Use of recombinant human thyroid-stimulating hormone for thyrotropin-stimulation testing of euthyroid cats

OBJECTIVE: To evaluate response of euthyroid cats to administration of recombinant human thyroid-stimulating hormone (rhTSH). ANIMALS: 7 healthy cats. PROCEDURE: Each cat received each of 5 doses of rhTSH (0, 0.025, 0.050, 0.100, and 0.200 mg), IV, at 1-week intervals. Serum concentration of total thyroxine (TT4) and free thyroxine (fT4) was measured immediately before each injection (time 0) and 2, 4, 6, and 8 hours after administration of each dose. RESULTS: Overall TT4 response did not differ significantly among cats when administered doses were > or = 0.025 mg. Serum TT4 concentrations peaked 6 to 8 hours after administration for all doses > or = 0.025 mg. For all doses > or = 0.025 mg, mean +/- SEM TT4 concentration at 0, 6, and 8 hours was 33.9 +/- 1.7, 101.8 +/- 5.9, and 101.5 +/- 5.7 nmol/L, respectively. For all doses > or = 0.025 mg, mean fT4 concentration at 0, 6, and 8 hours was 38.7 +/- 2.9, 104.5 +/- 7.6, and 100.4 +/- 8.0 pmol/L, respectively. At 8 hours, the fT4 response to 0.025 and 0.050 mg was less than the response to 0.100 and 0.200 mg. Adverse reactions after rhTSH administration were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: The TSH stimulation test can be performed in cats by IV administration of 0.025 to 0.200 mg of rhTSH and measurement of serum TT4 concentrations at time of injection and 6 or 8 hours later. Clinical validation of the TSH stimulation test would facilitate development of additional tests of thyroid gland function, such as a TSH assay.     

Effect of recombinant human TSH on the uptake of radioactive iodine (I) by the thyroid gland in healthy beagles

In human medicine, recombinant human thyroid-stimulating hormone (rhTSH) increases thyroid radioactive iodine uptake (RAIU), allowing radioiodine-131 (¹³¹I) dose reduction and greater efficacy in the treatment of differentiated thyroid cancer and multinodular goiter. The goal of this study was to evaluate the effect of rhTSH, administered 24 h and 48 h before radioiodine-123 (¹²³I), on the thyroid RAIU in healthy dogs. Seven healthy euthyroid beagles were randomly allocated to 3 groups (2 groups of 2 dogs and 1 group of 3 dogs) in a prospective, blinded, crossover study. At Week 1, 1 group received ¹²³I for a baseline RAIU; 1 group received 100 μg of rhTSH IV 24 h before ¹²³I, and 1 group received 100 μg of rhTSH IV 48 h before ¹²³I. All dogs received 37 MBq of radioactive ¹²³I IV, and thyroid RAIU was determined 8 h, 24 h, and 48 h thereafter. The study was designed in such a manner that each dog received the 3 treatments and a wash-out period of 3 wk was respected in between. Blood samples were taken for measurement of serum total thyroxine (TT4) and thyrotropin (TSH) concentrations at baseline and 6 h, 12 h, 24 h, and 48 h after rhTSH administration. Recombinant human TSH caused no significant change on thyroid RAIU. The overall mean thyroid RAIU significantly decreased during the study independent of the treatment. Recombinant human TSH significantly increased serum TT4 concentration, which peaked 6 h after rhTSH administration. Compared to baseline, serum TSH concentration remained higher at 6 h, 12 h, 24 h, and 48 h. However, a statistically significant difference was reached only at 6 h and 12 h after rhTSH administration. No adverse effects of rhTSH were observed during the study. Further studies are needed to determine the best timing and dosage of administration of rhTSH in healthy and thyroid carcinoma dogs.     

