Evaluation of relationships between pretreatment patient variables and duration of isolation for radioiodine-treated hyperthyroid cats

OBJECTIVE: To determine relationships between commonly measured pretreatment variables and duration of isolation for unrestricted dismissal after oral administration of iodine 131 (131I) for treatment of hyperthyroidism in cats. ANIMALS: 149 hyperthyroid cats treated with 131I. PROCEDURE: A dose of 131I (2.9 to 6.04 mCi [1.07 to 2.23 x 10(8) Bq]) was administered orally to all cats after hyperthyroidism was confirmed by evaluation of serum total thyroxine (T4) concentrations. Forward stepwise regression analysis was used to determine whether pretreatment total T4 concentration, serum creatinine concentration, body weight, age, 131I dose, or concurrent administration of cardiac medication (specifically excluding thyroid suppression drugs) could be used as pretreatment predictors of duration of isolation in a clinical setting. Gamma radiation emission rate at dismissal was < 2.0 mR/h at skin surface over the thyroid region. RESULTS: Mean +/- SD duration of isolation was 16.67 +/- 4.42 days (95% confidence interval, 9.2 to 24.1 days). The regression equation for duration of isolation calculated on the basis of dose of 131I (duration of isolation [days] = 3.2 + [2.66 X mCi - 131I dose]) yielded a regression line with a 95% confidence interval of +/- 3.3 days; only 15% of the variation was explained. CONCLUSIONS AND CLINICAL RELEVANCE: A pretreatment estimate for duration of isolation could be determined only from an equation based on the orally administered dose of 131I. These findings suggest that administration of the lowest efficacious dose possible is the dominant factor in reduction of duration of isolation for cats treated with 131I.     

Recombinant human thyrotropin administration enhances thyroid uptake of radioactive iodine in hyperthyroid cats

BACKGROUND: Hyperthyroidism is the most diagnosed endocrine disorder in cats and radioiodine (131I) is the treatment of choice. The dose emission rate and radioactivity in urine, saliva, and on hair and paws are determined by the dose of administered 131I. A dose reduction of therapeutic 131I could possibly be achieved after recombinant human thyrotropin (rhTSH) administration as in humans with nodular goiter. HYPOTHESIS: rhTSH will increase radioiodine uptake in hyperthyroid cats. ANIMALS: Five hyperthyroid cats. METHODS: Twenty-five micrograms rhTSH (day 1) or 2 mL 0.9% sodium chloride (NaCl) (day 9) was injected IV. One hour later, 11.4 +/- 4.1 (mean +/- SD) MBq 123I was injected IV. Radioactive iodine uptake (RAIU) was measured 6, 12, and 24 hours after rhTSH (RAIU-rhTSH) or NaCl (RAIU-blanco) injection. Blood samples for measurement of TT4 were taken before injection of rhTSH or NaCl (TT4(0)) and at the time of imaging. RESULTS: Percentages of RAIU-rhTSH (and RAIU-blanco) at 6, 12, and 24 hours after administration of rhTSH were 34 +/- 18 (31 +/- 21), 46 +/- 20 (38 +/- 18), and 47 +/- 15 (36 +/- 14). There was a statistically significant effect of rhTSH administration on RAIU (P = .043) but not on serum TT4 concentration. Baseline serum TT4(0) concentration influenced RAIU-rhTSH significantly at 6 hours (P = .037). CONCLUSION AND CLINICAL IMPORTANCE: The increased RAIU observed after rhTSH administration in hyperthyroid cats could lead to a lower therapeutic dose of 131I after rhTSH administration in hyperthyroid cats and decreased risk of environmental and owner contamination during and after hospitalization.     

