Screening criteria for feline renal transplant recipients and donors

Renal transplantation is associated with several potential complications. Early selection and appropriate screening of candidates has reduced the morbidity and mortality associated with this procedure in human beings. In veterinary medicine, the important process of identification and screening of candidates for renal transplantation occurs primarily in private general or specialty practice. This article reviews guidelines for screening of candidates for renal transplantation and related publications in both veterinary and human literature in an attempt to provide comprehensive information to practitioners involved in the selection process. It is anticipated that early referral of stable cats for renal transplantation will further improve the likelihood of a successful outcome.     

Evaluation of ionized and total serum magnesium concentrations in hyperthyroid cats

Hyperthyroidism can increase the renal excretion of magnesium and thus cause hypomagnesemia in various species. Anaerobically collected blood samples from 15 hyperthyroid and 40 normal, healthy cats were analyzed with an ion-selective electrode analyzer and a serum biochemical analyzer. There was no significant difference in ionized or total serum magnesium concentration between the 2 groups, but there was a significant difference (P = 0.004) in the ratio of ionized to total serum magnesium concentrations between the healthy cats and the hyperthyroid cats with thyroxine (T4) concentrations at or above the median. There was a significant correlation (r = 0.894, P = 0.000) between the ionized and total magnesium concentrations in the hyperthyroid cats. The hyperthyroid cats had a significantly lower (P = 0.003) total serum protein concentration than the healthy cats. A significant negative correlation (r = -0.670, P = 0.006) was detected between the ionized magnesium and logarithmically transformed total T4 concentrations in the hyperthyroid cats, which suggests that the severity of hyperthyroidism may contribute to a decrease in the ionized magnesium concentration.     

Post‐transplant malignant neoplasia associated with cyclosporine‐based immunotherapy: prevalence,risk factors and survival in feline renal transplant recipients

The study objective was to compare the prevalence of malignant neoplasia in feline renal transplant recipients (n = 111) with a control population of cats that did not receive transplantation (n = 142); and to determine whether the development of post‐transplant malignant neoplasia (PTMN) affects long‐term survival. Twenty‐five (22.5%) renal transplant recipients were diagnosed with PTMN, and of those 14 (56%) were diagnosed with lymphoma. The overall survival time in cats that developed PTMN following renal transplantation (median 646 days, IQR 433–1620 days) was not significantly different from the survival time in cats that did not develop PTMN (median 728 days, IQR 201–1942 days), although median survival after diagnosis of PTMN was only 13 days. Six control cats (4.2%) were diagnosed with malignant neoplasia. Compared to the control population, transplant cats had a 6.6 times higher odds of developing malignant neoplasia and a 6.7 times higher odds of developing lymphoma.     

The effects of surgery and anesthesia on blood magnesium and calcium concentrations in canine and feline patients

OBJECTIVE: To demonstrate the effect of anesthesia and surgery on serum ionized magnesium and ionized calcium concentrations in clinical canine and feline patients. ANIMALS: 37 client-owned dogs, ASA PS I-III and 10 client-owned cats, ASA PS I, all receiving anesthesia for elective or emergent surgery at a Veterinary Teaching Hospital. MATERIALS AND METHODS: Plasma ionized and serum total magnesium, and plasma ionized calcium were measured prior to and after a group-standardized anesthetic protocol. RESULTS: Regardless of pre-operative medication (hydromorphone or butorphanol), anesthetic induction (thiopental or lidocaine/hydromorphone/diazepam (LHD) and propofol combination), or type of surgical procedure (peripheral surgery or laparotomy), post-operative plasma ionized calcium concentration decreased in all groups of dogs, while post-operative plasma ionized magnesium increased in all groups, although the changes were not always significant. The dogs who were induced with an LHD and propofol technique had a greater increase in ionized magnesium (0.36 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1)) than the group in which anesthesia was induced with thiopental (0.41 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1), p = 0.009). The cats showed similar changes in ionized magnesium and ionized calcium, and also had a significant increase in serum total magnesium (2.17 +/- 0.20 to 2.31 +/- 0.25 mg dL(-1), p = 0.009) CONCLUSIONS, CLINICAL RELEVANCE: A post-operative decrease in ionized calcium was demonstrated in healthy animals, as well as an increase in ionized or total magnesium after various anesthetic protocols and surgeries. These changes, while statistically significant, do not appear to be clinically significant, as values remained within reference ranges at all times.     

