Relative potency of ketamine and S(+)-ketamine in dogs

The aim of this study was to determine the relative potency of racemic ketamine and S(+)-ketamine for the hypnotic effect and to evaluate the clinical anesthesia produced by equianesthetic doses of these two substances in dogs. One hundred and eight dogs were allocated in groups R2, R2.5, R3, R6, R9, R12, S2, S2.5, S3, S6, S9, and S12, to receive by intravenous route 2, 2.5, 3, 6, 9, and 12 mg/kg of ketamine or S(+)-ketamine, respectively. A dose-effect curve was drawn with the dose logarithm and the percentage of dogs that presented hypnosis in each group. The curve was used to obtain a linear regression, to determine the effective doses 100 and the potency relationship. In another experimental phase, eight groups of five dogs received 3, 6, 9 and 12 mg/kg of ketamine or S(+)-ketamine to evaluate the periods of latency, hypnosis, and total recovery. The times in which the dogs reached the sternal position, attempted to stand up for the first time, recovered the standing position, and started to walk were also recorded. The hypnotic dose for ketamine was 9.82 +/- 3.02 (6.86-16.5) mg/kg and for S(+)-ketamine was 7.76 +/- 2.17 (5.86-11.5) mg/kg. The time of hypnosis was longer in R3 and the first attempt to stand up occurred early in R6 when compared with S3 and S6 respectively. When R9 (100% of hypnosis with ketamine) and S6 [100% of hypnosis with S(+)-ketamine] were compared (1:1.5 ratio), the time to sternal position (12 +/- 2.5 and 20.2 +/- 5.6 min respectively) and the total recovery time (45 +/- 5.5 and 60.2 +/- 5.2 min respectively) were significantly shorter with S(+)-ketamine. It was concluded that the potency ratio between ketamine and S(+)-ketamine in dogs is smaller than the one reported in other species, and that the dose obtained after a reduction of 50%, as usually performed in humans, would not be enough to obtain equianesthetic effects in dogs.

Comparison between two methods for cardiac output measurement in propofol-anesthetized dogs: thermodilution and Doppler

ObjectiveTo compare cardiac output (CO) measured by Doppler echocardiography and thermodilution techniques in spontaneously breathing dogs during continuous infusion of propofol. To do so, CO was obtained using the thermodilution method (CO(TD)) and Doppler evaluation of pulmonary flow (CO(DP)) and aortic flow (CO(DA)).Study designProspective cohort study.AnimalsEight adult dogs weighing 8.3 +/- 2.0 kg.MethodsPropofol was used for induction (7.5 +/- 1.9 mg kg-1 IV) followed by a continuous rate infusion at 0.7 mg kg-1 minute-1. The animals were positioned in left lateral recumbency on an echocardiography table that allowed for positioning of the transducer at the 3rd and 5th intercostal spaces of the left hemithorax for Doppler evaluation of pulmonary and aortic valves, respectively. CO(DP) and CO(DA) were calculated from pulmonary and aortic velocity spectra, respectively. A pulmonary artery catheter was inserted via the jugular vein and positioned inside the lumen of the pulmonary artery in order to evaluate CO(TD). The first measurement of CO(TD), CO(DP) and CO(DA) was performed 30 minutes after beginning continuous infusion (T0) and then at 15-minute intervals (T15, T30, T45 and T60). Numeric data were submitted to two-way anova for repeated measurements, Pearson's correlation coefficient and Bland & Altman analysis. Data are presented as mean +/- SD.ResultsAt T0, CO(TD) was lower than CO(DA). CO(DA) was higher than CO(TD) and CO(DP) at T30, T45 and T60. The difference between the CO(TD) and CO(DP), when all data were included, was -0.04 +/- 0.22 L minute-1 and Pearson's correlation coefficient (r) was 0.86. The difference between the CO(TD) and CO(DA) was -0.87 +/- 0.54 L minute-1 and r = 0.69. For CO(TD) and CO(DP), the difference was -0.82 +/- 0.59 L minute-1 and r = 0.61.ConclusionDoppler evaluation of pulmonary flow was a clinically acceptable method for assessing the CO in propofol-anesthetized dogs.