Relationship between orally administered dose, surface emission rate for gamma radiation, and urine radioactivity in radioiodine-treated hyperthyroid cats

OBJECTIVE: To determine the relationship between surface emission rate of gamma radiation and urine concentration of I131 (urine radioactivity) during the period 7 to 21 days after oral or SC administration of I131 to hyperthyroid cats. ANIMALS: 47 hyperthyroid cats administered I131 PO and 24 hyperthyroid cats administered I131 SC. PROCEDURE: A dose of I131 (1.78 to 2.04 X 10(2) MBq [4.8 to 5.5 mCi]) was administered orally. Surface emission at the skin adjacent to the thyroid gland on days 7, 10, 14, 18, and 21 and number of counts/30 s in a urine sample (1 mL, obtained via cystocentesis) on days 7, 14, and 21 after oral administration were measured. Effective half-life (T1/2E) was derived for each point. Surface emission thresholds for maximum urine radioactivity values were established. A dose of I131 (1.48 X 10(2) MBq [4.0 mCi]) was administered SC. Urine radioactivity and surface emission rates for SC administration were compared with values for oral administration. RESULTS: The T1/2E for surface emissions and urine radioactivity progressively increased toward values for physical T1/2 over time. The T1/2E for surface emissions was 2.19 to 4.70 days, and T1/2E for urine radioactivity was 2.16 to 3.67 days. Surface emission rates had a clinically useful threshold relationship to maximum urine concentrations of I131. CONCLUSIONS AND CLINICAL RELEVANCE: Surface emission rates for cats administered I131 appeared useful in determining upper limits (threshold) of urine radioactivity and are a valid method to assess the time at which cats can be discharged after I131 administration.     

REPEATABILITY AND RELIABILITY OF GLOMERULAR FILTRATION RATE DETERMINATION VIA GAMMA CAMERA UPTAKE OF TC‐99M‐DTPA IN CATS WITH CHRONIC KIDNEY DISEASE

Measurement of glomerular filtration rate (GFR) via gamma camera uptake of 99mTc‐diethylenetriaminepentaacetic acid is a standard method for quantifying renal function. Aims of this retrospective, observer agreement study were to determine intra‐ and interobserver variation in GFR values for cats with chronic kidney disease and to determine whether renal insufficiency classification changed between observers. Guideline cut‐points were established for the difference in repeated GFRs to differentiate changes caused by therapeutic effect vs. inherent variation. Included cats had a diagnosis of chronic kidney disease and had undergone GFR examinations between the years of 2010 and 2013. Twenty‐nine GFR studies were sampled. Each study was read twice, 6 months apart, by two veterinary radiologists and one radiology resident. Modified Bland–Altman plots were used to investigate differences between readings 1 and 2 by observer and between pairs of observers by reading. Reliability of clinical classification was assessed through comparisons between readings and observers. Measurements were not systematically different between readings for the experienced observers but were higher in reading 1 than reading 2 for the inexperienced observer. Measurements were not systematically different between the experienced observers in reading 1 or between any two observers in reading 2. Reliability for GFR measurements was high among experienced observers; variations in GFR measurements rarely led to differences in clinical classification. Results suggested that, for experienced observers, changes in GFR values following treatment in cats with chronic kidney disease between ?0.4 and 0.4 mL/min/kg may be due to inherent variability rather than treatment effect.     

Measuring statistical agreement between four point of care (POC) lactate meters and a laboratory blood analyzer in cats

The use of blood lactate concentrations as a prognostic indicator and therapeutic gauge in feline medicine has been hindered by the inability to obtain values in a timely manner with minimal quantities of blood. Recently, hand-held point-of-care (POC) lactate meters have become commercially available. The objective of this prospective study was to determine if lactate values produced by three commercially available and one medical grade POC meter were in agreement with a laboratory blood analyzer. Blood samples from 47 cats were collected on presentation to an emergency service and processed on four POC meters and a Stat Profile Critical Care Xpress blood analyzer. The results were analyzed using the Bland-Altman method. The blood lactate values produced by the hospital grade POC meter and one of the commercially POC meters were in good agreement with the Critical Care Xpress blood analyzer. Other commercially available POC meters produced acceptable agreement.     

