Serum Ionized Calcium Concentration Research Articles

Successful Detection and Removal of a Functional Parathyroid Adenoma in a Pony Using Technetium Tc 99m Sestamibi Scintigraphy

Successful Detection and Removal of a Functional Parathyroid Adenoma in a Pony Using Technetium Tc 99m Sestamibi Scintigraphy

Is ionized calcium a reliable predictor of hypocalcemia after total thyroidectomy? A before and after study

Wanting to find a way of identifying patients suitable for early discharge after thyroidectomy, we set out to establish whether ionized calcium concentration is a better predictor of post-surgical hypocalcemia than total serum calcium. Data were analyzed to establish whether serum ionized calcium concentrations are correlated with total serum calcium levels and symptomatic hypocalcemia after thyroidectomy. Sixty-two patients undergoing total thyroidectomy at the Department of Surgical Sciences of the "Sapienza" University of Rome, Italy, in 2010. Ionized calcium was measured before (day 0) and after surgery (days 1, 2 and 60) in all the patients. These measurements were compared with preoperative (day 0) and postoperative total serum calcium levels (days 1, 2 and 60). The preoperative ionized calcium levels differed from the ionized calcium levels recorded on days 1 and 2; this pattern was not observed for the total calcium concentrations. Conversely, total calcium on days I and II correlated significantly with the various ionized calcium measurements. The presence of parathyroid glands in the surgical specimen did not seem to affect suitability for discharge. The statistical analysis showed that ionized calcium measurements are more reliable than total calcium measurements in the immediate and long-term follow-up of total thyroidectomy patients. Applying a 95% confidence interval we established reference values for both total serum calcium and ionized calcium, below which all patients develop postoperative symptomatic hypocalcemia. In conclusion, measurement of ionized calcium, as opposed to total calcium, should be strongly recommended in the immediate and longterm follow-up of total thyroidectomy patients.

Ionized hypocalcemia is an early event and is associated with organ dysfunction in children admitted to the intensive care unit

PurposeThe purpose was to determine the frequency and risk factors of ionized hypocalcemia and to evaluate this disturbance as a predictor of mortality in a pediatric intensive care unit (ICU). Materials and MethodsIn a prospective cohort study, 337 children admitted consecutively to an ICU were monitored regarding serum ionized calcium concentrations during the first 10 days of admission. The following variables were analyzed as independent of hypocalcemia: age; malnutrition; sepsis; Pediatric Index of Mortality 2; first 3 days organ dysfunction score (Pediatric Logistic Organ Dysfunction); and use of steroids, furosemide, and anticonvulsants. Hypocalcemia was defined as a serum ionized calcium concentration less than 1.15 mmol/L. ResultsThe rate of hypocalcemia was 77.15%. In a multivariate model, higher Pediatric Logistic Organ Dysfunction scores during the first 3 days of ICU stay were independently associated with hypocalcemia (odds ratio, 2.24; 95% confidence interval, 1.23-4.07; P = .008). Medications associated with hypocalcemia were furosemide (dose ≥2 mg/[kg d]) and methylprednisolone (dose ≥2 mg/[kg d]). No significant association was found between hypocalcemia and 10-day mortality. ConclusionsIonized hypocalcemia is common during the ICU stay, particularly in the first 3 days of admission. This disturbance was not found to be a predictor of mortality, but it is independently associated with more severe organ dysfunction.

Calcium Metabolism and Hyper and Hypoparathyroidism

Calcium balance refers to the state of calcium body stores which are primarily in bone, determined largely as a function of dietary intake, intestinal absorption, renal excretion, and bone remodeling. Calcium homeostasis refers to the hormonal regulation of serum ionized calcium concentrations by parathyroid hormone (PTH), the release and effect of which is dependent on the availability of 1,25-dihydroxyvitamin D, and levels of serum ionized calcium, which together regulate calcium absorption and transport in the tissues of the gut, kidney, and bone. Primary hyperparathyroidism is diagnosed on the basis of a raised PTH level in the presence of hypercalcemia. Hypoparathyroidism refers to the failure of the body to produce levels of PTH sufficient to maintain a normal level of serum calcium. Pseudoparathyroidismis characterized by end-organ resistance to PTH which presents as hypocalcemia and hyperphosphatemias under high PTH levels.

