Why use more propofol as 2% formulation?

Propofol is believed to be the most widely used sedative in the adult intensive care unit (ICU). Its pharmacokinetic profile produces easily controllable sedation. 1 Propofol is prepared in 10% intralipid emulsion (0.1 g ml −1 of fat). Critically ill patients may have impaired lipid tolerance and they may also be the recipients of total parenteral nutrition, hence, ‘creaming' may be a consequence. 2 Because of the problem of fat load we chose to introduce 2% formulation. We observed that waking of some patients using 2% propofol was delayed and the total cost of propofol supplied increased. The cause for this was not clear. We retrospectively surveyed our use of propofol during periods of changeover from 1 to 2%. We reviewed the ICU charts of all patients admitted from September 1998 to February 1999 who received propofol (either 1% or 2%) with or without alfentanil. Patients receiving midazolam, fentanyl, morphine or other sedatives were excluded from the study. The sedation scores were noted at 12 noon (period of activity) and 12 midnight (period of quietness) each day. APACHE II diagnosis and APACHE II scores were also noted. We calculated propofol and alfentanil consumption for the patients who received 1% or 2% propofol. Our results demonstrate that patients receiving 1% infusion received 75% of the dose of those receiving 2% propofol (Table 22). The dose of alfentanil used was not significantly different in each group ( P >0.05). In a 24-h period sedation using 2% propofol cost £18.83 more than when using 1% preparation. This excludes the additional cost of any wasted drug. This may be because of differences in availability and activity of propofol in a concentrated emulsion, by chemical loss due to deterioration of the drug or by the way drug was administered. The record of sedation scores suggests that the level of sedation fluctuated more when 2% was used. We speculate that alteration to the amount of propofol given is made in increments of 1 ml irrespective of concentration of propofol used. Changing staff practices to alter infusion rates in 10 mg increments may produce less variation in sedation scores.