QUANTITATIVE THYROID SCINTIGRAPHY IN GREYHOUNDS SUSPECTED OF PRIMARY HYPOTHYROIDISM

The existence of hypothyroidism in greyhounds remains controversial and its investigation is complicated by the low circulating thyroid hormone concentrations typically found in healthy dogs of this breed. Quantitative measurement of thyroidal technetium-99m pertechnetate (^99mTcO₄⁻) uptake is known to be useful in assessing thyroid function in other breeds. The aim of this study was to evaluate thyroid scintigraphy as a method of assessing thyroid function in greyhounds suspected of primary hypothyroidism. Twenty greyhounds (eight females, 12 males) were studied. Thirteen had bald thigh syndrome and seven poor performance and low total T4. Total T4 concentrations were decreased in 18 (90%), and free T4 in two (10%) dogs. All canine thyroid stimulating hormone concentrations were within the reference interval. Thyroidal ^99mTcO₄⁻ uptake values (mean ± SD, 0.76 ± 0.26%) were within the reference limits published for euthyroid dogs (0.39–1.86%) making hypothyroidism highly unlikely. There were no significant differences ( P <0.05) when comparing data between dogs with bald thigh syndrome (13 dogs) and the remaining dogs (seven dogs). Seventeen (85%) dogs had higher uptake in the left thyroid gland than in the right that might reflect an anatomic feature of the greyhound breed. Calculation of percent thyroidal uptake of ^99mTcO₄⁻ is more accurate than thyroid:salivary gland ratios because of high variability in salivary gland uptake. Percent thyroidal uptake of ^99mTcO₄⁻ should be used when assessing thyroid function scintigraphically in the greyhound breed.     

COMPARISON OF TRANSCOLONIC 123I-IODOAMPHETAMINE AND PORTAL VEIN INJECTION OF 99mTc-MACROAGGREGATED ALBUMIN SHUNT FRACTION CALCU-LATIONS IN EXPERIMENTAL DOGS WITH ACQUIRED POR-TOSYSTEMIC SHUNTS

Shunt fraction was determined using transcolonic ¹²³I-iodoamphetamine (IMP) and portal vein injection of ^99mTc-macroaggregated albumin (MAA) in a group of eight dogs with chronic cirrhosis and acquired portosystemic shunts subsequent to total common bile duct ligation. Hepatic parenchymal damage was confirmed by alterations in liver function tests and liver histology. Seven of the eight dogs developed portal hypertension and had angiographic evidence of hepatofugal portal blood flow with multiple peripheral portosystemic anastomoses. Shunt fractions determined in the seven dogs with shunts varied from 39 to 100 using IMP and 45 to 93 using MAA. The remaining dog had normal portal pressure, a normal portal angiogram, and normal IMP and MAA scintigraphic studies. There was an excellent correlation between the two methods of shunt fraction calculation (R²= 0.98) and the line of regression was not significantly different from unity (IMP = 1.09 × MAA - 0.03).     

THE INSENSITIVITY OF 99mTc PERTECHNETATE FOR DETECTING METASTASES OF A FUNCTIONAL THYROID CARCINOMA IN A DOG

This report describes the use of ^99mtechnetium pertechnetate (^99mTcO₄⁻) and ¹³¹[for imaging of a metastatic thyroid carcinoma in a dog. The ¹³¹] imaging showed metastatic lesions undetected by the ^99mTcO₄⁻ imaging on 2 separate occasions. The possible mechanisms for the discrepancies between ¹³¹I and ^99mTcO₄⁻ imaging of thyroid carcinomas are discussed. The use of ¹³¹I for the imaging of functional thyroid carcinomas in the dog is recommended.     

