The Journal of veterinary medical science
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This study was aimed at characterizing the superior laryngeal nerve (SLN) afferent activities under four different respiratory conditions, i.e., tracheostomy breathing (TB), upper airway breathing (UAB), tracheal occlusion (TO) and upper airway occlusion (UAO), and investigating respiratory changes in response to transmural pressures applied to the larynx in anesthetized Shiba goats. The activity recorded from the whole SLN increased at both inspiration and expiration during TB, UAB and TO, while an expiratory augmentation accompanied by an inspiratory inhibition was found during UAO. Based on recordings from 109 thin filament-preparations, 47 units were identified as 'drive' receptors, 31 as 'pressure' receptors (22 'positive' and 9 'negative' pressure receptors), and the rest 31 as 'non-modulated type' of receptors. ⋯ No significant changes were found in the respiratory cycle during application of negative pressures to the larynx. The respiratory modulation of the SLN in Shiba goats was essentially identical to that reported for rabbits, rats and guinea pigs, but not in dogs. The reflex response of the upper airway muscles to the laryngeal pressure changes in Shiba goats were found to be less noticeable than in rabbits and dogs.
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Cardiovascular reflex mechanisms by topical laryngeal instillation of capsaicin (CAPS) or distilled water were evaluated in anesthetized chronic tracheostomized dogs. Both CAPS (10 micrograms/ml) and water instillation into the isolated upper airway caused a significant decrease in heart rate (P < 0.05) and a significant increase in blood pressure (P < 0.05) from the values before instillation under both spontaneous and controlled ventilation. ⋯ All the reflex responses to CAPS and water were eliminated by topical anesthesia with lidocaine. It was concluded that the laryngeal cardiovascular reflex responses were mediated by the afferents such as the laryngeal CAPS-sensitive presumably C-fiber endings or water-responsive receptors and by both the parasympathetic and sympathetic nervous systems as efferents.
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Effects of a combination of medetomidine-ketamine as a chemical restraint and antagonistic effects of atipamezole on this combination were investigated in 5 lions. The medetomidine (47.6-58.4 micrograms/kg) and ketamine (1.9-5.7 mg/kg) combination provided complete immobilization with good analgesia and muscle relaxation in 4 lions, while one lioness was poorly sedated by medetomidine, and additional injections of medetomidine and ketamine were required. ⋯ Atipamezole, at four times the preceding dose of medetomidine, provided a smooth recovery and animals were able to stand up 17-61 min after its injection. Side effects were limited to vomiting after walking in 3 of 5 lions.
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Case Reports
Multifocal ventricular tachycardia after resuscitation by direct current counter shock in a dog.
Cardiac arrest occurred in a male Labrador Retriever dog weighing 27.8 kg during induction to anesthesia. Immediately after the failure of resuscitation by the external cardiac compression, thoracotomy was performed and open chest direct current (DC) counter shocks were applied with routine emergency medications. ⋯ Although cardiac rhythm just after resuscitation was sinus tachycardia with paroxysmal supraventricular tachycardia, multifocal ventricular arrhythmia occurred 2 hr after resuscitation. This arrhythmia might be the result from reversible cardiac lesions due to DC counter shock.
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The effects of ventilation at positive end-expiratory pressure (PEEP) on extravascular lung water (EVLW) and cardiopulmonary function were studied in dogs with experimental severe hydrostatic pulmonary edema, which was generated by inflating a left atrial balloon and simultaneously injecting warm 5% glucose solution into the pulmonary artery. The EVLW was measured by the double indicator dilution method using heat and sodium ions. All the dogs were ventilated at zero end-expiratory pressure (ZEEP) until the EVLW had increased by 200-300% (maximal edema), when they were divided into two groups, one of which (n = 6) was ventilated at a PEEP of 10 cm H2O throughout the 4 hr study period (PEEP group) and the other (n = 6) was maintained at ZEEP during their survival period (ZEEP group). ⋯ The EVLW of the PEEP group remained unchanged throughout the 4 hr study period, whereas that of the ZEEP group showed a tendency to increase. The arterial oxygen tension (PaO2) increased significantly throughout the 4 hr period of ventilation in the PEEP group but tended to decrease in the ZEEP group. In conclusion, PEEP improves gaseous exchange, but does not decrease the EVLW in dogs with experimental severe hydrostatic edema.