Acute stress hyperglycemia in cats is associated with struggling and increased concentrations of lactate and norepinephrine

We characterized the changes in blood glucose concentrations in healthy cats exposed to a short stressor and determined the associations between glucose concentrations, behavioral indicators of stress, and blood variables implicated in stress hyperglycemia (plasma glucose, lactate, insulin, glucagon, cortisol, epinephrine, and norepinephrine concentrations). Twenty healthy adult cats with normal glucose tolerance had a 5-minute spray bath. Struggling and vocalization were the most frequent behavioral responses. There was a strong relationship between struggling and concentrations of glucose and lactate. Glucose and lactate concentrations increased rapidly and significantly in all cats in response to bathing, with peak concentrations occurring at the end of the bath (glucose baseline 83 mg/dL, mean peak 162 mg/dL; lactate baseline 6.3 mg/dL, mean peak 64.0 mg/dL). Glucose response resolved within 90 minutes in 12 of the 20 cats. Changes in mean glucose concentrations were strongly correlated with changes in mean lactate (r = .84; P < .001) and mean norepinephrine concentrations (r = .81; P < .001). There was no significant correlation between changes in mean glucose concentrations and changes in mean insulin, glucagon, cortisol, or epinephrine concentrations. Struggling and lactate concentrations were predictive of hyperglycemia. Gluconeogenesis stimulated by lactate release is the likely mechanism for hyperglycemia in healthy cats in this model of acute stress. Careful handling techniques that minimize struggling associated with blood collection may reduce the incidence of stress hyperglycemia in cats.     

Comparison of peritoneal fluid and peripheral blood pH,bicarbonate, glucose,and lactate concentration as a diagnostic tool for septic peritonitis in dogs and cats

OBJECTIVE: To establish a reliable diagnostic tool for septic peritonitis in dogs and cats using pH, bicarbonate, lactate, and glucose concentrations in peritoneal fluid and venous blood. STUDY DESIGN: Prospective clinical study. ANIMALS: Eighteen dogs and 12 cats with peritoneal effusion. METHODS: pH, bicarbonate, electrolyte, lactate, and glucose concentrations were measured on 1- to 2-mL samples of venous blood and peritoneal fluid collected at admission. The concentration difference between blood and peritoneal fluid for pH, bicarbonate, glucose, and lactate concentrations were calculated by subtracting the peritoneal fluid concentration from the blood concentration. Peritoneal fluid was submitted for cytologic examination and bacterial culture. Peritonitis was classified as septic or nonseptic based on cytology and bacterial culture results. RESULTS: In dogs, with septic effusion, peritoneal fluid glucose concentration was always lower than the blood glucose concentration. A blood-to-fluid glucose (BFG) difference > 20 mg/dL was 100% sensitive and 100% specific for the diagnosis of septic peritoneal effusion in dogs. In 7 dogs in which it was evaluated, a blood-to-fluid lactate (BFL) difference < -2.0 mmol/L was also 100% sensitive and specific for a diagnosis of septic peritoneal effusion. In cats, the BFG difference was 86% sensitive and 100% specific for a diagnosis of septic peritonitis. In dogs and cats, the BFG difference was more accurate for a diagnosis of septic peritonitis than peritoneal fluid glucose concentration alone. CONCLUSIONS: A concentration difference > 20 mg/dL between blood and peritoneal fluid glucose concentration provides a rapid and reliable means to differentiate a septic peritoneal effusion from a nonseptic peritoneal effusion in dogs and cats. CLINICAL RELEVANCE: The difference between blood and peritoneal fluid glucose concentrations should be used as a more reliable diagnostic indicator of septic peritoneal effusion than peritoneal fluid glucose concentration alone.     

Serum fructosamine concentration in cats with overt hyperthyroidism.