Yohimbine prevents the retrograde flow of spermatozoa into the urinary bladder of dogs induced by xylazine

This study was carried out to determine whether yohimbine antagonizes the retrograde flow of spermatozoa into the urinary bladder of dogs caused by xylazine. Adult dogs were assigned to one of four groups of six dogs each and treated as follows: saline control, xylazine (2.2 mg/kg, i.m.), yohimbine (0.2 mg/kg, im.), yohimbine/xylazine (yohimbine, 0.2 mg/kg, i.m., followed 10 min later by xylazine. 2.2 mg/kg, i.m.). Pre- and post-treatment urine were collected by cystocentesis from all dogs. The mean (± SD) adjusted total number of spermatozoa in the post-treatment urine of xylazine-treated dogs (141.02 ± 136.75 × 10⁶) was 15 times higher ( P < 0.05) than the number in the post-treatment urine of control dogs (9.16 ± 20.26 × 10⁶), 1763 times higher ( P < 0.05) than the number in the urine of yohimbine-treated dogs (0.08 ± 0.20 × 10⁶), and 56 times higher ( P < 0.05) than the total number in the post-treatment urine of yohimbine/xylazine-treated dogs (2.54 ± 4.54 × 10⁶). These results confirm that xylazine induces a significant ( P = 0.007) displacement of spermatozoa into the urinary bladder of dogs and demonstrate that pre-treatment with yohimbine prevents this effect.     

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.     

TREATMENT OF DIFFERENTIATED THYROID CARCINOMA IN 7 DOGS UTILIZING 131I

Seven dogs with thyroid gland carcinoma were treated with ¹³¹I and hormone suppressive therapy either alone (3 dogs) or in combination with surgery (3 dogs) or ¹³⁷Cs teletherapy and chemotherapy (1 dog). Empirically chosen doses of 75 to 137 mCi of ¹³¹I were given orally (2 dogs) and intravenously (5 dogs). Adverse effects were limited to acute, transient bone marrow hypoplasia and pancytopenia. Nominal objective reduction in tumor volume or size and number of pulmonary metastases was observed in 4 dogs treated with ¹³¹I and thyroxine. Of these 4 dogs, 2 had stable disease for periods of 4 and 12 months while a third dog had stable disease for 27 months following two ¹³¹I treatments at 3 month intervals. The fourth dog had progressive disease. Two dogs with mediastinal metastases showed reduction in localization of ^99mTc pertechnetate and radioiodine following 2 and 3 treatments using ¹³¹I. It appears that relatively high doses of ¹³¹I can be used safely for the treatment of canine thyroid tumors and that further investigation can be justified to define its efficacy.     

IN VITRO EVALUATION OF CANINE GRANULOCYTES LABELED WITH 99mTC-HEXAMETHYLPROPYLENEAMINE OXIME:

Technetium-99m hexamethylpropyleneamine oxine (^99mTc-HMPAO) and Indium-111 oxine (¹¹¹In-oxine) labeled canine gramulocytes were evaluated in vitro over a six hour period. Labeling efficiency for ^99mTC-HMPAO and ¹¹¹In-oxine labeled granulocytes was 39.6%± 8.0% and 60.6%± 17.6% (mean ± SD) respectively. The mean in vitro elution of the radiolabel ranged from 8.7-14.0% for the ^99mTc-HMPAO grannulocytes and from 6.1-9.0% for the ¹¹¹In-oxine granulocytes. Mean cell viability, for the ^99mTc-HMPAO, ¹¹¹In-oxine and non-radiolabeled control granulocytes ranged from 97.8-99.4%, 96.4-98.5% and 98.2-99.0%, respectively. The phagocytic ability of the ^99mTc-HMPAO, ¹¹¹In-oxine and control granulocytes ranged from 47.5-54.1%, 38.9-56.2% and 46.6-57.8% respectively over the six hour study period. Although labeling efficiency using ¹¹¹In-oxine was significantly (P=0.05) better than ^99mTc-HMPAO, there was no significant difference in label retention of the two radiolabels. There was no significant difference in viability or phagocytic function during the six hour study period. Considering the potential cost advantage and the superior imaging qualities of Technetium-99m relative to Indium-111, ^99mTc-HMPAO appears to be a good alternative to ¹¹¹In-oxine as a granulocyte label.     

