This study was aimed at examining the anesthetic effects and spinal cord injuries in the rats by intrathecal injection of levobupivacaine at different concentrations. Rats with successful intrathecal cannulation were selected and randomly divided into six groups (n = 72), and administered 0.1 mL of 0.125%, 0.25%, 0.5%, or 0.75% levobupivacaine, saline or 5% lidocaine via intrathecal catheters. The potency of levobupivacaine was evaluated by walking behavior. To identify the motor and sensory function, walking behavior and paw withdrawal thresholds (PWTs) were measured once a day. After 7 days, the L4–5 spinal cord segments were removed for histological examination. The onset time of 0.125% levobupivacaine intrathecal injection was 70.0 ± 8.9 s, and the maintenance time was 9.5 ± 1.8 min. The onset time of 0.75% levobupivacaine intrathecal injection was significantly shortened to 31.0 ± 5.5 s, and the maintenance time was significantly extended to 31.3 ± 5.4 min. The severe injury was observed in the 5% lidocaine group, while milder injury was observed in the 0.75% levobupivacaine group. The damage in the 0.5% levobupivacaine group was mild, and there were no histological abnormalities in the 0.125%, 0.25% levobupivacaine and saline groups. The neurotoxicity of intrathecally administered levobupivacaine was concentration dependent. In addition, higher concentrations of levobupivacaine were associated with shorter onset and longer maintenance times. The clinical concentration of levobupivacaine should not exceed 0.5% to avoid potential damage.

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Introduction Etomidate has been advocated to be used in anesthesia of the elderly and the critically ill patients due to its faint effect on cardiovascular system. But the dose-dependent suppression of etomidate on adrenal cortex function leads to the limitation of its clinical application. Clinical research shows that dexmedetomidine can reduce the dose requirements for intravenous or inhalation anesthetics and opioids, and the hemodynamics is more stable during the operation. The objective is to observe the effect of etomidate combined with dexmedetomidine on adrenocortical function in elderly patients. Methods 180 elder patients scheduled for elective ureteroscopic holmium laser lithotripsy were randomly allocated to PR group anesthetized with propofol- remifentanil, ER group anesthetized with etomidate-remifentanil, and ERD group anesthetized with dexmedetomidine combined with etomidate-remifentanil. Patients in each group whose operation time was less than or equal to 1h were incorporated into short time operation group (PR1 group, ER1 group and ERD1 group), and whose operation time was more than 1h were incorporated into long time operation group (PR2 group, ER2 group and ERD2 group). The values of SBP, DBP, HR and SpO2 were recorded at T0, T1, T2, T3, T4, T5, T6 and T7.The time of operation, the dosage of etomidate and remifentanil administrated during surgery, the time to spontaneous respiration, recovery and extubation, and the duration of stay in the PACU were recorded. The serum cortisol and ACTH concentration was measured at t0, t1, t2, t3, t4 and t5. Results The dosage of etomidate was significantly lower in ERD1 group and ERD2 group compared with ER1 group and ER2 group(P < 0.05), respectively. The SBP in ER2 and ERD2 group were higher at T1 and T3 compared to PR2 group (P < 0.05). The DBP in ER1 and ERD1 group were higher at T1compared to PR1 group (P < 0.05). The Serum cortisol concentration were higher at t1 ~ 2 in ERD1 group compared to ER1 group (P < 0.05). The Serum cortisol concentration were higher at t1 ~ 3 in ERD2 group compared to ER2 group (P < 0.05).The Serum ACTH concentration were lower at t1 ~ 2 in ERD1 group compared to ER1 group (P < 0.05). The Serum ACTH concentration were lower at t1 ~ 3 in ERD2 group compared to ER2 group (P < 0.05). Conclusion The administration of dexmedetomidine combined with etomidate can attenuate the inhibition of etomidate on adrenocortical function in elderly patients and maintain intraoperative hemodynamic stability.