Effects of ketamine, midazolam and methadone, combined with local anesthesia, in cats undergoing orchiectomy / Efeitos da cetamina, midazolam e metadona, associados à anestesia local, em gatos submetidos à orquiectomia

Different anesthetic combinations are used for orchiectomy in cats. This study aimed to evaluate the anesthetic and cardiopulmonary effects on the physiological variables of ketamine (10 mg/kg), midazolam (0.2 mg/kg) and methadone (0.3 mg/kg), combined with local anesthesia, in cats undergoing orchiectomy (n = 19 cats). The time for lateral recumbency, degree of sedation, muscle relaxation and nociception were recorded preoperatively. The propofol rescue dose was recorded. The time to head up and quality of recovery were evaluated postoperatively. The time for lateral recumbency was 5 ± 2 minu-tes. Fifteen minutes after the administration of the ketamine-midazolam-methadone combination, a greater sedative effect, muscle relaxation and less response to noxious stimulation were observed. Propofol was administered to twelve cats under local anesthesia, at a total dose of 1.5 ± 0.8 mg/kg. Surgery was started 28 ± 5 minutes after the administration of ketamine--midazolam-methadone combination. There were no differences in the physiological variables evaluated over the other evalu-ation times (p > 0.05). The recovery quality scores were adequate, and the time to head up was 51 ± 10 minutes. Under the conditions of this study, the ketamine-midazolam-methadone combination did not allow local anesthesia for orchiectomy. Many cats required propofol rescue prior to surgery. This combination promoted minimal changes in physiological variables and prolonged anesthetic recovery.(AU)

Diferentes combinações anestésicas são usadas para orquiectomia em gatos. O objetivo deste estudo foi avaliar o efeito anestésico e as alterações promovidas nas variáveis fisiológicas pela cetamina (10 mg/kg), midazolam (0.2 mg/kg) e metadona (0.3 mg/kg), combinados com anestesia local, em gatos submetidos à orquiectomia (n = 19 gatos). O tempo para adoção do decúbito lateral, grau de sedação, relaxamento muscular e nocicepção foram registrados no pré-operatório. A dose de resgate de propofol foi registrada. O tempo para o gato erguer a cabeça e a qualidade da recuperação foram avaliados no pós-operatório. O tempo para adoção do decúbito lateral foi de 5 ± 2 minutos. Quinze minutos após a administração da associação cetamina-midazolam-metadona, observou-se maior efeito sedativo e relaxamento muscular, e menor resposta à estimulação nociva. O propofol foi administrado em doze gatos para realização de anestesia local, utilizando a dose total de 1.5 ± 0.8 mg/kg. A cirurgia foi iniciada 28 ± 5 minutos após a administração de cetamina-midazolam-metadona. Não houve diferença nas variáveis fisiológicas avaliadas em relação aos demais tempos de avaliação (p > 0.05). Os escores de qualidade de recuperação foram adequados e o tempo para o gato erguer a cabeça foi de 51 ± 10 minutos. Nas condições deste estudo, cetamina-midazolam-metadona não permitiu a realização da anestesia local para orquiectomia. Muitos gatos precisaram de resgate com propofol antes de iniciar a cirurgia. Essa associação promoveu alterações mínimas nas variáveis fisiológicas e longa recuperação anestésica.(AU)

Effects of oxygen supplementation in ewes subjected to laparoscopic ovum pick-up under total intravenous anesthesia / Efeitos da suplementação de oxigênio em ovelhas submetidas à aspiração de folículos por laparoscopia sob anestesia intravenosa total

Laparoscopy procedures are useful tools to perform some assisted reproductive biotechnologies in ewes, it requi-res general anesthesia and manoeuvres that might result in alteration of the cardiopulmonary function. For this reason, this study aimed to investigate the effects of oxygen supplementation as a therapeutic measure to mitigate these alterations in ewes submitted to laparoscopic ovum pick-up (LOPU) under total intravenous anesthesia (TIVA). Twenty-four healthy adult ewes were submitted to two LOPUs with a 21 days interval, under ketamine-midazolam anesthesia, and receiving each of the two experimental in random order, oxygen treatment (OT) 50 mL/kg/min of oxygen via endotracheal tube and control treatment (CT) not receive any inhalation treatment. Heart rate (HR), respiratory rate (fR), peripheral oxygen saturation (SpO2), mean arterial pressure (MAP), rectal temperature (RT), end-tidal CO2 concentration (EtCO2) and recovery anesthesia time were evaluated during LOPU, arterial blood gases and electrolytes were evaluated after induction of anesthesia and at the end of the LOPU. Variables were compared between groups and moments using ANOVA. MAP, SpO2, PaO2, SaO2 and pH were higher in OT, while EtCO2, PaCO2, temperature loss and recovery time were lower. These results allow to conclude that oxy-gen supplementation in ewes submitted to LOPU under TIVA provides benefits in order to mitigate physiological alterations.(AU)

