Computed tomographic bronchial collapsibility values over 50% may be detected in healthy dogs

Bronchomalacia and bronchial collapse are important causes of chronic coughing in dogs. The current reference standard diagnostic tests for these problems are flexible bronchoscopy and biopsy. Previous human studies have also supported inspiration/expiration computed tomography (CT) as a diagnostic test. The current prospective, pilot study aimed to determine whether inspiration/expiration CT is also a feasible test for quantifying bronchial collapsibility in dogs. Thoracic CT images were acquired using a 64‐row multidetector CT for 10 healthy Beagle dogs during maximal inspiration and expiration. For each scan, one observer measured transverse sectional areas of the mainstem and lobar bronchi, and the dorsal and ventral segmental bronchi of the left cranial lobar bronchus. Diameters for each bronchus were also measured in transverse, sagittal, and dorsal planes. Bronchial collapsibility (%) was calculated as the difference between inspiration/expiration transverse sectional areas divided by the inspiration transverse sectional areas. Mean bronchial collapsibility of all bronchi was 38.20 ± 15.17%. A collapsibility of over 50% was found in the dorsal (n = 7) and ventral (n = 4) segmental bronchi of the left cranial lobar bronchus, and the left caudal (n = 5) and right middle (n = 2) lobar bronchus. Bronchial collapsibility measurements were greater in the dorsal and ventral segmental bronchi of the left cranial lobar bronchus and the left caudal lobar bronchus (P < 0.001). Findings supported inspiration/expiration CT as a modality to noninvasively assess bronchial collapse in dogs and a bronchial collapsibility value greater than 50% for detecting pathologic bronchial collapse in clinically affected dogs.     

Two-dimensional cardiothoracic ratio for evaluation of cardiac size in German shepherd dogs

ObjectivesTo evaluate cardiac size in normal German shepherd dogs (GSD) using the two-dimensional cardiothoracic ratio (CTR) and to use this measure for diagnosing GSD with altered cardiac size.AnimalsOne hundred clinically normal GSD as well as 46 GSD with altered cardiac size (microcardia or cardiomegaly).MethodsThe CTR was computed as the percentage area of the cardiac silhouette relative to the area of the dog's thorax. Measurements were performed using a digital software program on lateral and ventro-dorsal radiographs at the points of peak inspiration and expiration. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic accuracy of the CTR for diagnosing cardiomegaly or microcardia.ResultsThe mean (±SD) CTR on lateral radiographs of normal dogs was 27.60% ± 1.10% and 30.13% ± 1.42% at the points of peak inspiration and expiration, respectively. For ventro-dorsal radiographs, mean CTR was 30.45% ± 1.39% at peak inspiration and 33.34% ± 1.46% at peak expiration. The cutoff value of the CTR for diagnosing microcardia on lateral radiographs was 22.98% (inspiration) and 25.06% (expiration), compared to 25.03% (inspiration) and 23.97% (expiration) on ventro-dorsal radiographs. Cutoff values for diagnosing cardiomegaly were 30.28% (inspiration) and 33.44% (expiration) on lateral radiographs and 36.80% (inspiration) and 37.99% (expiration) on ventro-dorsal radiographs.ConclusionsCTR may provide a clinically useful tool for evaluating cardiac size in dogs.     

RADIOGRAPHIC LIVER SIZE IN PEKINGESE DOGS VERSUS OTHER DOG BREEDS

Differential diagnoses for canine liver disease are commonly based on radiographic estimates of liver size, however little has been published on breed variations. Aims of this study were to describe normal radiographic liver size in Pekingese dogs and to compare normal measurements for this breed with other dog breeds and Pekingese dogs with liver disease. Liver measurements were compared for clinically normal Pekingese (n = 61), normal non‐Pekingese brachycephalic (n = 45), normal nonbrachycephalic (n = 71), and Pekingese breed dogs with liver disease (n = 22). For each dog, body weight, liver length, T11 vertebral length, thoracic depth, and thoracic width were measured on right lateral and ventrodorsal abdominal radiographs. Liver volume was calculated using a formula and ratios of liver length/T11 vertebral length and liver volume/body weight ratio were determined. Normal Pekingese dogs had a significantly smaller liver volume/body weight ratio (16.73 ± 5.67, P < 0.05) than normal non‐Pekingese brachycephalic breed dogs (19.54 ± 5.03) and normal nonbrachycephalic breed dogs (18.72 ± 6.52). The liver length/T11 vertebral length ratio in normal Pekingese (4.64 ± 0.65) was significantly smaller than normal non‐Pekingese brachycephalic breed dogs (5.16 ± 0.74) and normal nonbrachycephalic breed dogs (5.40 ± 0.74). Ratios of liver volume/body weight and liver length/T11 vertebral length in normal Pekingese were significantly different from Pekingese with liver diseases (P < 0.05). Findings supported our hypothesis that Pekingese dogs have a smaller normal radiographic liver size than other breeds. We recommend using 4.64× the length of the T11 vertebra as a radiographic criterion for normal liver length in Pekingese dogs.     