Équilibre phosphocalcique : régulation et explorations

Calcium and phosphate play a key role in bone mineralization but have also many other physiological functions. The control of serum phosphate concentration is mandatory to avoid the occurrence of severe metabolic disorders, but is less tightly regulated than serum ionized calcium concentration, which is maintained in a very limited range thanks to parathyroid hormone (PTH) and the active vitamin D metabolite calcitriol. Any change in serum ionized calcium concentration is detected by the calcium sensing receptor (CaSR), a membranous protein located principally in the parathyroid glands and the kidney. A decrease in ionized calcium level inactivates the CaSR, thus stimulating PTH secretion. PTH in turn stimulates the release of calcium and phosphate from bone, renal calcium reabsorption and calcium and phosphate intestinal absorption by inducing renal calcitriol production. Moreover, PTH inhibits phosphate reabsorption in proximal tubular cells, thus contributing towards phosphate homeostasis. Fibroblast growth factor 23 (FGF23) is a circulating factor that decreases serum levels of inorganic phosphate by inhibiting renal phosphate reabsorption and calcitriol production and may have a great physiological role in phosphate homeostasis. Recently, vitamin D actions independent of calcium and phosphate homeostasis were discovered. Basal exploration of phosphocalcic metabolism abnormalities consists in measurement of serum calcium (ionized calcium if possible), phosphate, 25-hydroxy vitamine D and PTH and of 24 hours urinary calcium excretion as well as renal function. Hence, the understanding of physiopathological mechanisms has been improved by newly identified genetic disorders responsible for phophocalcic homeostasis disturbances.

Calcium bioavailability from a fortified cereal-legume snack ( laddoo)

Objective Calcium intakes in underprivileged Indian children are often low. Improving calcium intake fortification of indigenous foods may be a viable strategy. The aim of this study was to evaluate calcium absorption, as judged by an acute increase in serum ionized calcium concentration, after ingestion of a calcium-fortified cereal-legume snack ( laddoo). Methods Three groups of eight children (8–12 y old) with low habitual dietary calcium intake were recruited for the study. After an overnight fast, a calcium-fortified (500 mg of calcium carbonate) cereal-legume snack ( laddoo) was given to group A, a similar but non-fortified snack was given to group B, and group C received calcium carbonate (500 mg) alone. Serum concentrations of ionized calcium and intact parathyroid hormone were measured at 0, 1, 2, 3, 4, and 5 h. Results In group A, a peak of 6% above baseline was observed at 1 h in serum ionized calcium, whereas group C showed a peak of 5.5% at 4 h and group B showed a small increase of 1.8% at 1 h. The change in area under curve of groups A and C were of similar order (4.6 and 5.5, respectively), whereas that of group B was significantly lower (0.82). Serum parathyroid hormone was lowest at 2 h in groups A and B and at 3 h in group C. Conclusion The fortified cereal-legume laddoo may act as a novel vehicle for increasing calcium intake in children.

Calcium and vitamin D supplementation in underprivileged indian toddlers using enriched “ladoos”

