Determination of the minimum alveolar concentration (MAC) of isoflurane and sevoflurane in Callithrix penicillatac

Background: The minimum alveolar concentration (MAC) is a measure of quantitative anesthetic potency and has become the standard index for the evaluation and comparison of volatile anesthetics, in addition to guiding dose administration. Black-tufted marmosets (Callithrix penicillata) are primates present in the clinical and surgical routine of veterinary hospitals, as well as experimental models, especially in neuroscience. Few studies have evaluated the potency of the main volatile anesthetics in this species. This study aimed to determine the MAC of isoflurane and sevoflurane in C. penicillata using the up-and-down method and to evaluate the effects of these drugs on the quality of anesthetic induction, maintenance, and recovery. Materials, Methods & Results: Twenty-four animals of undetermined age were used. All marmosets were healthy according to hematological and physical evaluation. The animals were randomly divided into 2 groups: ISOMAC and SEVOMAC. Each animal was induced to general anesthesia in an anesthetic box with oxygen (5 L/min) and sevoflurane at 7% in the SEVOMAC group or isoflurane at 5% in the ISOMAC. Upon reaching lateral decubitus, orotracheal intubation was performed. General anesthesia was maintained with isoflurane or sevoflurane diluted in oxygen (0.8 L/min) using a non-rebreathing delivery system under spontaneous ventilation. As defined in the pilot study, the first animal from ISOMAC started the maintenance of anesthesia with 2.6% isoflurane, while the first animal in SEVOMAC received 4% sevoflurane. After finishing the instrumentation to assess heart rate, respiratory rate, systolic blood pressure, pulse oximeter oxygen saturation, end-tidal carbon dioxide concentration, and rectal temperature, a 15-min wait to reach anesthetic equilibrium was allowed, and then an electrical noxious stimulation (50 mA and 50 Hz) was performed on the lateral aspect of the thigh (a faradic current of 3 consecutive single stimuli, followed by 2 continuous stimuli). The animals' responses to the electrical stimulus were observed. The presence of a positive response (gross movement of the limbs, head, or vocalization) or a negative response (absence of gross movements) determined the increase or reduction, respectively, of the inhalation anesthetic concentration by 10% in the subsequent marmoset. The quality of anesthetic induction and recovery from anesthesia was evaluated using a scale that measured the intensity of agitation, coughing, nausea, and vomiting. Physiological variables were recorded before (M0) and after (M1) applying the nociceptive stimulus. Isoflurane and sevoflurane MAC values in C. penicillata were 2.29 ± 0.10% and 3.93 ± 0.61 % respectively. Physiological parameters, quality of anesthetic induction and recovery did not differ significantly between groups. However, isoflurane caused irritation of the airway and ocular mucous membranes, more coughing episodes, and tearing at induction. There was no difference between groups for time to extubation and recovery time to regain sternal position. Discussion: Previous studies in primates found lower MAC values for both anesthetics, except for Lemur catta. Those findings may be explained by the use of different nociceptive stimuli and the MAC determination method employed, although no differences in MAC values have been described between bracketing or up-and-down methods in human primates and dogs. It is unlikely that the stimulus and technique alone are the determining factors for the high concentration of isoflurane and sevoflurane observed in the present study since MAC was high with both halogenates, indicating that dose extrapolation from other species can lead to the wrong anesthetic dosage.

Papiloma de plexo coroide em uma cadela / Choroid plexus papilloma in a bitch

Background: Choroid plexus papilloma is a benign neoplasm derived from the neuroepithelium of the choroid plexus of the ventricular cavity, commonly located in the fourth ventricle, affecting dogs of different age groups and without predilection for sex. There is a range of therapeutic options, and the treatment to be chosen will be defined based on tumor localization and development. Due to the difficulties in accessing treatments, tutors opt for euthanasia or death occurs with the worsening of the clinical condition. This case report aims to present the symptomatology, treatment and evolution of the case until the death of the animal, as well as the pathological findings. Case: A 12-year-old bitch, mixed breed, was treated presenting behavior alteration, with unusual aggressiveness, perceived by the tutor four weeks ago. Neurological examination revealed changes in behavior, compulsive walking and focal epileptic seizures. After the presumptive diagnosis of brain neoplasia, the dog underwent symptomatic treatment with prednisolone (1 mg/kg, orally, every 24 h, for 15 days, with subsequent reduction to 0.5 mg/kg for another 15 days) and phenobarbital (3 mg/kg, every 12 h, orally), until death. After the beginning of the treatment, no more epileptic seizures and aggressive behavior were observed. After 5 months of consultation, the dog returned with aggressive and anorexic behavior. Due to the worsening of clinical signs, with the possibility of brain neoplasia, the tutor opted for euthanasia. Necropsy was performed and macroscopic examination was observed in the telecephalus, occlusion of the third ventricle by grayish mass, soft, 1.2 cm in diameter with slight dilation of lateral ventricles. On histological examination, it was observed that the third ventricle was occluded, epithelial proliferation of arboriform aspect, composed of cuboidal cells to columnares sustained by moderate fibrovascular stroma. Based on macroscopic and histopathological findings of the telecephalus, the alterations determined the diagnosis of choroid plexus papilloma. Discussion: The diagnosis of choroid plexus papilloma was confirmed by observing the neurological signs and pathological findings that characterize this neoplasm. Choroid plexus tumors are less common, in the third ventricle, only in 36% of all reports are of tumors in that area. The search for care is mainly due to clinical signs that include behavioral, and locomotor changes and sometimes epileptic seizures, such clinical signs were found in the dog. Choroid plexus papilloma affects dogs of all ages, but more in adults and increasing the occurrence as they age. The tumor is still correlated in a higher occurrence in large animals, the evaluated dog was of age, but small in size. During anamnesis, in addition to the clinical history, neurological examinations provide a good basis for the presumptive diagnosis that can be complemented by an imaging diagnosis. Sometimes such technologies are not available for use, therefore, more comprehensive knowledge about clinical signs and anamnesis are indispensable for a correct diagnosis. Palliative drug therapies are an excellent option for most cases presented in the literature and clinical routine, since they provide better quality of life by decreasing or eliminating clinical signs, besides being easily administered by tutors. The therapy proved to be of great value for the improvement of the clinical signs of the evaluated dog, confirming the importance of knowledge of the appropriate prescriptions for each case and reinforcing that consultation with one was important in defining the diagnosis and symptomatic treatment.