The effects of 2 levels of the inspired oxygen fraction on blood gas variables in propofol-anesthetized dogs with high intracranial pressure

The influence of 2 different levels of the inspired oxygen fraction (FiO(2)) on blood gas variables was evaluated in dogs with high intracranial pressure (ICP) during propofol anesthesia (induction followed by a continuous rate infusion [CRI] of 0.6 mg/kg/min) and intermittent positive pressure ventilation (IPPV). Eight adult mongrel dogs were anesthetized on 2 occasions, 21 d apart, and received oxygen at an FiO(2) of 1.0 (G100) or 0.6 (G60) in a randomized crossover fashion. A fiberoptic catheter was implanted on the surface of the right cerebral cortex for assessment of the ICP. An increase in the ICP was induced by temporary ligation of the jugular vein 50 min after induction of anesthesia and immediately after baseline measurement of the ICP. Blood gas measurements were taken 20 min later and then at 15-min intervals for 1 h. Numerical data were submitted to Morrison's multivariate statistical methods. The ICP, the cerebral perfusion pressure and the mean arterial pressure did not differ significantly between FiO(2) levels or measurement times after jugular ligation. The only blood gas values that differed significantly (P < 0.05) were the arterial oxygen partial pressure, which was greater with G100 than with G60 throughout the procedure, and the venous haemoglobin saturation, that was greater with G100 than with G60 at M0. There were no significant differences between FiO(2) levels or measurement times in the following blood gas variables: arterial carbon dioxide partial pressure, arterial hemoglobin saturation, base deficit, bicarbonate concentration, pH, venous oxygen partial pressure, venous carbon dioxide partial pressure and the arterial-to-end-tidal carbon dioxide difference.

Cardiac function in dogs with chronic Chagas cardiomyopathy undergoing autologous stem cell transplantation into the coronary arteries

This study assessed the effects of a single intracoronary injection of autologous stem cells on the cardiac function of dogs with Chagas cardiomyopathy. Bone-marrow-derived stem cells were delivered into the right and left coronary arteries of 5 mature dogs with mildly compromised cardiac function due to chronic Chagas cardiomyopathy. Blood pressure and electrocardiographic and echocardiographic parameters were recorded at monthly intervals for 6 mo in the 3 dogs that survived. Although no changes were observed in the electrocardiogram and blood pressure, there was a significant increase in peak velocity of aortic flow 3 mo after stem cell transplantation. Pre-ejection period, isovolumic relaxation time, and the Tei index of myocardial performance were reduced significantly 4 mo after the procedure. All significant changes persisted to the end of the study. The results suggest that the transplantation of autologous bone-marrow-derived stem cells into the coronary arteries of dogs with Chagas cardiomyopathy may have a beneficial effect but the small number of dogs studied was a limitation.

Effects of isoflurane on echocardiographic parameters in healthy dogs

Obejective To study the echocardiographic effects of isoflurane at an end-tidal concentration approximating 1.0 times the minimum alveolar concentration (MAC) in healthy unpremedicated dogs.Study design Prospective experimental trial.Animals Sixteen mature mongrel dogs of either sex weighing 11.06 +/- 2.72 kg.Methods After performing a baseline echocardiogram in the awake animal, anesthesia was induced with increasing inspired concentrations of isoflurane via a face mask until tracheal intubation was possible. Following intubation, the end-tidal concentration was decreased to 1.4% for the rest of the anesthetic period. Serial echocardiograms were recorded at 25, 40, and 55 minutes after the end-tidal concentration was reached.Results No changes were observed in heart rate. However, significant decreases were seen in left ventricular end-diastolic diameter (Mean maximal change: 13.8%), interventricular septal thickness during systole (15.2%), interventricular septal thickening fraction (72.2%), left ventricular free wall thickening fraction (63.5%), ejection fraction (39.9%), and fractional shortening (46.7%). In addition, peak flow velocities across mitral, pulmonic, and aortic valves were significantly lower than baseline values. Decreases were also observed in end-diastolic left ventricular volume index (approximately 32.1% from the awake value), stroke index (58.2%), and cardiac index (55.3%) when compared with awake measurements.Conclusions Our results indicate that 1 x MAC isoflurane caused significant myocardial depression in healthy dogs. These changes in myocardial function need to be considered carefully when isoflurane is to be used in dogs with poor cardiovascular reserve.

Postoperative analgesic effects of epidural administration of neostigmine alone or in combination with morphine in ovariohysterectomized dogs