Evaluation of the Perkins® handheld applanation tonometer in the measurement of intraocular pressure in dogs and cats

Objective  To evaluate and to validate the accuracy of the Perkins^® handheld applanation tonometer in the measurement of IOP in dogs and cats.
Animals  Twenty eyes from 10 dogs and 10 cats immediately after sacrifice were used for the postmortem study and 20 eyes from 10 clinically normal and anesthetized dogs and cats were used for the in vivo study. Both eyes of 20 conscious dogs and cats were also evaluated.
Procedure  Readings of IOP postmortem and in vivo were taken using manometry (measured with a mercury column manometer) and tonometry (measured with a Perkins^® handheld applanation tonometer). The IOP measurement with Perkins^® tonometer in anesthetized and conscious dogs and cats was accomplished by instillation of proxymetacaine 0.5% and of 1% fluorescein eye drops.
Results  The correlation coefficient ( r ²) between the manometry and the Perkins^® tonometer were 0.982 (dogs) and 0.988 (cats), and the corresponding linear regression equation were y  = 0.0893 x  + 0.1105 (dogs) and y  = 0.0899 x  + 0.1145 (cats) in the postmortem study. The mean IOP readings with the Perkins^® tonometer after calibration curve correction were 14.9 ± 1.6 mmHg (range 12.2–17.2 mmHg) in conscious dogs, and were 15.1 ± 1.7 mmHg (range 12.1–18.7 mmHg) in conscious cats.
Conclusion  There was an excellent correlation between the IOP values obtained from direct ocular manometry and the Perkins^® tonometer in dogs and cats. The Perkins^® handheld tonometer could be in the future a new alternative for the diagnosis of glaucoma in veterinary ophthalmology.     

Hypocalcaemia associated with low serum vitamin D metabolite concentrations in two dogs with protein-losing enteropathies

Protein-losing enteropathies were diagnosed in two dogs that were initially presented with diarrhoea and weight loss. Plasma biochemistry in both cases revealed low concentrations of albumin, calcium and ionised calcium. Both dogs had an elevated plasma parathyroid hormone concentration and low serum 25-hydroxyvitamin D (25[OH]D) concentration. The first dog was diagnosed with lymphangiectasia on postmortem examination, and the second dog was diagnosed with chronic lymphocytic/ plasmacytic enteritis and severe cystic mucoid changes based on endoscopic duodenal biopsies. While a causal effect was not demonstrated, the protein-losing enteropathies may have caused reduced intestinal absorption of vitamin D leading to low plasma concentrations of ionised calcium and secondary hyperparathyroidism. To the authors' knowledge, this is the first report of low ionised calcium concentrations, low 25(OH)D and 1,25-dihydroxyvitamin D concentrations, and high parathyroid hormone concentrations in dogs with protein-losing enteropathies.     

Cutaneous presentation of canine intravascular lymphoma (malignant angioendotheliomatosis)

A 9-year-old female spayed Boxer dog presented with variably sized, firm, black, raised, exudative subcutaneous masses on her head, neck and trunk, that tended to fluctuate in size and frequently ulcerate. Skin biopsy showed that the dermis was expanded by a densely cellular mass of proliferative capillaries distended with large pleomorphic neoplastic round cells mixed with fibrin and erythrocytes. Intravascular lymphoma was diagnosed and immunostains were compatible with a CD8⁺ T lymphocyte histogenesis (CD3⁺/CD79a⁻/TCRαβ⁺/CD8α⁺). Post-mortem examination, four months after diagnosis, revealed neoplastic T-cells within meningeal arteries. We are unaware of other reports of a cutaneous presentation and ante-mortem diagnosis of intravascular lymphoma in the dog. Additionally, this vasoproliferative form of intravascular lymphoma has not been previously described in dogs.     

18FDG-PET IMAGING IN CANINE LYMPHOMA AND CUTANEOUS MAST CELL TUMOR

Positron Emission Tomography (PET) using the glucose analog 2-deoxy-2-[¹⁸F]fluoro- d -glucose (¹⁸FDG) is a common imaging modality for diagnosis and management of many human malignancies. We evaluated ¹⁸FDG-PET in dogs with either multicentric lymphoma (LSA) or cutaneous mast cell tumor (MCT). A prototype large field-of-view PET scanner was used to collect whole-body images in nine dogs with LSA or MCT. Both tumors were characterized by avidity for ¹⁸FDG. In dogs with LSA, ¹⁸FDG-PET correctly identified involvement of superficial and internal lymph nodes, liver, and spleen. Repeated PET scans after induction chemotherapy demonstrated resolution of abnormal ¹⁸FDG uptake within these sites. In dogs with MCT, ¹⁸FDG-PET correctly identified MCT metastasis to regional lymph nodes in all dogs in which this was suspected or confirmed with cytology or biopsy before the PET scan. In two dogs, additional sites of mast cell disease were identified with ¹⁸FDG-PET that were undetected on physical examination and/or regional lymph node cytology. ¹⁸FDG-PET holds promise as a whole-body staging method for canine LSA and MCT.     

