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October 16-20, 2010 San Diego, CA Home Abstract Archive Search Abstracts 2010 Session Grid 2010 Meeting Website Policy Statements ASA Website Feedback 
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A685
October 19, 2008 2:00 PM - 4:00 PM Room Hall E2-Area M, |
| Simulating Remifentanil-Propofol Dosing Schedules That Allow Esophageal Instrumentation |
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Cris D. LaPierre, B.S., Ken B. Johnson, M.D., Talmage D. Egan, M.D. Anesthesiology, University of Utah, Salt Lake City, Utah |
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Introduction: Previous work has found that it is not possible to successfully instrument an airway and remain in the moderate sedation range when administering propofol (P) and remifentanil (R).1 However, adverse events such as respiratory depression and airway obstruction are associated with deeper sedation. Because more drug is necessary to place a bougie than is required to tolerate a placed bougie, we hypothesized that a dosing schedule exists that allows esophageal instrumentation (EI) while minimizing time at deeper sedation. Methods: Simulations were run in MatLab (Mathworks, Natick, MA). Effect site concentrations were computed using Schnider2 and Minto3 kinetics for propofol and remifentanil, respectively. Probability of response was calculated using a Greco4 construct, with the coefficients computed from data collected previously.1 For simplicity, all simulations were run for a 75 kg male 175 cm tall. [P] was always 10 mg/mL, all infusions were for 60 minutes at a constant rate, and the ratio of drugs was held constant for the duration of each simulation. Simulations were constrained to P infusion rates of 10-150 μg/kg/min (Δ10), cocktail bolus sizes of 0-20 mL (Δ1), and [R] of 0-25 μg/mL (Δ1.25). Results: Simulations demonstrated that dosing schedules exist which allow for EI while minimizing time at deeper sedation. Of the 6615 simulations run, 113 reached EI C95 in under 2 minutes, remained above it for less than 2 minutes and recovered (P(OAA/S<2) <5%) in less than 3 minutes. Bolus size has the greatest influence on time to EI C95. [R] determined the angle of ascent/descent because [P] was always 10 mg/mL. Infusion rate established the effect site concentration seen for the balance of the infusion (Fig. 1). Recovery time depended on [R] and infusion rate. Low P/high R effect site concentrations recover quicker than high P/low R ones. Discussion: Dosing schedules exist which allow for EI while minimizing time at deeper sedation. A bolus aids rapid time to EI C95 while allowing a rapid drop to EI C50. Recovery times decrease when higher R/lower P combinations are used, but an increase in airway complications was noted in the study. Continued exploration by simulation and experimentation are needed to further define a preferred drug combination and dosing schedule.[figure1]Reference: 1. ASA.2007; A18. 2. Anesth.1998; 88(5):1170-1182. 3. Anesth.1997; 86(1):10-23. 4. PharmRev.1995; 47:331-85. Anesthesiology 2008; 109 A685 |
Figure 1
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