OBJECTIVE: To determine the effect of hyperthyroidism on serum fructosamine concentration in cats. DESIGN: Cohort study. ANIMALS: 22 cats with overt hyperthyroidism. PROCEDURE: Hyperthyroidism was diagnosed on the basis of clinical signs, detection of a palpable thyroid gland, and high total serum thyroxine (T4) concentrations. Hyperthyroid cats with abnormal serum albumin, total protein, and glucose concentrations were excluded from the study. Samples for determination of serum fructosamine concentration were obtained prior to initiating treatment. Results were compared with fructosamine concentrations in healthy cats, cats in which diabetes had recently been diagnosed, and cats with hypoproteinemia. In 6 cats, follow-up measurements were obtained 2 and 6 weeks after initiating treatment with carbimazole. RESULTS: Serum fructosamine concentrations ranged from 154 to 267 mumol/L (median, 198 mumol/L) and were significantly lower than values in healthy cats. Eleven (50%) of the hyperthyroid cats had serum fructosamine concentrations less than the reference range. Serum fructosamine concentrations in hyperthyroid, normoproteinemic cats did not differ from values in hypoproteinemic cats. During treatment, an increase in serum fructosamine concentration was detected. CONCLUSIONS AND CLINICAL RELEVANCE: In hyperthyroid cats, concentration of serum fructosamine may be low because of accelerated protein turnover, independent of blood glucose concentration. Serum fructosamine concentrations should not be evaluated in cats with overt hyperthyroidism and diabetes mellitus. Additionally, concentration of serum fructosamine in hyperthyroid cats should not be used to differentiate between diabetes mellitus and transitory stress-related hyperglycemia.     

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.     

Artifactual hypoglycemia associated with hemotrophic mycoplasma infection in a lamb

Background: A 35-day-old male lamb with Mycoplasma ovis infection (previously Eperyihrozoon avis ) was evaluated because of severe hypoglycemia (serum glucose 4 mg/dL, Hitachi 704 automated chemistry analyzer) inconsistent with the animal's condition. Whole blood glucose concentration measured with a glucometer was 74 mg/dL. Objective: The purpose of this study was to investigate this discrepancy through in vitro evaluation of the patient's blood.
Methods: Blood was incubated alone, with increasing concentrations of plasma, or with equine serum of known glucose concentration for 0,15, 30, and 60 minutes at room temperature; end-point glucose concentrations were compared with blood from a control sheep handled similarly.
Results: A rapid decline in glucose concentration was observed in heparinized or EDTA anticoagulated whole blood from the infected lamb incubated alone or with the equine serum. Glucose concentrations in incubated samples from a control sheep remained stable. Incubation of increasing concentrations of heparinized blood with autologous plasma resulted in decreased glucose concentrations in patient, but not control, blood. As parasitemia decreased after treatment, serum glucose concentration increased, serum lactate concentration decreased, and in vitro glucose concentration stabilized.
Conclusions: These findings are consistent with parasite-associated in vitro glucose consumption. An increase in the lamb's plasma glucose concentration associated with reduction of parasite load suggested excess glucose consumption also may have occurred in vivo.     

Serum cobalamin concentrations in healthy cats and cats with non-alimentary tract illness in Australia

Objective   To determine a reference range for serum cobalamin concentration in healthy cats in Australia using a chemiluminescent enzyme immunoassay and to prospectively investigate the prevalence of hypocobalaminaemia in cats with non-alimentary tract disease.
Design   Prospective study measuring serum cobalamin concentrations in clinically healthy cats and cats with non-alimentary tract illness.
Procedure   Blood was collected from 50 clinically healthy cats that were owned by staff and associates of Veterinary Specialist Services or were owned animals presented to Creek Road Cat Clinic for routine vaccination. Blood was collected from 47 cats with non-alimentary tract illness presented at either clinic. Serum cobalamin concentration was determined for each group using a chemiluminescent enzyme immunoassay.
Results   A reference range for Australian cats calculated using the central 95th percentile in the 50 clinically healthy cats was 345 to 3668 pg/mL. Median serum cobalamin concentration in 47 cats with non-alimentary tract illness (1186 pg/mL; range 117–3480) was not significantly different to the median serum cobalamin of the 50 healthy cats (1213 pg/mL, range 311–3688). Using the calculated reference range one sick cat with non-alimentary tract illness had a markedly low serum cobalamin concentration.
Conclusion   Although hypocobalaminaemia is uncommon in sick cats with non-alimentary tract illness in Australia, its occurrence in this study warrants further investigation.     

