Abstract
Propofol is an intravenous anesthetic commonly used due to its favorable pharmacokinetic and pharmacodynamic profile. There are discrepancies in the literature about the most appropriate sample for determining propofol concentrations. Although plasma has been used for determining propofol concentrations, whole blood has been the preferred sample. There is also a lack of consistency in the literature on the effect of storage time and temperature on propofol concentrations and this may lead to errors in the design of pharmacokinetic/pharmacodynamics studies. The purpose of this study was to determine the difference in propofol concentrations in whole blood versus plasma and to evaluate the influence of storage time (56 days) and temperature (4 °C, −20 °C, −80 °C) on the stability of propofol concentrations in blood and plasma samples. Results from the study indicate that whole blood and plasma samples containing propofol stored at −80 °C have concentrations as high as or higher than those stored at 4 °C or −20 °C for 56 days; thus, −80 °C is an appropriate temperature for propofol sample storage. Plasma propofol concentrations were consistently higher than whole blood for all three storage temperatures. Consequently, plasma is the most appropriate sample for propofol analysis due to its consistent determinations.
Highlights
Concentrations were determined with the exception of two blood samples (17 and 150 ng/mL) on day 56 stored at −20 ◦C that did not result in any detectable propofol
In both sample media, samples stored at −20 ◦C resulted in the lowest propofol measurements of all 3 storage temperatures evaluated
Blood has been recommended as the preferred sample for the analysis of propofol concentrations by some authors (Adam et al, 1981; Plummer, 1987; Chan & So, 1990; Zonca et al, 2012; Cattai et al, 2016) the results of the present study indicate a difference between blood and plasma propofol concentrations, at least under the experimental conditions applied in the study
Summary
Propofol is a short-acting intravenous anesthetic, which is associated with smooth and rapid inductions and recovery and is commonly used in dogs and other veterinary patients (Robertson, Johnston & Beemsterboer, 1992; Zoran, Riedesel & Dyer, 1993; Mandsager et al, 1995; Lee et al, 2012; Zonca et al, 2012; Miryabe-Nishiwake et al, 2013; Gomulka et al, 2015; Cattai et al, 2016). Drugs of this type are generally considered to bind to albumin in plasma. It is a lipophilic drug, and despite being highly (98%) bound to serum/plasma proteins (Servin et al, 1988; Campos et al, 2016), it is approximately 50% bound to erythrocytes (Mazoit & Samili, 1999). Data from pharmacokinetic/pharmacodynamics studies based on the relationship between blood propofol concentrations and its effects have been used to design propofol dosage regimens for anesthesia (Cuadrado et al, 1998); differences in measured propofol concentrations due to the effects of storage time and temperature on plasma and whole. There is discussion in the literature as to whether propofol concentrations should be determined in whole blood or serum/plasma samples
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