Hypoalbuminaemia does not impair Diprifusor performance during sedation with propofol

Background. About 98% of plasma propofol is bound to albumin. We investigated if severe hypoalbuminaemia may affect the accuracy of a target-controlled infusion (TCI) device, the Diprifusor, during sedation in critically ill patients. Methods. Ten critically ill hypoalbuminaemic patients (< 24 g litre(-1)) and 10 critically ill normoalbuminaemic patients (> 32 g litre(-1)) were included in this study. They underwent sedation with propofol, aimed at a Ramsey sedation score of 4-5. The Diprifusor was used to achieve target propofol plasma concentrations that ranged between 0.6 and 1.5 mg litre(-1). Propofol concentration was measured by high-performance liquid chromatography 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, 6 h and 8 h after starting TCI. The accuracy of TCI was evaluated by calculating performance errors [PE=100x(measured concentration-predicted concentration)/predicted concentration], absolute and relative individual median performance errors (MDAPE and MDPE) and divergence (the slope of individual regression lines between PEs and time). Results. PEs [median (range)] were -7 (-65, 79) in hypoalbuminaemic patients and -2 (-53, 188) in normoalbuminaemic patients; absolute PEs were 21 (1, 79) and 22 (0, 188). No significant difference was observed between the two groups. MDPE, MDAPE and divergence values were also similar. In most patients the accuracy of TCI increased with time because higher PE values were observed during the first 30 min. Conclusions. Hypoalbuminaemia does not affect the accuracy of Diprifusor during sedation with propofol in critically ill patients.