PROPOFOL The active ingredient in propofol, 2,6-diisopropylphenol, is essentially insoluble in aqueous solutions and is formulated only for IV administration as a 1% (10 mg/ml) emulsion in 10% soybean oil, 2.25% glycerol, and 1.2% purified egg phosphatide. In the United States, disodium EDTA (0.05 mg/ml) or sodium metabisulfite (0.25 mg/ml) is added to inhibit bacterial growth. The induction dose of propofol in a healthy adult is 1.5 to 2.5 mg/kg and it has an onset and duration of anesthesia similar to thiopental. As with barbiturates, dosages should be reduced in the elderly and in the presence of other sedatives and increased in young children. Because of its reasonably sho elimination half-life, propofol often is used for maintenance of anesthesia as well as for induction. For sho procedures, small boluses (10% to 50% of the induction dose) every 5 minutes or as needed are effective. An infusion of propofol produces a more stable drug level (100 to 300 mg/kg per minute) and is better suited for longer-term anesthetic maintenance. Infusion rates should be tailored to patient response and the levels of other hypnotics. Sedating doses of propofol are 20% to 50% of those required for general anesthesia. However, even at these lower doses, caregivers should be vigilant and prepared for all of the side effects of propofol discussed below, paicularly airway obstruction and apnea. Propofol elicits pain on injection that can be reduced with lidocaine and the use of larger arm and antecubital veins. Excitatory phenomena during induction with propofol occur at about the same frequency as with thiopental, but much less frequently than with methohexital. Side Effects: Nervous System: The CNS effects of propofol are similar to those of barbiturates. Propofol decreases CMRO2, cerebral blood flow, and intracranial and intraocular pressures by about the same amount as thiopental. Like thiopental, propofol has been used in patients at risk for cerebral ischemia; however, no human outcome studies have been performed to determine its efficacy as a neuroprotectant. Results from studies on the anticonvulsant effects of propofol have been mixed; some data even suggest it has proconvulsant activity when combined with other drugs. Thus, unlike thiopental, propofol is not a proven acute intervention for seizures. Cardiovascular. Propofol produces a dose-dependent decrease in blood pressure that is significantly greater than that produced by thiopental. The fall in blood pressure can be explained by both vasodilation and mild depression of myocardial contractility. Propofol appears to blunt the baroreceptor reflex or is directly vagotonic because smaller increases in hea rate are seen for any given drop in blood pressure after doses of propofol. As with thiopental, propofol should be used with caution in patients at risk for or intolerant of decreases in blood pressure. Respiratory and Other Side Effects: At equipotent doses, propofol produces a slightly greater degree of respiratory depression than thiopental. Patients given propofol should be monitored to ensure adequate oxygenation and ventilation. Propofol appears to be less likely than barbiturates to provoke bronchospasm. It has no clinically significant effects on hepatic, renal, or endocrine organ systems. Unlike thiopental, propofol appears to have significant anti-emetic action and is a good choice for sedation or anesthesia of patients at high risk for nausea and vomiting. Propofol provokes anaphylactoid reactions and histamine release at about the same low frequency as thiopental. Although propofol does cross placental membranes, it is considered safe for use in pregnant women, and like thiopental, only transiently depresses activity in the newborn.