A Single Sample Method for Evaluating 51Chromium-Ethylene Diaminic Tetraacetic Acid Clearance in Normal and Hyperthyroid Cats

Background: Chronic kidney failure is frequently seen in middle-aged and elderly cats. ⁵¹Chromium-ethylene diaminic tetraacetic acid (⁵¹Cr-EDTA) clearance and single blood sample (SBS) method are used in several species to estimate the glomerular filtration rate (GFR).
Hypothesis: The hypothesis of this study was that ⁵¹Cr-EDTA clearance could be determined using an SBS method in normal and hyperthyroid cats.
Animals: Forty-six cats were included in this study, with an average age of 9.5 years. Of these cats, 27 had hyperthyroidism; 19 were healthy.
Methods: After IV injection of ⁵¹Cr-EDTA (average dose: 4.25 MBq), 7 blood samples were obtained between 5 and 240 minutes. Reference clearance was calculated in mL/min and mL/min/kg body weight, using a 2-compartment model. Optimal time for clearance measurement with SBS was then determined by systematically comparing each individual plasma concentration to the reference multisample clearance.
Results: The average reference plasma clearance of ⁵¹Cr-EDTA for all cats was 14.9 mL/min (3.7 mL/min/kg). The clearance in hyperthyroid cats averaged 16.4 mL/min (4.3 mL/min/kg) and in normal cats averaged 10.3 mL/min (2.4 mL/min/kg).
The optimal time for the SBS was 48 minutes after injection of tracer ⁵¹Cr-EDTA ( R ²= 0.9414), giving the following converting equation: clearance = (0.0066 × DV_{48 minutes}) – 0.9277 (in mL/min).
Conclusions and Clinical Importance: In this study, the single sample ⁵¹Cr-EDTA clearance method was used to estimate the global GFR in cats. The method identified differences in clearance between normal and hyperthyroid cats. The optimal time for an SBS was 48 minutes.     

Assessment of the hemodynamic effects of lidocaine administered IV in isoflurane-anesthetized cats

OBJECTIVE:To determine the hemodynamic effects of lidocaine (administered IV to achieve 6 plasma concentrations) in isoflurane-anesthetized cats. ANIMALS: 6 cats. PROCEDURE: Cats were anesthetized with isoflurane in oxygen (end-tidal isoflurane concentration set at 1.25 times the predetermined individual minimum alveolar concentration). Lidocaine was administered IV to each cat to achieve target pseudo-steady-state plasma concentrations of 0, 3, 5, 7 9, and 11 microg/mL, and isoflurane concentration was reduced to an equipotent concentration. At each plasma lidocaine concentration, cardiovascular and blood gas variables; PCV; and plasma total protein, lactate, lidocaine, and monoethylglycinexylidide concentrations were measured in cats before and during noxious stimulation. Derived variables were calculated. RESULTS: n isoflurane-anesthetized cats, heart rate, cardiac index, stroke index, right ventricular stroke work index, plasma total protein concentration, mixed-venous PO2 and hemoglobin oxygen saturation, arterial and mixed-venous bicarbonate concentrations, and oxygen delivery were significantly lower during lidocaine administration, compared with values determined without lidocaine administration. Mean arterial pressure, central venous pressure, pulmonary artery pressure, systemic and pulmonary vascular resistance indices, PCV, arterial and mixed-venous hemoglobin concentrations, plasma lactate concentration, arterial oxygen concentration, and oxygen extraction ratio were significantly higher during administration of lidocaine, compared with values determined without lidocaine administration. Noxious stimulation did not significantly affect most variables. CONCLUSIONS AND CLINICAL RELEVANCE: In isoflurane-anesthetized cats, although IV administration of lidocaine significantly decreased inhalant requirements, it appeared to be associated with greater cardiovascular depression than an equipotent dose of isoflurane alone. Administration of lidocaine to reduce isoflurane requirements is not recommended in cats.     

