[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(-1) h(-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.