Risk factors, mechanisms and therapy for postoperative nocturnal desaturations

术后睡眠期间严重的低氧血症可能增加术后心血管并发症的风险。我们检查了术后夜间去饱和的危险因素和机制，并评估了氧治疗的有效性。我们对接受大手术的患者术前进行了夜间血氧测定，并在术后第2天至第4天进行了夜间血氧测定。我们计算了血氧饱和度参数，如氧去饱和指数（ODI: h^<-1>），定义为氧去饱和超过基线以下4%的次数，SpO^2<90%的时间百分比（CT_<90>, %）和最低SpO^2。术后ODI虽无明显变化，但CT_<90>及最低SpO^2加重明显。术后去饱和可能危险因素的多因素分析显示，术前ODI和他人目睹的呼吸暂停是与术后ODI高度相关的变量。我们得出结论，术前SDB的存在是术后睡眠期间发生严重去饱和的重要危险因素。虽然SDB患者术后给氧改善了夜间氧合，但由于反复上呼吸道阻塞引起的心率变异性并没有消除。在重度SDB患者中，氧疗并不能消除夜间去饱和事件，在一些病例中还延长了呼吸暂停时间。这表明氧疗可能不适用于术后夜间血饱和度过低的治疗。

Severe postoperative hypoxemia during sleep may increase the risk of postoperative cardiovascular complications. We examined risk factors and mechanisms of postoperative nocturnal desaturations, and usefulness of oxygen therapy for the treatment was evaluated. We performed overnight oximetry preoperatively and during one night between the second and fourth postoperative days in patients undergoing major surgeries. We calculated oximetry parameters such as oxygen desaturation index (ODI : h^<-1>) defined as the number of oxygen desaturations exceeding 4% below the baseline, the percentage of time spent at SpO^2<90% (CT_<90>, %), and lowest SpO^2. Postoperatively, although change of ODI was insignificant, aggravation of CT_<90> and lowest SpO^2 were significant.Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative ODI and apnea witnessed by others were the variables highly correlated with postoperative ODI.We conclude that the presence of preoperative SDB is a significant risk factor for the development of severe postoperative desaturations during sleep.Although administration of oxygen to patients with SDB postoperatively improved nocturnal oxygenation, heart rate variability due to repeated upper airway obstructions was not eliminated. In patients with severe SDB,oxygen therapy did not eliminate events of nocturnal desaturations, and prolonged duration of apnea in some cases. This indicates that oxygen therapy may not be appropriate for the treatment of postoperative nocturnal desaturations.