Transdermal methimazole treatment in cats with hyperthyroidism

The objectives of this study were to assess serum thyroxine concentrations and clinical response in hyperthyroid cats to treatment with transdermal methimazole, and to determine if further investigation is indicated.Clinical and laboratory data from 13 cats with hyperthyroidism were retrospectively evaluated. Methimazole (Tapazole, Eli Lilly) was formulated in a pleuronic lecithin organogel (PLO)-based vehicle and was applied to the inner pinna of the ear at a dosage ranging from 2.5mg/cat q 24h to 10.0mg/cat q 12h. During the treatment period, cats were re-evaluated at a mean of 4.3 weeks (recheck-1), and again at a mean of 5.4 months (recheck-2).Clinical improvement was observed, and significant decreases in thyroxine concentrations were measured at recheck-1 (mean: 39.57nmol/L, SEM: 14.4, SD: 41.2) and recheck-2 (mean: 36.71nmol/L, SEM: 13.9, SD: 45.56) compared to pretreatment concentrations (mean: 97.5nmol/L, SEM: 11.42, SD: 39.5). No adverse effects were reported.     

Common two-dimensional echocardiographic estimates of aortic linear dimensions are interchangeable

ObjectiveTo compare two echocardiographic methods of measuring aortic diameter in short-axis projections.MethodsRight-parasternal short-axis 2-dimensional projections of the left atrium and aorta were obtained from dogs and cats undergoing routine cardiac evaluation. Two investigators measured the aortic valve linear dimension using 2 methods: along the commissure between the non-coronary and right-coronary cusps and along the commissure between the non-coronary and left-coronary cusps. Inter-observer and intra-observer variability and agreement were assessed by comparing blinded measurements with each method by 4 trained observers on a standardized set of images. Measurements were compared for agreement using the limits of agreement analysis. Variability between observers was compared by examining residuals and intraclass correlation.Results274 canine and 100 feline aortic valve images were measured in the first part of the study. One observer demonstrated slight proportional bias, while the other observer showed more variability (less agreement). When results were pooled for both investigators, no bias was identified, and 95% limits of agreement were ±10% of the mean measurement for both species. In the second part of the study, 106 images were measured. Intraobserver variability was <4% for all observers. Inter-observer agreement was very high. Individual bias was identified in some observers, but was considered clinically inconsequential. Normalized differences between the 2 methods of measurement were below ±15% of the measured value for all observers.ConclusionsOur results show sufficient agreement between two common methods used to measure aortic linear dimensions to suggest that these methods are interchangeable.     

Evaluation of the reproducibility and accuracy of pH-determining devices used to measure urine pH in dogs

OBJECTIVE: To evaluate the reproducibility and accuracy of 4 portable pH meters, a reagent strip, and pH paper for measuring urine pH in dogs. DESIGN: Prospective masked randomized study. SAMPLE POPULATION: 201 free-catch urine samples from 114 hospitalized dogs. PROCEDURES: Urine samples were divided into 2-mL aliquots. Measurements of urine pH were obtained by use of a laboratory benchtop pH meter, 4 portable pH meters, a urine reagent strip, and pH paper. The pH of each aliquot was measured within 4 hours of collection by an evaluator unaware of the aliquot's origin.To assess reproducibility, the coefficient of variation for each pH measurement device was calculated. To determine which device was most accurate, the degree of agreement among the different devices was assessed in comparison with the benchtop pH meter, which was considered the reference method. RESULTS: 3 of the 4 portable pH meters had nearly perfect agreement with the reference method. The reagent strip and pH paper had moderate to poor agreement with the reference method. CONCLUSIONS AND CLINICAL RELEVANCE: Urine pH measurements should be made by use of a portable or benchtop pH meter when accurate measurements are crucial for diagnosis or treatment. Reagent strips and pH papers are useful in obtaining pH approximations but are not recommended when accurate measurements of urine pH are required.     

