Influence of body position on the measurement of electrocardiographic waves in healthy dogs / Influência do posicionamento corporal na mensuração das ondas eletrocardiográficas em cães sadios

The agreement between the electrocardiographic waves measured from tracings recorded in right lateral recumbency and several other unusual body positions was assessed. Electrocardiograms were recorded in 160 healthy dogs in right lateral, left lateral, dorsal and sternal recumbencies, as well as in standing position. Considering the right lateral recordings as the gold standard, the lowest biases for the majority of ECG parameters were calculated from left lateral recordings, whereas the highest biases were documented from dorsal and standing positions. For the mean electrical axis, the dorsal recumbency produced the lowest bias, while the greatest one was identified in sternal position. An analysis of variance indicated differences when the means of P wave duration and amplitude, duration of QRS and QT, and mean electrical axis obtained in unusual positions were compared with right lateral. In conclusion, left lateral recumbency produced the most similar measurements as compared to right lateral, but the wide limits of agreement preclude the use and interpretation of these positions interchangeably.(AU)

A concordância entre a mensuração das ondas eletrocardiográficas a partir de traçados registrados em cães mantidos em decúbito lateral direito e em vários outros posicionamentos corporais foi avaliada nesta pesquisa. Para tanto, traçados eletrocardiográficos de 160 cães saudáveis foram registrados com os pacientes posicionados nos decúbitos lateral direito, lateral esquerdo, dorsal e esternal, assim como em posição quadrupedal. Tomando como padrão ouro os registros obtidos em decúbito lateral direito, as menores diferenças médias para a maioria dos parâmetros eletrocardiográficos foram obtidas a partir dos traçados registrados com o cão mantido em decúbito lateral esquerdo, enquanto as maiores diferenças médias foram documentadas nos registros obtidos nos decúbitos dorsal e quadrupedal. Para o eixo elétrico médio, o decúbito dorsal produziu a menor diferença média, enquanto a maior foi identificada no registro em posição esternal. A análise de variância mostrou diferenças entre as médias da duração e amplitude da onda P, duração do QRS e do intervalo QT e o eixo elétrico médico quando as posições não usuais foram comparadas com o decúbito lateral direito. Esta pesquisa mostrou que o decúbito lateral esquerdo produziu as medidas mais semelhantes quando comparado àquelas obtidas em decúbito lateral direito. No entanto, os limites de concordância amplos impedem que essas posições sejam utilizadas e interpretadas de maneira intercambiável.(AU)

Blood pressure and renal injury in dogs with visceral leishmaniasis / Pressão sanguínea e lesão renal em cães com leishmaniose visceral

Systemic hypertension is known to be a common consequence of chronic renal disease, which is frequently diagnosed in dogs with visceral leishmaniasis. Although many veterinary investigations have looked at the renal injury caused by Leishmania spp., the role played by this complication in the development of arterial hypertension documented in some animals with visceral leishmaniasis is not completely understood. In this study, 18 adult dogs with naturally-occurring visceral leishmaniasis and varying clinical signs underwent an indirect blood pressure measurement. Also, sera and spot urine were used for laboratory tests. The median systolic blood pressure was 135.2mmHg (95% confidence interval: 128.5-147.7), median mean arterial pressure was 105.8mmHg (98.3-110.4), and median diastolic arterial pressure was 88.5mmHg (77.8-92.5). No differences existed between asymptomatic and symptomatic animals regarding arterial pressure, and no correlations were documented between blood pressure and serum creatinine, blood urea, urine protein-to-creatinine ratio, urine specific gravity, and the fractional excretion of sodium and potassium. Although an association between hypertension and the identification of inflammation on histopathology could not be demonstrated in hypertensive animals, the assessment of kidney samples from 12 dogs indicated mild inflammation with a lymphoplasmacytic infiltrate (6/12), moderate inflammation with multifocal lymphoplasmacytic and histiocytic infiltrates (3/12), and multifocal degeneration and protein casts (2/12). Anti-Leishmania spp. immunohistochemistry assays stained the renal epithelium in 2/12 of the animals. Even though mild systemic hypertension was documented in a small subset of animals, no relationship between the severity of clinical signs and hypertension could be anticipated.(AU)