Vitamin D deficiency is common among children in India, in spite of abundance in sunshine. Calcium intake among such children is often low. These children might benefit from calcium and vitamin D supplementation; however, oral pharmacological preparations of these nutrients are often unpalatable. The authors used “Ladoo”, a much cherished Indian sweet, as a novel vehicle for administering calcium and vitamin D supplements. Toddlers from an urban slum in Pune, India, with low dietary calcium intake ( Ladoo containing, 700 mg elemental calcium (n=30; 2.9±0.5 years), or a control Ladoo , containing 170 mg of elemental calcium (n=30; 2.6±0.5 years), for one year. Subjects in both groups also ate a Ladoo supplemented with 30.000 i.u. of Cholecalciferol, once a month, during the trial. The main outcome measure was the increment in size adjusted total body bone mineral content (TBMC), measured using the GE-Lunar DPX Pro dual energy x-ray absorptiometry. Serum concentration of 25-hydroxy vitamin D in the calcium enriched Ladoo group increased from 25±27 nmol/l to 40±39 nmol/l, and in the control group from 25±27 nmol/l to 39±27 nmol/l. At the end of the trial the change in serum ionised calcium concentration in the calcium enriched Ladoo group (+0.14±0.23 mmol/l) was greater (p=0.004) than in the control group (−0.07±0.19). Serum parathyroid hormone concentration and alkaline phosphatase activity fell in the both groups; however, the change was not statistically different between the groups. The increment in size adjusted TBMC in the calcium enriched Ladoo group was greater (p From these results we conclude that monthly consumption of a cholecalciferol fortified Ladoo can be used to improve the vitamin D status of underprivileged Indian toddlers. Daily consumption of a calcium fortified Ladoo has the potential of improving skeletal mineralisation of toddlers with low dietary calcium intake.

Normocalcemic primary hyperparathyroidism

Primary hyperparathyroidism is a common disorder of mineral metabolism characterized by incompletely regulated, excessive secretion of parathyroid hormone from one or more of the parathyroid glands. The historical view of this disease describes two distinct entities marked by two eras. When primary hyperparathyroidism was first discovered about 80 years ago, it was always symptomatic with kidney stones, bone disease and marked hypercalcemia. With the advent of the multichannel autoanalyzer about 40 years ago, the clinical phenotype changed to a disorder characterized by mild hypercalcemia and the absence of classical other features of the disease. We may now be entering a 3rd era in the history of this disease in which patients are being discovered with normal total and ionized serum calcium concentrations but with parathyroid hormone levels that are consistently elevated. In this article, we describe this new entity, normocalcemic primary hyperparathyroidism, a forme fruste of the disease.

Oral calcium supplementation reverses the biochemical pattern of parathyroid hormone resistance in underprivileged Indian toddlers

Background:Toddlers in Pune, India, accustomed to low dietary calcium intake but vitamin D replete have low serum ionised calcium and inappropriately raised serum inorganic phosphorus concentrations together with elevated serum...

Parenteral calcium for intensive care unit patients

Hypocalcemia is prevalent among critically ill patients requiring intensive care. Several epidemiological studies highlight a direct association between hypocalcemia and mortality. These data provide the impetus for current guidelines recommending parenteral calcium administration to normalize serum calcium. However, in light of the considerable variation in the threshold for calcium replacement, the lack of evidence to support a causal role of hypocalcemia in mortality, and animal studies illustrating that calcium supplementation may worsen outcomes, a systematic review is essential to evaluate whether or not the practice of calcium supplementation for intensive care unit (ICU) patients provides any benefit. To assess the effects of parenteral calcium administration in ICU patients on the following outcomes: mortality, multiple organ dysfunction, ICU and hospital length of stay, costs, serum ionized calcium concentration, and complications of parenteral calcium administration. We searched The Cochrane Library, MEDLINE, EMBASE, Current Controlled Trials, and the National Research Register. We hand-searched conference abstracts from the Society of Critical Care Medicine, the European Society of Intensive Care Medicine, the American Thoracic Surgery, the American College of Surgeons, the American College of Chest Physicians, the American College of Physicians, and the International Consensus Conference in Intensive Care Medicine. We checked references of publications and attempted to contact authors to identify additional published or unpublished data. Randomised controlled and controlled clinical trials of ICU patients comparing parenteral calcium chloride or calcium gluconate administration with no treatment or placebo. Two reviewers independently applied eligibility criteria to trial reports for inclusion and extracted data. There are no identifiable studies that have evaluated the association between parenteral calcium supplementation in critically ill ICU patients and the following outcomes: mortality, multiple organ dysfunction, ICU and hospital length of stay, costs, and complications of calcium administration. Serum ionized calcium concentration was reported in 5 studies (12 trial arms, 159 participants). These trials showed a small but significant increase in serum ionized calcium concentration after calcium administration. These trials showed considerable statistical heterogeneity and differed extensively in the population studied (adult versus neonate), the indication (hypocalcemia versus prophylaxis) and threshold of hypocalcemia for which parenteral calcium was administered, and the timing of subsequent measurement of serum ionized calcium concentration to the extent that we consider a pooled estimate almost inappropriate. There is no clear evidence that parenteral calcium supplementation impacts the outcome of critically ill patients.

