults and children with epilepsy. Studies reporting the total number of seizures recorded and the number of seizures with IH were included in a random-effects meta-analysis. A random-effects meta-regression was used to identify variables affecting study heterogeneity. Results: Twenty-one studies, including 917 participants and 1840 with SpO2 data available were included. The meta-analysis showed a pooled incidence of IH of 35/100 seizures (95% CI 27-44). SpO2 desaturation threshold was associated with the incidence of IH, with less severe desaturations resulting in higher IH frequencies. The incidence of IH was 41/100 seizures (95% CI 29-54) for adults and 47/100 seizures (95% CI 15-78) for tonic-clonic seizures. The meta-regression showed that SpO2 desaturation severity was the sole variable significantly correlated with the incidence of ictal hypoxemia (p = 0.00). Conclusion: In a population with refractory epilepsy IH is a frequent phenomenon, especially in adults and in patients presenting with tonic-clonic seizures. The severity of IH appeared independent from the age group and from seizure type and is probably the major clinical concern for its correlation with potentially life-threatening cardiorespiratory alterations and sudden unexpected death in epilepsy (SUDEP).