Pain management/original researchDoes End Tidal CO2 Monitoring During Emergency Department Procedural Sedation and Analgesia With Propofol Decrease the Incidence of Hypoxic Events? A Randomized, Controlled Trial
Introduction
Procedural sedation and analgesia for the management of acute procedural pain and anxiety in the emergency department (ED) is part of core competency in emergency medicine.1 The American College of Emergency Physicians and the American Society of Anesthesiology recommend continuous monitoring of pulse rate and rhythm, respiratory rate, blood pressure, and pulse oximetry during moderate and deep sedation.2, 3
The use of real-time capnography as an adjunct to current procedural sedation safety and monitoring practice is under increasing scrutiny. Capnography noninvasively measures the partial pressure of carbon dioxide in exhaled breath and is tightly correlated with arterial CO2 in patients with normal lung function. Capnography is a well-researched technology that has been used in anesthesia practice for patient safety monitoring for more than 35 years.4, 5
Minute ventilation is depressed by sedatives by reducing respiratory rate or tidal volume.6 Respiratory depression may produce hypercapnia (respiratory rate is affected proportionally greater than tidal volume) or hypocapnia (tidal volume is affected proportionally greater than respiratory rate).6 An absolute change from baseline of greater than 10 mm Hg or loss of the end tidal CO2 (etco2) waveform has been suggested to identify patients at risk of developing significant respiratory depression.7
There is now compelling evidence that capnography identifies respiratory depression well before the onset of hypoxia.8, 9, 10 This modality should allow physicians to intervene to improve ventilatory status. Whether physicians can use capnography to decrease sedation-associated hypoxia remains unclear.
Although pulse oximetry, pulse rate, and blood pressure monitoring are considered routine practice during ED procedural sedation and analgesia, capnography is not. If the addition of capnography helps physicians reduces hypoxia, then perhaps it should also be routine.
We determine whether physician use of real-time capnography is associated with a 15% decrease in the incidence of hypoxia compared with standard monitoring alone during ED procedural sedation with propofol.
Section snippets
Study Design
This is a prospective, randomized controlled trial conducted from November 2006 to February 2008. The institutional review board approved the study.
Setting and Selection of Participants
The study was conducted at Albert Einstein Medical Center, a 600-bed teaching hospital located in Philadelphia, PA, with an annual ED census of 75,000 patients.
We attempted to enroll consecutive (24 hours a day, 7 days a week) adults older than 18 years and selected for propofol sedation in accordance with our usual practice. Patients were excluded
Characteristics of Study Subjects
Two hundred ten patients were screened during the study period, of whom 132 composed the study group (Figure 2). Patient characteristics were similar between the 2 groups (Table 1). Hypoxia occurred in 44 subjects overall (33%; 95% confidence interval [CI] 25% to 41%).
Main Results
Although respiratory depression occurred at similar rates between groups, hypoxia was significantly more frequent in the blinded capnography group (Table 2). Seventeen patients in the nonblinded group and 27 patients in the
Limitations
We had a higher-than-expected disqualification rate, leaving slightly less than calculated 72 patients per group for analysis. However, we found a significant difference in our main outcome, and thus the study was not underpowered.
Our observed rate of hypoxia (32.5%) was higher than that observed in most other studies of propofol for ED procedural sedation.8, 10, 17 A rate of hypoxia more consistent with previous studies may have produced a smaller, nonsignificant difference between groups.
We
Discussion
Physicians performing ED procedural sedation with propofol decreased the rate of hypoxic events by using capnography in conjunction with standard monitoring. The measured difference (17%) is both statistically and clinically significant. Capnographic respiratory depression occurred before the onset of hypoxia and was temporally linked to subsequent hypoxic events.
We found that capnography was 100% sensitive for predicting hypoxia because every patient with hypoxia first exhibited capnographic
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Supervising editor: Steven M. Green, MD
Author contributions: KD, JM, and CRC conceived the study and designed the trial. KD, CRC, and PD supervised the conduct of the trial and data collection. KD, CRC, and PD managed the data, including quality control. PD and DL provided statistical advice on study design and analyzed the data. KD drafted the article. CRC and JM provided editorial support and contributed substantially to its revisions. KD takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.The Capnostream 20 was donated for research purposes by Oridian Medical, Needham, MA.
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Please see page 259 for the Editor's Capsule Summary of this article.
Publication date: Available online September 24, 2009.