Monitoring Procedural Sedation with End Tidal Carbon Dioxide and Bispectral Analysis
Miner, et al.

Overview: The objective of this study was to determine the feasibility of using ETCO2 and BIS monitors to obtain objective data on a patient’s level of sedation and degree of respiratory depression for use in future studies of ED PS.
 

Primary Endpoints: 1. Sedation as assessed by Observer Assessment of Alertness Scale (OAAS) and BIS 2. RD as assessed by pulse oximetry and ETCO2
 

Eligible Patients: Patients >18 years undergoing procedural sedation (PS) in the ED.
 

Study Design: Prospective, randomized clinical trial.
 

Anticipated Benefits: none.
 

Potential Risks: Risks associated with procedural sedation.
 

Research Associate’s Role:  Research Associates were responsible for setting up BIS and ETCO2 monitors on patients and for collecting vitals, BIS and ETCO2 data during the course of the sedation.
 

Physician’s Role: none
 

Number of Patients Enrolled: n = 33, propofol = 15, methohexital = 14, etomidate = 2, fentanyl w/ midozalam = 2.
 

Results:
1. BIS scores at an OAAS score of 1 (unresponsive) varied from 45-80.  No patients were noted to have an OAAS score > 4 (awake) and have a BIS score <90.  The OAAS score and the BIS score were associated by Spearman’s rank correlation (p=0.008).
2. A decrease in Etco2 waveform was noted by the clinician in four patients, with corresponding BIS scores of 45-61.  A 25% increase from baseline Etco2 was noted in 3 patients, with corresponding BIS scores of 45-52.
3. Three patients had VAS scores for pain > 15 mm post procedure.  Two of these patients had VAS scores for recall of the procedure >15 mm.  The BIS nadirs of the two patients with pain and memory of the procedure were 87 and 91.  The patient who reported pain with the procedure without memory of the procedure had a BIS nadir of 66.
 

Interpretation of Results / Affect on Clinical Practice:
It is feasible to use ETCO2 and BIS monitors to objectively measure sedation in ED PS.  Current clinical practice at Hennepin uses the Rule of 85 – 60.  If a patient is below 85 on the BIS, he or she has a high probability of not remembering the procedure.  If a patient is below 60, he or she has a high probability of respiratory depression.