Interference of iohexol with radioiodine thyroid uptake in the hyperthyroid cat

Absorbed thyroid dose and effective half-life were determined in 46 hyperthyroid cats after treatment with a low dose (mean 111MBq) of radioiodine intravenously. Thirteen of these cats had received iohexol for glomerular filtration rate (GFR) measurement within 24h before treatment with radioiodine in view of another ongoing study at our institution. Pre-therapy values were obtained for total thyroxine (TT(4)) and for the thyroid to salivary gland ratio with sodium pertechnetate gamma-camera imaging. All cats underwent post-therapy scans at 24, 48 and 120 h for evaluation of radioactive iodine uptake (RAIU) and the effective half-life of radioiodine. The absorbed dose was calculated from the cumulative activity with Olinda software. Both groups were comparable in age, TT(4) and the ratio of thyroid activity to salivary gland activity. Statistical analysis revealed a significant decreased absorbed dose in the thyroid in the iohexol group. This decreased uptake was not accompanied by an decreased effective half-life of the radioiodine. The variation of inter-individual RAIU decreased in this group and more homogenous absorbed doses were obtained. No significant difference in outcome could be demonstrated. However, a tendency towards a higher number of residual hyperthyroidism in the iohexol group was noted (15 versus 6% in control group). This study demonstrates that iohexol interferes with the uptake of radioiodine in the hyperthyroid cat but does not provoke increased turnover. In this study, albeit including a small number of cats, outcome did not seem to be significantly affected.     

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.     

Effect of recombinant human thyroid stimulating hormone on serum thyroxin and thyroid scintigraphy in euthyroid cats

This study investigated the thyroidal response to administration of recombinant human thyroid stimulating hormone (rhTSH) by means of serum total thyroxine (TT(4)) concentration and pertechnetate uptake by the thyroid gland in six healthy euthyroid spayed female cats. A pertechnetate scan was performed on day 1 to calculate thyroid/salivary gland (T/S) uptake ratio. On day 3, 25 microg rhTSH was injected intravenously. Six hours later the thyroid scan was repeated as on day 1. Blood was drawn for serum TT(4) measurement prior to injection of rhTSH and performance of the pertechnetate scan. Statistically significant differences in mean serum TT(4) concentration, T/S uptake ratio before and 6h after rhTSH administration and T/S uptake ratio between left and right lobes were noted. We can conclude that 25 microg rhTSH increases pertechnetate uptake in the thyroid glands of cats, this should be taken into account when thyroid scintigraphy after rhTSH administration is interpreted.     

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.     

Effect of storage of reconstituted recombinant human thyroid-stimulating hormone (rhTSH) on thyroid-stimulating hormone (TSH) response testing in euthyroid dogs

Bovine thyrotropin (bTSH) stimulation testing has long been considered the gold standard for diagnosis of canine hypothyroidism. Unfortunately, bTSH is no longer commercially available. Recently, the use of recombinant human thyrotropin (rhTSH) to perform thyroid-stimulating hormone (TSH) stimulation testing in dogs was described. The cost of an rhTSH vial (1.1 mg) limits the practical use of this product. The study reported here was performed to determine the effects of storing rhTSH on the post-TSH increase of serum total (TT4) and free (FT4) thyroxine concentrations during TSH stimulation testing in 12 euthyroid Beagles in a crossover trial. Three TSH tests with recombinant human thyrotropin (rhTSH; 91.5 microg IV) were performed on each dog during 3 different periods: 1 with freshly reconstituted rhTSH (fresh); 1 with rhTSH, reconstituted and stored at 4 degrees C for 4 weeks (refrigerated); and 1 with rhTSH, reconstituted and frozen at -20 degrees C for 8 weeks (frozen). Blood samples for determination of TT4 and FT4 concentrations were collected before and 4 and 6 hours after rhTSH administration. There was no significant difference in TT4 or FT4 concentration after stimulation with fresh, refrigerated, and frozen rhTSH. Furthermore, there was no significant difference between TT4 or FT4 serum concentration observed 4 and 6 hours after rhTSH administration. In conclusion, reconstituted rhTSH can be stored at 4 degrees C for 4 weeks and at -20 degrees C for 8 weeks without loss of biological activity, allowing clinicians to perform more TSH response tests per vial.     