Remission of diabetes mellitus in cats cannot be predicted by the arginine stimulation test

Background: Cats with diabetes mellitus frequently achieve clinical remission, suggesting residual β‐cell function. Responsiveness of β‐cells to arginine persists the longest during diabetes progression, making the intravenous arginine stimulation test (IVAST) a useful tool to assess residual insulin and glucagon secretion. Hypothesis: Diabetic cats with and without remission will have different arginine‐induced insulin or glucagon response. Animals: Seventeen cats with diabetes, 7 healthy cats. Methods: Blood samples collected on admission and during subsequent IVAST. Glucose, insulin, and glucagon were measured. Response to IVAST was assessed by calculating the insulin and glucagon area under the curve (AUC) and the AUC glucagon‐to‐insulin ratio. Diabetic cats were treated with insulin and were followed for 18 weeks. Remission was defined as normoglycemia and disappearance of clinical signs of diabetes for ≥4 weeks, without requiring insulin. Results: Seven diabetic cats (41%) achieved remission. On admission, blood glucose concentration was significantly lower in cats with remission (median, 389 mg/dL; range, 342–536 mg/dL) than in those without remission (median, 506 mg/dL; range, 266–738 mg/dL). After IVAST, diabetic cats with remission had higher AUC glucagon‐to‐insulin ratios (median, 61; range, 34–852) than did cats without remission (median, 26; range, 20–498); glucose, insulin, and glucagon AUCs were not different. Diabetic cats had lower insulin AUC than did healthy cats but comparable glucagon AUC. Conclusions and Clinical Importance: Diabetic cats with and without remission have similar arginine‐stimulated insulin secretion on admission. Although cats with remission had lower blood glucose concentrations and higher AUC glucagon‐to‐insulin ratios, large overlap between groups prevents use of these parameters in clinical practice.     

Prognostic value of blood lactate, blood glucose, and hematocrit in canine babesiosis

Canine babesiosis typically causes hemolytic anemia but also can result in multiple organ dysfunction. Human patients with severe disease often have persistent hyperlactatemia, and blood lactate concentration is correlated with survival rate. In dogs, blood lactate concentration has been shown to be of prognostic value in patients with gastric dilatation-volvulus and in dogs admitted to intensive care units. Serial blood lactate and glucose concentrations and hematocrit on admission were determined in 90 dogs with naturally occurring, severe or complicated canine babesiosis. Forty-five dogs (50%) had hyperlactatemia (blood lactate concentration >22.5 mg/dL) and 20 (22.2%) had hypoglycemia (blood glucose concentration <59.4 mg/dL) at presentation. Measurements significantly associated with mortality were hypoglycemia on admission, blood lactate concentration >45 mg/dL on admission, blood lactate concentration >22.5 mg/dL at 8, 16, and 24 hours after admission, and increase or <50% decrease in blood lactate concentration within 8 and 16 hours after admission. Blood lactate concentration persistently >40 mg/dL indicated a very poor prognosis. We conclude that serial blood lactate measurements are useful in predicting survival in dogs with severe and complicated canine babesiosis.     

Fructosamine concentrations in hyperglycemic cats.

