The effect of positive end‐expiratory pressure ventilation on propofol concentrations during general anesthesia in humans

The present study investigated the effects of positive end-expiratory pressure (PEEP) on propofol concentrations in humans. Eleven patients undergoing elective surgery were enrolled in this study. Anesthesia was induced with propofol, then maintained using 60% nitrous oxide in oxygen, fentanyl 10-20 μg/kg and continuous infusion of propofol. Vecuronium was used to facilitate the artificial ventilation of the lungs. Propofol was administered to all subjects via target-controlled infusion to achieve a propofol concentration of 6.0 μg/mL at intubation and 2.0 μg/mL after intubation. Before, during and after PEEP level of 10 cmH 2 O, cardiac output (CO) and effective liver blood flow (LBF) was measured using indocyanine green as an indicator and blood propofol concentration was determined using high-performance liquid chromatography. Data are expressed as median and range. After PEEP of 10 cmH 2 O was applied, CO and effective LBF was significantly decreased from 5.5 (3.8-6.8) L/min to 4.5 (3.2-5.8) L/min (P < 0.05), 0.78 (0.65-1.21) L/min to 0.65 (0.50-0.89) L/min (P < 0.05), respectively. Propofol concentration was significantly increased from 2.21 (1.46-2.63) μg/mL to 2.45(1.79-2.89) μg/mL (P < 0.05). These data indicate that propofol concentrations can be increased by PEEP, suggesting the possibility of overdosing following PEEP.