To the Editor:
The characterization by Dahan et al. 1of overt opioid-induced respiratory depression (OIRD) requiring intervention in postoperative patients as rare and uncommon is troubling.
“Failure to Rescue” and postoperative respiratory failure (also known as Code Blue) are the first and third most common patient safety-related adverse events affecting the Medicare population in U.S. hospitals, accounting for 113 events per 1,000 at-risk patient admissions, and they result in death or anoxic brain injury in the majority of cases.*The resuscitation literature suggests that the most common antecedent vital sign abnormality to a cardiopulmonary arrest is respiratory in nature, and the worst outcomes often occur on the general care floor (GCF) and in patients whose preexisting morbidity score is low.2–4Fifty percent of Code Blue events involve patients receiving opioid analgesia.5
Diagnosing narcotic overdoses in hospitalized patients is difficult and often missed; yet, this circumstantial evidence implicating opioids in serious adverse events in the resuscitation literature is not apparent in the anesthesia literature. This may be because the anesthesia literature myopically focuses on surrogate measures of respiratory depression such as respiratory rate and Spo2. These measures not only provide very “limited information” and are “loose indicators” of ventilatory adequacy, as acknowledged by Dahan et al. , but our literature also suffers from a lack of standardization, uses arbitrary threshold criteria, and predominantly comprises retrospective analysis of intermittent and manually charted data.6As such, these data are unreliable when compared with automated and continuous vital sign measurements, are prone to undersampling, and are likely underpowered to “connect the dots” with regard to the outcomes in the resuscitation literature.
Our failure on the GCF is not one of “rescue” but of “recognition.” OIRD is a preventable adverse event, and 78% of cardiac arrests on the GCF are deemed avoidable in root cause analysis.3The odds of a potentially avoidable cardiac arrest were five times higher on the GCF than in an intensive care setting, and outcomes are worst during periods of decreased vigilance, such as nights and weekends.7,8Recent vital signs, such as a respiratory rate, are missing in as many as 75% of patients for whom a Code Blue or a rapid response team is summoned.9
The Anesthesia Patient Safety Foundation convened a symposium in 2006 on the dangers of postoperative opioids, and the consensus opinion was that OIRD remains a significant and preventable threat to patient safety for which institutions must have zero tolerance.†In recognition of the gravity of the problem, the 2011 edition of a preeminent nursing text on monitoring patients on opioids recommends that the monitoring interval for vital signs GCF could be greatly reduced, despite the additional burden imposed on the GCF nursing staff.10
Three demographic trends are likely to make OIRD more prevalent in the future. The population is aging and obesity is more common, both of which predispose patients to obstructive sleep apnea. Recurrent airway obstruction due to opioid-mediated suppression of the arousal response and the upper airway dilators is the predominant feature of respiratory compromise in postoperative patients with obstructive sleep apnea.11Chronic opioid use for both medical and nonmedical reasons is escalating, and these patients are predisposed to have ataxic breathing patterns and frequent central apneas.12This predisposition in combination with the higher opioid doses and multimodal opioid therapy they require for adequate pain relief places them at an increased risk of respiratory compromise. Yet, the irregular breathing patterns and transient desaturations that precede respiratory decompensation in these patients are unlikely to be detected by intermittent respiratory rate and Spo2measurements.
Improved understanding by clinicians of the complex pharmacologic nuances of opioids and expanded use of multimodal, opioid-sparing analgesic techniques are important contributors to reducing OIRD. But recognition of the scope of OIRD and improving its detection remain pressing unresolved issues in postoperative pain management.
Medical University of South Carolina, Charleston, South Carolina. overdykf@musc.edu
