Application Of Volatile Anesthetics On Controlled Hypotension And Spinal Cord Monitoring In Spinal Surgery

[Study Objective] To explore the change of isoflurane and desflurane's BRS ( baroreflex sensitivity) depression effect when induced hypotension was applied in scoliosis correction with low-flow desflurane or isoflurane anesthesia.[Design] Prospective study.[Setting] Operating theater of a university hospital.[Patients] 30 consecutive ASA I~II adolescent patients with idiopathic scoliosis were randomly assigned to group D (n=15) or group I (n=15).[Interventions] During scoliosis correction operation, patients in group I and patients in group D received isoflurane and desflurane inhalation respectively. Target hypotension (MAP 55~65mmHg) was induced by increasing the inhaled concentration of two anesthetics slowly.[Measurements] BRS was measured with Oxfod's method by injection of phenylephrine. BRS was measured before induction (T0), after induction(T1), before body position change(T2), after body position change to prone(T3), and at 30min following hypotension status (T4).[Main Results] All patients were safe during whole operation and no postoperative paraplegina and other complications detected after operation. As the end-tidal concentration of two anesthetics increased to nearly 1.6 MAC(9.9±0.4% in group D and 1.6±0.1% in group I), target hypotension was induced. But it took less time for patients in group D to reach target hypotension than those in group I (P<0.05). Except for no significant difference of BRS between T2 and T3 (P>0.05), the difference between other BRS results within each group at different stage was significant (P<0.05). But there was not marked difference between two groups at same stage (P>0.05). BRS was depressed to the utmost at T4 when the end-tidal desflurane/isoflurane concentration was 1.6 MAC.[Conclusion] This study demonstrated that the two anesthetics could depress BRS and cause hypotension for scoliosis correction surgery. BRS depression might be involved in the mechanism of induced hypotension. [Objective] To study the method of spinal cord monitoring by using ankle clonus test and trachea mucosae stimulation.[Design] Prospective, observational study.[Setting] Clinical center in a teaching hospital.[Patients] 110 patients with scoliosis or spinal tumor, who needed receiving spinal cord function monitor during operation.[Interventions] Spinal cord function was monitored in 110 patients with scoliosis or spinal tumor during operation. All patients were anesthetized by isoflurane or desflurane. Anesthesia depth was decreased when spinal cord function was monitored during operation. Ankle clonus test and trachea mucosae stimulation test were performed by end-tidal anesthestics'concentration guiding.[Results] When end-tidal anesthetics'concentration reached 0.8MAC~0.5MAC, positive ankle clonus were induced. When the end-tidal concentration of desflurane or isoflurane reached 0.5MAC~0.2MAC, all the patients received trachea mucosae stimulation and causing extremities movement. All patients were not conscious when tests were performed and had no recollection of operation after operation.[Conclusion] Guided by end-tidal anesthetics'concentration, combined positive results of ankle clonus test and trachea mucosea stimulation testified integrity of spinal cord function. Comparing with sole ankle clonus test, the combined results were more convincing. And disadvantage of wake-up test were avoided by using the two tests. It suggested that the combined method be easily used in clinic.