The aims of this study were 1) to establish a reference range for fructosamine in cats using a commercial fructosamine kit; 2) to demonstrate that the fructosamine concentration is not increased by transient hyperglycemia of 90 min duration, simulating hyperglycemia of acute stress; and 3) to determine what percentage of blood samples submitted to a commercial laboratory from 95 sick cats had evidence of persistent hyperglycemia based on an elevated fructosamine concentration. Reference intervals for the serum fructosamine concentration were established in healthy, normoglycemic cats using a second generation kit designed for the measurement of the fructosamine concentration in humans. Transient hyperglycemia of 90 min duration was induced by IV glucose injection in healthy cats. Multisourced blood samples that were submitted to a commercial veterinary laboratory either as fluoride oxalated plasma or serum were used to determine the percentage of hyperglycemic cats having persistent hyperglycemia. The reference interval for the serum fructosamine concentration was 249 to 406 mumol/L. Transient hyperglycemia of 90 min duration did not increase the fructosamine concentration and there was no correlation between fructosamine and blood glucose. In contrast, the fructosamine concentration was correlated with the glucose concentration in sick hyper- and normoglycemic cats. It is concluded that the fructosamine concentration is a useful marker for the detection of persistent hyperglycemia and its differentiation from transient stress hyperglycemia. Fructosamine determinations should be considered when blood glucose is 12 to 20 mmol/L and only a single blood sample is available for analysis.     

Plasma lactate as a predictor of colonic viability and survival after 360 degrees volvulus of the ascending colon in horses

Objectives— To determine the relationship between plasma lactate concentration and colonic viability and survival in horses with ≥360° volvulus of the ascending colon.
Study Design— Retrospective study.
Animals— Horses (n=73) with ≥360° volvulus of the ascending colon.
Methods— Medical records (January 2000–November 2005) of all horses examined for colic at Michigan State University Veterinary Teaching Hospital were reviewed. Horses were included only if plasma lactate concentration was measured preoperatively and a diagnosis of ≥360° volvulus of the ascending colon was confirmed by surgery or necropsy. Non-survivors were only included if the ascending colon was evaluated histopathologically. Logistic regression analysis was used to model the relationship between lactate, colonic viability, and survival.
Results— Of 73 horses, 61 were discharged. Mean (±SD) plasma lactate concentration was significantly lower in survivors (2.98±2.53 mmol/L) compared with non-survivors (9.48±5.22 mmol/L; odds ratio [OR]=1.628, 95% confidence limit [CI]=1.259–2.105). Plasma lactate concentration was significantly lower in horses with a viable colon (3.30±2.85 mmol/L) compared with horses with a non-viable colon (9.1±6.09 mmol/L; OR=1.472, 95% CI=1.173–1.846). Plasma lactate concentration <6.0 mmol/L had a sensitivity of 84% and a specificity 83% for predicting horse survival.
Conclusions— Our results demonstrate a strong association between plasma lactate concentration at the time of hospital admission and outcome in horses with ≥360° volvulus of the ascending colon.
Clinical Relevance— Plasma lactate concentration may help predict colonic viability and horse survival after ascending colon volvulus in horses.     

Accuracy and precision of a point-of-care hemoglobinometer for measuring hemoglobin concentration and estimating packed cell volume in horses

OBJECTIVE: To determine accuracy and precision of a point-of-care hemoglobinometer for measuring hemoglobin concentration and estimating PCV in horses. DESIGN: Prospective trial. ANIMALS: 55 horses. PROCEDURE: Blood samples were obtained from 43 horses examined at a veterinary teaching hospital. Hemoglobin concentration was measured with the hemoglobinometer and by means of the standard cyanmethemoglobin method; PCV was measured by centrifugation. Blood samples were also obtained from 12 healthy horses, and PCV of aliquots of these samples was altered to approximately 5 to 80% by removing or adding plasma. Hemoglobin concentration and PCV were then measured. RESULTS: For samples from the clinic patients, hemoglobin concentrations obtained with the hemoglobinometer were less than concentrations obtained with the cyanmethemoglobin method; however, there was a linear relationship between concentrations obtained with the 2 methods. Breed, sex, body weight, and duration of sample storage did not significantly affect the difference between hemoglobin concentrations obtained with the 2 methods. There was a significant linear relationship between PCV and hemoglobinometer hemoglobin concentration (PCV = [2.83 x hemoglobin concentration] - 0.62). For samples from the healthy horses, a substantial negative bias was evident with the hemoglobinometer when hemoglobin concentration exceeded 16 g/dL. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that this hemoglobinometer is reasonably accurate and precise when used to measure hemoglobin concentration in blood samples from horses with a hemoglobin concentration < 16 g/dL.     

