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A515
October 18, 2009 1:00 PM - 2:30 PM Room Room 357 |
| A Preliminary Clinical Evaluation of a Pharmacokinetic-Pharmacodynamic Display |
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* Noah D. Syroid, M.S., Ken B. Johnson, M.D., Dwayne R. Westenskow, Ph.D., Robert W. Albert, M.A., Talmage D. Egan, M.D. Anesthesiology, University of Utah, Salt Lake City, Utah |
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Introduction:
We have developed a real-time graphical presentation of anesthetic pharmacology. The display improves upon a previously developed prototype[1] and is intended for use by anesthesiologists to predict the probability of response to verbal-tactile stimulation, tracheal intubation and postoperative pain. The display is based on pharmacokinetic-pharmacodynamic models that include sedative-opioid interactions, which when run in faster than real time, allows the anesthesiologist to anticipate needed changes in anesthetic technique. It is hypothesized that use of the display alters anesthetic management at the end of the anesthetic. Methods: The display was evaluated during 30 anesthetics for patients undergoing abdominal, gynecological, and extremity surgeries. For half of the anesthetics, the resident and attending anesthesiologist were able to view the display and titrate anesthesia accordingly to their judgment. The display was not shown for the remaining half of the anesthetics. Anesthesia consisted of a propofol and fentanyl induction. Maintenance was with isoflurane and fentanyl. The model predicted probabilities of sedation and the predicted drug effect site concentrations (Ce) were recorded and compared at the end of surgery. A repeated measures ANOVA was used to assess differences in model predicted probabilities in the "with display" and "without display" groups from 5 minutes before end of surgery to 5 minutes after the end of surgery. Resident anesthesiologists were surveyed on their perceived workload (NASA-TLX)[2] encountered during the anesthetics and their perceptions of the display's utility. Results: Fourteen attending and 14 resident anesthesiologists participated in the study. From 5 minutes before to 5 minutes after the end of surgery, the probability of unconsciousness was significantly lower in the display group (F(1,28) = 5.3, p<0.03, Fig. 1A). At end of surgery, the predicted fentanyl Ce was higher with the display (2.0 ± 0.8 ng/ml with versus 1.5 ±0.5 ng/ml without, p<0.04), while the predicted isoflurane Ce was lower (0.4±0.1% with versus 0.6±0.2% without, p<0.01). See Fig. 1B. There were no differences in perceived workload, and residents identified the display's usefulness as favorable.[figure1] Discussion: Use of the display altered clinical practice. With the display, the results indicate an earlier downward titration of sedation levels near the end of surgery while maintaining a higher fentanyl Ce. The display did not increase residents' perceived workload; they viewed the display's clinical usefulness positively. These results are consistent with previous simulation-based studies of the display.[1,3] [1] Syroid et. al. Anesthesiology. 2002 Mar;96(3):565-75. [2] Hart SG and Staveland LE. In: Human Mental Workload. 1988:239-250. [3] Drews et. al. Hum Factors. 2006;48(1):85-94. From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists. |
Figure 1
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