The physiology and pharmacology of growing old, as shown in body simulation.

Geriatric medicine is becoming increasingly important, due to the aging of our population. Healthcare givers need methods that can teach efficiently and painlessly the complexities involved with aging. One important tool in this area comprises modeling and simulation. Accordingly, we present a detailed model and simulation of the aging process. To implement the aging process, we changed over 50 existing parameters that are part of a physiologic, pharmacologic multiple transport model of the human body. To evaluate the new patients, we imposed three stresses: anesthesia induction, hemorrhage and apnea. Five patients were used: a young healthy patient and four healthy, but elderly, patients, aged 65, 75, 85 and 95 years. We observed an age-related response to the stresses. The elderly patients fared worse with anesthetic induction and with hemorrhage, but better with apnea. Some independent data support our results.

Physiologic and chemical simulation of cyanide and sarin toxicity and therapy.

The possibility of mass terrorism has become increasingly apparent. Accurate and relevant teaching tools are needed for healthcare givers and emergency personnel of all experience. We describe one of these tools, BODY Simulation, and its use in training caregivers to respond to chemical terrorism. We have implemented two chemical agents--cyanide and sarin, the latter a nerve agent--in a detailed whole-body model and simulation. In the simulation, each agent was administered to a healthy young adult, first without therapy, then with therapy, for a total of four runs. We recorded several variables, each appropriate to the agent used. The recorded variables included physiological variables in addition to the blood and brain concentrations of each agent and its antidotes. In addition, for cyanide, the compounds that resulted as the byproducts of therapy (methemoglobin, for example) were plotted. The results were consistent with those described in the literature, including agent concentrations and pathophysiologic changes.

Performance of the ARX-derived auditory evoked potential index as an indicator of anesthetic depth: a comparison with bispectral index and hemodynamic measures during propofol administration.

BACKGROUND: Autoregressive modeling with exogenous input of middle-latency auditory evoked potential (A-Line autoregressive index [AAI]) has been proposed for monitoring anesthetic depth. The aim of the current study was to compare the accuracy of this new index with the Bispectral Index (BIS), predicted effect-site concentration of propofol, and hemodynamic measures. METHODS: Twenty female patients scheduled for ambulatory gynecologic surgery received effect compartment controlled infusion of propofol. Target effect-site concentration was started at 1.5 microg/ml and increased every 4 min by 0.5 microg/ml. At every step, sedation level was compared with monitoring values using different clinical scoring systems and reaction to noxious stimulus. RESULTS: Bispectral Index, AAI, and predicted propofol effect-site concentration were accurate indicators for the level of sedation and loss of consciousness. Hemodynamic variables were poor indicators of the hypnotic-anesthetic status of the patient. BIS correlated best with propofol effect-site concentration, followed by AAI. Hemodynamic measurements did not correlate well. No indicators predicted reaction to noxious stimulus. Poststimulus, BIS and AAI showed an increase as a result of arousal. This reaction occurred more rapidly with the AAI than with BIS. CONCLUSION: Bispectral Index, AAI, and predicted propofol effect-site concentration revealed information on the level of sedation and loss of consciousness but did not predict response to noxious stimulus.