Comparison of glucose concentrations in canine whole blood,plasma, and serum measured with a veterinary point-of-care glucometer

Previous studies have determined that, compared to whole blood, serum or plasma used in a portable blood glucometer (PBG) may provide more accurate results. We investigated the accuracy of a veterinary PBG (AlphaTRAK 2; Zoetis) for the measurement of glucose concentrations in serum, plasma, and whole blood compared to plasma glucose concentration measured by a biochemical analyzer. Blood samples from 53 client-owned dogs were collected. Lin concordance correlation coefficient (ρ_c) and Bland–Altman plots were used to determine correlation and agreement between the results obtained for the different sample types. Glucose concentration in whole blood measured by the veterinary PBG was more strongly correlated with the glucose concentration measured by the biochemical analyzer (ρ_c = 0.92) compared to plasma and serum glucose concentrations (ρ_c = 0.59 and 0.57, respectively). The mean differences between the glucose concentrations in whole blood, plasma, and serum measured by the veterinary PBG and the glucose concentration determined by the biochemical analyzer were 1.0, 6.3, and 6.7 mmol/L (18, 113, and 121 mg/dL), respectively. Our findings suggest that, when using this veterinary PBG, the accuracy of a glucose measurement obtained is higher when using whole blood compared to plasma or serum. Use of whole blood allows for more correct assessment and diagnosis, which are necessary for appropriate therapeutic intervention.     

Evaluation of a Novel Real-Time Continuous Glucose-Monitoring System for Use in Cats

Background: The Guardian REAL‐Time is a continuous glucose‐monitoring system (CGMS) recently developed to provide instantaneous interstitial glucose concentrations; the system does not require a monitor being fixed to the animal. Hypothesis: The CGMS provides accurate and reproducible real‐time readings of glucose concentration in cats. Animals: Thirty‐two diabetic cats, 2 cats with suspected insulinoma, and 5 healthy cats. Methods: Prospective, observational study. CGMS accuracy was compared with a reference glucose meter at normal, high, and low blood glucose concentrations using error grid analysis. Reading variability of 2 simultaneously used CGMS was determined in diabetic cats by calculating correlation and percentage of concordance of paired data at different glycemic ranges. The time interval between increasing glycemia and a rise in interstitial fluid glucose measured by the CGMS was assessed in healthy cats receiving glucose IV; the time point of maximal increase in interstitial glucose concentrations was calculated. Results: The CGMS was 100, 96.1, and 91.0% accurate at normal, high, and low blood glucose concentrations. Measurements deviated from reference by ?12.7 ± 70.5 mg/dL at normal, ?12.1 ± 141.5 mg/dL at high, and ?1.9 ± 40.9 mg/dL at low glucose concentrations. Overall, paired CGMS readings correlated significantly (r= 0.95, P < .0001) and concordance was 95.7%. The median delay after IV administration of glucose to an increase in interstitial glucose was 11.4 minutes (range: 8.8–19.7 minutes). Conclusions and Clinical Importance: Although some readings substantially deviated from reference values, the CGMS yields reproducible results, is clinically accurate in cats with hyperglycemia and euglycemia, and is slightly less accurate if blood glucose concentrations are low. Rapidly increasing interstitial glucose after a glycemic rise suggests that the CGMS is suitable for real‐time measurement under clinical conditions.     