Pharmacokinetics of intravenous ketorolac in cats undergoing gonadectomy

AIM: To determine the pharmacokinetics of ketorolac tromethamine (0.5?mg/kg) when administered I/V to cats undergoing gonadectomy.

METHODS: Ketorolac was administered to nine female and three male shorthair domestic cats as an I/V bolus of 0.5?mg/kg after intubation, and 20 minutes prior to ovariectomy or orchiectomy. Intra-operative cardiorespiratory variables were monitored and blood samples were collected over 24 hours. Concentrations of ketorolac in serum were determined by high-performance liquid chromatography to establish pharmacokinetic parameters.

RESULTS: During surgery, mean end tidal isoflurane concentration was 1.63 (SD 0.24)% and normocapnia and spontaneous ventilation were maintained in all animals. The kinetics of ketorolac was described by a two-compartment model. The distribution and elimination half-lives were 0.09 (SD 0.06) and 4.14 (SD 1.18) hours, respectively. The body clearance was 56.8 (SD 33.1) mL/h/kg. The volume of distribution at steady-state and the mean residence time were 323.9 (SD 115.7) mL/kg and 6.47 (SD 2.86) hours, respectively.

CONCLUSION AND CLINICAL RELEVANCE: On the basis of the results, concentrations of ketorolac in serum in cats were above the human effective concentrations for 5–6 hours postoperatively. However, other studies including a control group are advocated to further investigate the ketorolac kinetics and the analgesic efficacy in this species.     

Agreement and Repeatability of Linear Vertebral Body and Canal Measurements Using Computed Tomography (CT) and Low Field Magnetic Resonance Imaging (MRI)

Objective— To evaluate agreement and repeatability of vertebral column measurements using computed tomography (CT) and magnetic resonance imaging (MRI).
Study Design— Retrospective observational study.
Animals— Dogs (n=18) with disc associated wobbler syndrome; Dog cadavers (n=3).
Methods— Five measurements of the 5th cervical vertebra were performed: vertebral body length (VBL), vertebral canal height (VCH), vertebral body height (VBH), vertebral canal width (VCW), and vertebral body width (VBW). Measurements were performed independently twice by 2 observers. Bland-Altman plots were created to evaluate agreement. Cadaveric vertebrae with soft tissue removed had the same variables and actual dimensions measured.
Results— The largest discrepancy between CT and MRI measurement was for VBL (mean difference±SD=1.262 mm±1.245; P <.001), with the difference for all the other variables being acceptable. The 1st measurement was significantly higher than the 2nd only for VBL using CT (mean difference=0.476 mm±1.120; P =.009), with all other variables having acceptable differences. Mean difference for all measurements between 2 observers was small, except for VBL using CT (mean difference=0.762 mm±1.042; P <.001). Only the difference for VBL between CT and cadaver specimens was statistically significant.
Conclusions— Our results suggest high repeatability and good agreement for most vertebral measurements of interest. VBL measurement using CT was considered problematic.
Clinical Relevance— Provided limitations are understood, linear measurements of vertebral dimensions from CT and MRI images can be used clinically.     