Os procedimentos de laparoscopia são ferramentas úteis para realizar algumas biotecnologias de reprodução assistida em ovelhas, requer anestesia geral e manobras que podem resultar em alteração da função cardiopulmonar. Por esse motivo, este estudo teve como objetivo investigar os efeitos da suplementação de oxigênio como medida terapêutica para atenuar as alterações em ovelhas submetidas à Aspiração Folicular guiada por Laparoscopia (LOPU) sob anestesia venosa total (TIVA). Vinte e quatro ovelhas adultas saudáveis foram submetidas a duas LOPUs com intervalo de 21 dias, sob anestesia com cetamina-midazolam, recebendo cada um dos dois experimentos em ordem aleatória, tratamento com oxigênio (OT) 50 mL/kg/min de oxigênio via tubo endotraqueal e tratamento de controle (CT) não recebem nenhum tratamento por inalação. Frequência cardíaca (FC), frequência respiratória (FR), saturação periférica de oxigênio (SpO2), pressão arterial média (PAM), temperatura retal (TR), concentração expirada de CO2 (EtCO2) e tempo de recuperação da anestesia foram avaliados durante LOPU, arterial gasometria e eletrólitos foram avaliados após a indução da anestesia e ao final da COL. As variáveis foram comparadas entre grupos e momentos por meio de ANOVA. PAM, SpO2, PaO2, SaO2 e pH foram maiores no TO, enquanto EtCO2, PaCO2, perda de temperatura e tempo de recuperação foram menores. Estes resultados permitem concluir que a suplementação de oxigênio em ovelhas submetidas a LOPU sob TIVA proporciona benefícios no sentido de atenuar as alterações fisiológicas.(AU)

Hypertrophic phenotypic cardiomyopathy in an ocelot (Leopardus pardalis)

Background: Hypertrophic cardiomyopathy phenotype (HCM) is the most common cardiac disease in domestic cats but is rarely described in wild species. This phenotype is characterized by concentric hypertrophy of the left ventricle and may be of familial inheritance or secondary to other diseases such as hyperthyroidism, chronic kidney disease, systemic arterial hypertension, and hyperaldosteronism. HCM can cause diastolic and systolic dysfunction and may cause congestive heart failure in affected animals. The present work aims to describe the first report of cardiomyopathy of the hypertrophic phenotype in a specimen of Leopardus pardalis, kept under human care. Case: A 11-year-old female ocelot (Leopardus pardalis) kept under human care, during a preventive care visit, had hypertrophic cardiomyopathy phenotype detected by cardiological evaluation with echocardiogram and a murmur grade III/ VI could be detected on cardiac auscultation. This preventive care occurred under chemical restraint with ketamine [6 mg/kg, i.m] associates with midazolam [0.5 mg/kg, i.m] and other evaluations have been done like complete blood count (CBC), biochemistry (alanine aminotransferase, aspartate aminotransferase, total proteins, albumin, albumin:globulin ratio, creatinine, urea, sodium, potassium, calcium, phosphorus, and globulin) and tyroid hormones [free tyroxine (T4) and thyroid-stimulating hormone (TSH)]. Medical management based on clopidogrel, and atenolol was administered for 3 months until the patient showed manifestations of congestive heart failure (CHF) 80 days later the initial evaluation. In this moment the patient presented with dyspnea, so a cardiological and laboratory evaluation was requested. On pulmonary auscultation crackling was identified, suggesting pulmonary edema and, on echocardiographic examination, some parameters had worsened. The CBC and biochemistry were all within reference ranges. Then, the beta-blocker was discontinued and replaced by pimobendan combined with furosemide as treatment of CHF, and the condition stabilized. After one year, the patient was re-evaluated and showed a slight improvement in the condition but still remained stable. Also, feline proBNP levels was tested (SNAP Feline proBNP® IDEXX) in this moment and it was increased. Discussion: The findings on echocardiography associated with the subjective evaluation associated with progressive worsening and clinical manifestation of CHF, as well as the response to treatment, even though there are no reference values for the species, reinforce the diagnosis. There is no evidence to suggest diseases that may contribute to secondary left ventricular hypertrophy. It is believed that pimobendan plays a key role in maintaining hemodynamic balance, since this has already been observed in other mammalian species. The use of beta blockers is commonly employed in domestic cats with HCM, and they have been prescribed in an attempt to promote greater ventricular relaxation, decrease left ventricular outflow obstruction, thus improving ventricular filling for maintenance of cardiac output. In view of the atrial enlargement and possible risk of thrombus formation, clopidogrel was prescribed, extrapolating what is known from domestic cats. It is reasonable to conclude that in this case, the cardiomyopathy behaved similarly to what is observed in domestic cats, both in its clinical evolution and in the means of diagnosis, and in its response to the therapy instituted.

