Journal of clinical monitoring and computing
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J Clin Monit Comput · Jul 1998
Hydraulic analog for simultaneous representation of pharmacokinetics and pharmacodynamics: application to vecuronium.
To facilitate teaching the pharmacologic determinants of clinically observed drug effect, we expand on the hydraulic representation of the pharmacokinetics and pharmacodynamics of intravenous drugs. ⋯ In the described hydraulic analog, fluid delivered into a central reservoir is representative of drug infusion, and the heights of the fluid columns in the central and peripheral reservoirs are representative of the drug concentrations in the corresponding pharmacologic compartments. The height of the fluid column in an 'effect reservoir' is representative of the apparent effect site concentration in a simultaneous pharmacokinetic-pharmacodynamic model. A non-linear scale on the effect reservoir represents the relationship between the effect site concentration and the clinical effect. Reservoir surface areas are equivalent to volumes of distribution and hydraulic resistances are inversely proportional to drug clearances. The proof of mathematical equivalency of the presented analog to simultaneous pharmacokinetic-pharmacodynamic models is given in an appendix. ILLUSTRATION OF THE EDUCATIONAL APPLICATION: The effect window can represent monitored twitch response following the administration of a neuromuscular blocking agent. Using pharmacokinetic-pharmacodynamic parameter values for vecuronium, we demonstrate how the hydraulic analog can be used to explain the priming principle and the clinically observed time-course disparity of two effect sites: the larynx and the adductor pollicis. (A companion web site: http://www.anest.ufl.edu/ha.html presents an interactive animation of the described analog.)
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J Clin Monit Comput · Jul 1998
Letter Randomized Controlled Trial Clinical TrialEffect of ketamine on bispectral index and levels of sedation.
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J Clin Monit Comput · Jul 1998
Sensitivity of near infrared spectroscopy to cerebral and extra-cerebral oxygenation changes is determined by emitter-detector separation.
To examine the effect of two emitter-detector separations (2.7 and 5.5 cm) on the detection of changes in cerebral and extra-cerebral tissue oxygenation using near infrared spectroscopy (NIRS). ⋯ The differing sensitivity of the proximal and distal channels to changes in cerebral and extracerebral oxygenation is compatible with theoretical models of NIR light transmission in the adult head and may provide a basis for spatially resolving these changes. The optimal emitter-detector separation for adult NIRS requires further investigation and may differ between individuals.