Increased noradrenaline release from rat preoptic area during and after sevoflurane and isoflurane anesthesia.

PURPOSE To study the effects of sevoflurane and isoflurane on noradrenaline release from the rat preoptic area (POA). METHOD Sixteen male Wistar rats were studied. A microdialysis probe with a 2 mm long semipermeable membrane was implanted in the POA. Dialysates were collected at intervals often minutes. After obtaining five control samples for 50 min, 30 min inhalation of 3% sevoflurane or 1.8% isoflurane was performed. After cessation of the inhalation, five more samples were obtained for 50 min as recovery phase. Noradrenaline (NA) concentration in the dialysates was measured by high pressure liquid chromatography with an electrochemical detector. RESULTS Both sevoflurane and isoflurane caused marked increases in NA release from the rat POA (sevoflurane 233% at 20 min, isoflurane 357% at ten minutes after the start of inhalation). The marked NA releases were also observed during the emergence from sevoflurane and isoflurane anesthesia (sevoflurane 269% at 20 min, isoflurane 368% at ten minutes in the recovery phase). CONCLUSION This study suggests that enhanced release of NA in the POA during sevoflurane and isoflurane may explain the excitatory phase observed during the peri-anesthetic period with these agents.