Mastectomia a campo em ruminantes - aspectos cirúrgicos e clínico-patológicos / Field mastectomy in ruminants - surgical and clinicopathological aspects

Background: We report the case of 3 cows, 1 ewe, and 1 doe, with chronic mastitis and which underwent a mastectomy. All animals had a history of mastitis, edema with purulent secretion in the udder region, areas of abscess formation, fibrosis, hypogalactia, and agalactia. The animals had already been treated with systemic antibiotic therapy and anti-inflammatory drugs without response. The objective of this work is to describe the surgical and clinicopathological aspects of performing a radical mastectomy in the field in 3 cows and 1 ewe, and a partial mastectomy in a doe, with both procedures performed successfully and considered efficient to maintain the survival of the affected animals, in addition to being economically viable. Cases: In all animals reported in the study, a general and a specific clinical examination were performed, where on palpation of the udder were observed an increase in the region of the mammary apparatus, fluid fluctuation, areas of fibrosis with increased stiffness, and loss of udder functionality. In the case of the doe, there was a functional teat, which was preserved during the surgical procedure. Radical mastectomy was performed in 3 cows and 1 ewe, and the doe underwent a partial mastectomy, with preservation of the functional teat. All animals have fasted for food and water for 48 h. In cows, the anesthetic protocol consisted of 2% xylazine hydrochloride [0.15 mg/kg, intramuscularly (IM)], followed by an epidural block in the lumbosacral region with 2% lidocaine hydrochloride [10 mL]. The midazolam hydrochloride [0.1 mg/kg, intravenously (IV)] and 2% xylazine hydrochloride [0.05 mg/kg, IM] were administered to the ewe and the doe, also associated with lumbosacral epidural anesthesia with 2% lidocaine hydrochloride [5 mL]. The animals were positioned in the right lateral decubitus position and the entire abdominal and udder region were shaved and sanitized for the surgical procedures of radical mastectomy and partial mastectomy, with the use of degerming and topical povidone-iodine. The postoperative period consisted of penicillin-based antibiotic therapy associated with streptomycin [24,000 IU/kg, IM, 10 consecutive days] and flunixin meglumine [2 mg/kg, IM, 3 consecutive days] in cows; enrofloxacin [2.5 mg/kg, IM, 7 consecutive days] and flunixin meglumine [0.5 mg/kg, IM, 5 consecutive days] in the ewe; oxytetracycline [10 mg/kg, IM, 5 applications on alternate days] and flunixin meglumine [0.5 mg/kg, IM, 3 consecutive days] in the doe. In all animals, the cleaning of the surgical wound was performed daily with 10% topical Povidone-iodine and Permethrin ointment, for 14 days, when the stitches were removed. Discussion: The choice of the surgical procedure resulted in improvement of the clinical conditions and increased survival of all animals, and in the case of the doe, partial mastectomy contributed to the preservation of the functional teat, preserving its productive capacity. All anesthetic protocols used and the anatomical positioning of the animals were satisfactory for performing the procedures. Although they are techniques described in the literature with great blood loss, especially in cows, blood transfusion was not required in any of the animals. The stitches were removed 14 days after the surgical procedures, and the surgical wound was completely healed.

