Effects of dexmedetomidine on hemodynamic, oxygenation, microcirculation, and inflammatory markers in a porcine model of sepsis

Purpose: To determine whether dexmedetomidine aggravates hemodynamic, metabolic variables, inflammatory markers, and microcirculation in experimental septic shock. Methods: Twenty-four pigs randomized into: Sham group (n = 8), received saline; Shock group (n = 8), received an intravenous infusion of Escherichia coli O55 (3 × 109 cells/mL, 0.75 mL/kg, 1 hour); Dex-Shock group (n = 8), received bacteria and intravenous dexmedetomidine (bolus 0.5 mcg/kg followed by 0.7 mcg/kg/h). Fluid therapy and/ornorepinephrine were administered to maintain a mean arterial pressure > 65 mmHg. Hemodynamic, metabolic, oxygenation, inflammatory markers, and microcirculation were assessed at baseline, at the end of bacterial infusion, and after 60, 120, 180, and 240 minutes. Results: Compared to Shock group, Dex-Shock group presented a significantly increased oxygen extraction ratio at T180 (23.1 ± 9.7 vs. 32.5 ± 9.2%, P = 0.0220), decreased central venous pressure at T120 (11.6 ± 1 vs. 9.61 ± 1.2 mmHg, P = 0.0214), mixed-venous oxygen saturation at T180 (72.9 ± 9.6 vs. 63.5 ± 9.2%, P = 0.026), and increased plasma lactate (3.7 ± 0.5 vs. 5.5 ± 1 mmol/L, P = 0.003). Despite the Dex-Shock group having a better sublingual vessel density at T240 (12.5 ± 0.4 vs. 14.4 ± 0.3 mL/m2; P = 0.0003), sublingual blood flow was not different from that in the Shock group (2.4 ± 0.2 vs. 2.4 ± 0.1 mL/kg, P = 0.4418). Conclusions: Dexmedetomidine did not worsen the hemodynamic, metabolic, inflammatory, or sublingual blood flow disorders resulting from septic shock. Despite inducing a better sublingual vessel density, dexmedetomidine initially and transitorily increased the mismatch between oxygen supply and demand.

Effect of hypertonic saline treatment on the inflammatory response after hydrochloric acid-induced lung injury in pigs

OBJECTIVES: Hypertonic saline has been proposed to modulate the inflammatory cascade in certain experimental conditions, including pulmonary inflammation caused by inhaled gastric contents. The present study aimed to assess the potential anti-inflammatory effects of administering a single intravenous dose of 7.5% hypertonic saline in an experimental model of acute lung injury induced by hydrochloric acid. METHODS: Thirty-two pigs were anesthetized and randomly allocated into the following four groups: Sham, which received anesthesia and were observed; HS, which received intravenous 7.5% hypertonic saline solution (4 ml/kg); acute lung injury, which were subjected to acute lung injury with intratracheal hydrochloric acid; and acute lung injury + hypertonic saline, which were subjected to acute lung injury with hydrochloric acid and treated with hypertonic saline. Hemodynamic and ventilatory parameters were recorded over four hours. Subsequently, bronchoalveolar lavage samples were collected at the end of the observation period to measure cytokine levels using an oxidative burst analysis, and lung tissue was collected for a histological analysis. RESULTS: Hydrochloric acid instillation caused marked changes in respiratory mechanics as well as blood gas and lung parenchyma parameters. Despite the absence of a significant difference between the acute lung injury and acute lung injury + hypertonic saline groups, the acute lung injury animals presented higher neutrophil and tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-8 levels in the bronchoalveolar lavage analysis. The histopathological analysis revealed pulmonary edema, congestion and alveolar collapse in both groups; however, the differences between groups were not significant. Despite the lower cytokine and neutrophil levels observed in the acute lung injury + hypertonic saline group, significant differences were not observed among the treated and non-treated groups. ...

