PRACTICALITY, USEFULNESS, AND LIMITS OF END-TIDAL CARBON DIOXIDE MONITORING IN CRITICAL SMALL ANIMAL PATIENTS

End-tidal monitors for measuring carbon dioxide (CO₂) have become widely available for clinical use in the last two decades. This non-invasive technology has been previously evaluated in anesthetized veterinary patients, but its accuracy has not been assessed in critical patients. We investigated the usefulness and limits of end-tidal CO₂ monitoring in two populations of critical small animal patients: spontaneously breathing dogs and mechanically ventilated patients with healthy and damaged lungs. In analyzing samples from 43 spontaneously breathing dogs and 34 ventilated patients (28 dogs and six cats), the end-tidal CO₂ was generally lower than pCO₂. The predictive value for hypoventilation was excellent in both populations (100%). The linear correlation of the end-tidal CO₂ and arterial pCO₂ in non-panting dogs with healthy lungs was 0.84 (p<0.0001), and the 95% confidence interval (CI) of the difference was ± 3.2 mm Hg. However, the measures were uncorrelated in panting dogs (r=0.37, p=0.27), and the 95% CI was ± 13.37 mm Hg. Furthermore, where multiple samples could be obtained in individual patients, the r values and differences of end-tidal compared to arterial pCO₂ varied unpredictably. These variations did not appear to be predicted by patient factors such as lung disease. We conclude that the end-tidal CO₂ monitor is clinically useful for detecting hypoventilation and monitoring apnea, but it should be supplemented with arterial pCO₂ determinations if it is important to obtain accurate pCO₂ measures.     

Bioavailability and pharmacokinetics of ibuprofen in the broiler chicken

The intravenous, intramuscular and oral pharmacokinetics of ibuprofen in broiler chickens were investigated. In a preliminary study, plasma ibuprofen concentration-time profiles, following i.v. (25 mg/kg) dosing were best described by a 2-compartment model. After intravenous administration, the volume of distribution at steady-state ( V _d(ss)), the total systemic clearance ( Cl _B), the elimination half-life (t_1/2p) and the MRT were 0.303 L/kg, 482.3 ml/h-kg, 2.71 h and 1.02 h, respectively. After intramuscular administration of ibuprofen, the t _max and C _max were 0.37 h, and 42.2μg/mL, respectively, with an estimated bioavailability of 46.7%. After oral administration of ibuprofen, the t _max and C _max were 0.31 h and 23.91 μg/mL, respectively, with an estimated bioavailability of 24.2%. This is a preliminary study, examining the use of ibuprofen in broiler chickens, and should be followed by tissue residue and efficacy studies in different disease states.     

Pharmacokinetics, bioavailability and dosage regimen of sulphadiazine (SDZ) in camels (Camelus dromedarius)

The pharmacokinetics of sulphadiazine (SDZ) (100 mg/kg, body weight) were investigated in six camels ( Camelus dromedarius ) after intravenous (i.v.) and oral (p.o.) administration. Following i.v. administration, the overall elimination rate constant (β) was 0.029±0.001/h and the half-life ( t _½β) was 23.14±1.06 h. The apparent volume of distribution ( V d_(area)) was 0.790±0.075 L/kg and the total body clearance ( Cl _B) was 23.29±2.50 mL/h/kg. After p.o. administration, SDZ reached a peak plasma concentration ( C _max(cal.)) of 62.93±2.79 μg/mL at a post injection time of ( T _max(cal.)) 22.98±0.83 h. The elimination half-life was 19.79±1.22 h, not significantly different from that obtained by the i.v. route. The mean absorption rate constant (K_a) was 0.056±0.002 h⁻¹ and the mean absorption half-life ( t _½Ka) was 12.33±0.37 h. The mean availability ( F ) of sulphadiazine was 88.2±6.2%.
  To achieve and maintain therapeutically satisfactory plasma SDZ levels of 50 μg/mL, the priming and maintenance doses would be 80 mg/kg and 40 mg/kg intravenously and 90 mg/kg and 45 mg/kg orally, respectively, to be repeated at 24 h intervals.     