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.     

Effect of lidocaine on the minimum alveolar concentration of sevoflurane in dogs

Objective  To investigate the effects of a low-dose constant rate infusion (LCRI; 50 μg kg⁻¹ minute⁻¹) and high-dose CRI (HCRI; 200 μg kg⁻¹ minute⁻¹) lidocaine on arterial blood pressure and on the minimum alveolar concentration (MAC) of sevoflurane (Sevo), in dogs.
Study design  Prospective, randomized experimental design.
Animals  Eight healthy adult spayed female dogs, weighing 16.0 ± 2.1 kg.
Methods  Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg⁻¹ saline loading dose or lidocaine (2 mg kg⁻¹ intravenously) was administered over 3 minutes, followed by saline CRI or lidocaine LCRI or HCRI. The sevoflurane MAC was determined using a tail clamp. Heart rate (HR), blood pressure and plasma concentration of lidocaine were measured. All values are expressed as mean ± SD.
Results  The MAC of Sevo was 2.30 ± 0.19%. The LCRI reduced MAC by 15% to 1.95 ± 0.23% and HCRI by 37% to 1.45 ± 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 ± 0.18 for LCRI and 1.89 ± 0.37 μg mL⁻¹ for HCRI. Seventy-five percent of HCRI dogs vomited during recovery.
Conclusion and clinical relevance  Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI.     

Clinical, immunological and histopathological findings in a subpopulation of dogs with pododermatitis

Abstract   Clinical, immunological and histopathological findings in 20 adult dogs of varying breeds with chronic (≥ 6 months) inflammation confined to the pedal skin were compared over a 2-year period with those of a group of age-matched controls ( n  = 20). All affected dogs were pruritic but systemically well. Lesions were present on all four feet in 18/20 cases. Affected feet were characteristically erythematous, swollen, painful and alopecic. Sinus tracts were evident in 4/20 dogs. Despite a methodical series of diagnostic tests, no underlying cause was identified. None of the dogs responded to antimicrobial therapy administered for 8 weeks, none had evidence of ectoparasitism and none satisfied the criteria for atopic dermatitis. There was no response to a dietary trial using a novel protein source. The condition was characterized histopathologically by epidermal hyperplasia, hyperkeratosis, spongiosis, dermal oedema and perivascular aggregates of lymphocytes and plasma cells. Clinical signs did not correlate with histopathological findings. Affected dogs had significantly elevated serum IgG and IgM concentrations. The results of lymphocyte proliferation assays and phenotypic studies to determine the relative percentage of CD3⁺, CD4⁺, CD8⁺ and CD21⁺ lymphocyte subsets, and the ratio of CD4⁺/CD8⁺ cells were not significantly different between groups. No age, sex or seasonal predilections were noted. All dogs subsequently responded to immunosuppressive doses of prednisolone or cyclosporin. The term immunomodulatory-responsive lymphocytic–plasmacytic pododermatitis is proposed to denote what may be a previously unrecognized condition in some dogs with pododermatitis of undetermined aetiology.     