Comparative study between S-(+)-ketamine­midazolam and fentanyl­droperidol in black-tufted marmosets (Callithrix penicillata) / Estudo comparativo entre S-(+)cetamina-midazolam e fentanil-droperidol em saguis-de-tufo-preto (Callithrix penicillata)

Sedative and antinociceptive effects of two anesthetic protocols in black-tufted marmosets were compared in this study. Twenty-six marmosets underwent chemical immobilization for physical examination, blood sampling, tattooing, and microchipping. Animals were randomly treated with S-(+)-ketamine (10 mg/kg) and midazolam (1 mg/kg) (KM) or fentanyl (12.5 µg/kg) and droperidol (625 µg/kg) (FD) given by intramuscular injection. Heart and respiratory rates were recorded. Sedation, antinociception, muscle relaxation, posture, auditory, and visual responses were evaluated using a scoring system. Sedation in KM was achieved faster (p < 0.001) and lasted for a shorter period of time (p = 0.0009). KM was similar to FD in its cardiorespiratory effects, auditory and visual responses. Both protocols promoted adequate sedation to allow manipulation. Animals in KM assumed lateral recumbency while animals in FD maintained a quadrupedal posture during evaluation. FD produced less intense sedation and muscle relaxation but a higher degree of antinociception compared to KM and is suitable for procedures that require analgesia in black-tufted marmosets.(AU)

O presente estudo comparou os efeitos cardiorrespiratórios, sedativos e antinociceptivos de dois protocolos anestésicos em saguis-de-tufo-preto (Callithrix penicillata). Vinte e seis saguis foram submetidos à contenção química para exame físico, coleta de sangue, tatuagem de identificação e microchip. Os animais foram tratados aleatoriamente com a associação de S-(+)-cetamina (10 mg/kg) e midazolam (1 mg/kg) (KM) ou fentanil (12,5 µg/kg) e droperidol (625 µg/kg) (FD), administrados por injeção intramuscular. Foram avaliadas frequência cardíaca, frequência respiratória, sedação, antinocicepção, relaxamento muscular, postura e resposta ao estímulo auditivo e visual. A sedação em KM foi alcançada mais rapidamente (p <0,001) e teve um tempo hábil mais curto (p = 0,0009). KM foi semelhante a FD nos efeitos cardiorrespiratórios, respostas auditivas e visuais. Os dois protocolos promoveram sedação adequada para manipulação. Os animais do grupo KM permaneceram em decúbito lateral durante a avaliação, enquanto os animais em FD mantiveram postura quadrupedal. FD resultou em sedação e relaxamento muscular de menor intensidade, porém com maior escore de antinocicepção em comparação com KM, sendo adequada para procedimentos que requerem analgesia em saguis-de-tufo-preto.(AU)

Iohexol gastrointestinal transit times in cockatiels under sedation with intranasal midazolam by computed radiography / Tempos de trânsito gastrintestinal com iohexol em calopsitas, sob sedação com midazolam intranasal, por meio de radiografia computadorizada

This study used contrast radiography to evaluate gastrointestinal transit times in cockatiels (Nymphicus hollandicus) and investigated the sedative effects of intranasal midazolam in this species and its usefulness in facilitating the manual restraint required for radiographic studies. Twelve healthy adult cockatiels received intranasal midazolam at dose of 2 mg/kg, and iohexol at 15 ml/kg by crop gavage. Radiographic images were obtained before contrast administration, 3 minutes after and then each 10 minutes for 90 minutes. Sedation quality of the bird was evaluated during the radiographic study and assessed according to an adapted visual sedation scale. Three minutes after iohexol administration, the cervical oesophagus and the crop were filled in all birds. At the same time, the contrast medium reached the thoracic oesophagus, proventriculus, isthmus and ventriculus in most birds. In all cockatiels, median (range) transit times were 3 (3-10) minutes for proventriculus and ventriculus, 10 (10-40) minutes for small intestine and 45 (30-70) minutes for large intestine. The overall gastrointestinal transit time was 50 (30-90) minutes.Crop remained filled with iohexol throughout the study, while oesophagus and isthmus presented a pattern of contrast progression different from the other gastrointestinal segments. According to the visual sedation scale, cockatiels presented a moderate to intense muscular relaxation, and intranasal midazolam seems to be an appropriate sedation protocol for radiographic study. All cockatiels remained healthy after the study and presented clear and watery stools at least 12 hours after, due to gastrointestinal emptying.

