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Predicting Apnea in Sedation

October 12, 2016

Short Attention Span Summary

Apnea (defined as 15 seconds of EtCO2 <10mm Hg) occurred in half of the procedural sedations in this study, but only 25% required clinical interventions, the majority of which were minor.  Apnea was predicted by EtCO2 – either <30 or >50mm Hg.  Clinical interventions were predicted by apnea, abnormal SpO2, or use of propofol.  Older age predicted both apnea and need for clinical interventions.

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Be careful sedating old people.  Use EtCO2 as an early warning system.  Be extra careful with propofol so things don’t go Bad – you want sedations to be mundane, not a Thriller.

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Ann Emerg Med. 2016 Aug 21. pii: S0196-0644(16)30379-1. doi: 10.1016/j.annemergmed.2016.07.010. [Epub ahead of print]

Characteristics of and Predictors for Apnea and Clinical Interventions During Procedural Sedation.

Krauss BS1, Andolfatto G2, Krauss BA3, Mieloszyk RJ4, Monuteaux MC5.

Author information:

1Division of Emergency Medicine, Boston Children’s Hospital, Department of Pediatrics, Harvard Medical School, Boston, MA. Electronic address: baruch.krauss@childrens.harvard.edu.

2University of British Columbia Department of Emergency Medicine, Lions Gate Hospital, North Vancouver, British Columbia, Canada.

3University of Massachusetts, Boston, MA.

4Institute for Medical Engineering and Science and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA.

5Division of Emergency Medicine, Boston Children’s Hospital, Department of Pediatrics, Harvard Medical School, Boston, MA.



We describe the characteristics of and predictors for apnea and clinical interventions during emergency department (ED) procedural sedation.


High-resolution data were collected prospectively, using a convenience sample of ED patients undergoing propofol or ketofol sedation. End tidal CO2 (etco2), respiratory rate, pulse rate, and SpO2 were electronically recorded in 1-second intervals. Procedure times, drug delivery, and interventions were electronically annotated. Kaplan-Meier curves were used to describe the onset of clinical interventions as a function of sedation time. The onset of apnea (15 consecutive seconds with carbon dioxide ≤10 mm Hg) and clinical interventions were estimated with a series of Cox proportional hazards survival models, with time to first apnea or clinical intervention as the dependent variable. Finally, we tested the association between apnea and clinical intervention.


Three hundred twelve patients were analyzed (53% male patients). Apnea was preceded by etco2 less than 30 mm Hg or greater than 50 mm Hg at 30, 60, and 90 seconds before its onset. Clinical interventions were predicted by apnea, SpO2, and propofol use. Increasing age predicted both apnea and interventions. Apnea was not predicted by respiratory rate or SpO2. Apnea occurred in half of the patients and clinical interventions in a quarter of them. Clinical intervention was not predicted by abnormal respiratory rate or abnormal etco2 level. The majority of clinical interventions (85%) were minor, with no cases of assisted ventilation, intubation, or complications.


Alterations in etco2 predicted apnea along a specific time course. Alterations in SpO2, apnea, and propofol use predicted clinical interventions. Increasing age predicted both apnea and clinical intervention.

Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

PMID: 27553482 [PubMed – as supplied by publisher]

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