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.     

Treatment of feline hyperthyroidism with radioactive iodine-131

Feline hyperthyroidism can be treated by thyroidectomy, antithyroid drugs, or radioactive iodine-131 (131I). The aim of this retrospective study was to evaluate the treatment of 83 hyperthyroid cats with 131I The dosage of 131I ranged from 4 to 6 milliCurie (mCi). Blood samples for determination of plasma concentrations of total thyroxine (TT4), urea, and creatinine were collected before, ten days after, and several months after treatment. In addition, arterial blood pressure was measured before and ten days after treatment. The median plasma TT4 concentration ten days after 131I treatment (27 nmol/L, 64 cats) was significantly lower than that before treatment (123 nmol/L). The median plasma TT4 concentration several months after 131I treatment was 22,5 nmol/L (40 cats). Ten days and several months after 131I treatment, plasma TT4 concentration had decreased below the upper limit of the reference range in 64 (77%) and 72 cats (87%), respectively. In four cats the plasma TT4 concentration had decreased below the lower limit of the reference range, but only two cats had symptoms of hypothyroidism. Plasma urea and creatinine concentrations were not increased ten days after 131I treatment, but the median plasma creatinine concentration was significantly higher several months after treatment when compared with before 131I treatment. Before treatment in 28 cats a high arterial blood pressure (> 180 mmHg) was measured, whereas after treatment in 25 cats a high arterial blood pressure was measured. The results of this study indicate that 131I treatment is an effective therapy in most cats with hyperthyroidism.     

THE EFFECT OF METHIMAZOLE ON THYROID UPTAKE OF PERTECHNETATE AND RADIOIODINE IN NORMAL CATS

Many hyperthyroid cats referred for thyroid imaging and 131I therapy are concurrently or recently receiving antithyroid medications. The effect of the antithyroid drug, methimazole, on thyroid uptake of 99mTcO4 and 123I was evaluated in 8 normal cats. Quantitative analysis was used to determine the normal percent dose uptake of 99mTcO4 and 123I, the change in thyroid:salivary ratios (T:S) of 99-TcO4 over time, and the duration of the methimazole effect on thyroid uptake of 123I. Methimazole was administered to 5 cats for 3 weeks in which a hypothyroid state was obtained; 3 cats served as non-treatment controls. 99mTcO4 and 8 and 24 hour 123I imaging was repeated after 3 weeks of methimazole therapy (time of maximum T4 suppression). Methimazole was then discontinued and 123I images and serum T4 concentrations were repeated at 1, 4, 9, 15, and 24 days post withdrawal. The percent dose uptake of 99mTcO4 increased throughout the acquisition period with maximum uptake occurring 4 hour post injection. The baseline 20 min. T:S ratio for controls and treatment cats were 0.79 +/- 0.08 and 0.81 +/- 0.05 respectively; with a peak value of 1.29 +/- 0.23 and 1.31 +/- 0.18 at 4 hours. The baseline T:S ratios were not significantly different from 20 minutes to 2 hours, however they were significantly elevated at 4 hours post injection. Baseline, 8 and 24 hour percent dose uptake of 123I were 2.1 +/- 0.42% and 7.04 +/- 1.24%, respectively. There was a significant increase in the T:S ratio in the treatment group at all time points. The 8 hour percent dose uptake of 123I at 1, 4, and 9 days post methimazole withdrawal were significantly increased and peaked at 4 days. The 24 hour uptake was significantly increased at 4 and 9 days, with peak uptake at 9 days post-methimazole withdrawal. The 123I percent dose uptake decreased to baseline values by day 15 post withdrawal. Radioiodine uptake is not inhibited by methimazole treatment in normal cats, and is significantly enhanced after recent withdrawal. This finding is supportive of a "short term rebund effect" with maximal enhanced uptake between 4 and 9 days after discontinuing antithyroid drugs. The increased uptake of 99mTcO4 may also affect the interpretation of 99mTcO4 thyroid scintigraphy for 2-3 weeks.     

