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October 17-21, 2009 New Orleans, LA Home Abstract Archive Search Abstracts 2009 Session Grid 2009 Meeting Website Policy Statements ASA Website Feedback 
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A18
October 13, 2007 9:00 AM - 10:30 AM Room Room 302 |
| Remifentanil-Propofol Concentrations That Allow Esophageal Instrumentation yet Avoid Unconsciousness |
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Ken B. Johnson, M.D., Cris D. LaPierre, B.S., Julia L. White, R.N., Talmage D. Egan, M.D. Anesthesiology, University of Utah, Salt Lake City, Utah |
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Introduction: Measurements of loss of responsiveness (LOR) and response to esophageal instrumentation (EI) were made in volunteers over a range of predicted remifentanil and propofol effect site concentrations (Rce, Pce ). We hypothesized that there would be a set of Rce and Pce that would provide adequate conditions for EI yet avoid LOR. Methods: Following IRB approval, 24 subjects received escalating target controlled infusions that targeted Pce (0-4.2 mcg/mL) and Rce (0-6.4 ng/mL) using a crisscross design with 15 targets per subject. At each target, a blunt end 1.4 cm diameter bougie was used to mimic EI. Assessments of LOR were made using a modified Observer's Alertness and Assessment Scale. To visualize the propofol-remifentanil interaction for LOR and EI, response surfaces were built using a Logit model structure. The probability that 50% of subjects would not respond (C50 isobol) were explored over a range of Rce and Pce to identify where subjects may tolerate EI yet not lose responsiveness. Results: Out of 336 assessments, subjects tolerated EI 124 times. Of these, 92 had a LOR (32 remained conscious). Rce and Pce where EI was tolerated AND subjects were responsive ranged from 3.0-6.0 ng/mL and 0.8-1.2 mcg/mL respectively. The C50 isobol for no response to EI dips below the C50 isobol for LOR at high target remifentanil (> 3.8 ng/ml) and low target propofol (< 1.05 mcg/ml) effect site pairs (Figure 1). Discussion: No Rce and Pce pairs were identified where EI was consistently tolerated while subjects remained awake. Our response surface analysis suggested that higher remifentanil lower propofol levels led to conditions where subjects were more likely to tolerate EI while awake.[figure1] Anesthesiology 2007; 107: A18 |
Figure 1
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