PULMONARY HYPERTENSION IN DOGS WITH MITRAL REGURGITATION ATTRIBUTABLE TO MYXOMATOUS VALVE DISEASE

Pulmonary hypertension has been associated with mitral insufficiency caused by chronic degenerative valve disease in dogs. Our aim was to search for associations between left atrial to aortic root ratio, end‐systolic and end‐diastolic volume indices, and changes in the right ventricular to right atrial pressure gradient as estimated by the peak velocity of tricuspid regurgitation in dogs with chronic degenerative valve disease and different classes of heart failure. Dogs, for which follow‐up was available were evaluated for changes in the right ventricular to right atrial systolic pressure gradient over time. Three hundred and forty‐four dogs were studied; 51 in the International Small Animal Cardiac Health Council class 1a, 75 in class 1b, 113 in class 2, 97 in class 3a, and 8 in class 3b. The mean values for right ventricular to right atrial systolic pressure gradient, end‐systolic volume index, end‐diastolic volume index, and left atrial to aortic ratio were 49.2 ± 17.1 mmHg, 149.12 ± 60.8 and 37.7 ± 21.6 ml/m², and 1.9 ± 0.5, respectively. A weak positive correlation was found between the right ventricular to right atrial systolic pressure gradient and the left atrial to aorta ratio (r=0.242, P<0.0001), end‐diastolic volume index (r=0.242, P<0.0001), and end‐systolic volume index (r=0.129, P<0.001). Follow up was available for 49 dogs. Of these, 18 had an increased, 12 a decreased, and 19 a stable right ventricular to right atrial systolic pressure gradient despite therapy. The equivalence point between the sensitivity and specificity curves of about 80% in the coincident point corresponded to a right ventricular to right atrial systolic pressure gradient of 48 mmHg. Our results suggest an association between the progressive nature of chronic degenerative mitral valve disease and pulmonary hypertension. It is of clinical interest that, with a right ventricular to right atrial systolic pressure gradient pressure gradient at or above 48 mmHg, pulmonary hypertension does not appear to improve despite therapy targeted at lowering the left atrial load.     

Hounsfield units are a useful predictor of pleural effusion cytological type in dogs but not in cats

All categories of pleural effusion subjectively display as soft tissue opacity on computed tomography (CT). Quantitative measurement using Hounsfield units (HU) has the potential to bring additional information regarding the nature of the fluid in a noninvasive way. The purposes of this retrospective cross‐sectional analytical study were to compare Hounsfield units of different pleural effusion categories in dogs and cats, assess association between specific cytologic parameters and Hounsfield units, and evaluate the effect of dependent vs. nondependent aspect of the effusion pool on Hounsfield unit. A total of 111 patients (74 dogs and 37 cats) with pleural effusion, that underwent thoracic CT and diagnostic thoracocentesis, were included in the study. Effusions were cytologically categorized as exudate, transudate, modified transudate, hemorrhage, or chyle. Significant differences existed in Hounsfield units between categories in dogs (P < 0.0001) but not in cats (P = 0.334). Canine chylous effusion (6.1 ± 4.7 HU (mean ± standard deviation)) and transudate (5.6 ± 2.0) were significantly lower than exudate (20.3 ± 9.5) and hemorrhage (21.4 ± 9.2). No significant differences were found between modified transudate (13.6 ± 10.3) and other categories. Significant, weak linear correlation was identified in dogs between Hounsfield units and total protein (P = 0.018, R² = 0.089), red blood cells (P = 0.021, R² = 0.077), and total nucleated cells (P = 0.013, R² = 0.089). The Hounsfield units of dependent effusion was not significantly higher than the nondependent effusion, except for canine chylous effusion (P = 0.008). Fourteen Hounsfield units was identified as the most clinically useful threshold: <14 HU identified transudate or chylous effusion with a sensitivity of 100% and a specificity of 69%. A threshold >14 HU had a specificity of 100% and a sensitivity of 69% for identifying exudate, modified transudate, or hemorrhage.     

