Featured Articles from March 2012

Perioperative Pulmonary Outcomes in Patients With Sleep Apnea After Noncardiac Surgery

Studies on perioperative outcomes in patients with sleep apnea and pulmonary hypertension are rare and existing analyses are limited primarily by insufficient sample size. Utilizing nationally representative data collected for the Nationwide Inpatient Sample, the largest all-payer database in the U.S., we were able to perform two studies determining the impact of 1) obstructive sleep apnea (OSA) and 2) pulmonary hypertension on in-hospital complications.

We determined that both orthopedic and general surgical patients suffering from OSAhad increased risk of pulmonary adverse events, including adult respiratory distress syndrome (ORs 2.39 and 1.58), aspiration pneumonia (ORs1.41 and 1.37), and the need for mechanical ventilation (ORs 5.20 and 1.95) vs. non-OSA patients. OSApatients undergoing hip or knee arthroplasty were also more likely to suffer from perioperative pulmonary embolism compared to non-OSA patients (OR 1.22).

When matching patients with pulmonary hypertension with those without the disease, the former exhibited significantly higher perioperative rates of complications and mortality. These findings confirm the long held believe amongst clinicians, that patients with OSA and pulmonary hypertension indeed represent at risk populations in the surgical setting.

They further support the hypothesis, that increased rates of pulmonary hypertension and right heart dysfunction among OSA patients may explain worse outcomes, especially in the orthopedic patients. Here, embolization of bone marrow and cement during instrumention of the joint may lead to increased risk of lung injury, and worsening of right heart dysfunction resulting in chamber dilatation, venostasis and subsequently increased risk for thromboembolism.


Obstructive Sleep Apnea and Incidence of Postoperative Delirium After Elective Knee Replacement in the Nondemented Elderly

Editorial: Bateman B, Eikermann M. Anesthesiology 2012;116: AprilDOI:10.1097/ALN.0b013e31824b96e11

Can we predict whether a patient will develop postoperative delirium? 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” the authors studied 106 healthy patients ≥ 65 years undergoing elective knee replacement surgery. They excluded patients with dementia and other central nervous system disorders. Despite patient exclusion, 25% developed postoperative delirium (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 had recovered by day 3. Obstructive sleep apnea (OSA) was the only significant predictor using multivariate analysis. Patient with delirium also had lower hemoglobin values but hemoglobin value was not retained in the multivariate analysis. In the accompanying editorial, “Obstructive Sleep Apnea Predicts Adverse Perioperative Outcome. Evidence for an Association between Obstructive Sleep Apnea and Delirium”, those authors noted that the mechanisms for the association betweenOSA and POD was 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 decrease the incidence of POD? More research is needed.