A hipertensão sistêmica é reconhecida como uma consequência comum da doença renal crônica, cujo diagnóstico é frequente em cães com leishmaniose visceral. Embora muitas pesquisas veterinárias tenham investigado a lesão renal causada pela Leishmania spp., o papel dessa complicação no desenvolvimento da hipertensão arterial documentada em alguns animais com leishmaniose visceral ainda não é completamente compreendido. Neste estudo, 18 cães adultos com diagnóstico de leishmaniose visceral e sinais clínicos variáveis foram submetidos à avaliação indireta da pressão arterial. Além disso, foram coletados soro e urina para análises laboratoriais. As medianas das pressões arteriais sistólica, média e diastólica foram 135,2mmHg (intervalo de confiança de 95%: 128,5-147,7), 105,8mmHg (98,3-110,4) e 88,5mmHg (77,8-92,5), respectivamente. Não foram constatadas diferenças entre os cães assintomáticos e sintomáticos em relação à pressão arterial, assim como não houve correlação entre a pressão arterial e a creatinina e uréia séricas, relação proteína-creatinina urinária, densidade urinária e excreção fracionada de sódio e potássio. Embora não tenha sido evidenciada associação entre hipertensão arterial e inflamação do tecido renal à histopatologia, a avaliação das amostras oriundas de 12 cães indicou inflamação leve, com infiltrado linfoplasmocitário (6/12), inflamação moderada com infiltrados linfoplasmocitário e histiocítico multifocais (3/12), além de degeneração multifocal e cilindros protéicos (2/12). Ensaios imunoistoquímicos anti-Leishmania spp. marcaram o epitélio renal em 2/12 animais. Apesar de hipertensão leve ter sido documentada em uma pequena parcela dos cães estudados, não se evidenciou relação entre a severidade dos sinais clínicos e o desenvolvimento de hipertensão arterial.(AU)

The effects of different inspired oxygen fractions on gas exchange and Tei-index of myocardial performance in propofol-anesthetized dogs.

OBJECTIVE: To evaluate the influence of different inspired oxygen fractions (FiO2) on pulmonary oxygen exchange and Tei-index of myocardial performance in propofol-anesthetized dogs. STUDY DESIGN: Prospective crossover, randomized, experimental trial. ANIMALS: Eight adult dogs weighing 8.6 ± 1.8 kg. METHODS: The animals were anesthetized on five occasions, receiving either an FiO2 = 1.0 (F100), 0.8 (F80), 0.6 (F60), 0.4 (F40) or 0.21 (F21). Propofol was used for induction (6.45 ± 0.69 mgkg(-1) IV) followed by a continuous rate infusion (CRI, 0.7 mgkg(-1) minute(-1)). The dogs breathed spontaneously. The initial measurements of arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2), arterial hemoglobin saturation (SaO2), heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), stroke index (SI), pre-ejection period (PEP) and left ventricular ejection time (LVET) were performed 30 minutes after beginning the CRI (T0) and then, at 15-minute intervals (T15-T60). From these measurements the following were calculated; alveolar oxygen partial pressure (PAO2), alveolar-arterial oxygen gradient (AaDO2), arterial oxygen partial pressure/inspired oxygen fraction ratio (PaO2/FiO2), arterial-to-alveolar oxygen tension ratio (PaO2/PAO2), respiratory index (RI), oxygen delivery (D·O2), PEP/LVET ratio, isovolumic relaxation time (IVRT) and Tei-index. RESULTS: At T30, PaCO2 in F100 was higher than in F21. The AaDO2 mean in F100 was greater than in other treatments. PaO2/FiO2 in F21 was lower than F100 and F80 at T0 and than in F80 and F60 at T15. At T15, PaO2/PAO2 and RI in F100 were higher than in F80, F60 and F21. At T30, PaO2/PAO2 in F21 was lower than in F100 and F60. At T30, PEP/LVET in F100 was higher than F80, F40 and F21, which was lower than F80 and F40. CONCLUSION: The Tei-index and cardiovascular parameters are not affected by different FiO2. CLINICAL RELEVANCE: An FiO2 of 1.0 and 0.21 impaired respiratory efficiency.

Assessment of the electrocardiogram in dogs with visceral leishmaniasis / Avaliação do eletrocardiograma em cães com leishmaniose visceral

As myocarditis and arrhythmias have been shown to occur in both human beings and dogs with leishmaniasis, electrocardiograms of 105 dogs serologically positive for this disease were assessed for rhythm disturbances and changes in ECG waves. A few expressive alterations were seen, including sinus arrest, right bundle branch block, and atrial premature beats in 14.3%, 4.8%, and 4.8% of the studied subjects, respectively. Also, the analysis of ECG waves showed changes suggestive of left atrium and ventricle enlargements, and myocardial hypoxia in some animals. Although cardiac compromise has been previously reported in dogs with leishmaniasis, only a small subset of dogs showed any alteration in the electrocardiogram, which cannot support the occurrence of myocarditis in this investigation.

