Monitoring Identifies Those at High Risk for Opioid-Induced Respiratory Depression

AUTHOR: Thomas Rosenthal

Anesthesiology News

A new monitoring tool helps predict those patients on a general care floor who are at high risk for developing opioid-induced respiratory depression (OIRD).

Ashish Khanna, MD, FCCP, FCCM, an anesthesiologist, intensivist and associate professor of anesthesiology at Wake Forest School of Medicine, in Winston-Salem, N.C., presented preliminary results from the PRODIGY (PRediction of Opioid-induced respiratory Depression In patients monitored by capnoGraphY) trial. These results, presented at the Society of Critical Care Medicine’s 2019 Critical Care Congress (abstract 36), showed a 46% incidence of episodes of respiratory depression.

The incidence of OIRD in patients on a general care floor is significantly higher than what has been reported in the clinical literature, Dr. Khanna told Anesthesiology News. “This means that almost every other patient on the general care floor getting opioids is having respiratory depression episodes, which we have been missing all these years. We didn’t know the larger problem existed until five years ago, when the group from Outcomes Research at Cleveland Clinic showed that postoperative hypoxemia is common and persistent on the general care floor.

“Importantly, large registry data from the United States have shown that the overall mortality associated with acute cardiorespiratory deterioration events on the general care floor is nearly 40%,” Dr. Khanna said, adding, “The general care floor is the connection between the post-anesthesia care unit or the intensive care unit and going home. It should be a safe haven and an environment for recovery for our patients.”

Respiratory Depression Occurred in Nearly Half

The PRODIGY trial, conducted from April 2017 to April 2018 at 16 sites in the United States, Europe and Asia, investigated the incidence of OIRD using the continuous cardiorespiratory and pulse oximetry monitoring of patients’ heart rate, oxygen saturation, end-tidal carbon dioxide and respiratory rate among patients on general care floors receiving opioid therapy.

All of the PRODIGY data, which were collected using Medtronic’s Microstream and Nellcor monitoring technology, were evaluated by a four-member independent clinical committee with expertise in perioperative respiratory medicine to determine whether the respiratory depressive episodes were true OIRD events due to opioid use and not artifactual noise, Dr. Khanna explained.

The PRODIGY study found that respiratory depression occurred in 46% of patients in the study, said Dr. Khanna, noting that the figure is updated from 41.1% in the initial abstract based on continued analysis. Publication of the full results of the PRODIGY study is expected later this year.

A modified full analysis set of 1,336 patients who were administered opioids on general care floors and underwent continuous capnography and oximetry monitoring found that positive predictors of an OIRD episode (P≤0.05) included male sex, age of at least 60 years, history of chronic heart failure, history of sleep disorders and opioid-naive status, Dr. Khanna said. These positive predictors of an OIRD episode were then used as the basis for a novel OIRD risk prediction scoring tool (the PRODIGY risk score) that measures the risk for a respiratory depressive episode.

Dr. Greenberg said, “The PRODIGY study suggests that OIVI occurred in over 40% of the patient cohort when monitoring with both continuous pulse oximetry and capnography. Further studies are warranted.”

Dr. Khanna said the PRODIGY trial and risk prediction tool were developed because OIRD events among patients were being missed on general care floors. “Our current monitoring standards across the United States are insufficient to pick up these events. We monitor patients in snapshots of time every four hours,” he said. “While best practices may need us to continuously monitor all patients on the general care floor, this may not always be possible.”

The OIRD risk prediction tool can serve as a guide to identify patients at the highest risk who may benefit from continuous monitoring of at least oxygenation and ventilation, Dr. Khanna said. “Implementation of improved monitoring strategies using this tool could prevent respiratory compromise using proactive interventions upon detection of changing patterns of respiratory behavior, improve patient safety on the general care floor, and decrease the burden of rapid response calls and unplanned ICU admissions.”