Serum thyroxine concentrations following fixed-dose radioactive iodine treatment in hyperthyroid cats: 62 cases (1986-1989)

The medical records of 62 hyperthyroid cats treated with a fixed dose of 4 mCi of radioactive iodine (131I) were reviewed. In 60 cats, serum thyroxine concentrations were determined after treatment, allowing evaluation of treatment success. Eighty-four percent of the cats had normal serum thyroxine concentrations after treatment. Five of the 60 cats (8%) remained hyperthyroxinemic after treatment. Five cats (8%) were hypothyroxinemic when evaluated within 60 days of treatment. Three of these cats had normal serum thyroxine concentrations 6 months after treatment, and none had clinical signs of hypothyroidism. The administration of a fixed dose of 4 mCi of 131I was determined to be an effective treatment for feline hyperthyroidism.     

Thyroidal radioiodine uptake in hyperthyroid cats

Thyroidal radioiodine uptake was measured in 10 healthy domestic cats and in 20 hyperthyroid cats. Compared with those in the healthy cats, the uptake curves in the hyperthyroid cats were characterised by elevated uptake and rapid thyroidal iodine turnover. For diagnostic purpose uptake measurements at 4 hours after administration of the tracer were found to be preferable to measurements at 24 hours or later.     

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.     

Plasma clearance of exogenous creatinine, exo-iohexol, and endo-iohexol in hyperthyroid cats before and after treatment with radioiodine

BACKGROUND: Glomerular filtration rate (GFR) can be measured by clearance methods of different markers showing discrepancies and different reproducibility in healthy cats. Studies comparing different methods of GFR measurement in hyperthyroid cats have not yet been performed. HYPOTHESIS: Plasma clearance of exogenous creatinine (PECCT), exo-iohexol (PexICT), and endo-iohexol (PenICT) could lead to differences in GFR measurement and the need to use the same clearance method when comparing GFR before and after radioiodine treatment in hyperthyroid cats. ANIMALS: Fifteen client-owned hyperthyroid cats. METHODS: GFR was measured 1 day before and 1, 4, 12, and 24 weeks after treatment. Intravenous injection of iohexol was followed immediately by IV injection of creatinine. Plasma creatinine was measured by an enzymatic method. Plasma endo- and exo-iohexol were measured by high-performance liquid chromatography coupled to ultraviolet detection. RESULTS: Globally, the 3 GFR methods resulted in significantly different (P < .001) GFR results. GFR results among the different methods were the same (P= .999) at all time points. All 3 techniques indicated decreasing GFR after (131)I treatment. For each GFR technique, a significant decrease in GFR was observed between time point 0 and all other time points. This decrease stabilized 4 weeks after treatment, with very little decline afterward. CONCLUSION AND CLINICAL IMPORTANCE: It is mandatory to use the same GFR technique in follow-up studies. GFR testing at 4 weeks posttreatment could allow assessment of the final renal functional loss after treatment in hyperthyroid cats.     

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.     

CALCULATION AND USAGE OF THE THYROID TO BACKGROUND RATIO ON THE PERTECHNETATE THYROID SCAN

Feline hyperthyroidism is a common endocrine disorder. A single dose of 148 MBq (4 mCi) ¹³¹I is 95–98% effective for the treatment of hyperthyroidism in cats; however, the cause for treatment failures has not been determined. In a series of 113 hyperthyroid cats having pertechnetate thyroid scintigraphy before treatment using a standard 148 MBq (4 mCi) ¹³¹I dose, the thyroid to salivary gland (T:S) ratio and the thyroid to background (T:B) ratio were calculated. Results in 107 (95%) cats successfully treated were compared with results in six (5%) cats that remained hyperthyroid after treatment. T:B ratio was significantly higher for cats that had treatment failure (median 13.0, range 3.6–73.0) than for cats successfully treated (median 4.4, range 1.2–69.0) (P=0.02), whereas there was no significant difference in their T:S ratios (P=0.2). The T:B ratio is a new approach to evaluating the thyroid pertechnetate scan with the intent of identifying which hyperthyroid cats may fail treatment using a standard 148 MBq (4 mCi) ¹³¹I dose and which, therefore, require a higher dose.     