Relationship between Doppler blood pressure and survival or response to treatment in critically ill cats: 83 cases (2003–2004)

To evaluate the relationship between Doppler blood pressure (DBP) and survival or response to treatment in critically ill cats. Retrospective case series. 83 cats. Medical records from cats admitted to the intensive care unit with at least 2 recorded DBP measurements were included in the study. Hypotension was defined as 1 or more DBP measurements d 90 mm Hg. Change in blood pressure, survival to hospital discharge, heart rate, rectal temperature, PCV, plasma pH, serum ionized calcium concentration, disease process, body weight, age, duration of hospitalization, and catecholamine treatment were also evaluated. 39 cats were included in the hypotensive group, and 44 were consistently normotensive. Overall survival rate was 53% (44/83), with a significantly higher mortality rate in the hypotensive group (64% vs 32%). Among other variables, only low rectal temperature and low PCV were significantly associated with hypotension. Hypotensive cats with an increase in blood pressure of >or=20 mm Hg during hospitalization were more likely to survive to discharge (mortality rate, 69% vs 17%). Hypotensive cats had increased mortality rate with lower rectal temperatures and lower PCV, compared with normotensive critically ill cats. The implications of these findings with regard to treatment remain to be elucidated, but addressing these abnormalities may be appropriate.

Index of Suspicion

Index of Suspicion

Low Serum Total Calcium Concentration as a Marker of Low Serum Ionized Calcium Concentration in Critically Ill Patients Receiving Specialized Nutrition Support

The intent of this study was to ascertain to what extent serum total calcium concentration (tCa) <7 mg/dL reflects hypocalcemia (defined by ionized calcium concentration [iCa] of < or = 1.12 mmol/L) in critically ill patients receiving specialized nutrition support. Adult patients (> or = 18 years) admitted to the trauma, surgical, medical, burn, or neurosurgical intensive care units, trauma stepdown unit, or progressive care unit and referred to the nutrition support service were retrospectively identified for potential inclusion into the study. Serum chemistries, arterial blood gas measurements, nutrition markers, and serum iCa were simultaneously obtained from each patient approximately 1 day after initiation of specialized nutrition support. Patients with a serum creatinine > or = 2 mg/dL, hyperphosphatemia (> or = 6 mg/dL), severe hypomagnesemia (< or = 1.12 mg/dL), history of metabolic bone disease, or parathyroid disease were excluded from the analysis. One hundred ninety-five patients (91% who had multiple trauma, with a mean Injury Severity Score 31 +/- 13) were enrolled into the study. Specialized nutrition support was initiated 2.8 +/- 1.8 days and calcium status was studied 4.2 +/- 3.1 days after hospital admission, respectively. The majority (28 of 33, or 85%) of patients with a tCa <7 mg/dL were hypocalcemic compared with 33% (22 out of 66) of patients with a tCa of 7-7.4 mg/dL, and 11% (11 of 96) of those with a tCa of 7.5-7.9 mg/dL (p < .001). Critically ill patients with a serum total calcium concentration of <7 mg/dL have a high rate of hypocalcemia (iCa < or = 1.12 mmol/L). Hypocalcemia, defined as a serum iCa of < or = 1.12 mmol/L, occurs in 85% of acutely ill patients with a serum tCa <7 mg/dL.