In vivo confocal microscopy in the normal corneas of cats, dogs and birds

OBJECTIVE: To evaluate the applicability of in vivo confocal microscopy (IVCM) in veterinary ophthalmology and analyze the morphology of living, healthy cornea. ANIMALS EXAMINED: Thirty-seven dogs, 34 cats and five birds. PROCEDURE: Various corneal sublayers were visualized in the central region using an in vivo confocal corneal microscope (HRTII/RCM). RESULTS: An investigation method was developed and adapted for use on animals with varying skull forms and eye positions. Real-time images of the epithelial cells, the corneal stroma and the endothelial layer were obtained. The corneal stromal nerve trunks and the subepithelial and basal epithelial nerve plexus were visualized. In dogs, full corneal thickness (FCT) was 585 +/- 79 microm (mean +/- SD) and endothelial cell density (ECD) 3175 +/- 776 cells/mm(2) (mean +/- SD). In cats, FCT was 592 +/- 80 microm and ECD 2846 +/- 403 cells/mm(2). There were no significant differences between canine and feline FCT and ECD and no morphologic differences could be seen between dogs and cats. The bird images revealed a number of structural differences. CONCLUSION: Noninvasive IVCM allows accurate detection of corneal sublayers, corneal pachymetry, endothelial cell density and corneal innervation in various animal species. For clinical usage, patients must be under general anesthesia. The confocal images provided anatomic reference images of various healthy corneal structures in dogs, cats and birds.     

Radioactive iodine therapy for feline hyperthyroidism: Efficacy and administration routes

The efficacy of radioactive iodine (¹³¹I) administration was studied in a series of 50 hyperthy-roid cats. The dose administered to each cat was based on the clinical severity of the thyrotoxicosis, the serum total thyroxine (TJ concentration and the size of the goitre estimated by palpation. The activity ranged from 80 to 200 MBq (mean ± SD, 143 ± 24 MBq}. The ¹³¹I was injected intravenously in 27 cases and subcutaneously in 23 cases. Each cat was hospitalised for 30 days after the injection. Regardless of the route of injection, none of the cats exhibited any side effects after therapy and all tolerated the hospitalisation period well. There was a significant (P<0.001) decrease in the serum total T₄ concentration (reference range, 10.4 to 42.0 nmol/litre) from a mean ± SD of 181.3 ± 111.4 nmol/litre (range, 43.8 to 575.6 nmol/litre) to a mean ± SD of 19.0 ± 29.6 nmol/litre (range, 2.0 to 175.7 nmol/litre) 30 days following the injection of the radioisotope. Five cats remained hyperthyroid, although in each case the serum total T₄ concentrations had decreased from pre-treatment values. Two of the cats subsequently became euthyroid within three and five months of therapy, respectively, two were lost to adequate follow-up and the remaining cat was successfully retreated four months later. Before treatment, four of these cases had high scores based on the three criteria used for dose estimation. Serum total T₄ concentrations below the reference range developed after treatment in many cases, but were often transient. Clinical evidence of hypothyroidism was not apparent in any cat. Recurrence of hyperthyroidism has not occurred in follow-up periods of up to 32 months. There was no difference in the outcome between the cats injected intravenously or subcutaneously and the latter was considered to be safer and simpler. The administration of an approximated dose of ¹³¹I proved to be an effective treatment for hyperthyroidism in 47 (94.0 per cent) of the cats and obviated the need for sophisticated nuclear computer facilities. There may be a lag period in some cases before euthy-roidism is achieved and this should be considered before the administration of a second dose. ¹³¹I can be administered subcutaneously without untoward effects.     

Pharmacokinetics and effects of alfaxalone after intravenous and intramuscular administration to cats

AIMS: To determine the pharmacokinetics, and anaesthetic and sedative effects of alfaxalone after I/V and I/M administration to cats.

METHODS: Six European shorthair cats, three males and three females, with a mean weight of 4.21 (SD 0.53) kg and aged 3.8 (SD 0.9) years were enrolled in this crossover, two–treatment, two-period study. Alfaxalone at a dose of 5?mg/kg was administered either I/V or I/M. Blood samples were collected between 2–480 minutes after drug administration and analysed for concentrations of alfaxalone by HPLC. The plasma concentration-time curves were analysed by non-compartmental analysis. Sedation scores were evaluated between 5–120 minutes after drug administration using a numerical rating scale (from 0–18). Intervals from drug administration to sit, sternal and lateral recumbency during the induction phase, and to head-lift, sternal recumbency and standing position during recovery were recorded.