Devido à identificação prévia de miocardite e arritmias tanto em seres humanos quanto em cães portadores de leishmaniose, 105 cães com sorologia positiva para tal enfermidade tiveram seus eletrocardiogramas avaliados quanto à presença de distúrbios do ritmo e alterações nas ondas eletrocardiográficas. Poucas variações expressivas foram observadas, exceto parada sinusal, bloqueio de ramo direito e complexos atriais prematuros em 14,3%, 4,8%, e 4,8% dos pacientes estudados, respectivamente. Ademais, a análise do ECG demonstrou alterações sugestivas de sobrecarga do átrio e do ventrículo esquerdos e hipóxia do miocárdio. Embora o comprometimento cardíaco em cães com leishmaniose já tenha sido demonstrado anteriormente, apenas uma pequena parte dos cães avaliados apresentou alteração no eletrocardiograma, não sendo possível correlacionar com a ocorrência de miocardite nesta pesquisa.

Agreement between auricular and rectal measurements of body temperature in healthy cats.

Measurement of body temperature is a routine part of the clinical assessment of a patient. However, this procedure may be time-consuming and stressful to most animals because the standard site of temperature acquisition remains the rectal mucosa. Although an increasing number of clinicians have been using auricular temperature to estimate core body temperature, evidence is still lacking regarding agreement between these two methods in cats. In this investigation, we evaluated the agreement between temperatures measured in the rectum and ear in 29 healthy cats over a 2-week period. Temperatures were measured in the rectum (using digital and mercury-in-glass thermometers) and ear once a day for 14 consecutive days, producing 406 temperature readings for each thermometer. Mean temperature and confidence intervals were similar between methods, and Bland-Altman plots showed small biases and narrow limits of agreement acceptable for clinical purposes. The interobserver variability was also checked, which indicated a strong correlation between two near-simultaneous temperature readings. Results are consistent with auricular thermometry being a reliable alternative to rectal thermometry for assessing core body temperature in healthy cats.

Comparison between auricular and standard rectal thermometers for the measurement of body temperature in dogs.

Although the rectal mucosa remains the traditional site for measuring body temperature in dogs, an increasing number of clinicians have been using auricular temperature to estimate core body temperature. In this study, 88 mature healthy dogs had body temperatures measured with auricular and rectal thermometers. The mean temperature and confidence intervals were similar for each method, but Bland-Altman plots showed high biases and limits of agreement unacceptable for clinical purposes. The results indicate that auricular and rectal temperatures should not be interpreted interchangeably.

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.

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

OBJECTIVE: To 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 DESIGN: Prospective cohort study. ANIMALS: Eight adult dogs weighing 8.3 +/- 2.0 kg. METHODS: Propofol 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. RESULTS: At 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. CONCLUSION: Doppler evaluation of pulmonary flow was a clinically acceptable method for assessing the CO in propofol-anesthetized dogs.

Hemodinâmica de diferentes frações inspiradas de oxigênio em cães submetidos à infusão contínua de propofol sob ventilação espontânea / Hemodyinamic effects of several inspired oxygen fractions in spontaneously breathing dogs submitted to continuous infusion of propofol

Avaliaram-se os efeitos do fornecimento de diferentes frações inspiradas de oxigênio (FiO2) sobre os parâmetros hemodinâmicos em cães submetidos à infusão contínua de propofol e mantidos em ventilação espontânea. Foram utilizados oito cães, os quais foram empregados em cinco grupos com diferentes FiO2, G100 (FiO2 = 1), G80 (FiO2 = 0,8), G60 (FiO2 = 0,6), G40 (FiO2 = 0,4) e G20 (FiO2 = 0,21), respeitando-se um intervalo de dez dias entre cada procedimento anestésico. Os animais foram induzidos e mantidos sob anestesia com propofol na dose de 0,7mg kg-1 min-1 e, após a intubação orotraqueal, iniciou-se o fornecimento de oxigênio conforme a FiO2 determinada para cada grupo. As primeiras mensurações, da freqüência cardíaca (FC), das pressões arteriais sistólica, diastólica e média (PAS, PAD e PAM), da resistência vascular periférica e pulmonar (RPT e RPV), do débito cardíaco (DC); da pressão venosa central (PVC), da pressão média da artéria pulmonar (PMAP), da pressão média capilar pulmonar (PMCP), da pressão parcial de oxigênio (PaO2) e do dióxido de carbono (PaCO2) no sangue arterial, foram efetuadas 30 minutos após o início da infusão do anestésico (M0), seguidas de intervalos de 15 minutos (M15, M30, M45 e M60). Os dados numéricos obtidos foram submetidos à Análise de Variância, seguida pelo teste Tukey (P<0,05). Os parâmetros hemodinâmicos não apresentaram diferenças significativas ao longo do tempo e entre os grupos. Os resultados obtidos permitiram concluir que as variáveis hemodinâmicas não são afetadas pelo emprego de diferentes FiO2.