Pharmacokinetics of marbofloxacin in dogs after oral and parenteral administration

Six dogs were treated with a single intravenous (i.v.) dose (2 mg/kg) of marbofloxacin, followed by single oral (p.o.) doses of marbofloxacin at 1, 2 and 4 mg/kg, according to a three-way crossover design. The same experimental design was used for the subcutaneous (s.c.) route. In addition, a long-term trial involving eight dogs given oral doses of marbofloxacin at 2, 4 and 6 mg/kg/day for thirteen weeks was carried out. Plasma and urine samples were collected during the first two trials, plasma and skin samples were collected after the second of these trials. Plasma, urine and skin concentrations of marbofloxacin were determined by a reverse phase liquid chromatographic method. Mean pharmacokinetic parameters after i.v. administration were the following: t1/2β=12.4h; Cl _B= 0.10 L/h.kg; V _area= 1.9 L/kg. The oral bioavailability of marbofloxacin was close to 100% for the three doses. At 2 mg/kg, C _max of 1.4 μg/mL was reached at t _max of 2.5 h. Mean AUC and C _max values had a statistically significant linear relationship with the doses administered. About 40% of the administered dose was excreted in urine as unchanged parent drug. After s.c. administration, the calculated parameters were close to those obtained after oral administration, except t _max (about 1 h) which was shorter. The mean skin to plasma concentration ratio after the long-term trial was 1.6, suggesting good tissue penetration of marbofloxacin.     

Disposition of metronidazole in hens (Gallus gallus) and quails (Coturnix coturnix japonica): pharmacokinetics and whole-body autoradiography

Hens were given single intravenous or oral doses (30 mg/kg body weight) of metronidazole and the plasma concentrations of the drug were determined by high-performance liquid chromatography (HPLC) at intervals from 10 min to 24 h after drug administration. Pharmacokinetic variables were calculated by the Lagrange algorithm technique. The elimination half-life ( t _1/2β) after the intravenous injection was 4.2 ± 0.5 h, the volume of distribution ( V _d(ss)) 1.1±0.2 L/kg and the total body clearance ( Cl _B) 131.2 ± 20 mL/h.kg. Oral bioavailability of the metronidazole was 78 ± 16%. The plasma maximum concentration ( C _max) 31.9 ± 2.3 μg/mL was reached 2 h after the oral administration and the oral elimination half-life ( t ₁/2β) was 4.7 ± 0.2 h. The binding of metronidazole to proteins in hen plasma was very low (less than 3%). Whole body autoradiography of [³H] metronidazole in hens and quails showed an even distribution of labelled material in various tissues at short survival intervals (1-4 h) after oral or intravenous administration. A high labelling was seen in the contents of the small and large intestines. In the laying quails a labelling was also seen in the albumen and in a ring in the periphery of the yolk at long survival intervals. Our results show that a concentration twofold above the MIC is maintained in the plasma of hens for at least 12 h at an oral dose of 30 mg/kg metronidazole.     

Evaluation of the urinary Cortisol: creatinine ratio in the diagnosis of hyperadrenocorticism in dogs

The diagnostic accuracy of the urinary cortisol:creatinine ratio (CCR), with the cortisol being measured by ELISA, was evaluated by subjecting data from 18 dogs with and 20 dogs without hyperadrenocorticism to recelver operating characteristic (ROC) curve analysis. The area under the ROC curve (W 0–93, SE_w 0–044) was much higher than 045, indicating that the CCR did distinguish between dogs with and without hyperadrenocorticism.A cutoff value of about 60 × 10^-6 was assoclated with the highest sensitivity (1.0)and speciflcity (0–85). At the disease prevalence rate of the present study (0 47), the positive and negative predictive values were 0–87 and 1.0, respectively. These numbers indicate that canine hyperadrenocorticism may be safely excluded when the CCR Is below 60 × 10^-6 but that a test of higher specificlty (eg, the ACTH stimulation test) should be used to confirm the diagnosis of canine hyperadrenocorticism when the CCR Is above 60 × 10^-6.     

