Determination of Respiratory Depression Measured by Capnography of Acutely Intoxicated Patients Presenting to an Urban Emergency Department
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INTRODUCTION: The standard of care for monitoring the respiratory status of patients with altered sensorium until recently has been pulse oximetry and observation. While pulse oximetry measures peripheral arterial oxygen saturation, it does not adequately detect hypoventilatory status. We hypothesized that intoxicated patients would demonstrate clinically significant signs of hypoventilation and that ETCO2 monitoring may detect these changes earlier than pulse oximetry. METHODS: This was a pilot observational data collection study of intoxicated patients presenting to a single urban emergency department between June 6, 2014 and August 1, 2014. Research assistants (RA's) monitored the ED tracking board for patients presenting with chief complaints suggesting possible intoxication with drugs or alcohol. Patients eligible for enrollment were between age 18-80 years, had a baseline Rikers Sedation Agitation Scale Score of < 3 and the treating ED physician believed that the patient's altered mental status was "possibly" or "probably" related to use of an intoxicant. Vital sign data and end-tidal CO2 readings were collected at Baseline, 30, 60, 90 and 120 minutes then hourly there after. End points for data collection were: 1) demonstration of alertness for at least 60 consecutive minutes 2) disposition to home or another hospital department or 3) decompensating respiratory status requiring bi-pap, c-pap or intubation. RESULTS: Seven hundred ninety four patients were screened. Thirty-five met all enrollment criteria and were assigned a de-identified patient number. Six patients were excluded from the final data analysis (5 for critical errors in ETCO2 data collection and 1 had AMS of non-intoxication etiology). Of the remaining 29 patients, 20 were male, 9 female. Ages ranged from 19-54 yrs. Alcohol was one of the intoxicants in almost half of patients. Other intoxicants included benzodiazepines, synthetic cannabinoids, cocaine, heroin and diet pills. Some patients had exposure to more than one intoxicant. ETCO2 values of > 45 mmHg were considered indicators of hypoventilatory state. There were a total of 19 episodes of hypoventilatory status as indicated by ETCO2 > 45 mmHg. Of the patients with multiple episodes (> 2) of hypoventilatory status, two had used heroin, one 62 mg lorazepam. Pulse oximetry reflected a normal oxygen saturation during at least 6 of the episodes. CONCLUSION: ETCO2 may detect hypoventilatory status before pulse oximetry and should be standard of care in patients presenting with intoxication associated with CNS depression.