Continuous positive airway pressure administered via face mask in tranquilized dogs

Objective – To evaluate the tolerance of a continuous positive airway pressure (CPAP) mask in tranquilized dogs and compare PaO₂ in arterial blood in dogs receiving oxygen with a regular face mask or CPAP mask set to maintain a pressure of 2.5 or 5 cm H₂O. Design – Prospective, randomized clinical study. Setting – University teaching hospital. Animals – Sixteen client‐owned dogs without evidence of cardiopulmonary disease were studied. Interventions – Eight animals were randomly assigned to each of 2 treatment groups: group A received 2.5 cm H₂O CPAP and group B received 5 cm H₂O CPAP after first receiving oxygen (5 L/min) by a regular face mask. Animals were tranquilized with acepromazine 0.05 mg/kg, IV and morphine 0.2 mg/kg, IM. An arterial catheter was then placed to facilitate blood sampling for pHa, PaO₂, and PaCO₂ determinations before and after treatments. Direct mean arterial pressure, heart rate, respiratory rate, and temperature were also recorded after each treatment. Measurements and Main Results – CPAP administration was well tolerated by all animals. The mean arterial pressure, heart rate, respiratory rate, temperature, PaCO₂, and pHa, did not differ at any time point between groups. Differences were seen in oxygenation; in group A, PaO₂ significantly increased from a mean of 288.3±47.5 mm Hg with a standard mask to a mean of 390.3±65.5 mm Hg with the CPAP mask and in group B, PaO₂ increased similarly from 325.0±70.5 to 425.2±63.4 mm Hg (P<0.05); no differences were detected between the 2 CPAP treatments. Conclusions – In healthy tranquilized dogs noninvasive CPAP is well tolerated and increases PaO₂ above values obtained when using a regular face mask.     

CT and radiographic evaluation of bronchial collapsibility at forced expiration in asymptomatic brachycephalic dogs

Bronchial collapse due to bronchomalacia is an important cause of chronic coughing in dogs. Radiographic and CT evidence of bronchial collapse has previously been reported in healthy Beagle dogs under forced expiration. However, published studies in brachycephalic dog breeds that are prone to bronchial collapse are currently lacking. In the present prospective analytical experimental study, CT and radiography were used to measure the bronchial diameter and collapsibility of each pulmonary bronchus during end‐expiratory, 5 mL/kg forced‐expiratory, and 10 mL/kg forced‐expiratory phases in 17 asymptomatic brachycephalic dogs and six healthy Beagle dogs. Bronchial collapsibility was significantly greater during forced expiration, than that at the end of expiration in both groups (P < .001). Bronchial collapsibility measurements of the left lung lobes and the right cranial, middle, and accessory lobes were significantly higher in asymptomatic brachycephalic dogs than those in healthy Beagle dogs, during all expiratory phases (P < .05). The higher bronchial collapsibility of brachycephalic dogs was also supported using CT multiplanar reconstruction images and radiography. In conclusion, radiographic and CT measures of bronchial collapsibility in asymptomatic brachycephalic dogs are higher than measures in healthy Beagle dogs. Therefore, measures of bronchial collapse in brachycephalic dogs should not be evaluated using the same baseline measures as those used for healthy Beagle dogs.     