Underlying cause, pathophysiologic abnormalities, and response to treatment in cats with septic peritonitis: 51 cases (1990-2001)

OBJECTIVE: To determine the underlying cause, pathophysiologic abnormalities, and response to treatment in cats with septic peritonitis and identify differences between cats that survived following treatment and cats that did not survive despite treatment. DESIGN: Retrospective study. ANIMALS: 51 cats with septic peritonitis. PROCEDURE: Medical records were reviewed for clinical findings; results of clinicopathologic testing, microbial culture, and radiography; diagnosis; treatment; and outcome. RESULTS: Signs of pain during palpation of the abdomen were reported for only 29 of 47 (62%) cats. Eight (16%) cats had relative bradycardia (heart rate < 140 beats/min). The most commonly isolated organisms included Escherichia coli, Enterococcus spp, and Clostridium spp. The most common cause of peritonitis was gastrointestinal tract leakage (24 cats). No definitive source could be identified in 7 cats. Treatment, including exploratory surgery, was pursued in 23 cats, of which 16 (70%) survived and were discharged. There were no significant differences between survivors and nonsurvivors in regard to heart rate, age, rectal temperature, serum lactate concentration, WBC count, PCV, blood glucose concentration, or serum albumin concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that clinicopathologic abnormalities and outcome in cats with septic peritonitis are similar to those reported for dogs. However, certain features may be unique, including an absence of signs of pain during abdominal palpation, relative bradycardia, and apparent spontaneous peritonitis in some cats.     

Optimal Testing for Thyroid Hormone Concentration after Treatment with Methimazole in Healthy and Hyperthyroid Cats

Background: Methimazole suppresses thyroid hormone synthesis and is commonly used to treat feline hyperthyroidism. The degree of variation in thyroid hormone concentrations 24 hours after administration of methimazole and optimal time for blood sampling to monitor therapeutic efficacy have not been determined.
Objective: To assess thyroid hormone concentration variation in serum of normal and hyperthyroid cats after administration of methimazole.
Animals: Four healthy cats and 889 retrospectively acquired feline thyroid hormone profiles.
Methods: Crossover and retrospective studies . In the crossover study, healthy cats were treated with increasing doses of oral methimazole until steady state of thyroid suppression was achieved. Thyroid hormones and thyroid stimulating hormone (TSH) were serially and randomly monitored after methimazole. Paired t -tests and a 3-factor analysis of variance were used to determine differences between thyroid hormone concentrations in treated and untreated cats in the crossover study. Thyroid profiles from methimazole-treated hyperthyroid cats were retrieved from the Diagnostic Center for Population and Animal Health database and reviewed. Linear regression analysis evaluated relationships of dosage (mg/kg), dosing interval (q24h versus q12h), and time after methimazole to all thyroid hormone concentrations.
Results: All serum concentrations of thyroid hormones were significantly suppressed and TSH was significantly increased for 24 hours after administration of oral methimazole in healthy cats ( P < .005). In hyperthyroid cats, there were no significant relationships between thyroid hormone concentrations and time postpill or dosing interval.
Conclusions: Timing of blood sampling after oral methimazole administration does not appear to be a significant factor when assessing response to methimazole treatment.     

Tissue sources of serum alkaline phosphatase in 34 hyperthyroid cats: a qualitative and quantitative study

The concentration of serum alkaline phosphatase (SALP) is commonly elevated in hyperthyroid cats. Agarose gel electrophoresis, in tris -barbital-sodium barbital buffer, with and without the separation enhancer neuraminidase, was used to investigate the sources of the constituent isoenzymes of SALP in serum samples from 34 hyperthyroid cats, comparing them to sera from five healthy cats and to tissue homogenates from liver, kidney, bone and duodenum. Contrary to previous reports, treatment of serum with neuraminidase made differentiation of the various isoenzymes more difficult to achieve. A single band corresponding to the liver isoenzyme (LALP) was found in 100 per cent of healthy cats. Eighty-eight per cent of the hyperthyroid cats showed two bands, corresponding to the liver and bone (BALP) isoenzymes while 12 per cent showed a LALP band alone. In hyperthyroid cats, there was a significant correlation between the serum L-thyroxine concentrations and the SALP concentrations. These findings suggest pathological changes in both bone and liver in most cases of feline thyrotoxicosis.     

