Effect of isoflurane on baroreflex sensitivity during induced hypotension in patients undergoing scoliosis surgery / 中华麻醉学杂志

ABSTRACT

Objective The purpose of this study was to investigate the effect of isoflurane on baroreflex sensitivity ( BRS ) during induced hypotension and to illucidate the mechanism of isoflurane-induced hypotension. Methods Fifteen female ASA I or II patients aged 13-16 yrs undergoing scoliosis surgery were studied. The patients were unpremedicated. Radial artery and internal jugular vein were cannulated for BP and CVP monitoring. EGG, BP and SpO2 were continuously monitored before and during anesthesia. Anesthesia was induced with midazolam 0.04 mg? kg-1 , fentanyl 2 ?g? kg-1 and propofol 2 mg? kg-1 . Tracheal intubation was facilitated with rocuronium 1 mg?kg-1 . Anesthesia was maintained with isoflurane inhalation and fentanyl infusion (0.4?g?kg-1?h-1). Nitroglycerin (NTG) was infused at 1 ?g?kg-1 ?min-1 at the beginning of surgery to control MAP at 55-65 mm Hg and esmolol 20 mg was given i. v. to control HR 0.8. BRS was measured before induction of anesthesia (T1), immediately after intubation (T2), when end-tidal concentration of isoflurane reached 0.7% (T3 , supine) (T4 , prone), when end-tidal concentration of isoflurane reached 1.3% (T5) , at 30 min after NTG infusion and esmolal bolus injection were stopped (T6) when end-tidal concentration of isoflurane was decreased to 0.7 % (prone, T7 ) and immediately after the patients were turned supine (T8 ) . Results When end-tidal isoflurane concentration reached 1.6%, the desired level of hypotension could be maintained without NTG infusion and esmolol injection. BRS gradually decreased with increasing end-tidal isoflurane concentration. BRS was the lowest at 30 min after termination of NTG infusion and esmolol bolus injection. Conclusion Isoflurane depresses BRS and BRS depression may be involved in the mechanism of isoflurane-induced hypotension.