The pharmacokinetics of midazolam after intravenous,intramuscular, and rectal administration in healthy dogs

Intravenous benzodiazepines are utilized as first‐line drugs to treat prolonged epileptic seizures in dogs and alternative routes of administration are required when venous access is limited. This study compared the pharmacokinetics of midazolam after intravenous (IV), intramuscular (IM), and rectal (PR) administration. Six healthy dogs were administered 0.2 mg/kg midazolam IV, IM, or PR in a randomized, 3‐way crossover design with a 3‐day washout between study periods. Blood samples were collected at baseline and at predetermined intervals until 480 min after administration. Plasma midazolam concentrations were measured by high‐pressure liquid chromatography with UV detection. Rectal administration resulted in erratic systemic availability with undetectable to low plasma concentrations. Arithmetic mean values ± SD for midazolam peak plasma concentrations were 0.86 ± 0.36 μg/mL (C₀) and 0.20 ± 0.06 μg/mL (C_max), following IV and IM administration, respectively. Time to peak concentration (T_max) after IM administration was 7.8 ± 2.4 min with a bioavailability of 50 ± 16%. Findings suggest that IM midazolam might be useful in treating seizures in dogs when venous access is unavailable, but higher doses may be needed to account for intermediate bioavailability. Rectal administration is likely of limited efficacy for treating seizures in dogs.     

The pharmacokinetics of pimobendan enantiomers after oral and intravenous administration of racemate pimobendan formulations in healthy dogs

Pimobendan is a benzimidazole‐pyridazinone derivative, marketed as a racemic mixture for the management of canine heart failure. Pharmacokinetics of the enantiomers of pimobendan and its oral bioavailability have not been described in dogs. The aim of this study was to describe pharmacokinetics of three formulations of pimobendan in healthy dogs: the licensed capsule product, and novel liquid and intravenous formulations. A three‐period, nested randomized two‐treatment crossover design was used. Pimobendan was administered p.o. at 0.25 and i.v. at 0.125 mg/kg. Blood and plasma samples were analysed by liquid chromatography–mass spectrometry. Noncompartmental modelling was used to describe the pharmacokinetics. Parameters were compared between formulations using a general linear model. Bioequivalence of the oral formulations was tested using CI90 for AUC_(0–∞) and C_max. Bioavailability of pimobendan after oral dosing was 70%. Liquid and capsule formulations were bioequivalent only for AUC. The positive enantiomer of pimobendan (PE) had a larger volume of distribution than the negative enantiomer (NE) (281 ± 48 vs. 215 ± 68 mL/kg; P = 0.003) and a shorter half‐life (21.7 vs. 29.9 min; P = 0.004). The NE was distributed more quickly than the PE into blood cells. Enantiomers of pimobendan have differing absorption, distribution and elimination. The pharmacokinetics of pimobendan in healthy dogs was described.     

Renal resistive index in 55 dogs with degenerative mitral valve disease

Background

Azotemia occurs frequently in dogs with degenerative mitral valve disease (DMVD). It could indicate changes in renal hemodynamics.

Hypothesis/Objectives

To assess the renal resistive index (RI) in dogs with DMVD, and the statistical link between heart failure class, azotemia, echo‐Doppler parameters, several plasma variables, and RI.

Animals

Fifty‐five dogs with naturally occurring DVMD were used (ISACHC class 1 [n = 28], 2 [n = 19], and 3 [n = 8]).

Methods

Observational, blinded study, performed under standardized conditions. Physical examination, renal ultrasonography, and echo‐Doppler examinations were performed in awake dogs. The RI of the renal, interlobar, and arcuate arteries were measured. Plasma creatinine, urea, and N‐terminal pro‐B‐type natriuretic peptide concentrations (NT‐proBNP) were determined. Statistical links between variables and RI were tested by means of a general linear model.

Results

Although the RI of renal and arcuate arteries were unaffected by ISACHC class, the left interlobar RI increased (P < .001) from 0.62 ± 0.05 (mean ± SD) in class 1 to 0.76 ± 0.08 in class 3. It was also higher (P < .001) in azotemic (0.74 ± 0.08) than in non‐azotemic (0.62 ± 0.05) dogs. Similar findings were observed for right interlobar RI. Univariate analysis showed a positive statistical link between NT‐proBNP (P = .002), urea (P < .001), creatinine (P = .002), urea‐to‐creatinine ratio (P < .001), left atrium‐to‐aorta ratio (P < .001), regurgitation fraction (P < .001), systolic pulmonary arterial pressure (P < .001), shortening fraction (P = .035), and RI.

Conclusion and Clinical Importance

In dogs with DMVD, interlobar RI increases with heart failure severity and azotemia but a cause and effect relationship remains to be established.     