The HemoCue® for point-of-care hemoglobin measurement and packed cell volume estimation in cats

Objective: To determine conversion formulas so that values from the HemoCue^® hemoglobinometer (Hb_HQ) could be equated to hemoglobin concentrations measured by the gold‐standard cyanomethemoglobin (Hb_CY) method and used for estimation of packed cell volume (PCV) in cats. Study design: Prospective, in vitro. Animals: Twelve healthy, adult, client‐owned cats. Interventions: The PCV of 12 parent blood samples was manipulated between ～3 and ～80% by removing or adding autologous plasma. Hemoglobin was measured by the Hb_CY method at a university clinical pathology laboratory and by the azidemethemoglobin method in a Hb_HQ. PCV was determined by micro‐centrifugation. Measurements and main results: Hemoglobin varied from 1–26 g/dL. Repeated‐measures regression of Hb_CY on Hb_HQ demonstrated that the Y‐intercept was not different from zero. When the regression was repeated, forcing the line through the origin the coefficient for converting Hb_HQ to Hb_CY was not significantly different from 1.0 (adjusted R²=99.7%). The conversion formula was Hb_CY=Hb_HQ. Using similar methods, the conversion formula for estimating PCV was PCV=3.1 Hb_HQ (adjusted R²=99.8%). Conclusion: Hemoglobin concentration measured by the HemoCue^® was indistinguishable from the (Hb_CY) method in feline blood over a wide range of hemoglobin concentrations. This study demonstrates that in cats PCV=3.1Hb_HQ. Clinical relevance: The HemoCue^® is useful for point‐of‐care hemoglobinometry and for estimating PCV in cats.     

Glycemic Status and Predictors of Relapse for Diabetic Cats in Remission

Background

It is unknown if diabetic cats in remission have persistent abnormalities of glucose metabolism and should be considered prediabetic, or have normal glucose tolerance.

Objective

To characterize glycemic status of diabetic cats in remission and to determine predictors of relapse.

Animals

A total of 21 cats in diabetic remission and 28 healthy control cats.

Methods

At a median of 107 days after remission, screening blood glucose concentration was measured on entry to the clinic. After a 24‐hour fast in hospital, fasting blood glucose, fructosamine and feline pancreatic lipase concentrations were measured, and 3 hours later, a simplified IV glucose tolerance test (1 g glucose/kg) performed. Twenty cats were monitored for relapse for at least 9 months.

Results

Of the 21 cats in remission, 19% (4/21) had impaired fasting glucose concentration and 76% (16/21) had impaired glucose tolerance. Of cats followed up for 9 months after testing, 30% (6/20) had relapsed and required insulin treatment. Fasting blood glucose concentration ≥7.5 mmol/L (≥135 mg/dL) (odds ratio [OR] = 12.8) and severely impaired glucose tolerance (≥5 hours to return to <6.5 mmol/L or <117 mg/dL; OR = 15.2) were significantly associated with relapse. Blood glucose concentration >14 mmol/L; 252 mg/dL at 3 hours was significantly associated with relapse (OR = 10.1).

Conclusion and Clinical Importance

Most cats in diabetic remission have impaired glucose tolerance and a minority have impaired fasting glucose concentration and should be considered prediabetic. More severe glucose intolerance and impaired fasting glucose concentration are predictors of relapse. Ongoing glucose monitoring of diabetic cats in remission is recommended.