In order to examine whether repeated sciatic nerve blocks showed tachyphylaxis and continuity of sciatic nerve with spinal cord affected development of tachyphylaxis when assayed in vivo by duration of depression compound action potentials (CAP), rats were anesthetized with halothane, ventilated, monitored and supported with stable hemodynamics and temperature. Posterior tibial nerve distally and sciatic nerve in thigh were exposed, placed on bipolar silver electrodes for stimulation and recording respectively. Three sequential sciatic nerve blocks were performed between these electrodes using 0.15 ml of 3% chloroprocaine. Nine rats were chosen to observe the effects of repeated sciatic nerve blocks on CAP. In another 18 rats, a second investigator exposed the sciatic nerve near its origin at spinal cord and randomly performed nerve cut and sham (n=9), and closed the incision blinding the electrophysiologic investigator. The results showed that electrical stimulated tibial nerve induced sciatic nerve Aalpha/beta, Adelta, C fiber mediated CAP waves. CAP amplitudes were remained stable during whole experimental procedure. CAP amplitudes were decreased completely with 3% chloroprocaine blocked sciatic nerve and recovered fully. The duration of CAP depression were reduced with repeated blocks. There were no selective blocked effects on Aalpha/beta, Adelta, C fiber mediated CAP. With sciatic nerve cut proximally, there was no statistical significant tachyphylaxis with 3% chloroprocaine repeated blocked sciatic nerve, and the duration of first and third blocked Adelta fiber mediated CAP was 108+/-20 and 92+/-14 min respectively (P>0.05). In normal rats the duration of first and third blocked Adelta fiber mediated CAP was 110+/-20 and 75+/-16 min respectively (P<0.05). It was suggested that tachyphylaxis to local anesthetics can occur in rats repeated blocked sciatic nerve when assayed in vivo by duration of depression CAP. The continuity of sciatic nerve with spinal cord is one of the important factors affecting the development of tachyphylaxis.
Anesthetics, Local/*administration & dosage ; Nerve Block ; Procaine/administration & dosage ; Procaine/analogs & derivatives ; Sciatic Nerve ; *Tachyphylaxis/physiology

In order to examine whether repeated sciatic nerve blocks showed tachyphylaxis and continuity of sciatic nerve with spinal cord affected development of tachyphylaxis when assayed in vivo by duration of depression compound action potentials (CAP), rats were anesthetized with halothane, ventilated, monitored and supported with stable hemodynamics and temperature. Posterior tibial nerve distally and sciatic nerve in thigh were exposed, placed on bipolar silver electrodes for stimulation and recording respectively. Three sequential sciatic nerve blocks were performed between these electrodes using 0.15 ml of 3% chloroprocaine. Nine rats were chosen to observe the effects of repeated sciatic nerve blocks on CAP. In another 18 rats, a second investigator exposed the sciatic nerve near its origin at spinal cord and randomly performed nerve cut and sham (n=9), and closed the incision blinding the electrophysiologic investigator. The results showed that electrical stimulated tibial nerve induced sciatic nerve Aalpha/beta, Adelta, C fiber mediated CAP waves. CAP amplitudes were remained stable during whole experimental procedure. CAP amplitudes were decreased completely with 3% chloroprocaine blocked sciatic nerve and recovered fully. The duration of CAP depression were reduced with repeated blocks. There were no selective blocked effects on Aalpha/beta, Adelta, C fiber mediated CAP. With sciatic nerve cut proximally, there was no statistical significant tachyphylaxis with 3% chloroprocaine repeated blocked sciatic nerve, and the duration of first and third blocked Adelta fiber mediated CAP was 108+/-20 and 92+/-14 min respectively (P>0.05). In normal rats the duration of first and third blocked Adelta fiber mediated CAP was 110+/-20 and 75+/-16 min respectively (P<0.05). It was suggested that tachyphylaxis to local anesthetics can occur in rats repeated blocked sciatic nerve when assayed in vivo by duration of depression CAP. The continuity of sciatic nerve with spinal cord is one of the important factors affecting the development of tachyphylaxis.
Anesthetics, Local ; administration & dosage ; Animals ; Nerve Block ; Procaine ; administration & dosage ; analogs & derivatives ; Rats ; Sciatic Nerve ; Tachyphylaxis ; physiology

OBJECTIVE: To explore the effectiveness and feasibility of dexamethasone combined with oxybuprocaine hydrochloride gel on the prevention of postoperative sore throat after nasal endoscopy. METHODS: In the study, 60 patients with American Society of Anesthesiologist (ASA) physical statuses Ⅰ to Ⅱ, aged 18 to 72 years, scheduled for elective nasal endoscope surgery under general anesthesia requiring endotracheal intubation were randomly divided into dexamethasone combined with oxybuprocaine hydrochloride gel group (G group, n=30) and control group (C group, n=30). The patients in the G group received dexamethasone 0.1 mg/kg before induction and the oxybuprocaine gel was applied to the endotracheal catheter cuff and the front end within 15 cm. The patients in the C group received the same dose of saline and the saline was applied to the endotracheal catheter cuff and the front end within 15 cm. Then, all the patients in the two groups received the same induction and anesthesia maintainance. The operation time, anesthesia time, emergence time, extubation time and departure time were recorded. The intraoperative infusion volume, blood loss volume, propofol, remifentanil, rocuronium dosage were also recorded. The adverse reactions such as intraoperative hypotension, bradycardia and postoperative agitation were recorded. The postoperative sore throat score was recorded at the end of operation and 4 h, 8 h, 12 h, and 24 h after operation. RESULTS: Compared with the C group, the emergence time [(8.4±3.9) min vs. (10.8±4.7) min], extubation time [(8.8±3.7) min vs. (11.9±4.8) min], and departure time [(20.0±5.3) min vs. (23.0±5.8) min] were significantly shorter, and the propofol dosage [(11.8±1.8) mg/kg vs. (15.9±4.6) mg/kg], remifentanil dosage [(10.9±4.7) μg/kg vs. (14.1±3.6) μg/kg] were significantly less in the G group, and there was no difference of rocuronium dosage in the two groups. Compared with the C group the incidence of intraoperative hypotension [10%(3/30) vs. 30%(9/30)], bradycardia [16.7%(5/30) vs. 20%(6/30)] and postoperative agitation [6.7%(2/30) vs. 23.3%(7/30)] were significantly lower in the C group. The postoperative sore throat score at the end of operation, 4 h, 8 h, 12 h and 24 h after operation in the G group were significantly lower than in the C group respectively [0 (0, 1) vs. 1 (1, 2), 0 (0, 0) vs. 1 (1, 2), 0 (0, 0) vs. 1 (1, 2), 0 (0, 0) vs. 1 (0.75, 1), 0 (0, 0) vs. 1 (0, 1)]. CONCLUSION Dexamethasone combined with oxybuprocaine hydrochloride gel was effective and feasible on the prevention of postoperative sore throat after nasal endoscopy.
Adolescent ; Adult ; Aged ; Bradycardia/drug therapy* ; Dexamethasone/therapeutic use* ; Endoscopy/adverse effects* ; Humans ; Hypotension/drug therapy* ; Intubation, Intratracheal/adverse effects* ; Middle Aged ; Pain/drug therapy* ; Pharyngitis/prevention & control* ; Postoperative Complications/prevention & control* ; Procaine/analogs & derivatives* ; Propofol ; Remifentanil ; Rocuronium ; Young Adult