Retinol-Binding Protein in Serum and Urine of Hyperthyroid Cats before and after Treatment with Radioiodine

Background: Retinol-binding protein (RBP) is suggested as a clinically useful marker of renal function in cats.
Hypothesis: Serum and urinary RBP concentrations in hyperthyroid (HT) cats differ from those in healthy (H) cats; radioiodine (¹³¹I) treatment influences serum and urinary RBP concentrations in HT cats.
Animals: Ten HT and 8 H cats.
Methods: RBP concentration was evaluated in feline serum and urine samples from a prospective study.
Results: There was a significant ( P = .003) difference in the urinary RBP/creatinine (uRBP/c) ratios of H (−) and untreated HT (1.4 ± 1.5 × 10⁻² μg/mg) cats. Serum total thyroxine concentration (1.8 ± 1.9 μg/dL, 24 weeks) and uRBP/c (0.6 ± 1.0 × 10⁻² μg/mg, 24 weeks) decreased significantly ( P < .001) in HT cats at all time points after treatment with ¹³¹I, and these variables were significantly correlated with one another ( r = 0.42, P = .007). Serum RBP concentrations from HT cats (199 ± 86 μg/L) did not differ significantly ( P = .98) from those of H cats (174 ± 60) and did not change after treatment with ¹³¹I (182 ± 124 μg/L, P = .80).
Conclusion and Clinical Importance: The presence of urinary RBP in HT cats is a potential marker of tubular dysfunction that is correlated to thyroid status, although it is independent of circulating RBP concentrations. The decreased uRBP/c combined with the absence of changes in serum RBP after treatment suggests that the suspected tubular dysfunction was partly reversible with treatment of ¹³¹I.     

Transcatheter Atrial Septal Defect Closure with the AMPLATZER® Atrial Septal Occluder in 13 Dogs: Short- and Mid-Term Outcome

Background: Transcatheter atrial septal defect (ASD) closure in the dog was first reported in 2005.
Objectives: Describe the technique and both short- and mid-term outcome of transcatheter ASD closure with the Amplatzer^® atrial septal occluder (ASO).
Animals: Thirteen client-owned dogs with ASD.
Methods: Records of the initial 13 dogs in which transcatheter ASD closure was attempted at Texas A&M University were reviewed.
Results: All dogs had hemodynamically relevant septum secundum ASD. Two dogs had concurrent congenital abnormalities. ASOs were deployed in 13 dogs and released in 12. Eleven were released by a right jugular approach and 1 by a transatrial approach through a right lateral thoracotomy. Transthoracic echocardiographic estimates of ASD size were 14.0 ± 5.4 mm (mean ± 1 standard deviation) with a range of 7–22 mm. Accidental right atrial release occurred in 1 dog and embolization after release occurred in 2 dogs. Transcatheter ASD closure was successful in 10 dogs. Transthoracic color Doppler echocardiography the day after ASD closure indicated complete occlusion in 5 dogs, trivial to mild residual shunting in 4 dogs, and moderate residual shunting in 1 dog. Follow-up echocardiograms (mean of 12.4 ± 7.4 months postprocedure) were available for 9 dogs. There was no residual ASD shunting in 6 dogs. In 3 of the 5 dogs with postoperative residual shunting it was judged to be decreased and hemodynamically unimportant relative to the dogs' postoperative evaluations. The mean length of event-free survival in the 10 dogs that underwent successful transcatheter ASD closure was 22.2 ± 10.2 months.     

Pharmacokinetics of sulphadimidine in normal and febrile dogs

Pharmacokinetic parameters which describe the distribution and elimination of sulphadimidine were determined in normal dogs and dogs in which fever was produced by an intravenous injection of escherichia and staphylococcal species of bacteria. Sulphadimidine was injected as a single intravenous bolus at the dose of 100 mg/kg and the kinetics of the drug were described in terms of the bi-exponential expression: C_p = Ae ^{-α t} + Be ^{-β t} . The distribution half-times of the drug were 1.52 h in the normal and 0.81 h in the febrile dogs. The drug distribution was significantly more rapid ( P < 0.05) in febrile than in normal dogs. Average ± SD values for the half-lives of the drug were 16.2 ± 5.7 h in normal and 16.7 ± 4.7 h in the febrile dogs. The apparent volume of distribution ( V ' _d (area)) was 628 ± 251 ml/kg in the normal dogs, and was not statistically different from 495 ± 144 ml/kg in the febrile dogs. The volume of the central compartment ( V ' _c ) was 445 ± 55 ml/kg in normal dogs and this was significantly higher ( P < 0.01) than the V ' _c of 246 ± 72 ml/kg in the febrile dogs. The body clearance was 22.4 ± 4.8 and 20.2 ± 3.6 ml/hour. kg in the normal and febrile dogs, respectively. The investigation revealed that the dosage regimen of sulphadimidine did not differ significantly between normal and febrile dogs.     

