It is possible to establish and maintain targeted blood and effect-site drug concentrations with reasonable accuracy using a ‘bolus, elimination, transfer’ (BET) infusion regimen. Simulation software that employs pharmacokinetic models can be used to drive infusion pumps or to design manually controlled BET infusions.
Prolonged infusions can result in prolonged recovery times. However, the elimination half-lives of infused lipid soluble drugs have little or no relevance to rates of recovery because elimination half-life does not take redistribution from peripheral compartments into account. A better method is to calculate the context-sensitive decrement times (context-sensitive referring to the infusion duration). These are not represented by a single number: they are a continuum of time values that are a function of infusion duration and can be represented by a graph. Considering that decrement times depend on the concentrations achieved as well as the dose history, it is often difficult for clinicians to anticipate a patient’s time to recovery. Pharmacokinetic simulation software continuously calculates and displays expected recovery times, helping clinicians to ascertain when to reduce or terminate the infusion.
Coetzee, J.F. (2015) Principles of intravenous drug infusion. Anaesthesia and Intensive Care Medicine. October 30th. . DOI: http://dx.doi.org/10.1016/j.mpaic.2015.09.003
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