Risk factors, mechanisms and therapy for postoperative nocturnal desaturations

睡眠中严重的术后低氧血症可能增加术后心血管并发症的风险。我们研究了术后夜间饱和度下降的危险因素和机制，并评估了氧疗治疗的有效性。我们对接受大手术的患者在术前和术后第二天至第四天之间的一个晚上进行了夜间血氧测定。我们计算了血氧饱和度参数，如氧饱和度下降指数（ODI：h^<-1>），定义为低于基线4%的氧饱和度下降次数，SpO^2&lt;90%的时间百分比（CT <90>%）和最低SpO^2。术后ODI无明显变化，但CT_<90>（1/2）和最低SpO_（1/2）明显升高，对术后去饱和度可能的危险因素进行多因素分析，发现术前ODI和其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的存在是术后睡眠严重去饱和度发展的重要危险因素。尽管对SDB患者术后给予氧疗改善了夜间睡眠质量，由于反复的上呼吸道阻塞，没有消除氧合、心率变异性。在重度SDB患者中，氧疗并不能消除夜间饱和度降低的事件，在某些情况下呼吸暂停的持续时间延长。这表明氧疗可能不适合治疗术后夜间去饱和。

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.