Serum total and ionized magnesium concentrations and urinary fractional excretion of magnesium in cats with diabetes mellitus and diabetic ketoacidosis

OBJECTIVE: To determine magnesium (Mg) status in cats with naturally acquired diabetes mellitus (DM) and diabetic ketoacidosis (DKA), evaluate changes in Mg status after treatment for DKA, and correlate Mg status with systemic blood pressure and degree of glycemic control. DESIGN: Case series and cohort study. ANIMALS: 12 healthy cats (controls), 21 cats with DM, and 7 cats with DKA. PROCEDURE: Serum total magnesium (tMg) and ionized magnesium (iMg) concentrations and spot urinary fractional excretion of magnesium (FEmg) were determined, using serum and urine samples obtained from all cats when they were entered in the study and from cats with DKA 12, 24, and 48 hours after initiating treatment. Indirect blood pressure and degree of glycemic control were determined in 10 and 21 cats with DM, respectively. RESULTS: Initially, 2 and 13 cats with DM and 1 and 4 cats with DKA had serum tMg and iMg concentrations, respectively, less than the low reference limit (mean-2 SD) determined for controls. In cats with DKA, serum tMg concentration decreased significantly over time after initiating treatment. Urinary FEmg was significantly higher in cats with DM or DKA, compared with controls. Systemic hypertension was not detected nor was there a correlation between Mg status and degree of glycemic control in cats with DM. CONCLUSIONS AND CLINICAL RELEVANCE: Hypomagnesemia was a common finding in cats with DM and DKA and was more readily identified by measuring serum iMg concentration than tMg concentration. The clinical ramifications of hypomagnesemia in such cats remain to be determined.     

Validation of the Nova CRT8 for the measurement of ionized magnesium in feline serum

Background: Evaluation of serum magnesium (Mg) concentration is becoming important in human and veterinary critical care medicine. An ion‐selective electrode can measure the physiologically active ionized fraction. Objectives: The purpose of this study was to validate an ion‐specific electrode analyzer and assay for measuring ionized Mg in feline serum and to determine a reference interval for this analyte in cats. Methods: Venous blood samples were collected anaerobically from clinically healthy cats, and the serum was used to validate the analyzer and assay. This included investigating the stability of samples stored at different temperatures, intra‐ and interassay precision, linearity, analytical sensitivity, and potential interferences from bilirubin, lipemia, hemoglobin, or serum separator tubes. A reference interval was calculated. Results: Serum samples evaluated for ionized Mg concentrations can be stored at 20°C for ≤24 hours, at 4°C for ≤72 hours, and at ?20°C for ≤4 weeks, when samples are minimally exposed to air. Intra‐ and interassay precisions had coefficients of variation (CVs) of 1.23% and 2.02%, respectively. There was good linearity using serum (r= .998; y=?0.0057 + 1.0256x) and manufacturer‐supplied aqueous solutions and quality control materials (r= .999; y= 0.0110 + 0.9213x). Apparent analytical sensitivity was at least 0.015 mmol/L. Mean recovery was good for ionized Mg in samples with ≤1+ icterus (104%), 4+ lipemia (99.3%) and 1–4+ hemolysis (98.6%). There was no significant difference (P= .52) in ionized Mg concentrations in serum collected in tubes containing no additives compared with serum collected in glass separator tubes. The serum ionized Mg reference interval was 0.47–0.63 mmol/L (n = 40). Conclusions: The Nova CRT8 analyzer and assay provide a precise and reliable method of measuring ionized Mg concentration in feline serum. Strict adherence to sampling techniques, handling, and storage are necessary for reliable results.     

Studies of serum total immunoglobulin E concentrations in atopic and non-atopic dogs

The serum total immunoglobulin E (IgE) concentrations of two groups of atopic dogs and three groups of non-atopic dogs were compared. There was a wide range of concentrations with a high degree of overlap between the groups. The serum total IgE concentrations of a group of 15 non-atopic racing greyhounds were significantly higher than those of all the other groups. Atopic and non-atopic dogs receiving stringent parasite control treatments could not be differentiated on the basis of their serum total IgE concentrations. In the non-atopic dogs there was no correlation between their serum total IgE concentrations and the number of allergen-specific positive results obtained in an ELISA, or between their serum total IgE concentrations and their age.     

Effect of magnesium-deficient diet on serum and urine magnesium concentrations in healthy cats.