O presente estudo objetivou determinar os tempos de trânsito gastrintestinal de calopsitas (Nymphicus hollandicus) por meio do estudo radiográfico contrastado e investigar os efeitos sedativos do midazolam intranasal nesta espécie, bem como a viabilidade do uso deste fármaco para facilitar a contenção manual durante o exame radiográfico. Doze calopsitas, adultas e saudáveis, receberam midazolam intranasal, na dose de 2 mg/kg, e 15 ml/kg de iohexol por gavagem. Imagens radiográficas foram obtidas antes da administração do meio de contraste, três minutos depois da administração e a cada 10 minutos, até 90 minutos de estudo. A qualidade da sedação foi avaliada durante todo o estudo radiográfico por meio de escala visual adaptada. Três minutos após a administração do iohexol, esôfago cervical e inglúvio foram preenchidos em todas as aves. Ao mesmo tempo, o meio de contraste alcançou esôfago torácico, proventrículo, istmo e ventrículo na maioria dos animais. Em todas as aves, a mediana e intervalo dos tempos de trânsito foram três (3-10) minutos em proventrículo e ventrículo, 10 (10-40) minutos em intestino delgado e 45 (30-70) minutos em intestino grosso, sendo que o tempo total de trânsito gastrintestinal foi 50 (30-90) minutos. Inglúvio permaneceu preenchido por meio de contraste durante todo o estudo radiográfico, enquanto esôfago e istmo apresentaram padrão de trânsito diferente dos demais segmentos avaliados. As aves apresentaram moderado a intenso relaxamento muscular durante o estudo e a administração de midazolam intranasal mostrou-se como protocolo sedativo apropriado em calopsitas. Todas as aves permaneceram saudáveis e apresentaram fezes com aspecto aquoso e esbranquiçado no mínimo 12 horas após o estudo radiográfico, devido ao esvaziamento gastrintestinal.

Bloqueio do plano transverso do abdômen em coelha submetida à mastectomia e ovariohisterectomia / Blockade of the transverse plane of the abdomen in a rabbit submitted to mastectomy and ovariohysterectomy

Os bloqueios locorregionais vêm sendo cada vez mais estudados na medicina veterinária, principalmente em pets não-convencionais e animais silvestres. O bloqueio do plano transverso do abdômen (TAP block) é uma técnica de anestesia locorregional capaz de promover anestesia e analgesia em regiões da pele, musculatura e peritônio parietal, as quais fazem parte da estratégia de analgesia multimodal. O objetivo deste trabalho é relatar o bloqueio do plano transverso em um coelho doméstico de quatro anos de idade submetido à mastectomia regional e ovariohisterectomia. Foram realizados dois pontos bilateralmente de bloqueio do espaço TAP guiado por ultrassom com 2mg/kg de bupivacaína a 0,25%, padronizando um volume total injetado de 2,4mL. Foram utilizados dexmedetomidina (5É¥g/kg) e midazolam (0,5mg/kg) por via intramuscular como medicação pré-anestésica, indução com isoflurano na máscara de oxigênio 100% e manutenção por anestesia inalatória com isoflurano. Os parâmetros fisiológicos mantiveram-se estáveis, sem necessidade de resgate analgésico, com extubação rápida e despertar tranquilo. Desta forma, conclui-se que o TAP block foi eficaz na analgesia para mastectomia regional e ovariohisterectomia como protocolo multimodal, aumentando o índice de segurança, além de ser de fácil execução mesmo com transdutores de baixa frequência.

The locoregional blocks have been increasingly studied in veterinary medicine, especially in non-conventional pets and wild animals. The transverse abdominis plane block (TAP block) is a locoregional anesthesia technique capable of promoting anesthesia and analgesia in the skin, muscle, and parietal peritoneum regions, which are is part of the multimodal analgesia strategy. This study aims to report the transverse plane block in a four-year-old domestic rabbit submitted to regional mastectomy and ovariohysterectomy. Two ultrasound-guided TAP space blocks were performed bilaterally with 2mg/kg of bupivacaine 0.25%, standardizing a total injected volume of 2.4mL. Dexmedetomidine (5É¥g/kg) and midazolam (0.5mg/kg) were used intramuscularly as pre-anesthetic medication, induction with isoflurane in a 100% oxygen mask, and maintenance by inhalation anesthesia with isoflurane. Physiological parameters remained stable, with no need for analgesic rescue, rapid extubation, and peaceful awakening. Thus, it is concluded that the TAP block was effective in analgesia for regional mastectomy and ovariohysterectomy as a multimodal protocol, increasing the safety index. Moreover, it is easy to perform even with low-frequency transducers.