Attenuation of acute plasma cortisol response in calves following intravenous sodium salicylate administration prior to castration

Pain associated with castration in cattle is an animal welfare concern in beef production. This study examined the effect of oral aspirin and intravenous (i.v.) sodium salicylate on acute plasma cortisol response following surgical castration. Twenty bulls, randomly assigned to the following groups, (i) uncastrated, untreated controls, (ii) castrated, untreated controls, (iii) 50 mg/kg sodium salicylate i.v. precastration and (iv) 50 mg/kg aspirin (acetylsalicylic acid) per os precastration, were blood sampled at 3, 10, 20, 30, 40, 50 min and 1, 1.5, 2, 4, 6, 8, 10 and 12 h postcastration. Samples were analyzed by competitive chemiluminescent immunoassay and fluorescence polarization immunoassay for cortisol and salicylate, respectively. Data were analyzed using noncompartmental analysis, a simple cosine model, anova and t -tests. Intravenous salicylate V _d(ss) was 0.18 L/kg, Cl _B was 3.36 mL/min/kg and t _{1/2 λ} was 0.63 h. Plasma salicylate concentrations above 25  μ g/mL coincided with significant attenuation in peak cortisol concentrations ( P  = 0.029). Peak salicylate concentrations following oral aspirin administration was <10  μ g/mL and failed to attenuate cortisol response. Once salicylate concentrations decreased below 5  μ g/mL, cortisol response in the castrated groups was significantly higher than uncastrated controls ( P  = 0.018). These findings have implications for designing drug regimens to provide analgesia during routine animal husbandry procedures.     

USE OF FORCE PLATE ANALYSIS TO EVALUATE THE EFFICACY OF EXTERNAL BEAM RADIATION TO ALLEVIATE OSTEOSARCOMA PAIN

A standard of therapy for osteosarcoma includes amputation with or without adjuvant chemotherapy. There is a subset of dogs with osteosarcoma that are unsuitable for amputation. We evaluated kinetic variables in dogs with appendicular osteosarcoma treated with a single 8 Gy dose of radiation. Eighteen pet dogs with appendicular osteosarcoma received one 8 Gy fraction of palliative radiation on day 0. Force plate measurements and clinical assessments were made on days 0, 7, 14, and 21. Peak vertical forces ( F _z) were recorded for each limb and a symmetric index (SI) was calculated. There were no significant changes in kinetic parameters after one 8 Gy dose of radiation therapy. Nine of these 18 dogs exhibited increased limb function at day 21 based on force plate analysis. Significant factors affecting F _z included gender and tumor location. There was a significant correlation between F _z and response to therapy based on SI at day 21. SI seems to be useful to objectively assess response in this mixed population of dogs. One 8 Gy fraction of radiation therapy alone did not reduce lameness associated with appendicular osteosarcoma, but a subset of dogs did have improved limb function after a single dose.     

A Simple Apparatus for Frequent Measurement of Gastrointestinal Intraluminal PCO2

The accuracy and precision of an end-tidal infrared CO₂ monitor and customized capnography tubing system designed to measure gastrointestinal intraluminal CO₂ partial pressure (P_iCO₂) were tested in vitro. Samples were taken from the customized capnography tubing placed in either 5% or 10% CO₂ gas at discrete intervals ranging from one minute to twelve minutes. For a given time interval, the tubing PCO₂ measurement was a constant fraction of the actual PCO₂ (all standard errors < 0.02). For increasing time intervals, the ratio of the tubing PCO₂ to actual PCO₂ increased logarithmically. In the 5% and 10% CO₂, the regression coefficients were 0.89 and 0.85 for 8 French tubing and 0.99 and 0.91 for 6 French tubing. Beacuase of its accuracy and precision, this system may provide automated gastrointestinal CO₂ partial pressure monitoring at short intervals (e.g. 5 minutes), facilitating testing of the role of gastrointestinal P_iCO₂ information in treatment algorithms. (Vet Emerg & Crit Care, 1998; 8: 109–116)     