The effects of several inspired oxygen fractions (FiO2) in hemodynamics parameters in spontaneously breathing dogs submitted to continuous infusion of propofol were evaluated. Eight adult mongrel dogs were studied and the animals underwent five anesthesias. In each procedure the patient was submitted to a different FiO2, thereby resulting in five groups, namely: G100 (FiO2 = 1), G80 (FiO2 = 0.8), G60 (FiO2 =0.6), G40 (FiO2 = 0.4), and G20 (FiO2 = 0.21). The dose of propofol was sufficient to abolish protector reflex and ensure endotracheal intubation, followed by immediate continuous infusion of that drug (0.7mg kg-1 min-1). The initial measurement (M0) of heart rate (HR); systolic (SAP), diastolic (DAP) and mean pressure (MAP), systemic (SVR) and pulmoary vascular resistance (PVR), cardiac output (CO); central venous pressures (CVP); mean pulmonary pressure (MPAP); pulmonary capillary wedge pressure (PCWP), arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2) were recorded thirty minutes after the beginning of propofol infusion. Additional recordings were performed at each 15-minute interval during 60 minutes (M15, M30, M45, and M60). Numeric data were submitted to Analysis of Variance followed by Tukey Test (P<0.05). Significant values of hemodynamic parameters were not recorded neither during the experiment period nor among the groups. In conclusion, different FiO2 does not impair hemodynamic parameters.

Effects of isoflurane on echocardiographic parameters in healthy dogs.

OBJECTIVE: 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: and clinical relevance 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.

Effects of isoflurane on Tei-index of myocardial performance in healthy dogs.

Recently, the Tei-index, a noninvasive index that combines systolic and diastolic time intervals, has been proposed to assess global cardiac performance. However, the effects of isoflurane on the Tei-index have not been characterized. This study aimed at studying the effects of 1.0 minimal alveolar concentration isoflurane anesthesia on the pre-ejection period (PEP), left ventricular ejection time (LVET), PEP/LVET ratio, isovolumic relaxation time (IVRT), stroke index (SI), cardiac index (CI), heart rate (HR), and the Tei-index in healthy unpremedicated dogs. We observed significant increases in PEP, PEP/LVET ratio, IVRT, and TEI, whose maximal increases obtained throughout the study were 47%, 48%, 78%, and 56%, respectively. The LVET and HR did not change significantly, whereas the SI and CI decreased during anesthesia (29% and 26%, respectively). In conclusion, isoflurane produced direct effects on the Tei-index. The changes in systolic and diastolic parameters were supportive of this finding and were consistent with an overall impairment of left ventricular function during anesthesia.

Efeitos de diferentes frações inspiradas de oxigênio sobre a dinâmica respiratória em cães submetidos à infusão contínua de propofol e mantidos em ventilação espontânea / Effects of several inspired oxygen fractions on the respiratory dynamics in spontaneously breathing dogs undergoing continuous infusion of propofol

Avaliaram-se os efeitos do fornecimento de diferentes fraçõesinspiradas de oxigênio (FiO2) sobre a dinâmica respiratória em cãessubmetidos a infusão contínua de propofol e mantidos em ventilaçãoespontânea. Oito cães foram submetidos a cinco anestesiasdiferenciando uma da outra pela FiO2 fornecida. Formaram-se cincogrupos denominados G100 (FiO2 = 1), G80 (FiO2 = 0,8), G60 (FiO2 = 0,6), G40 (FiO2 = 0,4) e G20 (FiO2 = 0,21). Os animais foraminduzidos à anestesia com propofol na dose necessária para intubação,e ato contínuo iniciou-se a infusão do fármaco e o fornecimento deoxigênio conforme a FiO2 determinada para cada grupo. As primeirasmensurações foram efetuadas 30 minutos após o início da infusãodo anestésico (M0), em seguida em intervalos de 15 minutos (M15,M30, M45 e M60). Os dados numéricos obtidos foram submetidosa Análise de Variância, seguida pelo teste Tukey (p<0,05). Os valoresregistrados de saturação de oxihemoglobina (SpO2) e SaO2 foramsignificativamente menores para G20, enquanto que a pressão parcialde oxigênio no sangue arterial (PaO2) variou conforme a fração deoxigênio fornecida. Para a pressão parcial de dióxido de carbono nosangue arterial (PaCO2) foram registradas diferenças em M30, no qualG100 apresentou médias superiores a G20. Conclui-se que ofornecimento de oxigênio a 100%, 80% e 21% devem ser evitados,pois proporciona prejuízos significativos ao sistema respiratório decães anestesiados com infusão contínua de propofol na dose de 0,7mg/kg/min sob ventilação espontânea.