Computed tomographic and radiographic bronchial collapse may be a normal characteristic of forced expiration in dogs

Tracheobronchomalacia has been diagnosed using radiography or bronchoscopy to confirm bronchial changes in luminal diameter during the respiratory cycle. However, studies in healthy humans suggest that some degree of bronchial collapse may be observed during the normal respiratory cycle. In this analytical study, the luminal diameter of the bronchus to each of the six pulmonary lobes and the mean percentage of expiratory collapse from end inspiratory, end expiratory, and two forced expiratory phases (10 and 15 ml/kg) were determined via computed tomography (CT) and radiography in 22 healthy Beagle dogs. The bronchial collapsibility was significantly greater during the forced expiration than the end expiration (P < 0.001); the same results were observed in dorsal and sagittal CT images and radiographs (P < 0.001). Median collapsibility values associated with 15 ml/kg forced expiratory collapse determined via cross‐sectional CT images were measured as 16.6–45.5% and differed according to the pulmonary lobe. Median collapsibilities on radiography with 15 ml/kg forced expiration were 57.8% and 62.1% in the right cranial lobe and right caudal lobe, respectively. In conclusion, bronchial diameter may change during the respiratory cycle, and some degree of reduction in bronchial diameter may be an incidental finding in healthy dogs. More rigorous criteria are needed with regards to bronchial collapsibility during normal respiration for the diagnosis of bronchomalacia in order to avoid false‐positive diagnoses.     

Pharmacokinetics and dynamics of mycophenolate mofetil after single‐dose oral administration in juvenile dachshunds

Mycophenolate mofetil (MMF) is recommended as an alternative/complementary immunosuppressant. Pharmacokinetic and dynamic effects of MMF are unknown in young‐aged dogs. We investigated the pharmacokinetics and pharmacodynamics of single oral dose MMF metabolite, mycophenolic acid (MPA), in healthy juvenile dogs purpose‐bred for the tripeptidyl peptidase 1 gene (TPP1) mutation. The dogs were heterozygous for the mutation (nonaffected carriers). Six dogs received 13 mg/kg oral MMF and two placebo. Pharmacokinetic parameters derived from plasma MPA were evaluated. Whole‐blood mitogen‐stimulated T‐cell proliferation was determined using a flow cytometric assay. Plasma MPA C_max (mean ± SD, 9.33 ± 7.04 μg/ml) occurred at <1 hr. The AUC_0–∞ (mean ± SD, 12.84±6.62 hr*μg/ml), MRT_inf (mean ± SD, 11.09 ± 9.63 min), T1/2 (harmonic mean ± PseudoSD 5.50 ± 3.80 min), and k/d (mean ± SD, 0.002 ± 0.001 1/min). Significant differences could not be detected between % inhibition of proliferating CD5+ T lymphocytes at any time point (p = .380). No relationship was observed between MPA concentration and % inhibition of proliferating CD5+ T lymphocytes (R = .148, p = .324). Pharmacodynamics do not support the use of MMF in juvenile dogs at the administered dose based on existing therapeutic targets.     

The effect of an L-type calcium channel blocker on the hemodynamics of orbital arteries in dogs

Purpose (1) To determine the effect of the l ‐type calcium channel blocker amlodipine on color Doppler ultrasound‐determined vascular resistance and blood flow velocities in the distal retrobulbar arteries of dogs; (2) to determine any effect of blood pressure and PCO₂ rate on such color Doppler‐determined circulatory measurements. Methods Color Doppler imaging measurements of the short posterior ciliary artery, long posterior ciliary artery, and ophthalmic artery of normal eyes of 10 dogs were obtained under isofluorane anesthesia before and 1 week after oral amlodipine administration. Mean systemic arterial blood pressure and PCO₂ were monitored. Results The mean resistive index decreased significantly in the short posterior ciliary artery (P = 0.0347), in the long posterior ciliary artery (P = 0.0092), and ophthalmic artery (P = 0.0004) following systemic amlodipine administration. The end diastolic velocity increased significantly in the long posterior ciliary artery (P = 0.0368) and ophthalmic artery (P < 0.0001). The peak systolic velocity increased significantly in the ophthalmic artery (P = 0.0256). Mean systemic arterial blood pressure was significantly negatively associated with resistive index (P < 0.0001) and significantly associated with the log of the end diastolic velocity (P < 0.0001). Conclusions Systemically administered amlodipine increases color Doppler imaging‐determined blood flow velocity and decreases vascular resistive index in the ophthalmic artery, short posterior ciliary artery and long posterior ciliary artery of normal dogs. Changes in systemic arterial blood pressure can significantly affect the measurement of color Doppler imaging parameters.     

