Anesthesiology
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Continuous epidural infusion of bupivacaine is widely practiced for postoperative pain relief in pediatric patients. However, bupivacaine may induce adverse effects in infants (convulsions or cardiac arrhythmias), likely because of decreased hepatic clearance and serum protein binding capacity. The authors wanted to examine the complex relations between age, alpha-1 acid glycoprotein (AAG) concentration, and unbound and total bupivacaine serum concentrations in infants receiving bupivacaine epidurally for 2 days. ⋯ Because of a low AAG concentration and a low intrinsic clearance, unbound bupivacaine increased to concentrations greater than 0.2 microg/ml in two infants younger than 2 months, after 2 days of infusion at a rate of 0.375 mg x kg(-1) x h(-1). The increase in AAG observed after surgery did not fully buffer this unbound fraction. Similarly, the buffer capacity of erythrocytes did not sufficiently increase at high concentration to compensate the saturation of the AAG system. Thus, we propose the use of a maximum dose of 0.25 mg x kg(-1) x h(-1) in infants younger than 4 months and a maximum of 0.3 mg x kg(-1) x h(-1) in infants older than 4 months.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of five experimental pain tests to measure analgesic effects of alfentanil.
Several experimental pain models have been used to measure opioid effects in humans. The aim of the current study was to compare the qualities of five frequently used experimental pain tests to measure opioid effects. ⋯ Electrical, pressure, and ice-water pain, but not ischemic and heat pain, provide significant concentration-response curves in the clinically relevant range of 200 ng/ml alfentanil or lower. The power to detect a clinically relevant shift of the curve is similar in the three tests. The appropriate test(s) for pharmacodynamic studies should be chosen according to the investigated drug(s) and the study design.
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Randomized Controlled Trial Clinical Trial
Moderate hypothermia depresses arterial baroreflex control of heart rate during, and delays its recovery after, general anesthesia in humans.
Effects of hypothermia on arterial baroreflex function during, and on its recovery after, general anesthesia were examined in humans. ⋯ The results indicate that moderate hypothermia enhances anesthesia-induced depression of baroreflex function in anesthetized humans and delays its recovery after general anesthesia.
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Comparative Study Clinical Trial
Comparison of closed-loop controlled administration of propofol using Bispectral Index as the controlled variable versus "standard practice" controlled administration.
This report describes a new closed-loop control system for propofol that uses the Bispectral Index (BIS) as the controlled variable in a patient-individualized, adaptive, model-based control system, and compares this system with manually controlled administration of propofol using hemodynamic and somatic changes to guide anesthesia. ⋯ A closed-loop system for propofol administration using the BIS as a controlled variable together with a model-based controller is clinically acceptable during general anesthesia.