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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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A17
October 13, 2007 9:00 AM - 10:30 AM Room Room 302 |
| Time-Based Online Display of a Noxious Stimulus Response Index Based on Pharmacological Data |
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Peter M. Schumacher, M.Sc., Ph.D., Thomas W. Bouillon, M.D., Daniel Leibundgut, M.Eng., Volker Hartwich, C.R.N.A., Martin Luginbuehl, M.D. Department of Anesthesiology, University Hospital, Bern, Switzerland |
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Background Pharmacokinetic and (interaction) pharmacodynamic information about drugs used in anesthesia should be the basis for dosing decisions. Although tantamount for optimal drug dosing, this information is not explicitly available in the OR. Drug concentrations are good predictors for patient's response to noxious stimulation [1]. A system visualizing the hypnotic and opioid drug concentrations and relating them to the probability of a response to noxious stimulation would therefore permit a more rational dosing. A time domain [2] and a concentration domain [3] system (isoboles display) have been proposed. We describe a novel and intuitive time domain display (TDD) of interaction PD data. Methods Based on the concentration domain display (CDD) as in [3] the following requirements were defined for a TDD: 1) to use the same interaction model [4,5] as in the CDD, 2) to provide consistent information between the two displays and 3) to present the PD information in a scale of 100 (awake) to 0 (deepest anesthesia) as a Noxious Stimulus Response Index (NSRI) representing the probability of a response to noxious stimulation. The presentation of information would thus be similar as in current EEG based hypnotic depth monitors (e.g. BIS, Entropy) with the potential to relate the time axes. A prototype for simultaneous administration of propofol, remifentanil and fentanyl was verified with dosing data from a previous study. Results Standard interaction surface models can be expressed as: P=Ng/(1 + Ng), where P is the probability that a certain stimulus is tolerated, N is the "driving force" (=combined drug concentrations normalized to their respective C50s and corrected for the effect of interaction) and g is the slope factor determining the steepness of the response curve. N as defined by the sequential model [4,5] could directly be used for an implementation of a TDD. Since N is unbounded and does not fit the common mental model this would violate requirement 3. Thus the driving force N is transformed to the NSRI according to this equation: NSRI = 100*(1-(N/2.83)sl/(1+(N/2.83)sl). This yields a value of 100 in the awake patient (no drugs), whereas drug concentrations associated with a 50 or 90% probability to tolerate laryngoscopy (TOL)[4] the index values are 50 or 20 respectively with sl = 2.18.[figure1]Verification: A typical TDD trace and the distributions of the NSRI for 3 defined events in 35 general anesthesia cases where propofol was given with remifentanil and fentanyl are shown. The dark and light gray areas indicate the range between 90 and 50% TOL and 90 to 50% tolerance of shake and shout (TOSS), respectively. Conclusions The NSRI combines the hypnotic and opioid drug effect and provides meaningful information for rational drug dosing during anesthesia. References [1] Luginbuhl et al. Br J Anaesth. 2006 Mar;96(3):323-9 [2] Syroid et al. Anesthesiology. 2002 Mar;96(3):565-75 [3] Schumacher et al. Anesthesiology. 2004; 101: A504 [4] Bouillon et al. Anesthesiology. 2004 Jun;100(6):1353-72 [5] Bouillon et al. Anesthesiology. 2004; 101: A503. Anesthesiology 2007; 107: A17 |
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