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SUMMARY

Blood, serum, and plasma total calcium concentrations and plasma and serum ionized calcium concentrations were anaerobically determined by use of a calcium-specific electrode for samples obtained from 39 healthy horses. Mean (± sd) serum ionized calcium concentration was 6.6 ± 0.3 mg/dl (1.6 ± 0.1 mmol/L) and the mean serum ionized calcium percentage was 58.2 ± 3.4%. Serum ionized calcium percentage was not significantly correlated with serum pH. Plasma ionized calcium percentage was weakly correlated with plasma pH (r = − 0.480; P ≤ 0.05). Ionized calcium concentration was determined in serum samples manipulated in vitro by additions of 1 to 80 μl of 0.1N hydrochloric acid or sodium hydroxide to yield 6 to 10 pH values between 6.8 and 8.2. In all horses, the relationship between serum ionized calcium percentage and serum pH at these pH values was then examined by use of a repeated-measures multiple regression analysis. Correlations between serum ionized calcium percentage and adjusted serum pH value for each horse were highly significant (P ≤ 0.05); however, analysis of pooled data from all horses indicated that a statistically significant relationship between serum pH and ionized calcium percentage did not exist. Lack of a significant relationship between these variables was most likely attributable to heterogeneity of variance of ionized calcium percentage among horses, reflecting variation in undefined biochemical constituents of serum that affect the equilibrium of calcium binding. When it is essential to evaluate the calcium status of a horse, direct measurement of serum ionized calcium concentration is recommended.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To identify factors in dry diets associated with the occurrence of calcium oxalate (CaOx) uroliths in dogs.

Animals—600 dogs with CaOx uroliths and 898 dogs without urinary tract diseases.

Procedure—Univariate and multivariate logistic regression were performed.

Results—Compared with diets with the highest concentrations of sodium, dry diets with the lowest concentrations of sodium, phosphorus, calcium, chloride, protein, magnesium, or potassium were linearly associated with increased risk of CaOx urolith formation. Significant nonlinear associations between increased occurrence of CaOx uroliths and urine acidifying potential and low moisture content were observed. Significant nonlinear associations between decreased occurrence of CaOx uroliths and carbohydrate and fiber contents were observed. A significant association between the occurrence of CaOx uroliths and dietary fat was not observed.

Conclusions and Clinical Relevance—Results suggest that dry diets formulated to contain high concentrations of protein, calcium, phosphorus, magnesium, sodium, potassium, and chloride may minimize formation of CaOx uroliths. In addition, comparison of risk and protective factors of various diet ingredients fed to dogs with CaOx uroliths suggests that although similar findings were observed in canned and dry formulations, in general, greater risk is associated with dry formulations. However, before these hypotheses about dietary modifications are adopted by food manufacturers, they must be investigated by use of appropriately designed clinical studies of dogs with CaOx urolithiasis. (Am J Vet Res 2002;63:330–337)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine concentrations of calcium (total [tCa], ionized [iCa], protein-bound [pCa], and complexed [cCa]) in dogs with chronic renal failure (CRF).

Animals—23 dogs with CRF.

Procedure—Serum calcium was fractionated by use of a micropartition system. Total calcium and iCa concentrations and pH were measured in unfractionated serum, and tCa concentration was measured in the ultrafiltrate. The pCa fraction was calculated by subtracting tCa of the ultrafiltrate from tCa concentration of unfractionated serum. The iCa concentration in unfractionated serum was subtracted from tCa concentration in the ultrafiltrate to determine the concentration of cCa.

Results—Concentrations of tCa, iCa, pCa, and cCa had wide ranges among dogs with CRF. Dogs with significantly low tCa concentration (7.70 ± 1.73 mg/dL) had cCa concentration (0.76 ± 0.38 mg/dL) within reference range, whereas dogs with reference range to high tCa concentration (10.85 ± 1.13 mg/dL) had significantly high cCa concentration (2.62 ± 1.04 mg/dL). There was no significant difference in iCa or pCa concentrations between groups.

Conclusions and Clinical Relevance—Concentrations of tCa, iCa, cCa, and pCa varied widely in dogs with CRF. Overall, cCa concentration was high, although subpopulations differed in cCa and tCa concentrations. Differences in tCa concentration were primarily attributable to differences in cCa fraction. (Am J Vet Res 2003;64:1181–1184)

Full access
in American Journal of Veterinary Research

antibiotics, which has the potential to lead to antibiotic resistance. 15 – 17 Currently, calcium sulfate is preferred for antibiotic beads as this material is biodegradable and absorbed by the body, therefore eliminating the need for surgical removal. 3 , 18

Open access
in American Journal of Veterinary Research

Summary

Administration of thiazide diuretics has been recommended to prevent calcium oxalate urolith development in dogs. To evaluate the effects of thiazide diuretics in dogs, 24-hour urine excretion of calcium was measured in 6 clinically normal Beagles after administration of chlorothiazide (ctz) for 2 weeks, administration of ctz for 10 weeks, and administration of calcium carbonate and ctz for 2 weeks. Compared with baseline values, 24-hour urine calcium excretion did not decrease after ctz administration. When ctz was given at a high dosage (130 mg/ kg of body weight), urinary calcium excretion was significantly (P < 0.04) higher than baseline values. Based on these observations, we do not recommend ctz for treatment or prevention of canine calcium oxalate urolithiasis.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether hydrochlorothiazide (HCTZ) reduces urinary calcium excretion in dogs with calcium oxalate urolithiasis.

