Can we predict whether an older patient, aged 65 years or older, will develop postoperative delirium (POD)? Specifically, are there medical conditions that can help predict this condition? In the study “Obstructive Sleep Apnea and Incidence of Postoperative Delirium after Elective Knee Replacement in the Nondemented Elderly,” Dr. Madan M. Kwatra, Associate Professor, Department of Anesthesiology, Duke University Medical Center, and colleagues studied 106 healthy patients ≥ 65 years of age undergoing elective single knee replacement surgery. They excluded patients with dementia and other central nervous system disorders. Patients received either general or regional anesthesia for the procedure at the discretion of the anesthesiologist caring for the patient. The diagnosis of delirium was made by the study psychiatrist. The diagnosis of sleep apnea was confirmed in 15 patients, 12 of whom had polysomnography reports.
Despite patient exclusion, 25% developed POD, a value similar to other studies that did not have such stringent entry criteria. Delirium incidence, of mild severity, was highest on the second day after surgery, though the majority of patients had recovered by day 3. Obstructive sleep apnea (OSA) was the only significant predictor of POD using multivariate analysis. Patients with delirium also had lower hemoglobin values but hemoglobin value was not retained in the multivariate analysis. Slightly more than 50% of patients with obstructive sleep apnea developed POD.
The mechanism for the relationship between sleep apnea and postoperative delirium was not specifically studied. The authors proposed reduced oxygen metabolism, postoperative hypoxemia and an increase in proinflammatory cytokines all as possible factors that deserve future study.
In the accompanying editorial, “Obstructive Sleep Apnea Predicts Adverse Perioperative Outcome: Evidence for an Association between Obstructive Sleep Apnea and Delirium,” Drs. Brian T. Bateman (Department of Anesthesiology, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School) and Matthias Eikermann (Department of Anesthesiology, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, and Klinik fuer Anaesthesiologie und Intensivmedizin, Universitaetsklinikum Essen, Duisburg-Essen University, Essen, Germany) noted that the mechanisms for the association between OSA and POD were not directly assessed, though airway collapse leading to episodes of hypoxia may be the reason. If there is a relationship between OSA and POD, might strategies to decrease OSA also decrease the incidence of POD? As they note,
“If it turns out that OSA does cause POD and that there are effective strategies to prevent it from doing so, than the paper by Flink et al. will be a landmark in the quest to address this most challenging perioperative complication.”
More research is needed.
The American Society of Anesthesiologists offers CME credit based on this article.