High-Frequency Jet Ventilation in Anesthetized, Paralyzed Dogs and Cats Via Transtracheal and and Endotracheal Tube Routes

The ability of the SAV 6 high-frequency jet ventilator to effectively ventilate three anesthetized, paralyzed cats (3.2–4.2 kg), two small dogs (7.2 and 10.0 kg), six medium-sized dogs (20.5–25.0 kg), and three large dogs (36.0–43.0 kg) via a 14-gauge (dogs) or a 16-gauge (cats) catheter placed percutaneously into the trachea via the cricothyroid membrane or into a preplaced endotracheal tube was evaluated. The lowest driving pressure within the range of 0.25 to 2.0 kg/cm² (1 kg/cm²= 14.2 psi) and the highest cycle rate within the range of 60 to 240 per minute that would generate a PaCO₂ of 30 ± 3 mm Hg were determined.
All animals could be ventilated to a PaC0₂ of 30 ± 3 mm Hg by the endotracheal tube and transtracheal route, except the largest dogs, which couid be ventilated to an average PaC0₂ of 36 mm Hg by the transtracheal route. The transtracheal route consistently required higher driving pressures and lower cycle rates than did the endotracheal tube route. Cats could be ventilated with a driving pressure of 0.25 kg/cm²; small dogs could be ventilated with 0.5 to 1.0 kg/cm₂; medium-sized dogs with 1.0 to 1.5 kg/cm²; and large dogs with 1.5 to 2.0 kg/cm².
The SAV 6 high-frequency jet ventilator can effectively ventilate cats and dogs (7.2–43.0 kg) via a transtracheal catheter and an endotracheal tube.     

Cytosine Arabinoside as a Single Agent for the Induction of Remission in Canine Lymphoma

Cytosine arabinoside (AraC) was administered as a continuous IV infusion to 15 dogs with malignant lymphoma at a dose of 300 mg/m²/d for 2 consecutive days. Dogs were re-examined 7 d after treatment for response to therapy and for hematologic toxicity. Regardless of response, all dogs were started on combination chemotherapy at this time. Other toxicities were reported by owners. No dog responded objectively to Ara-C treatment, although 1 dog with circulating lymphoblasts had partial regression of lymphadenopathy but persistent blastemia. Thrombocytopenia (platelet count < 200,000/μL) 7 days posttreatment was the most commonly encountered hematologic toxicity, occurring in 10 of 14 dogs. Three of these 10 dogs were also mildly neutropenic (neutrophil counts of 2000 to 3000 cell/μL). Nonhematologic toxicity occurred in 8 of 15 dogs and was principally gastrointestinal in nature and mild in severity. Cytosine arabinoside at a dose of 300 mg/m²/day was not considered an active drug for the induction of remission in dogs with lymphoma.     

PULMONARY MINERALIZATION IN FOUR DOGS WITH CUSHING'S SYNDROME

The clinical and imaging features of four dogs with Cushing's syndrome and pulmonary mineralization are reviewed. Three dogs presented with a primary complaint of respiratory distress/dyspnea. Three dogs had pituitary dependent Cushing's syndrome, while the remaining one dog had iatrogenic Cushing's syndrome. Each dog had clinical features typical for Cushing's syndrome. Two of the dogs were euthanized due to progressive hypoxemia. In each dog, the serum calcium, phosphorous, blood urea nitrogen and creatinine were normal.
A generalized increase in unstructured interstitial pulmonary opacity with diffuse mineralization was noted on thoracic radiographs of all dogs. In one dog, an ill-defined nodular interstitial pattern of mineralization was present. Delayed bone phase scintigraphy using ^99mTechnetium methylene diphosphonate documented generalized pulmonary uptake in two dogs. ^99mTechnetium labeled microaggregated albumin lung perfusion scans were normal in these two dogs. ^99mTc-MDP scintigraphy can provide useful information in diagnosing pulmonary mineralization in Cushingoid dogs.