|
|
October 16-20, 2010 San Diego, CA Home Abstract Archive Search Abstracts 2010 Session Grid 2010 Meeting Website Policy Statements ASA Website Feedback 
Visit Anesthesiology.org |
| Previous Abstract | Next Abstract |
| Printable Version |
|
A1054
October 20, 2009 8:00 AM - 9:30 AM Room Room 356 |
| Pharmacokinetic Optimization of Post-Surgery Wake Up and Analgesia for Propofol and Remifentanil |
|
**
Carl Tams, B.S., Noah Syroid, M.S., Ken Johnson, M.D., Talmage Egan, M.D., Dwayne Westenskow, Ph.D. Anesthesiology, University of Utah, Salt Lake City, Utah |
|
Intro - Differences in anesthetic technique when using propofol, remifentanil and fentanyl can result in different emergence and nociception outcomes. After surgery, a brief emergence period combined with an extended duration of analgesia is desired. We propose to use pharmacokinetic (PK) [1,2] and pharmacodynamic (PD) [3, 4] models to find optimized ratios of propofol and remifentanil that may shorten emergence time and extend the time until inadequate analgesia is experienced during patient recovery. Modeling has been used to find the optimum effect site concentrations (CEFFs) for rapid wake up;[5] however, an optimization technique which also accounts for analgesic effect is desirable.
Method - Anesthesiologists gave general anesthesia to 20 patients for laparoscopic procedures using propofol, remifentanil, and fentanyl using a standard of care anesthetic technique. Baseline model predictions for CEFFs were calculated for remifentanil, fentanyl, and propofol. PD response surface models were used to calculate the probabilities of unconsciousness and response to noxious stimulus (30 PSI tibial pressure algometry, a surrogate of postoperative pain) during and after the anesthetic. Post-hoc optimized PK and PD model predictions were made for both sedation and analgesia by varying the ratio of propofol and remifentanil CEFFs, constrained to the same or higher PD model predicted probabilities, and leaving fentanyl CEFFs unchanged from baseline. For each patient, optimized changes to the recorded propofol and remifentanil infusions were made every 5 minutes during the general anesthetic. The theoretical improvement provided by the optimization was measured by comparing the time differences between the baseline model predictions and the optimized prediction of the emergence time and time to inadequate analgesia. Results - The average surgical time was 165 ± 96 minutes. Figure 1 shows the expected emergence and time to inadequate analgesia for both baseline and optimized simulations. The baseline model predictions found an average emergence time of 8.2 ± 5.6 minutes after end of surgery and a duration of analgesia of 9.9 ± 13.6 minutes after patient emergence. The optimized remifentanil and propofol CEFFs theoretically reduced the emergence time to 3.9 ± 1.6 (p < 0.01, t-test) minutes and increased the duration of adequate analgesia to 15.4 ± 12.5 (p < 0.05, t-test) minutes.[figure1]Discussion - Optimized ratios of propofol and remifentanil, resulted in a theoretically shorter emergence time and a longer period of adequate postoperative analgesia. These results require clinical verification in a new study, but the optimization algorithm shows potential promise for real-time clinical guidance in drug management. 1 Anesthesiology 1998: 88(5) 1170-82 2 Anesthesiology 1999: 90(6) 1502-16 3 Kern S; Opioid-Hypnotic Synergy. Anesthesiology 2004. 100; 1373-81 4 Johnson KB, Anesth Analg. 2008 Feb; 106(2):471-9 5 Vuyk J; Propofol Anesthesia Opioid Selection. Anesthesiology 1997. 87: 1549-62. From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists. |
Figure 1
 |