RESULTS: The mean half-life and mean residence time of alfaxalone were longer after I/M (1.28 (SD 0.21) and 2.09 (SD 0.36) hours, respectively) than after I/V (0.49 (SD 0.07) and 0.66 (SD 0.16) hours, respectively) administration (p<0.05). Bioavailability after I/M injection of alfaxalone was 94.7 (SD 19.8)%. The mean intervals to sternal and lateral recumbency were longer in the I/M (3.73 (SD 1.99) and 6.12 (SD 0.90) minutes, respectively) compared to I/V (0 minutes for all animals) treated cats (p<0.01). Sedation scores indicative of general anaesthesia (scores >15) were recorded from 5–15 minutes after I/V administration and deep sedation (scores 11–15) at 20 and 30 minutes. Deep sedation was observed from 10–45 minutes after I/M administration. One cat from each group showed hyperkinesia during recovery, and the remainder had an uneventful recovery.

CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone administered I/V in cats provides rapid and smooth induction of anaesthesia. After I/M administration, a longer exposure to the drug and an extended half life were obtained compared to I/V administration. Therefore I/M administration of alfaxalone could be a reliable, suitable and easy route in cats, taking into account that alfaxalone has a slower onset of sedation than when given I/V and achieves deep sedation rather than general anaesthesia.     

Association of the risk of development of hypothyroidism after iodine 131 treatment with the pretreatment pattern of sodium pertechnetate Tc 99m uptake in the thyroid gland in cats with hyperthyroidism: 165 cases (1990-2002)

OBJECTIVE: To assess whether the risk of development of hypothyroidism after treatment with iodine 131 (131I) was associated with the pattern of sodium pertechnetate Tc 99m activity in the thyroid gland detected via scintigraphy before treatment in cats with hyperthyroidism. DESIGN: Retrospective study. ANIMALS: 165 cats. PROCEDURE: Medical records of cats with hyperthyroidism that had been treated with 131I (from 1990 to 2002) and had undergone scintigraphy of the thyroid gland before treatment were reviewed; data regarding signalment, scintigraphic findings (classified as unilateral, bilateral-asymmetric, bilateral-symmetric, or multifocal patterns), serum total thyroxine (T4) concentrations before treatment and prior to hospital discharge, and 131I treatment were collected. A questionnaire was sent to each referring veterinarian to obtain additional data including whether the cats subsequently developed hypothyroidism (defined as serum total T4 concentration less than the lower reference limit > or = 3 months after treatment). RESULTS: 50 of 165 (30.3%) 131I-treated cats developed hypothyroidism. Hypothyroidism developed in 39 of 109 cats with bilateral, 10 of 50 cats with unilateral, and 1 of 6 cats with multifocal scintigraphic patterns of their thyroid glands. Cats with a bilateral scintigraphic pattern were approximately 2 times as likely to develop hypothyroidism after 131I treatment than were cats with a unilateral scintigraphic pattern (hazard ratio, 2.1; 95% confidence interval, 1.04 to 4.2). CONCLUSIONS AND CLINICAL RELEVANCE: Cats with hyperthyroidism that have a bilateral scintigraphic pattern in the thyroid gland before 131I treatment appear to have a significantly higher risk of subsequently developing hypothyroidism, compared with cats with a unilateral scintigraphic pattern.     

Serum thyroxine concentrations after radioactive iodine therapy in cats with hyperthyroidism