Comparison of full-field electroretinogram in diabetic and non diabetic dogs with cataracts / Estudo comparativo do eletrorretinograma de campo total em cães diabéticos e não diabéticos com catarata

Being the commonest ocular disorder, dense cataracts disable fundoscopic examination and the diagnosis of retinal disorders, which dogs may be predisposed. The aim of this study was to compare the electroretinographic responses recorded according to the International Society for Clinical Electrophysiology of Vision human protocol to evaluate retinal function of diabetic and non diabetic dogs, both presenting mature or hypermature cataracts. Full-field electroretinogram was recorded from 66 dogs, with ages varying from 6 to 15 years old allocated into two groups: (1) CG, non diabetic cataractous dogs, and (2) DG, diabetic cataractous dogs. Mean peak-to-peak amplitude (microvolts) and b-wave implicit time (milliseconds) were determined for each of the five standard full-field ERG responses (rod response, maximal response, oscillatory potentials, single-flash cone response and 30 Hz flicker). Comparing CG to DG, ERGs recorded from diabetic dogs presented lower amplitude and prolonged b-wave implicit time in all ERG responses. Prolonged b-wave implicit time was statistically significant (p< 0.05) at 30 Hz flicker (24.0 ms versus 22.4 ms). These data suggests full-field ERG is capable to record sensible alterations, such as flicker's implicit time, being useful to investigate retinal dysfunction in diabetic dogs.

Catarata madura e hipermadura, alteração frequentemente observada em cães, impossibilita a visibilização do fundo do olho e provável diagnóstico de degenerações retinianas. Objetivou-se comparar as respostas retiniana de cães diabéticos e não diabéticos, ambos portadores de catarata madura ou hipermadura, com auxílio do eletrorretinograma de campo total, utilizando o protocolo da International Society for Clinical Electrophysiology of Vision. Sessenta e seis cães, com idades variando entre 6 a 15 anos de idade foram divididos em dois grupos: (1) CG, cães não diabéticos com catarata madura ou hipermadura e (2) DG, cães diabéticos com catarata madura ou hipermadura. Mensurou-se amplitude pico a pico (microvolts) e tempo de culminação da onda-b (milisegundos) para as cinco respostas do ERG (resposta de bastonetes, máxima resposta, potencial oscilatório, resposta de cones e flicker a 30Hz). Avaliando-se as respostas obtidas com o exame, o grupo de cães diabéticos apresentou menor amplitude e maior tempo de culminação da onda-b em todas as respostas. O aumento do tempo de culminação da onda-b em DG foi estatisticamente significante (p<0.05) no flicker a 30 Hz (24.0ms versus 22.4ms). ERG de campo total é capaz de registrar alterações em respostas sensíveis como o tempo de culminação da onda-b do flicker, podendo ser útil para investigar retinopatias em cães diabéticos.

Padronização do eletrorretinograma de campo total em cães / Full field electrorretinogram standartization in dogs

Eletrorretinograma (ERG) é o meio diagnóstico objetivo e não-invasivo para avaliar a função retiniana e detectar precocemente, em várias espécies, lesões nas suas camadas mais externas. As indicações mais comuns para ERG em cães são: avaliação pré-cirúrgica de pacientes com catarata, caracterização de distúrbios que causam cegueira, além de servir como importante modelo para o estudo da distrofia retiniana que acomete o homem. Vários são os fatores que podem alterar o ERG tais como: eletrorretinógrafo, fonte de estimulação luminosa, tipo do eletrodo, tempo de adaptação ao escuro, tamanho pupilar, opacidade de meios e protocolo de sedação ou anestesia; além da espécie, raça e idade. Objetivou-se com este estudo padronizar o ERG para cães submetidos à sedação, seguindo o protocolo da International Society for Clinical Electrophysiology of Vision (ISCEV), utilizando Ganzfeld e eletrodos Burian Allen. Foram realizados 233 eletrorretinogramas em cães, 147 fêmeas e 86 machos, com idades entre um e 14 anos. Dos 233 cães examinados, 100 apresentavam catarata em diferentes estágios de maturação, 72 eram diabéticos e apresentavam catarata madura ou hipermadura, 26 apresentaram eletrorretinograma compatível com degeneração retiniana progressiva, três apresentaram eletrorretinograma compatível com síndrome da degeneração retiniana adquirida subitamente e 32 não apresentaram lesão retiniana capaz de atenuar as respostas do ERG, sendo considerados normais quanto à função retiniana. A sedação foi capaz de produzir boa imobilização do paciente sem rotacionar o bulbo ocular, permitindo adequada estimulação retiniana bilateralmente, com auxílio do Ganzfeld. O sistema eletrodiagnóstico Veris registrou com sucesso e simultaneamente de ambos os olhos, as cinco respostas preconizadas pela ISCEV. Como o ERG de campo total tornou-se exame fundamental na rotina oftalmológica, sua padronização é indispensável quando se objetiva comparar resultados de laboratórios distintos...