OBJECTIVE: To evaluate the efficacy of using serum total and ionized magnesium (Mg) concentrations and urine Mg concentrations to identify Mg deficiency in cats. ANIMALS: 6 healthy castrated male cats. PROCEDURE: A Mg-replete diet was fed for 37 days, followed by a Mg-deficient diet for 37 days. On days 1, 3, and 7 of the last week of each diet, serum ionized and total Mg concentrations were determined; in addition, urine Mg concentration was determined each day of the last week. Serum total and ionized Mg concentrations were compared with urine Mg concentration, amount of Mg excreted during 24 hours (24-hour urine Mg excretion), ratio of urine Mg concentration to urine creatinine concentration (Umg:Ucr), and urinary fractional excretion of Mg (FEmg) to determine which variable best predicted Mg status. RESULTS: Cats fed Mg-deficient diets had significantly lower serum total and ionized Mg concentrations and 24-hour urine Mg excretion values, compared with cats fed Mg-replete diets. Serum total Mg concentration was the best predictor of Mg status. Twenty-four-hour urine Mg excretion was a repeatable, reliable measurement and had the best correlation with serum total Mg concentration. Serum total Mg concentration also correlated with urine Mg concentration, Umg:Ucr, and FEmg. CONCLUSIONS AND CLINICAL RELEVANCE: Serum total and ionized Mg concentrations can be used to identify cats with dietary-induced Mg deficiencies. Twenty-four-hour urine Mg excretion and urine Mg concentration correlated best with serum total Mg concentration and, therefore, may be the most useful urine variables for identifying Mg deficiency.     

Effects of deficient and adequate dietary magnesium concentrations on body magnesium concentrations in wethers

Effects of 2 dietary Mg concentrations (deficient and adequate: 0.04 and 0.12 g of Mg/100 g of dry matter, respectively) on body fluid and tissue Mg concentrations and performance of wether lambs were evaluated in a 28-day trial. Nine blood and 6 urine samples were collected from each wether. After 28 days, CSF and wool samples were collected, and diet, body fluids, and tissues were analyzed for mineral concentration. Diet effects on serum and urine Mg concentrations were noticed after day 3 (P less than 0.01; P less than 0.05, respectively). Mean serum and urine Mg concentrations for 6 sampling periods were correlated (r = 0.83, P less than 0.001; No. of samples = 12). The effect of dietary Mg on CSF Mg concentrations approached significance (P less than 0.10). Effects of diet on cardiac muscle, liver, and 3rd metatarsal bone Mg contents or hematologic criteria were not observed. Diet affected wool and kidney cortex Mg contents (P less than 0.02). Individual mean 28-day serum Mg concentration was correlated with wool Mg content (r = 0.73, P less than 0.05; n = 8) and with kidney cortex Mg content (r = 0.75, P less than 0.05; n = 8). Wethers fed low Mg diet excreted less urine Ca (P less than 0.001) and had slightly lower serum Ca and K values (P less than 0.10) than did wethers fed high Mg. Significant differences in cardiac muscle, liver, spleen, or kidney cortex Ca contents were not observed. Wethers fed low Mg diet consumed less dry matter and gained less weight (P less than 0.001) than did wethers fed high Mg diet. Body fluid and tissue macromineral concentrations of 1 wether with hypomagnesemic tetany are presented for prognostic and diagnostic purposes.     

Evaluation of oxidative stress markers for the early diagnosis of allograft rejection in feline renal allotransplant recipients with normal renal function

The purpose of this study was to identify oxidative damage to renal allografts during graft rejection by evaluating changes in oxidative markers and plasma lactate levels in feline renal allotransplant recipients. Heterotopic renal allotransplantations were performed between 8 adult feline cross-matched donors. Following 14 d of immunosuppression, the drugs were discontinued to allow allograft rejection. Baseline and serial postoperative evaluations of serum creatinine, plasma lactate, plasma thiobarbituate reactive substances (TBARS), plasma creatol, urine creatol, and renal sonographic cross-sectional area were performed. When sonographic evaluation revealed the absence of blood flow to the allograft, the rejected kidney was nephrectomized and evaluated histopathologically. Allograft rejection occurred in all cats by day 26. A significant elevation in body temperature occurred during the rejection period. No significant change was observed between any of the time periods for plasma TBARS, creatol, or urine creatol. There was a significant decrease in plasma lactate levels throughout the study. Markers of oxidative stress from venous blood did not reflect renal allograft rejection in cats with a normally functioning native kidney. Renal allograft rejection may be associated with significant increases in body temperature and warrants further investigation.     

