Perioperative Complications and Myocardial Injury Risk in Arthoplasty Patients Suspected of Having Obstructive Sleep Apnea

Obstructive Sleep Apnea (OSA) is a common and under-diagnosed breathing disorder characterized by recurrent partial or complete collapse of the upper airway (tongue, soft palate) during sleep. It causes recurrent episodes of asphyxia (suffocation) resulting in fragmented sleep, low blood oxygen levels (hypoxemia), and high carbon dioxide concentrations. Untreated OSA is associated with serious heart/lung and metabolic diseases including strokes, diabetes, and heart attacks.

When a patient with OSA undergoes surgery, the symptoms of OSA are exacerbated afterwards due to the effects of anesthesia and related medications such as those used for pain control. This puts patients at higher risk for complications and necessitates nursing care and monitoring that are resource intensive. In many hospitals, patients with an OSA diagnosis are monitored after surgery in "high acuity" wards where the nurse to patient ratio is higher than usual. These high acuity/monitored beds are often in high demand, and their unavailability may sometimes mean cancellation of surgery or prolonged patient stay in the Post-operative Recovery Room, further causing operating room backlog.

Another serious issue is that many patients do not know they actually have the OSA condition. It is estimated that up to 20% (1) of people in the general public have OSA and that 75% (2) of them are not diagnosed. When someone with OSA goes for surgery without previously being diagnosed, special precautions in care and monitoring may not be in place, until a complication develops. For this reason, this population - those most susceptible to have OSA, but with no previous formal testing for the condition - is the most at risk for complications, and is the target group for this trial.

We plan to identify the study population by screening for OSA using the STOP-BANG questionnaire. Those who score high on this 8 item screening test have high likelihood of actually having OSA if they were to undergo formal testing and diagnosis in a Sleep Lab.

We will identify cardio-respiratory complications by conducting a chart review and determine whether admission to a "high acuity" bed had any impact. As OSA patients are at higher risk for cardiovascular complications at baseline and around the time of surgery, blood test for troponin will be performed on post-op day 1 and 2 to investigate the rate of myocardial injury. With the rate of MINS (myocardial injury after non-cardiac surgery) reported to be 8% with almost 10% 30 day mortality (per VISION trial), this pilot project which focuses on arthroplasty patients with suspected OSA, will inform us of the arthroplasty surgery specific MINS risk for comparison.