[Maintenance of the hypnotic component of general anesthesia with feed-back regulation]

The purpose of the study was to design and investigate the closed-loop propofol system (CLPS) with a mean arterial pressure (MAP) controller in open-heart surgery. CLPS consists of a 386 PC, a blood pressure sensor and an infusion pump. The C language computer program sets the propofol infusion rate based on an empirical algorithm including proportional component to maintain the measured MAP more closely to the target MAP (85% of patient standard MAP). The propofol concentrations were calculated by the pharmacokinetic/pharmacodynamic model differential equations solving every 30s. CLPS was used in 214 NYHA II-IV patients, aged 16-74, undergoing various open-heart procedures. The mean target MAP was 75.2 +/- 4.5 mm Hg. The measured and target MAP difference did not exceed 22% perioperatively. The bispectral index varied from 42.7 +/- 1.2 (tracheal intubation) to 41.8 +/- 0.1 (skin suture) with a variation of the propofol site effect concentration ranging from 2.9 +/- 0.09 to 1.8 +/- 0.1 microg/ml. It was a closed negative correlation (r = 0.84; p < 0.01) between the propofol site effect and the MAP during the initial period of anesthesia. There were not any significant changes in the blood cortisole level during the procedures. The recovery time was 1.4 +/- 1.5 min after propofol infusion; 95.5% of patients were extubated in the operating room.