Obstructive Sleep Apnea in Elective Orthopaedic Surgery

Demand for Total Knee Arthroplasty (TKA) and Total Hip Arthroplasty (THA) is increasing
steadily and is projected to continue trending upwards in the coming years. Concomitant with
that trend is the increase in prevalence of obesity. Obesity serves as a common risk factor
for osteoarthritis, obstructive sleep apnea and medical complications.

Obstructive Sleep Apnea (OSA) is defined as episodes of obstructive apneas and hypopneas
during sleep, with daytime somnolence. It occurs commonly in obese, middle age and elderly
men and has an estimated prevalence of 5% - 9%.

Pre-operative screening for elective surgical procedures is a critical component of a
successful surgical outcome. Patients with medical comorbidities ideally will undergo medical
treatment or optimization to minimize the risk peri-operatively and post-operatively.
Obstructive sleep apnea has been shown in numerous studies to be a risk factor for
cardiopulmonary complications following surgery. The contributing factors include alterations
in REM sleep post-operatively and opioid induced respiratory suppression post-operatively.

The STOP-BANG patient questionnaire is a validated patient survey that uses both objective
and subjective data to screen patients for their risk of OSA. The sensitivity of the
STOP-BANG questionnaire for moderate-to-severe OSA has been estimated as high as 97.74%.
Authors have also shown that higher STOP-BANG scores are independently associated with
increased risk for post-operative complication.

Other authors have utilized similar pre-operative questionnaires to screen for occult
pulmonary disease in patients scheduled for elective joint arthroplasty. They found a
slightly increased incidence of OSA in this population as compared with the national average,
over 50% of which were previously undiagnosed.

The American Society of Anesthesiologists task force on perioperative management of patients
with OSA published extensive guidelines aimed at reducing morbidity and mortality. Improved
diagnosis pre-operatively could aid in proper compliance with these guidelines. These
recommendations include preferential use of regional analgesia, reduction in systemic
opioids, monitoring of oxygen saturation and nonsupine posture.

The mainstay of treatment for OSA is a positive pressure airway device such as Continuous
Positive Airway Pressure (CPAP) or in severe cases Nasal Intermittent Positive Pressure
Ventilation (NIPPV). Post-operatively continuation of these treatments in patients with known
OSA is often recommended. Some authors have demonstrated reductions in Apnea-Hypopnea Index
postoperatively through the use of CPAP.

However, a recent meta-analysis evaluating the effect of pre-operative or post-operative CPAP
in patients with OSA concluded that the use of CPAP did not reduce post-operative adverse
events.

Given the projected increase in demand for joint arthroplasty, the ever-increasing incidence
of obesity, the ambiguity surrounding the topic and the potential to clinically impact
post-operative morbidity, mortality and health care costs, shows the need for further
studies.