Thirty-one cats with hyperthyroidism were given one dose of radioactive iodine (131I) IV. Serum thyroxine (T4) concentrations were measured before treatment in all cats, at 12-hour intervals after treatment in 10 cats, and at 48-hour intervals after treatment in 21 cats. Serum T4 concentrations also were measured one month after 131I therapy in 29 cats. Activity of 131I administered was 1.5 to 6.13 mCi, resulting in a dose of 20,000 rads to the thyroid. Serum T4 concentrations before 131I administration were 5.3 to 51.0 micrograms/dl, with a median T4 concentration of 11.0 micrograms/dl. Serum T4 decreased most rapidly during the first 3 to 6 days after treatment. Sixteen cats (55%) had normal serum thyroxine concentrations by day 4 after 131I administration, and 23 cats (74%) were euthyroxinemic by day 8 after treatment. One month after administration of 131I, the 29 cats evaluated were clinically improved, and 24 (83%) of the 29 cats evaluated had normal serum T4 concentrations, 3 cats (10%) remained hyperthyroxinemic, and 2 cats (7%) were hypothyroxinemic. Therefore, administration of 131I was a safe and effective method to quickly decrease serum T4 concentrations in hyperthyroid cats.     

Liver function in cats with hyperthyroidism before and after 131I therapy

BACKGROUND: The clinical significance of high serum concentration or activity of markers of liver damage in cats with hyperthyroidism is unknown. OBJECTIVE: To evaluate serum markers of liver function and damage, and ultrasonographic changes in cats with hyperthyroidism and with high liver enzymes, and to determine if abnormalities resolve after treatment with 131I. ANIMALS: Nineteen cats with hyperthyroidism (15 with high serum activities of liver enzymes) and 4 age-matched healthy control cats. METHODS: Serum bile acids, albumin, ammonia, cholesterol, and blood urea nitrogen concentrations, and activities of liver-derived enzymes, and blood glucose concentrations were measured before and after 131I therapy. These values were compared with those of cats that were euthyroid. In addition, gross liver parenchymal changes detected by abdominal ultrasonographic examination, before and after 131I therapy were evaluated. RESULTS: High serum liver enzyme activities were not associated with abnormalities in hepatic parenchyma and liver functional variables, regardless of the degree of increase. Serum liver enzyme activities return to normal after control of hyperthyroidism with 131I therapy. Cats with hyperthyroidism have a significantly higher serum fasting ammonia concentration than cats who were euthyroid (P = .019). Cats with hyperthyroidism also have significantly lower serum cholesterol (P = .005) and glucose (P = .002) concentrations before compared with after 131I therapy. Nine of 19 cats with hyperthyroidism had trace ketonuria. CONCLUSIONS AND CLINICAL IMPORTANCE: These results demonstrate that extensive examination for hepatobiliary disease in most cats with hyperthyroidism is unnecessary.     

Radio-iodine treatment of hyperthyroid cats

Thirty-two elderly domestic shorthaired cats (mean age 12.9 years) were treated with radioiodine (131I). The dose of 131I administered ranged from 39 mBq to 134 mBq. Twenty-eight cats became euthyroid after treatment, one became hypothyroid and three remained hyperthyroxaemic. Two of the hyperthyroxaemic cats were successfully re-treated with 131I. Five cats died from concurrent diseases within one year of treatment. The administration of a dose of 131I selected by assessing the severity of the clinical signs, the size of the thyroid gland(s) and the serum level of thyroxine was an effective treatment for hyperthyroidism.     

Administration of certain sedative drugs is associated with variation in sonographic and radiographic splenic size in healthy cats

Ultrasonography and radiography are standard diagnostic tests for cats with suspected splenic disease, however published information on outside sources of variation are currently lacking. The purpose of this prospective, randomized, crossover group study was to evaluate effects of common sedative drugs on the sonographic and radiographic characteristics of the spleen in healthy cats. Fifteen healthy adult research cats were randomly assigned into one of three groups corresponding to different sequences of administration of five sedative drugs/drug combinations (acepromazine; butorphanol; dexmedetomidine; midazolam and butorphanol (MB); and dexmedetomidine, butorphanol, and ketamine (DBK)), administered at 1‐week intervals. At each visit, three‐view abdominal radiographic and ultrasonographic examinations were performed prior to sedation and repeated 15‐30 min and 2‐3 h post sedation. Two board‐certified radiologists (one ACVR and one ACVR/ECVDI) evaluated the anonymized and randomized images. Acepromazine resulted in significantly increased sonographic and radiographic splenic measurements from baseline, which remained significantly increased 2‐3 h post sedation. The mean magnitude of this change ranged from 0.9 mm (tail height, SD 1.4 mm) to 1.8 mm (body height, SD 1.7 mm) for ultrasound, and was 2.2 mm (ventrodorsal width, SD 2.3 mm) for radiographs. With butorphanol, there was no significant change in splenic size. For dexmedetomidine, MB, and DBK, there was a trend toward increased splenic size from baseline to the first post‐sedation timepoint, which was statistically significant for radiographic measurements, although not for ultrasound. Findings indicated that acepromazine should be avoided prior to imaging while butorphanol may be used when sedation is needed in cats presenting for potential splenic disease.     

