Laboratory animals
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Intratracheal instillation (ITI) of a test compound is an alternative method to inhalation methods that require complex aerosol generation, exposure chambers and airflow monitoring instruments for exposing the lungs of animals to a test compound. For ITI in the rat, a laryngoscope is generally used for endotracheal intubation, and the procedure is difficult to perform. Therefore, we designed and constructed an automatic video instillator (AVI) for the accurate delivery of a dose of a test compound into the trachea of rats. ⋯ After a 2 h training session on the use of the AVI in an anaesthetized rat, we assessed the utility of the device by ITI of 0.25% (w/v) solution of Evans Blue dye into the lungs of 30 isoflurane-anaesthetized rats. Necropsy examinations were performed on 20 rats immediately after the completion of the procedure, and on 10 rats three days after the procedure. Based on the results of these examinations, we concluded that the device could be used for rapid, reproducible and successful ITI of a test compound into the lungs of a rat by one operator.
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Endotracheal intubation in mice is both a common and important technique. However, it is a difficult procedure because of the small orotracheal size and the success rate is variable. There have been many reports of refined techniques that facilitate intubation but only a few reports have proposed how to verify the proper placement of the endotracheal tube. ⋯ When the catheter was inserted correctly into the trachea, the water in the extension tube oscillated in synchrony with the movement of the mouse's thorax, indicating correct placement of the catheter. This method was simple, reliable and use materials that are routinely available. This method is helpful for experimental mouse models that require airway access.
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This report describes a simple, non-invasive electronic device that employs a compact accelerometer integrated circuit to transduce movements in the chest wall of an anaesthetized animal into an analogue signal that can be used to calculate the rate and relative depth of respiration. The device requires amplification by signal processing hardware/software which are common to most experimental laboratories. We assessed the sensitivity of the device by its ability to detect changes in respiratory patterns produced by modulating the depth of anaesthesia in isoflurane-anaesthetized Wistar rats. ⋯ Deepening the anaesthesia produced a gradual decrease in RR, a decrease in dominant spectral frequency of the electroencephalogram (EEG) but no change in the heart rate. There was a significant correlation between RR and the dominant spectral frequency of the EEG, indicating that one useful application of the monitor could be to identify anaesthetic stages. The results demonstrate that respiratory parameters can be recorded using a simply constructed, low-cost device and suggest an application in the monitoring of anaesthetic depth.
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The present work determined the minimum alveolar concentrations (MAC) of halothane, isoflurane and sevoflurane in adult female gerbils (n=24). Animals were placed in a chamber for anaesthetic induction before performing tracheal intubation. The tracheal tube was connected to a non-rebreathing circuit with minimal dead space. ⋯ Cardiovascular parameters at 1xMAC did not differ significantly among anaesthetics but the respiratory rate was significantly higher in the halothane group than in the isoflurane and sevoflurane groups. The SpO2 values recorded throughout anaesthesia and the pH and partial oxygen pressure values determined at the end of the study did not differ among the studied anaesthetics at 1xMAC. These data suggest that the MAC for halogenated inhalant anaesthetics in gerbils is lower than the average MAC values obtained in rats and mice.
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The purpose of the study was to assess the haemodynamic (blood pressure and heart rate) changes and stress responses (serum cortisol and serum amyloid A [SAA] concentrations) to surgery in piglets during total intravenous anaesthesia (TIVA) with propofol and fentanyl. After preanaesthetic medication with intramuscular midazolam (0.5 mg/kg body mass), ketamine (10 mg/kg) and butorphanol (0.5 mg/kg) anaesthesia was induced in five piglets, with intravenous propofol (1 mg/kg) followed by tracheal intubation and mechanical lung ventilation. Soft tissue surgery was performed in the jugular and inguinal regions during TIVA with propofol (8 mg/kg/h) and fentanyl (35 microg/kg/h). ⋯ Neither heart rate nor lactate concentrations changed significantly over the same time points: heart rate was 104+/-11 and 103+/-15 beats/min whereas mean lactate concentrations were reduced from 1.14+/-0.45 mmol/L to 0.90+/-0.22 mmol/L. Haemodynamic stability, a decrease in serum cortisol and a non-statistically significant rise in mean SAA concentrations suggest that the anaesthetic described suppresses the stress response of piglets to surgery without adverse cardiovascular effects. Therefore, it may prove useful in cardiovascular research.