Computed tomographic morphometry of the biceps brachii muscle tendon of dogs affected by the medial coronoid disease

The objective of this study was to measure the biceps brachii muscle (BBM) attachment to the medial coronoid process (MCP) using computed tomography images and to compare these data between clinically healthy and dogs affected by medial coronoid disease (MCD). Computed tomography was performed in MCD-affected and healthy dogs. Multiplanar reconstruction views were obtained to measure distance (cm) of the BBM attachment point to the MCP. Results showed that the mean BBM attachment point-to-MCP was 1.42 ± 0.23 cm in MCD-affected and 1.27 ± 0.20 cm in healthy dogs, respectively. In dogs with MCD, the BBM attachment point-to-MCP was significantly more abaxial than in clinically healthy dogs (p < .001). The results of this study support the hypothesis that the BBM attachment site is more abaxial to the MCP and therefore may contribute to supraphysiological overload leading to MCD. Albeit more research is necessary, this study proves a relationship between the BBM attachment point and the development of MCD.     

Clinical Efficacy of Sildenafil in Treatment of Pulmonary Arterial Hypertension in Dogs

Background: Pulmonary arterial hypertension (PAH) in dogs carries a poor prognosis. Sildenafil increases exercise capacity and improves hemodynamics in people with PAH. Hypothesis/Objectives: Dogs receiving sildenafil will have lower pulmonary arterial pressure, increased exercise capacity, and better quality of life (QOL) than dogs receiving placebo. Animals: Thirteen dogs with echocardiographic evidence of PAH. Methods: Prospective short‐term, randomized, placebo controlled, double‐blind, crossover study. Dogs with PAH were randomly allocated to receive sildenafil or placebo for 4 weeks, followed by the alternative treatment for 4 weeks. Results: Dogs receiving sildenafil had a significantly lower estimated pulmonary arterial pressure (median, 56 mmHg; range, 34–83 mmHg) than at baseline (median, 72 mmHg; range, 61–86 mmHg; P= .018), but not significantly lower than those receiving placebo (median, 62 mmHg; range, 49–197 mmHg). Exercise capacity was significantly greater in dogs receiving sildenafil than those receiving placebo (mean activity count per minute: 101 ± 47 versus 74 ± 32; P= .05). QOL scores were significantly higher in dogs receiving sildenafil than dogs receiving placebo. Conclusions and Clinical Importance: Sildenafil decreases systolic pulmonary arterial pressure from baseline in dogs with PAH and is associated with increased exercise capacity and QOL when compared to treatment with placebo.     

Efficacy of a mephentermine‐based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle

The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY^® INJETÁVEL (POT), a mephentermine‐based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized‐complete‐block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume‐matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six‐day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end‐tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady‐state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post‐treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dt_max: +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dt_min: +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo‐control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection.     

Evaluation of cardiac performance of the dog after induction of portal hypertension and gastric ischemia

Objective: To determine changes in hemodynamic and cardiac energetic parameters in dogs after induction of portal hypertension and gastric ischemia. These blood flow alterations are similar to changes seen in splanchnic blood flow in dogs with gastric dilatation volvulus syndrome (GDV). Design: Original experimental study. Setting: Veterinary teaching hospital. Animals: Seven purpose‐bred, intact male dogs. Interventions: Standard midline laparotomy and median sternotomy were performed under general anesthesia. Dogs were instrumented to obtain arterial blood pressure, aortic flow, cardiac chamber pressures, central venous pressure, portal flow, and portal pressure. Colored microsphere technology was used for the determination of myocardial blood flow. Measurements and samples were obtained at baseline, following induction of portal hypertension, and after induction of portal hypertension and gastric ischemia. Measurements and main results: Left ventricular myocardial blood flow was increased from 81.8±20.1 mL/100 g/min at baseline to 127.7±57.2 mL/100 g/min (P=0.02) after induction of portal hypertension and gastric ischemia. Myocardial oxygen consumption increased from 142.2±27.4 J/min/100 g at baseline to 219.1±33.4 J/min/100 g (P=0.003) after induction of portal hypertension and gastric ischemia, but cardiac external work remained unchanged (13.67±6.2 to 13.27±9.6 J/min; P=0.78; power=0.79). Cardiac efficiency decreased from 11.6±6.1% at baseline to 7.6±5.1% (P=0.017) after induction of portal hypertension and gastric ischemia. Conclusions: Transfer of energy within the myocardium was less efficient after induction of portal hypertension and ischemia of the stomach wall. On the basis of these results, alterations in cardiac function associated with GDV may result from deterioration of cardiac efficiency.     