Thyroidal radioiodine uptake in hyperthyroid cats

Summary

Thyroidal radioiodine uptake was measured in 10 healthy domestic cats and in 20 hyperthyroid cats. Compared with those in the healthy cats, the uptake curves in the hyperthyroid cats were characterised by elevated uptake and rapid thyroidal iodine turnover. For diagnostic purposes uptake measurements at 4 houts after administration of the tracer were found to be preferable to measurements at 24 hours or later.     

Serum fructosamine concentrations in hyperthyroid cats.

Serum fructosamine concentrations were measured in 35 healthy cats and in 30 hyperthyroid cats before and 30 days after curative radioiodine ((131)I) treatment. Hyperthyroid cats were divided into those with 30 day post-treatment total thyroxine (T4) concentrations within (EuT4) or below (HypoT4) the reference range. The median (semi-interquartile range, SIR) fructosamine concentration was significantly lower in hyperthyroid compared with healthy cats (295. 0 (18.5) micromol l(-1)) both before (254.0 (27.6) micromol l(-1)) and after (268.5 (28.0) micromol l(-1)) treatment (P < 0.001 in each case). (131)I therapy was associated with increases in serum fructosamine (mean increase 20.4 micromol l(-1), P = 0.039) and total protein (6.3 g l(-1), P < 0.002) in the HypoT4 group and in globulin concentration in both EuT4 (5.9 g l(-), P < 0.002) and HypoT4 (5.2 g l(-1), P = 0.023) groups. There were no direct relationships between the observed elevations in fructosamine concentration and those in total protein or globulin concentrations suggesting that the effect may be due to reduced rates of protein turnover. Reduced values may need to be considered when interpreting serum fructosamine concentrations for monitoring the degree of glycaemic control in diabetic cats with concurrent hyperthyroidism.     

Small-volume resuscitation with hypertonic saline solution in hypovolemic cats

We evaluated the hemodynamic effects of IV and intraaortic (aortic root) administration of 7.5% NaCl solution on hemodynamics in anesthetized cats with severe hypovolemia. Hypovolemic shock was induced by exsanguinating cats to a mean arterial blood pressure of 50 mm of Hg, which was maintained for 30 minutes prior to treatment. Shed blood volume was 38.4 +/- 2.1 ml/kg of body weight. The cats were treated with a small volume (4 ml/kg) of 0.9% NaCl solution IV, 7.5% NaCl solution IV, or 7.5% NaCl solution administered into the aortic root. The IV administration of 0.9% NaCl solution did not improve hemodynamics. The IV administration of 7.5% NaCl solution induced rapid restoration of arterial blood pressure, aortic blood flow, and cardiac contractility. Total peripheral vascular resistance decreased. The administration of 7.5% NaCl solution into the aortic root induced a further deterioration in hemodynamics resulting in death in 3 cats and a marked improvement in hemodynamics similar to that observed after IV administration of 7.5% NaCl solution in 2 cats. The duration of the beneficial hemodynamic effects after IV or intra-aortic administration of 7.5% NaCl solution did not exceed 60 minutes. Results of these studies suggested that either the IV or intra-aortic administration of 7.5% NaCl solution in cats can induce beneficial hemodynamic effects that may be of value in the field resuscitation of hypovolemic patients.     

Radio-iodine treatment of hyperthyroid cats

Thirty-two elderly domestic shdrthaired 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 hyperthyrox-aemic. 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.