Evaluation of a new analyser for rapid measurement of blood propofol concentration during cardiac surgery

Abstract

SummaryWe report laboratory and clinical evaluations of a blood propofol concentration analyser. Laboratory experiments used volunteer blood spiked with known propofol concentrations over the clinically relevant concentrations from 0.5 to 16 lg.ml )1 to assess linearity and the influence of haematocrit and concurrent drug administration. Analyser concentrations demonstrated excellent linearity (R 2 = 0.999). Blood spiked with commonly used drugs showed no significant variation compared to unspiked controls. Propofol measurements were largely independent of haemoglobin concentration. A 6% decay in propofol concentration was observed at the highest prepared concentration. Clinical performance of the analyser was assessed using 80 arterial blood samples from 72 patients receiving propofol infusions during cardiac surgery. Samples were processed using the propofol analyser, and high performance liquid chromatography (HPLC) used as a gold-standard comparator. These data demonstrated excellent agreement between the propofol analyser and HPLC with a bias of 0.13 lg.ml )1 and precision of )0.16 to 0.42 lg.ml Target-controlled infusion (TCI) is a common method of propofol administration. The ability of TCI algorithms to predict blood propofol concentrations accurately is poor [1, 2], with measures of precision demonstrating errors of up to 60% [3]. Significant bias and large errors in precision are also identified in groups falling outside of limits used in the development of these algorithms [4][5][6]. Conventional methods of measuring propofol concentrations in blood include high performance liquid chromatography (HPLC), gas chromatography and liquid chromatography mass spectroscopy. These are labour intensive and time consuming methods and cannot be used to deliver clinically useful information. Estimation of blood propofol from expired gases has yet to demonstrate consistent and reliable results [7].We assessed a device designed to measure the concentration of propofol in a blood sample in 4 min by extracting propofol from 0.5 ml of whole blood using solid phase extraction and quantifying the amount of propofol in the extract using colorimetric detection techniques. This technique for propofol extraction was first described in 2006 in a proof of concept study [8]. We conducted both laboratory and clinical evaluations of the device, the latter using samples from patients undergoing propofol-based general anaesthesia for cardiac surgery.

Real time monitoring of propofol blood concentration in ponies anaesthetized with propofol and ketamine

“…Propofol measurement was performed using the Pelorus 1000 analyser (Cowley et al. , 2012; Liu et al.…”

“…Propofol measurement was performed using the Pelorus 1000 analyser (Cowley et al, 2012;Liu et al, 2012). No sample preparation was needed, each measurement required injection of approximately 0.5 mL whole heparinized blood into the system.…”

Ion mobility spectrometry as a simple and rapid method to measure the plasma propofol concentrations for intravenous anaesthesia monitoring

“…At this optimized temperature, an individual measurement can be accomplished within 1 min. This measurement process is much faster than that from other analyzers1213.…”

“…In Fig. 8, the agreement between these two methods is assessed using Bland-Altman method12. The result shows a small positive bias of 0.15 μg mL −1 (mean difference between the propofol concentration measured by the IMS and HPLC), with a standard deviation (SD) of 0.49 μg mL −1 .…”

“…So far, the high performance liquid chromatography (HPLC) is the most commonly used analytical method for measuring the propofol concentrations in plasma4567891011, and it is also used as a reference to evaluate other methods1213. However, due to the complex matrix of plasma, the complicated sample pretreatment must be implemented before the HPLC separation process can be carried out.…”