Lithium dilution cardiac output and oxygen delivery in conscious dogs with systemic inflammatory response syndrome

Objective: Compare cardiac index (CI) and oxygen delivery index (DO₂I) in conscious, critically ill dogs to control dogs; evaluate the association of CI and DO₂I with outcome. Design: Prospective non‐randomized clinical study. Setting: Veterinary teaching hospital. Animals: Eighteen client‐owned dogs with systemic inflammatory response syndrome (SIRS) and 8 healthy control dogs. Measurements and Main Results: CI of dogs with SIRS was measured using lithium dilution at times 0, 4, 8, 16, and 24 hours. Data collected included physical exam, arterial blood gas (ABG) and hemoximetry. CI of control dogs was measured 3 times with 1 measurement of ABG. Mean CI ± SE in SIRS patients was 3.32 ± 0.95 L/min/m²; lower than controls at 4.18 ± 0.22 L/min/m² (P<0.001). Mean DO₂I ± SE in SIRS patients was 412.91 ± 156.67 mL O₂/min/m²; lower than controls at 785.24 ± 45.99 mL O₂/min/m² (P<0.001). There was no difference in CI (P=0.49) or DO₂I (P=0.51) for dogs that survived to discharge versus those that did not. There was no difference in mean CI (P=0.97) or DO₂I (P=0.50) of survivors versus non‐survivors for 28‐day survival. Survivors had lower blood glucose (P=0.03) and serum lactate concentrations (P=0.04) than non‐survivors. Conclusions: CI and DO₂I in conscious dogs with SIRS were lower than control dogs, which differs from theories that dogs with SIRS are in a high cardiac output state. CI and DO₂I were not significantly different between survivors and non‐survivors. Similar to previous studies, lactate and glucose concentrations of survivors were lower than non‐survivors.     

Comparison of a computed tomographic pulmonary trunk to aorta diameter ratio with echocardiographic indices of pulmonary hypertension in dogs

There are limited criteria for the detection of pulmonary hypertension in dogs undergoing computed tomography (CT) for pulmonary disease. This retrospective analytical exploratory study compared a CT pulmonary trunk to aorta ratio with echocardiographic estimates of pulmonary hypertension. Dogs having both a contrast thoracic CT and echocardiogram were selected and maximal pulmonary trunk and descending aorta diameters were measured by two observers on a single transverse CT image. Computed tomographic diameter ratios were compared with the echocardiographic parameters of tricuspid regurgitation gradient, right ventricular acceleration time‐to‐ejection time ratio, pulmonary insufficiency gradient, and pulmonary artery to aorta diameter. A total of 78 dogs were sampled, with 44 dogs having one or more finding suggestive of pulmonary hypertension. A moderate positive correlation was shown between tricuspid regurgitation gradient and CT pulmonary trunk to aorta ratio (r = 0.61, P‐value < 0.0001). Mean CT pulmonary trunk to aorta ratio of dogs with moderate (P = 0.0132) and severe (P < 0.0003) pulmonary hypertension were significantly higher than normal dogs. There was no significant difference in mean CT pulmonary trunk to aorta ratio between normal and mild pulmonary hypertension dogs (P = 0.4244). The intraclass correlation coefficient (0.72) showed good reproducibility of the ratio. Findings indicated that CT pulmonary trunk to aorta ratio is a reproducible and potentially useful method to predict moderate and severe pulmonary hypertension in dogs, but not mild pulmonary hypertension. In dogs undergoing thoracic CT for pulmonary disease, an increased ratio should prompt follow up echocardiography.