Electroencephalographic Burst Suppression by Propofol Infusion in Humans

The hemodynamic effects of a propofol infusion adjusted to achieve and maintain a burst-suppression pattern [episodes of depressed background activity (electrical silence) more than 4 s alternating with a high-voltage slow activity], were studied in 10 patients without cardiorespiratory disease undergoing elective neurosurgical interventions. Propofol infusion was started after a bolus dose of 1 mg/kg at a rate of 20 mg.kg-1 x h-1, reduced after 30 min to 15 mg.kg-1 x h-1, and terminated after 60 min (1926 +/- 346 mg cumulative propofol dose, maximal serum concentration 9.2 +/- 2.9 micrograms/dL; mean +/- SD). Hemodynamic data and arterial blood samples were collected during a sedated, resting control period, and then every 15 min during drug infusion. Lactated Ringer's solution was infused at a rate sufficient to maintain pulmonary capillary wedge pressure at or above control levels (20-30 mL.kg-1 x h-1). Burst-suppression pattern in the electroencephalogram was achieved after 15.7 +/- 3.2 min and maintained until 10.9 +/- 2.6 min after the propofol infusion was terminated. Significant decreases (% of control, Friedman and Wilcoxon Wilcox test, P < 0.05) were found in heart rate (19%), mean arterial pressure (20%), cardiac index (23%), and left ventricular stroke work index (26%). No adverse consequences were caused by the propofol or crystalloid infusion. The results demonstrate that doses of propofol sufficient to silence the electroencephalogram are associated with venodilating and myocardial depressant properties. However, propofol can be administered with minimal hemodynamic risk in healthy patients when cardiac filling pressures are maintained by intravenous fluid administration.