Sleep-disordered breathing is a risk factor for delirium after cardiac surgery: a prospective cohort study

Abstract

IntroductionDelirium is a frequent complication after cardiac surgery. Although various risk factors for postoperative delirium have been identified, the relationship between nocturnal breathing disorders and delirium has not yet been elucidated. This study evaluated the relationship between sleep-disordered breathing (SDB) and postoperative delirium in cardiac surgery patients without a previous diagnosis of obstructive sleep apnea.MethodsIn this prospective cohort study, 92 patients undergoing elective cardiac surgery with extracorporeal circulation were evaluated for both SDB and postoperative delirium. Polygraphic recordings were used to calculate the apnea-hypopnea index (AHI; mean number of apneas and hypopneas per hour recorded) of all patients preoperatively. Delirium was assessed during the first four postoperative days using the Confusion Assessment Method. Clinical differences between individuals with and without postoperative delirium were determined with univariate analysis. The relationship between postoperative delirium and those covariates that were associated with delirium in univariate analysis was determined by a multivariate logistic regression model.ResultsThe median overall preoperative AHI was 18.3 (interquartile range, 8.7 to 32.8). Delirium was diagnosed in 44 patients. The median AHI differed significantly between patients with and without postoperative delirium (28 versus 13; P = 0.001). A preoperative AHI of 19 or higher was associated with an almost sixfold increased risk of postoperative delirium (odds ratio, 6.4; 95% confidence interval, 2.6 to 15.4; P <0.001). Multivariate logistic regression analysis showed that preoperative AHI, age, smoking, and blood transfusion were independently associated with postoperative delirium.ConclusionsPreoperative SDB (for example, undiagnosed obstructive sleep apnea) were strongly associated with postoperative delirium, and may be a risk factor for postoperative delirium.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0477-1) contains supplementary material, which is available to authorized users.

Patients prone for postoperative delirium

“…Other clinically important factors identified in prospective studies were depression [28,29], preoperative pain [29], and the complex of sleep disordered breathing, including, among others, snoring, obstructive sleep apnea syndrome, and the upper airway resistance syndrome [30]. ApoE4, a marker of Alzheimer's disease, was no risk factor in surgical patients [31,32].…”

Sleep apnea – another piece of the postoperative delirium puzzle?

“…Portable sleep monitoring is relatively inexpensive and convenient but the lack of technical oversight during the study can lead to inadequate data, as was found in 19% of the recordings in this study where insufficient data resulted in the exclusion of 22 patients [1]. In addition, the inability of portable systems to monitor sleep often leads to an underestimation of the true AHI, which could affect the nature of the relationship between sleep apnea and postoperative delirium.…”

“…In this edition of Critical Care, Roggenbach and colleagues provide additional support to an association between obstructive sleep apnea (OSA) and postoperative delirium [1]. OSA has been linked to poor cardiovascular and neurologic outcomes, including cognitive dysfunction, in the outpatient setting [2,3].…”

“…Utilizing a portable limited-channel sleep monitoring system, they found that 59% of the study population had at least moderate to severe sleep apnea (apnea-hypopnea index (AHI) ≥15), and that the presence of preoperative sleep disordered breathing was associated with the development of delirium in the first 48 hours following surgery [1]. A preoperative AHI of 19 or higher correlated with a sixfold increased risk of postoperative delirium, and, after multivariate logistic regression analysis, the preoperative AHI, age, smoking and intraoperative blood transfusion remained the significant factors associated with postoperative delirium.…”

Perioperative Complications in Obstructive Sleep Apnea Patients

“…More recently, two prospective studies utilizing PSG-or HSAT-confirmed diagnoses of OSA and a standardized definition of postoperative delirium have found significant correlations between OSA and the incidence of delirium after surgery [116,117]. One investigation found the rate of delirium after orthopedic surgery to be increased 2.5 fold if OSA was present [117], while the other noted a sixfold increase in delirium following cardiac surgery in patients with an AHI ≥ 19 [116]. Neither study noted a correlation with hypoxemia and incidence of delirium.…”