Plasma glucocorticoid concentrations after fentanyl-droperidol, ketamine-xylazine and ketamine-diazepam anaesthesia in New Zealand white rabbits

Continuous Rate Infusion of Ketamine Hydrochloride and Dexmedetomidine for Maintenance of Anesthesia during Laryngotracheal Surgery in New Zealand White Rabbits (Oryctolagus cuniculus)

New Zealand white rabbits (Oryctolagus cuniculus) are an established in vivo model for the study of structural and functional consequences of vocal-fold vibration. Research design requires invasive laryngotracheal procedures, and the presence of laryngospasms or pain responses (or both) hinder phonation-related data collection. Published anesthesia regimens report respiratory depression and muscle tone changes and have been unsuccessful in mitigating autonomic laryngeal responses in our protocol. Infusion of ketamine hydrochloride and dexmedetomidine hydrochloride in pediatric medicine provides effective analgesia and sedation for laryngotracheal procedures including intubation and bronchoscopy; however, data evaluating the use of ketamine-dexmedetomidine infusion in rabbits are unavailable. This study reports a new infusion regimen, which was used in 58 male New Zealand white rabbits that underwent a nonsurvival laryngotracheal procedure to induce phonotraumatic vocal-fold injury. Animals were sedated by using ketamine hydrochloride (20 mg/kg IM) and dexmedetomidine (0.125 mg/kg IM). Maintenance anesthesia was provided by using continuous rate intravenous infusion of ketamine hydrochloride (343 μg/kg/min) and dexmedetomidine (1.60 μg/kg/min). A stable plane of anesthesia with no autonomic laryngeal response (laryngospasm) was achieved in 32 of the 58 rabbits (55%). Laryngospasms occurred in 25 of 58 animals (43%) and were controlled in 20 cases (80%) by providing 0.33 mL 2% topical lidocaine, incremental increase in infusion rate, or both. Continuous rate infusion of ketamine hydrochloride-dexmedetomidine with prophylactic topical lidocaine provides a predictable and adjustable surgical plane of anesthesia, with minimal confounding respiratory and autonomic laryngeal responses, during extended-duration laryngotracheal surgery in rabbits. This regimen should be considered as an alternative to injection maintenance for prolonged, invasive procedures.

Impacts of Different Anesthetic Agents on Left Ventricular Systolic Function in Mice Assessed by Echocardiography

The present experiments were performed to study the effects and time trends of different anesthetic agents on the left ventricular (LV) systolic function and heart rate by high-resolution echocardiography in mice. Ten male C57BL/6J mice were submitted to echocardiography imaging separated by 72-hour intervals under the following conditions: 1) conscious mice, 2) mice anesthetized with isoflurane (ISO, inhaled), 3) mice anesthetized with tribromoethanol (TBE, intraperitoneal), 4) mice anesthetized with chloral hydrate (CH, intraperitoneal), and 5) mice anesthetized with pentobarbital sodium (PS, intraperitoneal). The effect of ISO, TBE, CH, and PS on LV systolic function was measured at 0, 1, 2, 3, 4, 6, 8, and 10 min after anesthesia. The results showed that LV systolic function and heart rate (HR) of anesthetized mice were reduced significantly (P<0.05), compared with results in the same mice studied in the conscious state. In addition, the results indicated that the anesthetic with the least effect on LV function was CH, and followed by TBE, PS, ISO. We conclude that different anesthetic agents always depressed the HR and LV systolic function of mice, and, furthermore, the effects and time trends of different anesthetics on LV function are different. In echocardiographic experiments, we should choose proper anesthetic agents according to the experimental requirements.