Relationship of serum ferritin and iron concentrations and serum total iron-binding capacity to nonheme iron stores in dogs

The relationships of various iron-related analytes were evaluated in 95 dogs. Liver and spleen nonheme iron content was determined coulometrically on acid-digested tissue specimens. Serum iron concentration and total iron-binding capacity also were measured coulometrically, whereas serum ferritin concentration was measured by ELISA. Significant (P less than 0.0002) correlation was found between serum ferritin concentration and nonheme iron stores. Significant correlation was not found between nonheme iron stores and serum iron concentration or total iron-binding capacity. Serum ferritin concentration should provide a convenient and relatively noninvasive means of estimating iron stores in dogs.     

Anesthetic management in feline renal transplantation

Objective To document perioperative and anesthetic management of 30 feline renal transplant recipients (1996–1998). Study design Retrospective clinical study. Animals Thirty adult cats in end‐stage renal failure that underwent heterotopic renal transplantation. Materials and methods The medical records were reviewed from 30 feline heterotopic renal transplant recipients. Cases were included only if they had been treated for hypertension using a beta‐adrenergic antagonist, a calcium channel blocker or hemodialysis. Data regarding signalment, preoperative management, surgical technique, type and doses of anesthetics administered, perioperative hemodynamics and intra‐ and postoperative complications, postoperative analgesia, morbidity and early mortality were recorded. Data were expressed as mean ± SD. Results Preanesthetic medication included a combination of an anticholinergic and an opioid (oxymorphone). Anesthesia induction was performed mostly with isoflurane and oxygen delivered by mask. Anesthesia maintenance was primarily achieved with isoflurane in 100% oxygen. Nitrous oxide was often used as part of the anesthetic technique. The mean duration of anesthesia was 4.6 hours ± 27 minutes. The mean renal allograft ischemic time was 60 minutes. During the anesthetic period, the majority of the recipient cats received either fresh whole blood (FWB) (N = 25, 83%), cross‐matched packed red blood cells (PRBC) (N = 3, 10%) or fresh frozen plasma (FFP) (N = 2, 7%) combined with a balanced electrolyte solution. Blood products administered averaged 63 ± 34 mL and crystalloid 94 ± 62 mL. The most common treated intraoperative complications were hypotension (N = 14, 47%), hypothermia (N = 13, 43%), metabolic acidosis (N = 11, 37%), hypocalcemia (N = 5, 17%), hypoglycemia (N = 4, 13%), hypertension (N = 2, 7%), bradycardia (N = 1, 3%), and ventricular premature contractions (N = 1, 3%). All cats received opioid analgesics postoperatively. Complications observed in the first 24 hours postoperatively were hypertension (N = 20, 67%), hematuria (N = 14, 47%), electrolyte disturbances (N = 9, 30%), temperature imbalances (N = 5, 17%), decreased PCV requiring blood transfusion (N = 5, 17%), decreased perfusion of a foot associated with external iliac anastomosis technique (N = 5, 17%), seizures associated with hypertension (N = 3, 10%), uroabdomen (N = 2, 7%), acute graft rejection (N = 1, 3%) and, corneal ulceration (N = 1, 3%). Survival rates in the perioperative period were 100, 96.7, and 93.4% intraoperatively, at 24 hours, and 7 days following surgery. Conclusion Successful anesthesia can be performed in critically ill renal transplant recipients. However, for optimal graft function and patient survival, normothermia, normovolemia, normotension, and normal acid–base and electrolyte balance should be carefully maintained. Successful anesthetic management requires understanding of the pathophysiology of end‐stage renal disease and the maintenance of homeostasis during the different stages of the perioperative period.     

Effect of pre-calving zeolite, magnesium and phosphorus supplementation on periparturient serum mineral concentrations

