Respiratory Depression on the Wards: Why Better Monitoring may be the Answer?

Ashish K. Khanna, MD

Assistant Professor of Anesthesiology Center for Critical Care Departments of General Anesthesiology and Outcomes Research Anesthesiology Institute Cleveland Clinic. 9500 Euclid Ave # G58 Cleveland, OH 44195, USA; Tel. 216-308-4948; Fax: 216-444-7360; E-mail: khannaa@ccf.org; ashish@OR.org

Although, deaths during anesthesia are rare, deaths in the post-operative period are not.¹ The third leading cause of death in the United States is mortality after surgery, during the ‘recovery and rehabilitation’ period.² The most common cause of 30-day post-operative mortality unsurprisingly, is cardiorespiratory complications.

The Agency for Healthcare Research and Quality (AHRQ) rated post-operative respiratory failureas the fourth most common patient safety event in its 2015 report. Unfortunately, there is no consensus on a true definition of respiratory depression. The incidence of respiratory depression, based on varied definitions and criteria ranges from as little as 0.3% to 17%³.

The ward (regular nursing floor) is usually a place of comfort for clinically stable patients. Continuous post-operative oxygen saturation in non-cardiac surgical patients was monitored for upto 48 hours after surgery. This monitoring started once the patient left the PACU or the ICU and reached the regular nursing floor. Importantly, bedside care providers were blinded to this oximetry. The nurses continued their routine checks on vital signs every 4 hours per protocol. Post-operative hypoxemia was common, serious, and prolonged. For example, 20% of patients demonstrated an average of 10 minutes of saturation <90% per hour over their entire hospitalization. And soberingly and rather shockingly, 90% of serious hypoxemic episodes (saturation <90% for ≥1 full hour) were completely missed by nurses conducting routine vital sign monitoring at 4-hour intervals.⁴

Patients continue to decompensate on the ward, resulting in emergency medical team activation and transfer to higher levels of care. Not only is post-operative hypoxemia common, unforeseen and persistent but unfortunately it remains difficult to predict. Surprisingly, a closer look at a vulnerable population, that with obstructive sleep apnea using the STOP-Bang scores (a validated measure of obstructive sleep apnea risk) showed that these scores were not associated with the amount of post-operative oxygen desaturation.⁵ Narcotics, are the stated culprit for a lot of emergent floor to ICU transfers. A recent closed claims analysis examined postoperative opioid induced respiratory depression.⁶ Sadly, atleast 77% of patients suffered death or severe brain damage. As our work has suggested previously, only 9% had abnormal STOPBANG scores. We examined the association of the type of narcotic (long- vs. short-acting) in patient controlled analgesia (PCA) systems and saw that the risk of hypoxemia was not reduced by using short-acting opioids.⁷ Using easily available information, it is not possible to reliably predict which post-operative inpatients will desaturate, or the severity of their hypoxemia.

Lee et al⁶ also showed that almost all of opioid induced respiratory depression events were deemed preventable with better monitoring and response. Importantly, 42% of these episodes occurred within 2 hours of the last nursing check. Monitoring may thus be the answer, but what, who and how to monitor are important facets as well. Manually recorded oxygen saturation data were, on average, 6.5% higher than those recorded via automated systems in a large tertiary care medical center patient cohort.⁸ While continuous pulse oximetry on the regular ward prevents ICU transfers and decreases rescue events, it is certainly not the be all and end all of respiratory monitoring.⁹ The American Society of Anesthesiologists (ASA) recommends continuous monitoring of patients with neuraxial blocks and extended monitoring of those with obstructive sleep apnea. In addition, the guidelines from the ASA stress monitoring a combination of oxygenation and ventilation.

Either tachycardia or hypoxemia may occur early on in a struggling patient, or the two may co-exist, and they often progress to hypotension, which is strongly associated with myocardial injury and death.^10,11 As a corollary, it is well established that vital signs deteriorate 6-12 hours before cardiac and respiratory arrests occur^12,13,14which is the basis for having hospital rapid-response teams which undoubtedly save lives.¹⁵

The problem of respiratory depression on the wards (regular nursing floor) is common and dangerous. It causes many surgical patients to be transferred from the floor to the ICU – sometimes once, sometimes repeatedly. The PRediction of Opioid-induced Respiratory Depression In Patients Monitored by capnoGraphY (PRODIGY) trial ClinicalTrials.gov Identifier: NCT02811302 is a global trial that is currently underway and may help answer some of those questions. For now, though, continuous automated cardiorespiratory monitoring appears to be the only real answer. A combination of oxygenation, ventilation and a minimum hemodynamic parameter should be monitored on everyone across the board. Moving forward, optimal handling of monitors and prevention of alarm fatigue are certainly important educational pieces for our colleagues on the regular nursing floors. As anesthesiologists and intensivists, we know respiratory depression too well. Eternal vigilance is also the motto behind sound anesthesia training and care. Continuous and improved monitoring practices on the wards will help ensure a safe and secure recovery environment for our patients.

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