Objective-To evaluate analgesic effects of epidurally administered neostigmine alone or in combination with morphine in dogs after ovariohysterectomy.Animals-40 healthy bitches.Procedures-After acepromazine premedication, anesthesia was induced. Dogs randomly received 1 of the following 4 epidural treatments 30 minutes before ovariohysterectomy (n = 10/group): saline (0.9% NaCl) solution (control), morphine (0.1 mg/kg), neostigmine (10 pg/kg), or morphine-neostigmine (0.1 mg/kg and 10 pg/kg, respectively). Analgesia was assessed for 24 hours after surgery by use of a visual analogue.scale (VAS; scale of 0 to 10) or numeric descriptive scale (NDS; scale of 0 to 24) and by the need for supplemental analgesia (morphine [0.5 mg/kg, IM] administered when VAS was >= 4 or NDS was >= 8).Results-Significantly more control dogs (n = 8) received supplemental analgesia, compared with the number of neostigmine-treated dogs (1); no dogs in the remaining groups received supplemental analgesia. Compared with values for the control dogs, the NDS scores were lower for morphine-neostigmine-treated dogs (from 2 to 6 hours and at 12 hours) and for morphine-treated dogs (all time points). The NDS scores were lower for morphine-treated dogs at 3, 12, and 24 hours, compared with values for neostigmine-treated dogs. The VAS was less sensitive than the NDS for detecting differences among groups.Conclusions and Clinical Relevance-Epidurally administered neostigmine reduced the use of supplemental analgesia after ovariohysterectorny in dogs. However, analgesic effects were less pronounced than for epidurally administered morphine or morphine-neostigmine. Adding neostigmine to epidurally administered morphine did not potentiate opioid-induced analgesia.

Effects of nitrous oxide on IOP and pupillary diameter in dogs anesthetized with varying concentrations of desflurane

Objective The aim of the present study was to evaluate the effects of nitrous oxide on TOP and pupillary diameter (PD) of dogs anesthetized with varying desflurane concentrations.Animals studied Twenty adult Mongrel dogs were used.Methods They were anesthetized with propofol (10 mg/kg, IV) and maintained with varying concentrations of desflurane (1.6, 1.4, and 1.2 MAC diluted in 100% oxygen (G1) or in 70% nitrous oxide and 30% oxygen (G2) (30 mL/kg/min). TOP was measured by applanation tonometry and horizontal PD was taken with a caliper adjacent to the cornea. Mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR), and end-tidal CO, (etCO(2)) were also measured. All parameters were measured at TO, T30, T45, and T60 time points. One-way repeated measures ANOVA and the t-test were used to assess statistical differences (P < 0.05).Results T30, T45, and T60 TOP measures were Within normal limits for both groups and TOP did not differ between groups at any time. There was a significant decrease in PD in G I between TO and T30, T45 and T60, and also between T30 and T60. PD did not differ between groups. All vital parameters were within normal limits throughout anesthesia.Conclusions Administration of nitrous oxide with desflurane results in maintenance of normal TOP and prevents a decrease in horizontal PD during anesthesia. Therefore, this may be a suitable protocol in dogs undergoing intraocular surgeries that require mydriasis and maintenance of normal TOP.

Bispectral index in dogs at three intravenous infusion rates of propofol

Objective To establish the correlation between the bispectral index (BIS) and different rates of infusion of propofol in dogs.Study design Prospective experimental trial.Animals Eight adult dogs weighing 6-20 kg.Methods Eight animals underwent three treatments at intervals of 20 days. Propofol was used for induction of anesthesia (10 mg kg(-1) IV), followed by a continuous rate infusion (CRI) at 0.2 mg kg(-1) minute(-1) (P2), 0.4 mg kg(-1) minute(-1) (P4) or 0.8 mg kg(-1) minute(-1) (P8) for 55 minutes. The BIS values were measured at 10, 20, 30, 40, and 50 minutes (T10, T20, T30, T40, and T50, respectively) after the CRI of propofol was started. Numeric data were submitted to analysis of variance followed by Tukey test (p < 0.05).Results The BIS differed significantly among groups at T40, when P8 was lower than P2 and P4. At T50, P8 was lower than P2. The electromyographic activity (EMG) in P2 and P4 was higher than P8 at T40 and T50.Conclusion An increase in propofol infusion rates decreases the BIS values and EMG.

Serum magnesium levels in healthy dogs submitted to the administration of cisplatin with fluid therapy

Cisplatin is an antineoplastic drug that is used to treat carcinomas and osteosarcomas in dogs. However, it can cause kidney damage which in turn leads to the loss of electrolytes. Concentration of magnesium was evaluated in the blood serum of eight dogs that had undergone therapy with cisplatin. The dogs were divided into two groups. Group 1 was supply with cisplatin (70 mg/m(2), iv) and to prevent nephrotoxcity, saline solution at 0.9% was administered (25 ml/kg/hour, iv in three hours). The animals in Group 2 were not supplied with cisplatin. There was no significant difference (P < 0.05) between the two groups and the results obtained indicated that the protocol used for Group 1 did not cause changes in the serum concentrations of magnesium. Therefore, it can be concluded that the administration of cisplatin does not cause variations if it is combined with the fluid therapy.