Predictive value of tracer studies for 131I treatment in hyperthyroid cats

In 76 cats with hyperthyroidism, peak thyroidal radioiodine (131I) uptakes and effective half-lives were determined after administration of tracer and therapeutic activities of 131I. In 6 additional hyperthyroid cats, only peak thyroidal uptakes after administration of tracer and therapeutic activities of 131I were determined. Good correlation was found between peak thyroidal uptakes of tracer and therapeutic 131I; however, only fair correlation was observed between effective half-lives. In 79% of the cats, the effective half-life for therapeutic 131I was longer than that for tracer 131I. After administration of therapeutic activity of 131I, monoexponential and biphasic decay curves were observed in 51 and 16 cats, respectively. Using therapeutic kinetic data, radiation doses to the thyroid gland were calculated retrospectively on the basis of 2 methods for determining the activity of 131I administered: (1) actual administration of tracer-compensated activity and (2) hypothetic administration of uniform activity (3 mCi). Because of the good predictive ability of tracer kinetic data for the therapeutic kinetic data, the tracer-compensated radiation doses came significantly (P = 0.008) closer to the therapeutic goal than did the uniform-activity doses. In addition, the use of tracer kinetic information reduced the extent of the tendency for consistently high uniform-activity doses. A manual method for acquiring tracer kinetic data was developed and was an acceptable alternative to computerized techniques. Adoption of this method gives individuals and institutions with limited finances the opportunity to characterize the iodine kinetics in cats before proceeding with administration of therapeutic activities of 131I.     

Evaluation of an oscillometric blood pressure monitor for use in anesthetized cats

OBJECTIVE: To determine accuracy of an oscillometric blood pressure monitor used over a wide range of pressures in anesthetized cats. DESIGN: Prospective study. ANIMALS: 6 healthy cats. PROCEDURE: 4 female cats and 2 male cats that weighed 2.7 to 4.5 kg (5.9 to 9.9 lb) and were 2 to 8 years old were anesthetized. Blood pressure was measured directly with an arterial catheter placed in the right femoral artery and indirectly from the left antebrachium by use of an oscillometric monitor. A series of diastolic arterial pressure (DAP), mean arterial pressure (MAP), and systolic arterial pressure (SAP) measurements were obtained during hypotension, normotension, and hypertension. Values obtained indirectly and directly were compared. RESULTS: The oscillometric monitor was accurate for DAP and MAP throughout the entire pressure range and met the standards of the Association for the Advancement of Medical Instrumentation (mean +/- SD difference from values obtained directly, < or = 5 +/- 8 mm Hg). The SAP was increasingly underestimated with increasing overall pressure; mean differences from direct measurements were -5.2, -12.1, and -17.7 mm Hg during hypo-, normo-, and hypertension, respectively. Standard deviations for SAP were all < or = 8 mm Hg. The monitor gave readings during all attempts. The direct blood pressure recording system appeared to perform well with neither under- nor overdamping. CONCLUSIONS AND CLINICAL RELEVANCE: Except for a minor underestimation of SAP during normo- and hypertension, the oscillometric monitor yielded reliable and easily obtainable blood pressure measurements in anesthetized cats.