Pharmacokinetics of oxolinic acid in sea-bass, Dicentrarchus labrax (L., 1758), after a single rapid intravascular injection

The pharmacokinetics of oxolinic acid was studied in sea-bass ( Dicentrarchus labrax ). The fish were kept in seawater at 15.2°C with a 12 h/12 h photoperiod. Oxolinic acid was injected in the caudal vein of anaesthetized sea-bass in a single rapid intravascular administration at a dose of 10 mg/kg of body weight. Plasma concentrations of oxolinic acid were determined using two analytical methods, a classic plate diffusion bioassay using Escherichia coli and a high performance liquid chromatography (HPLC) using solid phase extraction with an internal standard and a U.V. detection. The mean recoveries were 99.6% and 110.8% and determination limits were 0.04 μg/mL and 0.02 μg/mL, for the bioassay and the HPLC respectively. Compared to other fish species, the oxolinic acid was rapidly (absorption half life, t_a1/2= 0.69 h) distributed to body tissues outside the blood volume (volume of central compartment, V_c= 0.4 L/kg) and presented a large volume of distribution (V_dss= 2.55 L/kg). Considering its disappearance from the central compartment (rate constant: central-eliminated, k ₁₀= 0.16 h^–1) and its total body clearance ( Cl _t= 0.066 L/kg.h), the elimination phase of the oxolinic acid in sea-bass was shorter than in trout kept in freshwater, and longer than in salmon in seawater. Consequently, the area under the concentration–time curve ( AUC = 157 μg.h/mL) and the mean residence time ( MRT = 42 h) were relatively low and short, respectively.     

SCINTIGRAPHIC EVALUATION OF FOUR DOGS WITH PROTEIN-LOSING ENTEROPATHY USING 111INDIUM-INDIUM-LABELED TRANSFERRIN

The purpose of this sutdy was to determine the clinical utility of ¹¹¹ In-labeled transferrin ( 111 In-TF) scintigraphy for evaluating dogs suspected of having protein-losing enteropathies. Four dogs were injected intravenoulsy with autologous ¹¹¹In-TF after 30 min incubation (at 37°C) of 18.5 MBq (0.5mCi) ¹¹¹In CI₃ with one ml of autologous plasma, Serial right lateral, left lateral and dorsal images were obtained 2, 4, and 24 hours post ¹¹¹ In-TF administration, Images were subjectively evaluated for the presence or absence of ¹¹¹ within the gastrointestinal tract. The results of total protein, albumin and globulin legels and results form gastrointestinal tract. the results of total protein, albumin and globulin levels and results from gastrointestinal biopsies were recorded. In one dog, a follow-up scientigraphic study was done six months after initial evaluation and initiation of treatment for plasmocytic-lymphocytic enteritis. Gastrointestinal activity was noted by two hours in two dogs, while all four dogs had gastrointestinal activity on the 24 hour images. The mean (±std dev) plasma protein, albumin and globulin levels were 3.5 (±0.9), 1.7 (±1) and 1.8 (±0.3) respectively at the time of initial presentation. In the one dog that was evaluated after therapy, faint visualization of radioactivity within the colon was noted on the 24 hour image. Based on this study, ¹¹¹In-TF appears to be a viable scientigraphic method for evaluating dogs with suspected dogs withfd suspected protein-losing enteropathies, Potential limitations of tjis radiopharmaceutical include cost and prolonged isolation of the animal prior to release to the client due to the long physical half-life (T_½= 2.82 days).     

GASTRIC EMPTYING OF SOLID RADIOPAQUE MARKERS IN HEALTHY DOGS

The gastric emptying of 1.5 mm diameter (small) and 5.0 mm diameter (large) radiopaque markers (BIPS) was assessed in 20 dogs. The markers were fed to the dogs in a test meal and abdominal radiographs were made hourly thereafter. Studies were repeated three times in each dog. The variation between two veterinarians interpreting the radiographs was low. The sex, age and day of the study did not have a significant effect on the lag phase or the time taken to empty 25%, 50% and 75% of the markers (T₂₅, T₅₀ and T₇₅ respectively). There was a weak but significant positive correlation between the body weight and T₅₀. There was no significant difference in gastric emptying parameters between the large and small markers.
The mean gastric emptying versus time curve of the small markers on day one was chosen to represent the reference curve for healthy dogs. The lag phase of the small markers on day one was 2.45 ± 2.04 hours, the T₂₅ was 4.85 ± 2.15 hours, the T₅₀ was 6.05 ± 2.99 hours and the T₇₅ was 8.32 ± 2.72 hours (mean ± SD).     