Design—Original study.

Animals—8 dogs with calcium oxalate urolithiasis.

Procedure—4 treatment protocols were evaluated in each dog (a low calcium, low protein diet designed to prevent calcium oxalate urolith formation with and without administration of HCTZ [2 mg/kg (0.9 mg/lb) of body weight, PO, q 12 h] and a maintenance diet with higher quantities of protein and calcium with and without administration of HCTZ). At the end of each 2-week treatment period, 24-hour urine samples were collected. Blood samples were collected during the midpoint of each urine collection period. Analysis of variance was performed to evaluate the effects of HCTZ and diet on urine and serum analytes.

Results—Hydrochlorothiazide significantly decreased urine calcium and potassium concentration and excretion. Hydrochlorothiazide also significantly decreased serum potassium concentration. Compared with the maintenance diet, the urolith prevention diet significantly decreased urine calcium and oxalic acid concentration and excretion. Dogs consuming the urolith prevention diet had significantly lower serum concentrations of albumin and urea nitrogen.

Conclusions and Clinical Relevance—Administration of HCTZ decreased urine calcium excretion in dogs with a history of calcium oxalate urolith formation. The greatest reduction in urine calcium concentration and excretion was achieved when dogs received HCTZ and the urolith prevention diet. Results of this study suggest that the hypocalciuric effect of HCTZ will minimize recurrence of calcium oxalate urolith formation in dogs; however, long-term controlled clinical trials are needed to confirm the safety and effectiveness of HCTZ. (J Am Vet Med Assoc 2001;218:1583–1586)

Full access
in Journal of the American Veterinary Medical Association

resected tumors. 1–10 However, many of these delivery systems are not commercially available, have resulted in unacceptable regional complications, or have resulted in minimal improvement in clinical outcome. 5,8,10,11 Carboplatin-impregnated calcium

Full access
in American Journal of Veterinary Research

Objective

To measure ionized calcium concentration in plasma from cats with urethral obstruction and to correlate these values with results of clinical biochemical analyses and physical examinations.

Design

Prospective study.

Animals

24 male cats.

Procedure

Blood samples were obtained from each cat on admission, and PCV, pH, and concentrations of ionized calcium, total calcium, glucose, total solids, sodium, potassium, BUN, creatinine, chloride, magnesium, albumin, and phosphorus were determined. Mentation, tissue perfusion, and ECG recordings were also assessed.

Results

18 (75%) cats had low ionized calcium concentrations (reference range, 2.4 to 2.8 mEq/L). Hypocalcemia was considered mild (2.0 to 2.36 mEq/L) in 9 (37.5%) cats, moderate (1.6 to 1.98 mEq/L) in 6 (25%), and severe (< 1.6 mEq/L) in 3 (12.5%). Significant positive correlations were found between ionized calcium concentration and heart rate, pH, and concentrations of sodium, chloride, and total calcium. Significant negative correlations were found between ionized calcium concentration and concentrations of potassium, BUN, creatinine, and phosphorus.

Clinical Implications

Most cats with urethral obstruction had a low concentration of ionized calcium. This may contribute to cardiac electrical and mechanical dysfunction in some severely affected cats. Although effects of IV administration of calcium were not evaluated, results of this study strengthen the rationale for its use in cats with urethral obstruction. (J Am Vet Med Assoc 1997;211:1392–1395)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate calcium balance and parathyroid gland function in healthy horses and horses with enterocolitis and compare results of an immunochemiluminometric assay (ICMA) with those of an immunoradiometric assay (IRMA) for determination of serum intact parathyroid hormone (PTH) concentrations in horses.

Animals—64 horses with enterocolitis and 62 healthy horses.

Procedures—Blood and urine samples were collected for determination of serum total calcium, ionized calcium (Ca2+) and magnesium (Mg2+), phosphorus, BUN, total protein, creatinine, albumin, and PTH concentrations, venous blood gases, and fractional urinary clearance of calcium (FCa) and phosphorus (FP). Serum concentrations of PTH were measured in 40 horses by use of both the IRMA and ICMA.

Results—Most (48/64; 75%) horses with enterocolitis had decreased serum total calcium, Ca2+, and Mg2+ concentrations and increased phosphorus concentrations, compared with healthy horses. Serum PTH concentration was increased in most (36/51; 70.6%) horses with hypocalcemia. In addition, FCa was significantly decreased and FP significantly increased in horses with enterocolitis, compared with healthy horses. Results of ICMA were in agreement with results of IRMA.

Conclusions and Clinical Relevance—Enterocolitis in horses is often associated with hypocalcemia; 79.7% of affected horses had ionized hypocalcemia. Because FCa was low, it is unlikely that renal calcium loss was the cause of hypocalcemia. Serum PTH concentrations varied in horses with enterocolitis and concomitant hypocalcemia. However, we believe low PTH concentration in some hypocalcemic horses may be the result of impaired parathyroid gland function. ( Am J Vet Res 2001;62:938–947)

Full access
in American Journal of Veterinary Research

diastolic blood pressures were measured at the times of blood sample collection in all groups. Concentrations of ionized calcium, sodium, potassium, and chloride and values of pHa, PaO 2 , and PaCO 2 were measured in arterial blood samples with selective

Full access
in American Journal of Veterinary Research