Comparative study between ketamine-S-dexmedetomidine and ketamine-S-midazolam-methadone in the anesthesia of capuchin monkeys (Sapajus apella) / Estudo comparativo entre quetamina-S-dexmedetomidina e quetamina-S-midazolam- metadona na anestesia de macacos-prego (Sapajus apella)

Anesthetic protocols have been developed to obtain the most effective and safe association in wildlife. This study compared the anesthetic effects and cardiorespiratory parameters of ketamine-S (+) (10 mg/kg)/dexmedetomidine (0.020 mg/kg) (KD ) and ketamine-S (+) (10 mg/kg)/midazolam (0.5 mg/kg)/methadone (1.0 mg/kg) (KMM ) in capuchin monkeys (Sapajus apella). Eight capuchin monkeys were randomly assigned to KD (n = 4) or KMM (n = 4) to evaluate induction, immobilization, and recovery scores, heart and respiratory rate parameters, besides systolic, mean, diastolic arterial pressure and arterial blood gas. There was no difference (P = 0.56) in the quality of induction, immobilization, and anesthetic recovery between the protocols. The time for anesthetic induction was 4 ± 1 min in the KD group and 5 ± 1 min in the KMM group, and these values were statistically equal (P = 0.28). The mean immobilization time in the KD and KMM groups were 35 ± 13 and 33 ± 15 min, respectively. Heart rate was lower in animals in the KD group (P < 0.001), while respiratory rate (P = 0.03), and mean blood pressure (P = 0.046) were higher than that of the animals in the KMM group. Respiratory acidosis occurred in the KMM group, with lower pH (7.25±0.047; P = 0.0055) and higher pCO2 (51 ± 6;mmHg; P = 0.008). Both protocols exhibited good induction quality, immobilization, and anesthetic recovery, despite cardiorespiratory and blood gas alterations observed, which warrants monitoring of cardiorespiratory variables during KD or KMM chemical restraint.

Protocolos anestésicos foram desenvolvidos para obter a associação mais eficaz e segura em animais selvagens. O objetivo deste estudo foi comparar os efeitos anestésicos e os parâmetros cardiorrespiratórios de cetamina-S (+) (10 mg / kg) / dexmedetomidina (0,020 mg / kg) (KD) e cetamina-S (+) (10 mg / kg) / midazolam (0,5 mg / kg) / metadona (1,0 mg / kg) (KMM) em macacos-prego (Sapajus apella). Oito macacos-prego foram distribuídos aleatoriamente em KD (n = 4) ou KMM (n = 4) para avaliar os escores de indução, imobilização e recuperação, parâmetros de frequência cardíaca e respiratória, além da pressão arterial sistólica, média, diastólica e gasometria arterial. Não houve diferença (P = 0,56) na qualidade da indução, imobilização e recuperação anestésica entre os protocolos. O tempo de indução anestésica foi de 4 ± 1 min no grupo KD e 5 ± 1 min no grupo KMM, sendo esses valores estatisticamente iguais (P = 0,28). O tempo médio de imobilização nos grupos KD e KMM foram 35 ± 13min e 33 ± 15 min, respectivamente. A frequência cardíaca foi menor nos animais do grupo KD (P < 0,001), enquanto a frequência respiratória (P = 0,03) e a pressão arterial média (P = 0,046) foram maiores do que nos animais do grupo KMM. Acidose respiratória ocorreu no grupo KMM, com menor pH (7,25 ± 0,047; P = 0,0055) e maior pCO2 (51 ± 6; mmHg; P = 0,008). Ambos os protocolos apresentaram boa qualidade de indução, imobilização e recuperação anestésica, apesar das alterações cardiorrespiratórias e gasométricas observadas, o que justifica o monitoramento das variáveis cardiorrespiratórias durante a contenção química com KD ou KMM.