The effect of inflammation on the disposition of phenylbutazone in Thoroughbred horses

The effect of inflammation on the disposition of phenylbutazone (PBZ) was investigated in Thoroughbred horses. An initial study ( n = 5) in which PBZ (8.8 mg/kg) was injected intravenously twice, 5 weeks apart, suggested that the administration of PBZ would not affect the plasma kinetics of a subsequent dose. Two other groups of horses were given PBZ at either 8.8 mg/kg ( n = 5) or 4.4 mg/kg ( n = 4). Soft tissue inflammation was then induced by the injection of Freud's adjuvant and the administration of PBZ was repeated at a dose level equivalent to, but five weeks later than, the initial dose. Inflammation did not appear to affect the plasma kinetics or the urinary excretion of PBZ and its metabolites, oxyphenbutazone (OPBZ) or hydroxyphenylbutazone (OHPBZ) when PBZ was administered at 8.8 mg/kg. However, small but significant increases ( P <0.05) in total body clearance ( CL _B; 29.2 ± 3.9 vs. 43.8 ± 8.1 mL/ h-kg) and the volume of distribution, calculated by area ( V _d(area); 0.18 ± 0.05 vs. 0.25 ± 0.03 L/kg) or at steady-state ( V _d(SS); 0.17±0.04 vs. 0.25 ± 0.03 L/ kg), were obtained in horses after adjuvant injection, compared to controls, when PBZ was administered at 4.4 mg/kg which corresponded to relatively higher tissues concentrations and lower plasma concentrations (calculated) at the time of maximum peripheral PBZ concentration. Soft tissue inflammation also induced a significantly ( P <0.05) higher amount of OPBZ in the urine 18 h after PBZ administration but the total urinary excretion of analytes over 48 h was unchanged. These results have possible implications regarding the administration of PBZ to the horse close to race-day.     

The pharmacokinetics of clomipramine and desmethylclomipramine in dogs: parameter estimates following a single oral dose and 28 consecutive daily oral doses of clomipramine

Clomipramine is a tricyclic antidepressant that has been recommended for the treatment of canine compulsive disorder. The pharmacokinetics of clomipramine in dogs have not been reported. This study describes the pharmacokinetics of clomipramine and its active metabolite, desmethylclomipramine, in six male dogs. Serial blood samples were collected following both a single oral dose of clomipramine (3 mg/kg) and 28 consecutive daily oral doses (3 mg/kg q 24 h). In addition, 'peak' and 'trough' samples were taken throughout the 28-day dosing period. Plasma was assayed for total (free and protein-bound) clomipramine and desmethylclomipramine, using gas-chromatography with mass spectrometric detection. Various pharmacokinetic parameters were then determined. Following a single dose of clomipramine, time of maximum plasma concentration ( t _max) of clomipramine was 0.75–3.1 h, maximum plasma concentration ( C _max) was 16–310 ng/mL and elimination half-life ( t _1/2el) was 1.2–16 h; t _max of desmethylclomipramine was 1.4–8.8 h, C _max was 21–134 ng/mL and t _1/2el was 1.2–2.3 h. Following multiple dosing, there was a numeric increase in these parameters; t _max of clomipramine was 3–8 h, C _max was 43–222 ng/mL and t _1/2el was 1.2–16 h; t _max of desmethylclomipramine was 1.4–8.8 h, C _max was 21–134 ng/mL and t _1/2el was 1.2–2.3 h. Clinically significant differences between dogs and humans in the pharmacokinetics of oral clomipramine are discussed.     

