Unrecognized hypoxia and respiratory depression in emergency department patients sedated for psychomotor agitation: pilot study.

INTRODUCTION: The incidence of respiratory depression in patients who are chemically sedated in the emergency department (ED) is not well understood. As the drugs used for chemical restraint are respiratory depressants, improving respiratory monitoring practice in the ED may be warranted. The objective of this study is to describe the incidence of respiratory depression in patients chemically sedated for violent behavior and psychomotor agitation in the ED.

METHODS: Adult patients who met eligibility criteria with psychomotor agitation and violent behavior who were chemically sedated were eligible. SpO2 and ETCO2 (end-tidal CO2) was recorded and saved every 5 seconds. Demographic data, history of drug or alcohol abuse, medical and psychiatric history, HR and BP every 5 minutes, any physician intervention for hypoxia or respiratory depression, or adverse events were also recorded. We defined respiratory depression as an ETCO2 of ≥50 mmHg, a change of 10% above or below baseline, or a loss of waveform for ≥15 seconds. Hypoxia was defined as a SpO2 of ≤93% for ≥15 seconds.

RESULTS: We enrolled 59 patients, and excluded 9 because of ≥35% data loss. Twenty-eight (28/50) patients developed respiratory depression at least once during their chemical restraint (56%, 95% CI 42-69%); the median number of events was 2 (range 1-6). Twenty-one (21/50) patients had at least one hypoxic event during their chemical restraint (42%, 95% CI 29-55%); the median number of events was 2 (range 1-5). Nineteen (19/21) (90%, 95% CI 71-97%) of the patients that developed hypoxia had a corresponding ETCO2 change. Fifteen (15/19) (79%, 95% CI 56-91%) patients who became hypoxic met criteria for respiratory depression before the onset of hypoxia. The sensitivity of ETCO2 to predict the onset of a hypoxic event was 90.48% (95% CI: 68-98%) and specificity 69% (95% CI: 49-84%). Five patients received respiratory interventions from the healthcare team to improve respiration [Airway repositioning: (2), Verbal stimulation: (3)]. Thirty-seven patients had a history of concurrent drug or alcohol abuse and 24 had a concurrent psychiatric history. None of these patients had a major adverse event.

CONCLUSION: About half of the patients in this study exhibited respiratory depression. Many of these patients went on to have a hypoxic event, and most of the incidences of hypoxia were preceded by respiratory depression. Few of these events were recognized by their treating physicians.