Electroretinogram (ERG) is an objective non invasive diagnostic method to evaluate retinal function which permits the early detection of lesions at retinal external layers, even before the appearance of clinical signs. In dogs, ERG is mostly utilized for preoperative evaluation in patients presenting cataracts; characterization of disturbances causing blindness, among the utilization of dogs as animal models in scientific research. Several factors interfere in ERG responses, such as the ERG machine, light stimulation, electrode, time spent on dark adaptation, pupil size, means opacity, sedation or anesthetization, species, breed and age. The purpose of this study was to standardize the full field ERG in sedated dogs, according to the International Society for Clinical Electrophysiology of Vision (ISCEV) protocol, using Ganzfeld and bipolar electrodes. Two hundred thirty threes ERGs were performed in 147 female and 86 male with ages from 1 to 14 years old. Among those 233 dogs, 100 presented cataracts in different stages of maturation, 72 were diabetic and presented mature or hypermature cataracts, 26 presented ERG compatible to progressive retinal degeneration, 3 presented ERG compatible to sudden acquired retinal degeneration syndrome; for 32 dogs no abnormal ERG was registered and they were considered as having normal retinal function. Sedation was capable to induce a good immobilization with no bulb rotation, resulting uniform retinal stimulation, using Ganzfeld. Veris system successfully registered all 5 ISCEV responses, simultaneously from both eyes, at the same time. Full field ERG became a fundamental ophthalmic exam, then, its standardization is mandatory to allow comparison between ERGs from different laboratories. The reliability and reproducibility of this protocol has shown very good responses, using ISCEV protocol, Veris system, Ganzfeld and Burian Allen electrodes in sedated dogs.

Outflow occlusion for circulatory arrest in dogs / "Outfow occlusion" para parada circulatória em cães

The purpose of this study was to evaluate the possibility of producing circulatory arrest by occlusion of the pulmonary trunk as an alternative to the venous inflow occlusion through the left hemithorax. Eight healthy mongrel dogs were divided in two groups. Group I underwent 4 minutes of outflow occlusion and Group II was submitted to 8 minutes of circulatory arrest. Outflow occlusion was performed through left thoracotomy and pericardiotomy by passing a Rumel tourniquet around the pulmonary trunk. Physical examination, electrocardiography, echocardiography, blood gas analyses, hemodynamic, and oxygen transport variables were obtained before and after the procedure. The dogs from Group I did not have any clinical, electrocardiographic, echocardiographic, or hemo-dynamic abnormalities after anesthetic recover. In the Group II, only one dog survived, which had no clinical, electrocardiographic, or echocardiographic abnormalities. In this last dog, just after releasing the occlusion, it was detected increases in the following parameters: heart rate (HR), systolic, diastolic and mean arterial blood pressure (SAP; DAP; MAP), pulmonary artery pressure (PAP), pulmonary wedge pressure (PWP), central venous pressure (CVP), cardiac output (CO), systolic index (SI), cardiac index (CI), left and right ventricular stroke work (LVSW; RVSW), oxygen delivery index (DO2), oxygen consumption index (VO2), and oxygen extraction (O2 ext). Moreover, the oxygen content of arterial and mixed venous blood (CaO2; CvO2), and the arterial and mixed venous partial pressure of oxygen (PaO2; PvO2) were decreased 5 minutes after circulatory arrest. Outflow occlusion is a feasible surgical procedure for period of 4 minutes of circulatory arrest.