Pulmonary vasculature in dogs assessed by three‐dimensional fractal analysis and chemometrics

Fractal analysis of canine pulmonary vessels could allow quantification of their space‐filling properties. Aims of this prospective, analytical, cross‐sectional study were to describe methods for reconstructing three dimensional pulmonary arterial vascular trees from computed tomographic pulmonary angiogram, applying fractal analyses of these vascular trees in dogs with and without diseases that are known to predispose to thromboembolism, and testing the hypothesis that diseased dogs would have a different fractal dimension than healthy dogs. A total of 34 dogs were sampled. Based on computed tomographic pulmonary angiograms findings, dogs were divided in three groups: diseased with pulmonary thromboembolism (n = 7), diseased but without pulmonary thromboembolism (n = 21), and healthy (n = 6). An observer who was aware of group status created three‐dimensional pulmonary artery vascular trees for each dog using a semiautomated segmentation technique. Vascular three‐dimensional reconstructions were then evaluated using fractal analysis. Fractal dimensions were analyzed, by group, using analysis of variance and principal component analysis. Fractal dimensions were significantly different among the three groups taken together (P = 0.001), but not between the diseased dogs alone (P = 0.203). The principal component analysis showed a tendency of separation between healthy control and diseased groups, but not between groups of dogs with and without pulmonary thromboembolism. Findings indicated that computed tomographic pulmonary angiogram images can be used to reconstruct three‐dimensional pulmonary arterial vascular trees in dogs and that fractal analysis of these three‐dimensional vascular trees is a feasible method for quantifying the spatial relationships of pulmonary arteries. These methods could be applied in further research studies on pulmonary and vascular diseases in dogs.     

Pharmacokinetics of enrofloxacin in the red pacu (Colossoma brachypomum) after intramuscular, oral and bath administration

The intramuscular (i.m.), oral (p.o.), and bath immersion disposition of enrofloxacin were evaluated following administration to a cultured population of red pacu. The half-life for enrofloxacin following i.m. administration was 28.9 h, considerably longer than values calculated for other animals such as dogs, birds, rabbits, and tortoises. The 4 h maximum concentration ( C _max) of 1.64 μg/mL following a single 5.0 mg/kg dosing easily exceeds the in vitro minimum inhibitory concentration (MIC) for 20 bacterial organisms known to infect fish. At 48 h post i.m. administration, the mean plasma enrofloxacin concentration was well above the MIC for most gram-negative fish pathogens. The gavage method of oral enrofloxacin administration produced a C _max of 0.94 μg/mL at 6–8 h. This C _max was well above the reported in vitro MIC. A bath immersion concentration of 2.5 mg/L for 5 h was used in this study. The C _max of 0.17 μg/mL was noted on the 2 hour post-treatment plasma sample. Plasma concentrations of enrofloxacin exceeded published in vitro MIC's for most fish bacterial pathogens 72 h after treatment was concluded. Ciprofloxacin, an active metabolite of enrofloxacin, was detected and measured after all methods of drug administration. It is possible and practical to obtain therapeutic blood concentrations of enrofloxacin in the red pacu using p.o., i.m., and bath immersion administration. The i.m. route is the most predictable and results in the highest plasma concentrations of the drug.     

PHYSIOLOGY OF THE RESPIRATORY SYSTEM, SIGNIFICANT SPECIES DIFFERENCES, MEASUREMENTS OF PULMONARY FUNCTION, NORMAL VALUES AND SIGNIFICANCE OF VARIATIONS FROM NORMAL

The respiratory system of animals can be divided for evaluation into pulmonary system and circulatory system. The pulmonary system is involved in external respiration whereas the circulatory system is involved in internal respiration. External respiration is the exchange of oxygen (O₂) and carbon dioxide (CO₂) between the environment and circulating blood by way of the lungs and internal respiration is the transport of O₂ and CO₂ between the lungs and the metabolic machinery of the body cells.     

