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Introduction: Measuring and ensuring an adequate level of analgesia in patients are of increasing interest in the area of automated drug delivery during general anesthesia. Therefore, the aim of this investigation was to develop a control system that may reflect the intraoperative analgesia value. Our hypothesis was that a feedback controller could be applied in clinical practice safely and at an adequate quality of analgesia. The purpose of this study was to evaluate the practical feasibility of such a system in a clinical setting., Methods: The control system for the level of analgesia described in this paper relies on a parameter combination of heart rate variability (HRV), heart rate (HR), and blood pressure (mean arterial pressure, MAP), which serve as input variables for an expert system. For this fuzzy system, the experience of the participating anesthesiologists was translated into a set of fuzzy rules. In a pilot trial, the control system for automated titration of remifentanil, a short-acting opioid, was tested combined with a closed-loop propofol infusion system for hypnosis. Ten adult patients (4 women, 6 men), aged 22-52 years (median, 45 years; range, 29-49 years), with an American Society of Anesthesiologists physical status class I or II and who were scheduled for elective trauma surgery in a supine position were enrolled in this prospective trial. The precision of the system was calculated using internationally defined performance parameters., Results: There was no human intervention necessary during the computer-controlled administration of propofol and remifentanil, and operating conditions were satisfactory in all patients. All patients assessed the quality of anesthesia as "good" to "very good". Median performance error, median absolute performance error, and wobble for HR and MAP during maintenance of anesthesia were -8.98 (5.32), 10.08 (4.17), and 2.68 (1.29) and -4.51 (12.73), 13.63 (2.27), and 3.90 (2.08) [mean (SD)], respectively., Conclusion: The control system, reflecting the level of analgesia during general anesthesia designed and evaluated in this study, allows for a clinically practical, nearly fully automated infusion of an opioid during medium-length surgical procedures with acceptable technical requirements and an adequate precision.

In an extracorporeal combination therapy, the impact of different replacement fluids on survival was tested in a bacterial sepsis model in pigs. In an animal study 19 pigs, weighing 7.5-11.1 kg, were included. All groups received an intravenous lethal dose of live Staphylococcus aureus over 1 h. The animals were treated by an extracorporeal circuit consisting of online centrifugation and subsequent plasma filtration for 4 h. The extracorporeal circuit was pre-filled with 400 mL replacement fluid. In the P0 group 100% hydroxyethyl starch 130/0.4 was used as replacement fluid; in the P30 group 30% pig plasma and 70% hydroxyethyl starch; and in the P100 group 100% pig plasma. The observation time was 7 days. All animals of the group P100 survived, while all animals of group P0 and five out of seven animals of the P30 group died during the observation time. Extracorporeal therapy consisting of online centrifugation and plasma filtration with 100% pig plasma as replacement fluid significantly improved survival in a pig model of sepsis. Further studies with this approach are encouraged., (© 2012 The Authors. Therapeutic Apheresis and Dialysis © 2012 International Society for Apheresis.)