Effects of Small- and Large-volume Resuscitation an Coagulation and Electrolytes During Experimental Endotoxemia in Anesthetized Horses

Small-volume resuscitation (SVR) has been advocated in place of large-volume isotonic resuscitation for the treatment of endotoxemia in horses. The effects of this type of therapy during experimental endotoxemia on electrolytes and coagulation have not been evaluated in the horse. As part of a larger project, the objective of this study was to determine the effects of SVR (hypertonic saline solution [HSS] plus hetastarch [HES]) on coagulation and serum electrolytes concentration, and to compare SVR with large- and small-volume isotonic resuscitation during experimental endotoxemia in anesthetized horses. SVR does not affect coagulation parameters or serum electrolyte concentrations when compared with either small- or large-volume isotonic crystalloids. Horses were randomly assigned to 1 of 3 groups. Under halothane anesthesia, endotoxemia was induced by administering 50 microg/kg Escherichia coli endotoxin i.v. The horses were treated for 30 minutes with 15 mL/kg of balanced polyionic crystalloid solution (control), 60 mL/kg of balanced polyionic crystalloid solution (ISO), or 5 mL/kg of HSS followed by 10 mL/kg HES (HSS-HES). Prospective randomized trial. Significant differences in coagulation parameters were not found among the groups. Thrombocytopenia was severe in all 3 groups. Serum ionized calcium concentration significantly decreased from baseline in control and ISO groups but not in the HSS-HES group. These results suggest that the HSS-HES combination, at the dosage used in this study had no adverse effects on coagulation beyond those produced by endotoxemia. HSS-HES may have a protective effect against endotoxemia-induced ionized hypocalcemia.

Immobilization and hip fracture

Hip fracture is among the most common causes of acute immobilization in elderly patients, and elderly patients with hip fracture are at high risk for a subsequent hip fracture. At baseline, both groups had high serum concentrations of ionized calcium, high urinary deoxypyridinoline (DPD) concentrations, suggesting immobilization-induced hypercalcemia. We previously showed deficiency of vitamins D and K(1) causes reduced bone mineral density (BMD) in female Alzheimer's disease (AD) patients. In a random and prospective study of AD patients, 100 patients received 45 mg menatetrenone, 1,000 IU ergocalciferol and 600 mg calcium daily for 2 years, and the remaining 100 (untreated group) did not. Treatment with MK-4 and vitamin D(2) with calcium supplements increases the BMD in elderly female patients with AD and leads to the prevention of nonvertebral fractures. The risk of hip fracture after stroke is 2 to 4 times as high as that in age-matched healthy controls. Hyperhomocysteinemia is a risk factor for both ischemic stroke and osteoporotic fractures in elderly persons. Randomized, controlled, double-blinded study of 628 consecutive elderly hemiplegic patients at least 1 year following first ischemic stroke. Patients were assigned to daily oral treatment with 5 mg of folate and 1,500 microg of mecobalamin or double placebos, and 559 completed the 2 year follow up. Plasma homocysteine levels in the decreased by 38% in the treatment group and increased by 31% in the placebo group. The number of the hip fractures per 1,000 patient-years was 10 and 43 for the treatment and placebo groups, respectively (p<0.001). In this Japanese population with a high baseline fracture risk, combined treatment with folate and vitamin B(12) is safe and effective in reducing the risk of a hip fracture in elderly stroke patients. Because of limited study power, the relative risk reduction may only be around 0.5.

Electrolytes Disturbances and Seizures

Electrolytes Disturbances and Seizures

Dose-dependent characteristics of intravenous calcium therapy for hypocalcemic critically ill trauma patients receiving specialized nutritional support