Comparison of Two Doses of the GnRH Antagonist, Acyline, for Pregnancy Termination in Bitches

Gonadotropin-releasing hormone (GnRH) antagonists are particularly useful when a rapid inhibitory effect on the gonadal axis is required. The aim of this study was to test the efficacy and clinical safety of a low and high dose of the third generation GnRH antagonist, acyline, on pregnancy termination in female dogs. The effect of the antagonist on the progesterone (P₄) serum concentration was also described. Twenty-one mid-pregnant bitches were randomly assigned to a single subcutaneous (SC) dose of a placebo (PLACE; n = 7), a low (ACY-L; 110 μg/kg; n = 6) or high (ACY-H; 330 μg/kg; n = 8) dose of acyline. The animals were followed up for 15 days. All ACY treated but no placebo-treated animals terminated their pregnancy by abortion (p < 0.01). The ACY-L and ACY-H groups interrupted their pregnancy 7 ± 1.9 and 6.4 ± 1.3   days after treatment, respectively (p = 0.7). A significant interaction between treatment and day was found (p < 0.01) for P₄ serum concentrations when PLACE was compared with both ACY groups. No difference was found for this hormone between both ACY groups (p > 0.05) where P₄ diminished throughout the study. The decreasing rate varied among animals and was closely related to the time of abortion when P₄ reached basal concentrations. In PLACE animals, gestation progressed normally and P₄ did not change throughout the study (p > 0.05). None of the bitches presented side effects. It was concluded that acyline safely terminated mid-pregnancy by permanently decreasing P₄ serum concentrations.     

THE USE OF99mTc RADIOAEROSOL VENTILATION AND MACROAGGREGATED ALBUMIN PERFUSION IMAGING FOR THE DETECTION OF PULMONARY EMBOLI IN THE DOG

This study was undertaken to design protocol for use of radioaerosol of technetium-99m-labeled diethylenetriaminepentacetic acid (^99mTc-DTPA) for ventilation imaging as clinical tool in the dog and to evaluate imaging characteristics in both normal dogs and dogs with simulated pulmonary embolism. Clearance of the 99mTc-DTPA radioaerosol from the lung was also evaluated. Six normal dogs were used in two phases: (1) as their own controls and (2) during pulmonary artery occlusion using Swan-Ganz catheter. Radioaerosol ventilation images were obtained and rate of clearance from normal and occluded lungs determined. Perfusion studies using technetium-99m-macroaggregated albumin (^99mTc-MAA) immediately followed. Clearance half-times (T_1/2) were found to be significantly increased (p < 0.05) in acutely occluded lungs; however, the small magnitude of this change was visually difficult to detect on the ventilation images. Good quality initial ventilation and perfusion images were obtained and provided ready evaluation of ventilation (V), perfusion (Q), and induced V/Q mismatches. A clinical case of pulmonary thromboembolic disease was also evaluated with diagnostic result, indicating that this method of V/Q scintigraphy can provide useful information in those clinical cases in which pulmonary thromboembolism is suspected.     

Frequency of pulmonary mineralization and hypoxemia in 21 dogs with pituitary-dependent hyperadrenocorticism

The purpose of this study was to determine the frequency of hypoxemia and pulmonary mineralization using ^99mTc-methylene diphosphonate (^99mTc-MDP) in dogs with pituitary-dependent hyperadrenocorticism (PDH). Twenty-one dogs with PDH were pro-spectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using ^99mTc-macro-aggregated albumin [^99mTc-MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco-lumbar vertebrae from lateral thoracic ^99mTc-MDP images. Thoracic: vertebral ratios were calculated using ^99mTc-MDP studies from 21 control dogs. The thoracic: vertebral ratios were compared between the 2 groups (PDH and control). The mean age (±SD) of the 21 PDH dogs was 10.2 (±3) years, whereas the mean age of the control group was 9.8 (±3) years. Seven of the 21 dogs with PDH were hypoxemic (denned as an arterial partial pressure of oxygen [PaO₂] <80 mm Hg) with an average PaO₂ (±SD) of 62 (±15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using ^99mTc-MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic. The average quantitative thoracic: vertebral ratio was not significantly different between the PDH and control dogs (0.5 ± 0.4 versus 0.4 ± 0.1, P = .16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hypoxemia in dogs with PDH.