The objective of this study was to test whether supplementing dry cow rations with phosphorus (P) and magnesium (Mg) would interfere with the beneficial effect of zeolite supplementation on the periparturient blood calcium (Ca) concentration in dairy cattle. Three groups (A-C) of 10 Danish Jersey cows were each given the following daily supplements from 2 weeks before the expected date of calving until actual calving: group A: zeolite, monoammonium phosphate, standard dry cow mineral and vitamin mix, containing 61g magnesium phosphate; group B: zeolite, standard mineral and vitamin mix without the magnesium phosphate and group C: standard mineral and vitamin mix, monoammonium phosphate. All cows in group B had an apparently less variable serum calcium concentration around calving with no cases of milk fever and no subclinical hypocalcaemia or hypomagnesaemia recorded. In contrast, a parturient drop in blood Ca was seen in group A as well as group C. In group A, one cow was hypocalcaemic at calving, and developed milk fever. In group C, 12 blood samples, representing six cows, were hypocalcaemic, and three of these cows were treated for milk fever. All groups remained normomagnesaemic and there were no significant differences in blood Mg across groups. In conclusion, the combined P and Mg supplementation in addition to zeolite supplementation did not increase the serum Mg level (forage Mg 16.9g/day; 0.21% of DM). Combined P and Mg supplementation reduced the zeolite-induced hypophosphataemia but also reduced the stabilising effect of zeolite on parturient serum Ca.     

Effect of vaccination on serum concentrations of total and antigen-specific immunoglobulin E in dogs

OBJECTIVE: To determine the effect of vaccination on serum concentrations of total and antigen-specific IgE in dogs. ANIMALS: 20 female Beagles. PROCEDURE: Groups of 5 dogs each were vaccinated repeatedly between 8 weeks and 4 years of age with a multivalent and rabies vaccine, a multivalent vaccine only, or a rabies vaccine only. A fourth group of 5 dogs served as unvaccinated controls. Serum concentrations of total immunoglobulins and antigen-specific IgE were determined following vaccination. RESULTS:-The multivalent vaccine had little effect on serum total IgE concentrations. The concentration of IgE increased slightly following vaccination for rabies at 16 weeks and 1 year of age and increased greatly after vaccination at 2 and 3 years of age in most dogs, with a distinct variation between individual dogs. Vaccination had no effect on serum concentrations of IgA, IgG, and IgM as measured at 2 and 3 years of age. The rabies vaccine contained aluminum adjuvant in contrast to the multivalent vaccine. An increase of IgE that was reactive with vaccine antigens, including bovine serum albumin and bovine fibronectin, was detected in some of the dogs vaccinated for rabies. There was no significant correlation between serum concentrations of total IgE and antigen-specific IgE following vaccination. Serum total IgE concentration rapidly returned to preimmunization concentrations in most dogs, but high concentrations of antigen-specific IgE persisted. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination of dogs for rabies increases serum concentrations of total IgE and induces IgE specific for vaccine antigens, including tissue culture residues. Vaccination history should be considered in the interpretation of serum total IgE concentrations.     

Effects of intravenous infusion of lipopolysaccharide on plasma micromineral, magnesium, and cytokine concentrations and serum cortisol concentrations in lactating goats

OBJECTIVE: To assess the effects of various doses of lipopolysaccharide (LPS) administered IV on plasma microminerals, magnesium, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-6 concentrations and serum cortisol concentrations in lactating goats. ANIMALS: 6 lactating goats. PROCEDURES: Goats were allotted to 3 LPS-treatment groups: control (0 microg/kg), low LPS (10 microg/kg), and high LPS (50 microg/kg). Rectal temperatures and behaviors of goats were recorded immediately before a 10-minute IV infusion of LPS and at 0.5, 1, 2, 4, 6, 8, and 24 hours after infusion. Blood samples were obtained before IV infusion and at 0.5, 1, 2, 4, 6, 8, and 24 hours after infusion. Plasma zinc, copper, iron, and magnesium concentrations were determined by atomic absorption spectrometry; plasma TNF-alpha and IL-6 concentrations were measured by use of an ELISA; and serum cortisol concentrations were determined by use of a radioimmunoassay. RESULTS: A monophasic fever developed in low-LPS and high-LPS groups. In the low-LPS and high-LPS group, plasma zinc concentrations decreased at 6 hours after infusion; compared with control groups. Plasma iron concentrations were lower at 24 hours after infusion in low-LPS and high-LPS groups than in the control group. Plasma TNF-alpha and IL-6 concentrations were higher in low-LPS and high-LPS groups than in the control group at 1, 2, and 4 hours after infusion. In low-LPS and high-LPS groups, serum cortisol concentrations increased from 0.5 hours onward and peaked at 1 (high-LPS group) and 2 (low-LPS group) hours after infusion. CONCLUSIONS AND CLINICAL RELEVANCE: Following IV infusion of LPS, the immune system is activated, which might affect micromineral homeostatic regulation and, subsequently, the metabolic health of lactating goats.