O objetivo deste estudo foi avaliar a possibilidade de se produzir uma parada circulatória pela oclusão do tronco pulmonar, como alternativa ao "inflow occlusion", pelo hemitórax esquerdo. Oito cães sem raça definida foram divididos em dois grupos. O Grupo I foi submetido a quatro minutos de parada circulatória e o Grupo II, a 8 minutos de parada. Realizou-se o "outflow occlusion" por meio de toracotomia intercostal esquerda e pericardiotomia, passando-se um torniquete de Rumel ao redor do tronco pulmonar. Foram realizados exame físico, eletrocardiografia, ecocardiografia, hemogasometria, avaliação hemodinâmica e cálculo de variáveis de transporte de oxigênio, antes e após o procedimento. Os cães do Grupo I não sofreram alterações clínicas, eletrocardiográficas, ecocardiográficas e hemodinâmicas após a recuperação anestésica. No Grupo II, apenas um animal sobreviveu, sem apresentar alterações clínicas, eletrocardiográficas e ecocardiográficas. Neste cão, após a liberação do torniquete, houve aumento nas seguintes variáveis: freqüência cardíaca, pressões arteriais sistólica, média e diastólica, pressão arterial pulmonar, pressão da artéria pulmonar ocluída, pressão venosa central, débito cardíaco, índice sistólico, índice cardíaco, trabalho ventricular esquerdo e direito, índice de transporte de oxigênio, índice de consumo de oxigênio e taxa de extração de oxigênio. O conteúdo de oxigênio arterial e venoso misto e a pressão parcial de oxigênio arterial e venosa mista diminuíram, cinco minutos após a parada circulatória. Concluiu-se que o "outflow occlusion" é um procedimento viável para a realização de parada circulatória por um período de quatro minutos.

Viabilidade da pneumonectomia direita em cães: uma avaliação paramétrica, hemogasométrica e radiográfica / Viability of the right pneumonectomy in dogs: a parametric, hemogasometric and radiological evaluation

Em cães, a comprovação da real viabilidade da pneumonectomia direita, bem como, o estudo das complicações resultantes deste procedimento cirúrgico, tornam-se importantes diante da pequena quantidade de estudos na literatura específicos sobre pneumonectomia nesta espécie. O objetivo deste trabalho foi realizar um estudo experimental para avaliar a viabilidade da pneumonectomia direita em cães, através da avaliação paramétrica, hemogasométrica e radiográfica Foram utilizados 10 cães adultos, sadios, machos e fêmeas sem raça definida, pesando entre 13 e 32 kg. Todos os cães foram submetidos à intubação seletiva e toracotomia direita no 5º espaço intercostal, onde foi realizada a pneumonectomia. Foi realizado estudo temporal aos 7, 30 e 60 dias de pós-operatório, onde foi feito avaliação radiográfica, bem como, avaliação paramétrica e hemogasométrica (antes da indução anestésica, 1 hora após extubação, 48 horas, 7, 30 e 60 dias após o procedimento cirúrgico), con,siderados importantes para avaliar as possíveis complicações relacionadas com a técnica anestésica, cirúrgica, assim como, as complicações resultantes deste procedimento cirúrgico. Os resultados encontrados foram analisados estatisticamente. Apesar das alterações dos índices paramétricos e hemogasométricos, todos os cães apresentaram compensação das trocas gasosas após retirada de 57 por cento do volume pulmonar. Na avaliação radiográfica, observamos que a expansão do pulmão remanescente causou deslocamento do coração e pulmão para hemitórax direito. Concluiu-se que a realização da pneumonectomia direita é plenamente viável no cão, permitindo evolução paramétrica, hemogasométrica e radiográfica satisfatória em todos os cães.

In dogs, the evidence of viability of the right pneumonectomy, as well as the study of complications resulting from surgical procedure, are very important regarding the few specific studies made on the pneumonectomy in this animal species. The objective of this project was to carry out an experimental study to evaluate the viability of the right pneumonectomy in dogs through parametric, hemogasometric and radiographic evaluation. Ten adult healthy mongrel dogs, males and females, weighing 13-32 kg, were used. The dogs were submitted to selective intubation and right thoracotomy at the 5th intercostal space, where the pneumonectomy was performed. A radiografic evaluation was made on days 7, 30 and 60 after the surgery, as well as parametric and hemogasometric evaluations were done (before anesthetic induction, 1 hour after extubation, 48 hours and on days 7, 30 and 60 after the surgical procedure), considered important to evaluate possible complications due to the anesthetic and surgical techniques, as well as complications resulting from these procedures. The results were analyzed statistically. Besides the parametric and hemogasometric alterations, all dogs showed compensation for the gaseous exchanges after removing 57 percent of the pulmonary volume. Regarding the radiographic evaluation, it could be observed that the expansion of the remaining lung caused heart and lung displacement into the right hemithorax. It can be concluded that the right pneumonectomy is completely feasible in dogs, allowing a parametric, hemogasometric and radiographic satisfactory evaluation in all the animals.