Preoperative nocturnal desaturations as a risk factor for late postoperative nocturnal desaturations

Severe postoperative hypoxaemia during sleep may increase the risk ofpostoperative cardiovascular complications. We hypothesized that theseverity of hypoxic episodes after surgery are related to the presence ofpreoperative sleep-disordered breathing (SDB). We tested this hypothesis ina multicentre study designed to elucidate the major risk factors fordevelopment of postoperative nocturnal desaturations. We performedovernight oximetry before operation and for one night between the secondand fourth day after operation in 80 patients undergoing major surgery. Wecalculated oximetry variables such as oxygen desaturation index (ODI),defined as the number of oxygen desaturations exceeding 4% below baseline,percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value.After operation, although the change in ODI was not significant (P = 0.34),deterioration in CT90 and lowest SpO2 values were significant (P = 0.036and P = 0.007, respectively). Multivariate analysis of possible riskfactors for postoperative desaturations revealed that preoperativehypoxaemia and apnoea witnessed by others were highly correlated withpostoperative hypoxaemia.