From the Guidelines
Patients with obesity hypoventilation syndrome (OHS) should be monitored post-operatively with continuous pulse oximetry, end-tidal CO2 monitoring, and frequent clinical assessments for the first 24-48 hours post-surgery, with a focus on minimizing opioid use and optimizing respiratory mechanics. The most recent and highest quality study, published in 2022 1, emphasizes the importance of careful post-operative management in patients with OHS, who are at increased risk of respiratory complications. Key recommendations include:
- Positioning patients with the head of bed elevated 30-45 degrees to optimize respiratory mechanics
- Continuing home non-invasive positive pressure ventilation (NIPPV) therapy as soon as possible after surgery, typically using home CPAP or BiPAP settings
- Titration of supplemental oxygen to maintain SpO2 between 88-92%, as excessive oxygen may suppress respiratory drive in these patients
- Regular arterial blood gas measurements to monitor for hypercapnia
- Early mobilization, with patients encouraged to ambulate as soon as medically appropriate
- Pain management emphasizing multimodal approaches with minimal opioid use, such as scheduled acetaminophen, NSAIDs if not contraindicated, and regional anesthesia techniques when possible. These recommendations are supported by the pathophysiology of OHS, which involves decreased respiratory drive, increased work of breathing due to excess weight on the chest wall, and potential upper airway obstruction, all of which can be exacerbated by anesthesia, sedatives, and the supine position during recovery. Additionally, the American Thoracic Society clinical practice guideline published in 2019 1 suggests that patients with OHS should be treated with positive airway pressure (PAP) therapy during sleep, and that weight-loss interventions that produce sustained weight loss of 25-30% of actual body weight may be beneficial in achieving resolution of hypoventilation.
From the Research
Monitoring Obesity Hypoventilation Syndrome (OHS) Post-Operatively
- The management of mechanical ventilation in obese ICU patients is one of the most challenging problems facing respirologists, intensivists, and anesthesiologists 2
- Monitoring the adequacy of spontaneous breathing is a major patient safety concern in the post-operative setting, particularly for obese patients who are at a higher risk for post-surgical respiratory complications 3
- Obese patients have greater variability in ventilation post-operatively when treated with standard opioid doses, and despite overall higher ventilation, many of them are still at risk for hypoventilation 3
Best Practices for Monitoring OHS Post-Operatively
- Cautious selection of the type of anesthesia, use of apneic oxygenation with high-flow nasal cannula during laryngoscopy, and better monitoring in the postanesthesia care unit (PACU) can help minimize adverse perioperative events 4
- Proper patient positioning, especially during intubation and extubation, multimodal analgesia, and cautious use of postoperative supplemental oxygen are also recommended 4
- The use of a non-invasive Respiratory Volume Monitor (RVM) can provide continuous and non-invasive assessment of respiratory function in both obese and non-obese patients 3
Importance of Preoperative Screening for OHS
- Patients with OHS are at higher risk for adverse postoperative events, and screening for OHS would require additional preoperative evaluation of morbidly obese patients with severe OSA and suspicion of hypoventilation or resting hypoxemia 4
- Better emphasis is needed on preoperative recognition of hypercapnia among patients with OSA or overlap syndrome undergoing elective noncardiac surgery 5
Consequences of Unrecognized OHS
- Patients with unrecognized OHS are more likely to experience postoperative respiratory failure, postoperative heart failure, prolonged intubation, postoperative ICU transfer, and longer ICU and hospital lengths of stay compared with patients with OSA alone 5