Altered plasma melatonin concentrations after administration of propofol in continuous infusion

OBJECTIVE: To determine possible variations in plasma ;;levels of melatonin in patients sedated with propofol ;;administered in continuous infusion. ;;PATIENTS AND METHODS: Healthy patients receiving ;;spinal anesthesia for lower limb orthopedic surgery were ;;randomized to 2 groups in this prospective study: group A ;;patients were sedated with intravenous propofol infused at ;;a rate of 3 to 4 mg·kg-1h-1 and group B underwent surgery ;;without sedation. Data from these groups were compared ;;with data from 2 other groups. Group C data, from healthy ;;volunteers who did not undergo surgery or sedation, were ;;compared with baseline values. Group D data were ;;theoretical reference values for plasma melatonin levels ;;taken from the literature, for comparisons at baseline and ;;in the range of hypnosis. Hormone levels were determined ;;by enzyme-linked immunosorbent assay at baseline, at 10 ;;and 60 minutes after the start of sedation, and 90 minutes ;;after withdrawal of sedation. ;;RESULTS: Twenty patients were enrolled. No significant ;;between-group differences were detected at baseline (P>.269), ;;60 minutes after starting sedation or 90 minutes after ;;withdrawing it (P>.347 and P>.057 respectively). Values were ;;significantly different between group B and groups A and D ;;10 minutes after starting sedation with propofol (P<.001). ;;CONCLUSIONS: Plasma levels of melatonin increased; during administration of propofol in continuous perfusion (AU)