Objective The purpose of this investigation was to evaluate the dose-dependent characteristics of intravenous calcium gluconate therapy for hypocalcemic critically ill patients. Methods The dose-dependent characteristics of 2 g versus 4 g of intravenous calcium gluconate therapy were evaluated in 25 critically ill, adult multiple trauma patients with hypocalcemia. The calcium gluconate was infused at a rate of 1 g/h for both groups. Patients weighed within 90% to 120% of ideal body weight, had normal renal function, did not receive diuretic therapy, and did not have anasarca. Results Fifteen patients with mild hypocalcemia (serum ionized calcium concentration [iCa] 1–1.12 mmol/L) were given 2 g of calcium gluconate. Ten patients with moderate to severe hypocalcemia (iCa <1 mmol/L) were given 4 g. Each dosage group had a significant ( P ≤ 0.001) increase in iCa (from 1.07 ± 0.05 to 1.17 ± 0.05 mmol/L and from 0.92 ± 0.08 to 1.16 ± 0.11 mmol/L, respectively). Each dosage group retained about half of the dose in the exchangeable calcium space ( P = NS between groups), but the higher dosage group retained significantly more elemental calcium overall (81 ± 38 versus 201 ± 50 mg, respectively, P ≤ 001). Serum ionized calcium concentrations achieved a plateau without a further decline in iCa by 10 h after completion of the infusion for each dosage. Conclusion About half of the administered elemental calcium dose was retained for each dosage group, with the higher dose (4 g) resulting in significantly more elemental calcium retention in the exchangeable calcium space. An iCa determination performed about ≥10 h after the completion of the calcium gluconate infusion should be sufficient time to ensure equilibration of iCa to assess the efficacy of the therapy. This mode of calcium therapy serves as an effective means for providing calcium to the acutely hypocalcemic, critically ill, multiple trauma patient.

Comparison of the Effects of Daily and Intermittent‐Dose Calcitriol on Serum Parathyroid Hormone and Ionized Calcium Concentrations in Normal Cats and Cats with Chronic Renal Failure

Background:Chronic renal failure is complicated by secondary hyperparathyroidism, which traditionally has been controlled by dietary restriction of phosphorus and administration of phosphorus binders. Early treatment of patients with chronic renal failure with calcitriol may be indicated because once established, parathyroid gland hyperplasia does not readily resolve with therapy.Hypothesis:Daily and intermittent dosing of calcitriol will decrease plasma parathyroid hormone concentration in normal cats and cats with chronic renal failure without causing ionized hypercalcemia.Animals:Ten normal cats; 10 cats with chronic renal failure.Methods:Phase 1 was daily calcitriol administration (2.5 ng/kg PO q24h) for 14 days. Phase 2 was intermittent calcitriol administration (8.75 ng/kg PO q84h) for 14 days. A 7‐day washout period separated phases 1 and 2. Before each phase, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured. On days 1, 2, and 3 of both phases, serum ionized calcium concentrations were measured. On the last day of both phases, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured 0, 2, 4, and 6 hours after calcitriol administration.Results:Overall, serum parathyroid hormone concentrations were significantly higher in cats with chronic renal failure than in normal cats (P= .022), but serum parathyroid hormone concentrations for both normal cats and cats with chronic renal failure were not significantly different before and after 14 days of treatment with calcitriol, regardless of whether calcitriol was administered daily or intermittently. Adverse effects of calcitriol administration (specifically ionized hypercalcemia) were not seen in either feline group during either phase of the study over the 3‐day evaluation after calcitriol administration was initiated.Conclusions and Clinical Importance: At the dosages used, calcitriol treatment did not result in significant differences in serum parathyroid hormone concentrations before and after treatment in both normal cats and cats with chronic renal failure. With these dosages, adverse affects of calcitriol administration were not seen. Potential reasons for lack of apparent effect include small sample size, insufficient duration of study, insufficient dosage of calcitriol, problems with formulation or administration of calcitriol, and variable gastrointestinal absorption of calcitriol.