Bispectral index in dogs with high intracranial pressure, anesthetized with propofol and submitted to two levels of FiO2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Histopathological and histomicrobiological study of root canal therapy medication, comparison of calcium hydroxide versus gutta-percha with zinc oxide/eugenol in the teeth of dogs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação radiográfica da cobertura acetabular à cabeça femoral, após osteotomia tripla e aplicação de cunha sacroilíaca, em pelve de cadáveres de cães

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Clinical characterization of chronic chagasic cardiomyopathy in dogs

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Participação da excreção renal de cálcio, fósforo, sódio e potássio na homeostase em cães sadios e cães com doença renal crônica

Na doença renal crônica (DRC) a manutenção da homeostase de água e sódio é o primeiro problema a ser contornado pelo organismo e com o agravamento das lesões renais surgem outros problemas graves relacionados à homeostase de cálcio e fósforo. O presente estudo tem por escopo avaliar a excreção renal de cálcio, fósforo, sódio e potássio, e o perfil sérico destes eletrólitos em cães normais e em cães com DRC naturalmente adquirida. Foram avaliados três grupos de cães adultos, machos ou fêmeas, de raças variadas. Animais normais compuseram o grupo controle (G1) e os cães com DRC foram distribuídos em dois grupos de acordo com os estágios de comprometimento da função renal (G2 e G3, respectivamente, estágios 1-2 e estágios 3-4, descritos pela IRIS 2006 staging CKD). Os cães do G3 apresentaram aumento das concentrações séricas de cálcio ionizado e fósforo, além de diminuição da concentração sérica de sódio. Quanto à excreção renal dos eletrólitos analisados, os animais dos grupos G1 e G2 apresentaram diminuição de carga filtrada e aumento de excreção fracionada, mas as excreções urinárias não variaram significativamente. Os resultados são indicativos de que os rins de cães com DRC podem manter a excreção urinária dos eletrólitos em valores se melhantes aos dos normais. O mecanismo envolve aumento da excreção fracionada na medida em que haja diminuição da filtração glomerular. Esse processo de compensação, entretanto, pode perder a eficiência nos estágios mais avançados da enfermidade no que se refere à manutenção das concentrações séricas de fósforo e sódio.

Prevalence of DEA 1 canine blood group system in dogs (Canis familiaris, Linnaeus, 1758) reared in Brazil

Os cães possuem cinco grupos sangüíneos bem estabelecidos, compostos por sete determinantes antigênicos eritrocitários, os quais são denominados de dog erythrocyte antigen (DEA). O grupo DEA 1 (subgrupos 1.1, 1.2 e 1.3) tem sido considerado o mais importante no que se refere às transfusões de sangue. Isto ocorre porque esse grupo possui um alto potencial para estimulação antigênica e, dessa forma, pode estimular a produção de anticorpos se um receptor DEA 1 negativo receber uma transfusão de sangue DEA 1 positivo, levando a uma reação transfusional hemolítica em uma segunda transfusão com hemácias do tipo DEA 1. A freqüência de aparecimento do grupo DEA 1 é bem conhecida em outros países, porém, até então, não havia informações disponíveis sobre o referido grupo no Brasil. No presente estudo, objetivou-se avaliar a prevalência do grupo sangüíneo DEA 1 (subgrupos 1.1 e 1.2) em cães criados no Brasil. Para tanto, 150 cães de raças, sexos e idades diferentes, triados junto ao Hospital Veterinário da FCAV/UNESP, Campus de Jaboticabal, foram submetidos a tipagem sangüínea para o grupo DEA 1 (subgrupos 1.1 e 1.2) canino, utilizando-se reagentes adquiridos comercialmente junto ao Laboratório de Imunoematologia e Sorologia da Universidade de Michigan (EUA). Os resultados obtidos neste ensaio revelaram que a prevalência geral para o grupo DEA 1 é de 91,3%, consideradas as condições e características da população estudada, compreendendo 51,3% de cães do tipo DEA 1.1, 40% de cães do tipo DEA 1.2, e os 8,7% restantes sendo negativos para o referido grupo. A partir das prevalências encontradas, calculou-se que a probabilidade de um cão DEA 1 negativo receber sangue DEA 1.1, em uma primeira transfusão feita ao acaso, é de aproximadamente 4,5%. Sendo assim, este índice reflete um risco potencial para a sensibilização de um receptor DEA 1 negativo, o que deflagraria a produção de anticorpos. Posteriormente, se este mesmo paciente recebesse uma segunda transfusão de sangue, feita ao acaso, a probabilidade de receber hemácias do tipo DEA 1.1 seria de aproximadamente 2,3%, o que representaria o risco potencial de ocorrência de uma reação transfusional hemolítica aguda. Por outro lado, a probabilidade de este cão receber sangue do tipo DEA 1.2 seria cerca de 1,8%, o que levaria a uma reação transfusional menos grave, porém potencialmente prejudicial. No presente estudo, observou-se que o risco potencial para uma reação transfusional é mínimo, quando se trata de um cão mestiço.