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

We 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 mu g.ml-1 to assess linearity and the influence of haematocrit and concurrent drug administration. Analyser concentrations demonstrated excellent linearity (R2 = 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 mu g.ml-1 and precision of -0.16 to 0.42 mu g.ml-1.