Bacterial contamination of propofol: the effects of temperature and lidocaine

The intravenous anaesthetic propofol may become contaminated once the ampoules have been opened. The effect of lidocaine and cooling was tested on the bacterial contamination of propofol.

The study was performed in two parts. In Part 1,1920 aliquots of propofol alone, and of a propofollidocaine mixture, were drawn into sterile syringes and stored at room temperature (24-26 degrees C) or in the refrigerator (12-14 degrees C). In Part 2, 1200 aliquots from opened ampoules of propofol alone, or as a propofol-lidocaine mixture, were stored at room temperature or in the refrigerator. Samples were aerobically cultured at 0, 1, 2, 4, 8 and 12 h.

In Part 1, diphtheroid bacillus was isolated from one aliquot (0.06%). In Part 2, there was bacterial growth in both groups; the number of contaminated ampoules increased with time and it was 20-26% at 12 h. Diphtheroid bacilli and coagulase-negative staphylococci were the most frequent micro-organisms.

When propofol is stored in opened ampoules, the bacterial contamination rate is high. Adding lidocaine, or storing opened ampoules at 12-14 degrees C, does not affect the contamination rate, except during the first few hours. It is advisable to draw propofol aseptically into a syringe in an amount that can be used during one procedure.