Parâmetros eletrocardiográficos e cardiovasculares em cães anestesiados pelo isofluorano e submetidos à hipovolemia aguda / Electrocardiographic and cardiovascular parameters in dogs anestethized with isoflurane submitted to acute hypovolemia

Avaliaram-se os efeitos da hipovolemia aguda em cães anestesiados pelo isofluorano sobre a eletrocardiografia com a duração e amplitude da onda P (Pms e PmV, respectivamente); intervalo entre as ondas P e R (P-R); duração do complexo QRS (QRS); amplitude da onda R (RmV); intervalo entre as ondas Q e T (Q-T) e intervalo entre as duas ondas (R-R), freqüência cardíaca (FC), índice cardíaco (IC), índice sistólico (IS) e pressões arteriais sistólica (PAS), diastólica (PAD) e média (PAM). Verificou-se também a possível influência do anestésico sobre a resposta compensatória à hipovolemia aguda. Para tal, foram utilizados 20 cães hígidos, sem raça definida, adultos, machos e fêmeas. Induziu-se a anestesia geral com isofluorano por meio de máscara naso-oral a 2,5 CAM e, após a intubação orotraqueal, o vaporizador foi ajustado em 1,5 CAM. Induziu-se a hipovolemia nos animais retirando-se volume total de 35 mlkg-1 de sangue. As mensurações foram realizadas antes da hipovolemia (M0), imediatamente após a retirada do volume total de sangue calculado (M1), e aos dez (M2), trinta (M3) e sessenta (M4) minutos. A avaliação estatística das variáveis foi efetuada por meio de Análise de Variância (ANOVA), seguida pelo teste de Tukey, considerando nível de significância de 5 por cento (P<0,05). Houve redução do tempo de condução elétrica átrio-ventricular, aumento da impedância da musculatura ventricular, redução da freqüência cardíaca, dos índices cardíacos e sistólico, porém sem alteração na despolarização ventricular, sendo que o isofluorano não influenciou no desencadeamento da resposta compensatória à hipovolemia aguda.

Eletrocardiografia em cäes anestesiados com cetamina-S ou cetamina / Electrocardiography in dogs anesthetized with S-ketamine or ketamine

A cetamina, fármaco derivado da fenciclidina, há muito é usada na anestesia veterinária, sendo que o seu isômero (+), a cetamina S, recém-lançada no mercado, tem tido emprego principalmente na anestesia humana. Em vista disso, objetivou-se, com este experimento avaliar comparativamente, as possíveis alteraçöes eletrocardiográficas em cäes anestesiados com cetamina S ou cetamina e avaliar as freqüências respiratória e cardíaca, saturaçäo de oxihemoglobina e pressäo arterial. Para tanto, foram utilizados 10 cäes adultos, machos e fêmeas, sem raça definida e hígidos. Os animais foram distribuídos em dois grupos (G1 e G2) de igual número. Ao G1 administrou-se, por via intramuscular, cetamina S na dose de 20mg/kg, e ao G2, cetamina na mesma dose e via de administraçäo empregados no G1. As observaçöes das variáveis tiveram início imediatamente antes da aplicaçäo dos fármacos (M1) e a cada 10 minutos (M2, M3 e M4, respectivamente). Os dados numéricos foram submetidos ao teste de Tukey, para análises repetidas no grupo, a fim de verificar significado estatístico ou näo entre as médias, nos vários momentos, sendo considerado o nível de significância de 5 por cento (p<0,05). Os resultados apresentados foram elevaçäo da freqüência cardíaca com o uso de ambos os fármacos, discretas alteraçöes na pressäo arterial, nenhuma variaçäo da SpO2 e impossibilidade de identificar alteraçöes eletrocardiográficas de importância clínica entre os grupos estudados. Assim, pode-se admitir como hipótese conclusiva que as cetaminas S e racêmica apresentam efeitos similares na condutividade elétrica do miocárdio.