Electrolyte disorders in horses with colic. Part 1: potassium and magnesium

Electrolyte disorders are common in horses with acute abdominal disease, and are a significant cause of morbidity. They are especially prevalent in horses treated surgically for colic, and may be present before, during and after surgery. In one study, 54% of horses admitted for surgical colic had preoperative serum ionised magnesium concentrations below the reference range and 86% subnormal serum ionised calcium concentrations (Garcia-Lopez et al. 2001). Electrolyte abnormalities are particularly prevalent in horses with strangulating obstructions of the intestine. These horses have lower preoperative serum concentrations of ionised magnesium and calcium than horses with nonstrangulating lesions (Dart et al. 1992; Garcia-Lopez et al. 2001). Horses with decreased preoperative ionised magnesium were also more likely to be subjected to euthanasia during surgery. The role of electrolyte derangements in contributing to adverse clinical events in horses with colic is still being investigated. The association between cardiac electrical disorders and blood calcium, magnesium and potassium concentrations is well established in the horse (Harrington 1974; Glazier et al. 1979, 1982; Reef 1999) (Fig 1). Derangements in blood electrolyte concentration might also be associated with a longer hospital stay. Martin et al. (1994) reported that dogs with low serum magnesium concentrations were hospitalised for twice as long as those with a normal serum magnesium concentration. Conversely, Garcia-Lopez et al. (2001) did not find any correlation between serum ionised magnesium or calcium concentrations and length of hospitalisation, incidence of complications or survival in horses treated surgically for colic. The association between serum concentrations of potassium, calcium and magnesium with post operative ileus is still unknown in the horse. Dart et al. (1992) speculated that decreased serum calcium concentrations might contribute to ileus. Garcia-Lopez et al. (2001) found lower serum concentrations of ionised magnesium and calcium in horses that developed post operative ileus, than in those that did not. These decreased electrolyte concentrations may be due to decreased intake and increased loss of electrolytes in gastric reflux. It is now possible to measure electrolytes using ‘patientside’ portable analysers. The introduction of these cartridgebased systems has enabled results to be obtained quickly and easily when laboratory techniques are unavailable (Grosenbaugh et al. 1998). Different sensors are available to measure different combinations of electrolytes, blood biochemistry, PCV and blood gas tensions. The price of these hand-held devices is rapidly decreasing and they are now affordable for many private practices. The normal range for any electrolyte may vary to some degree between analysers. Therefore, horse specific normal ranges should be obtained from the manufacturers, if possible. In Part 1, we discuss the importance of potassium and magnesium and Part 2 covers calcium, sodium, chloride and phosphorus.

Comparison of the Effects of Daily and Intermittent-Dose Calcitriol on Serum Parathyroid Hormone and Ionized Calcium Concentrations in Normal Cats and Cats with Chronic Renal Failure

Chronic renal failure is complicated by secondary hyperparathyroidism, which traditionally has been controlled by dietary restriction of phosphorus and administration of phosphorus binders. Early treatment of patients with chronic renal failure with calcitriol may be indicated because once established, parathyroid gland hyperplasia does not readily resolve with therapy. Daily and intermittent dosing of calcitriol will decrease plasma parathyroid hormone concentration in normal cats and cats with chronic renal failure without causing ionized hypercalcemia. Ten normal cats; 10 cats with chronic renal failure. Phase 1 was daily calcitriol administration (2.5 ng/kg PO q24h) for 14 days. Phase 2 was intermittent calcitriol administration (8.75 ng/kg PO q84h) for 14 days. A 7-day washout period separated phases 1 and 2. Before each phase, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured. On days 1, 2, and 3 of both phases, serum ionized calcium concentrations were measured. On the last day of both phases, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured 0, 2, 4, and 6 hours after calcitriol administration. Overall, serum parathyroid hormone concentrations were significantly higher in cats with chronic renal failure than in normal cats (P = .022), but serum parathyroid hormone concentrations for both normal cats and cats with chronic renal failure were not significantly different before and after 14 days of treatment with calcitriol, regardless of whether calcitriol was administered daily or intermittently. Adverse effects of calcitriol administration (specifically ionized hypercalcemia) were not seen in either feline group during either phase of the study over the 3-day evaluation after calcitriol administration was initiated. At the dosages used, calcitriol treatment did not result in significant differences in serum parathyroid hormone concentrations before and after treatment in both normal cats and cats with chronic renal failure. With these dosages, adverse affects of calcitriol administration were not seen. Potential reasons for lack of apparent effect include small sample size, insufficient duration of study, insufficient dosage of calcitriol, problems with formulation or administration of calcitriol, and variable gastrointestinal absorption of calcitriol.