Bezold-Jarisch reflex induced by dopamine during isoflurane anesthesia in small dogs

Background: Unlike other major reflexes contributing to hemodynamic homeostasis, the Bezold-Jarisch reflex (BJR)paradoxically decreases heart rate (HR) and mean arterial pressure (MAP) despite hypotension. In the veterinary field,there are few reported cases of BJR induced by dopamine, which is often used to manage hypotension. Herein, 2 casesinvolving small dogs exhibiting BJR due to dopamine infusion during general anesthesia are described.Cases: Case 1: A 7-year-old, 7 kg, mongrel was referred for external skeletal fixator removal. The patient was premedicatedwith 0.3 mg/kg midazolam and 0.2 mg/kg butorphanol intravenously (IV). General anesthesia was induced with 6 mg/kgpropofol and maintained with 1.6% isoflurane in oxygen. The patient was given 5 mL/kg/h of Hartmann’s solution IV. Therespiratory rate (RR) was set to 9 breaths/min with a ventilator. The HR and MAP values were initially 120 bpm and 76mmHg and gradually decreased to 70 bpm and 40 mmHg, respectively. The end-tidal CO2 partial pressure (ETCO2) was 39mmHg, and the patient was administered 2.5 μg/kg glycopyrrolate IV. Then, 5 μg/kg/min dopamine was administered IVsince the MAP did not improve. The HR, MAP, and ETCO2 increased to 113 bpm, 72 mmHg, and 47 mmHg, respectively.Subsequently, HR and MAP dramatically decreased to 50 bpm and 43 mmHg, respectively. A second-degree atrioventricularblock was detected, prompting dopamine infusion discontinuation, and 2.5 μg/kg glycopyrrolate was again administeredIV. Within 5 min, HR and MAP values normalized, and postoperative patient recovery was typical. Case 2: A 2-year-old,8.6 kg, mongrel underwent surgery to correct a medial luxating patella of the right leg. The patient was premedicated with0.3 mg/kg midazolam and 0.2 mg/kg butorphanol IV. Anesthesia was induced with 4 mg/kg propofol IV and maintained...

Bezold-Jarisch reflex induced by dopamine during isoflurane anesthesia in small dogs

Background: Unlike other major reflexes contributing to hemodynamic homeostasis, the Bezold-Jarisch reflex (BJR)paradoxically decreases heart rate (HR) and mean arterial pressure (MAP) despite hypotension. In the veterinary field,there are few reported cases of BJR induced by dopamine, which is often used to manage hypotension. Herein, 2 casesinvolving small dogs exhibiting BJR due to dopamine infusion during general anesthesia are described.Cases: Case 1: A 7-year-old, 7 kg, mongrel was referred for external skeletal fixator removal. The patient was premedicatedwith 0.3 mg/kg midazolam and 0.2 mg/kg butorphanol intravenously (IV). General anesthesia was induced with 6 mg/kgpropofol and maintained with 1.6% isoflurane in oxygen. The patient was given 5 mL/kg/h of Hartmanns solution IV. Therespiratory rate (RR) was set to 9 breaths/min with a ventilator. The HR and MAP values were initially 120 bpm and 76mmHg and gradually decreased to 70 bpm and 40 mmHg, respectively. The end-tidal CO2 partial pressure (ETCO2) was 39mmHg, and the patient was administered 2.5 μg/kg glycopyrrolate IV. Then, 5 μg/kg/min dopamine was administered IVsince the MAP did not improve. The HR, MAP, and ETCO2 increased to 113 bpm, 72 mmHg, and 47 mmHg, respectively.Subsequently, HR and MAP dramatically decreased to 50 bpm and 43 mmHg, respectively. A second-degree atrioventricularblock was detected, prompting dopamine infusion discontinuation, and 2.5 μg/kg glycopyrrolate was again administeredIV. Within 5 min, HR and MAP values normalized, and postoperative patient recovery was typical. Case 2: A 2-year-old,8.6 kg, mongrel underwent surgery to correct a medial luxating patella of the right leg. The patient was premedicated with0.3 mg/kg midazolam and 0.2 mg/kg butorphanol IV. Anesthesia was induced with 4 mg/kg propofol IV and maintained...(AU)