Biomedical subjects

C W Kohn

Publications and source records attributed to C W Kohn.

At least 19 recordsLinked to original sources

PubMed2006

Report of the equine herpesvirus-1 Havermeyer Workshop, San Gimignano, Tuscany, June 2004.

Amongst the infectious diseases that threaten equine health, herpesviral infections remain a world wide cause of serious morbidity and mortality. Equine herpesvirus-1 infection is the most important pathogen, causing an array of disorders including epidemic respiratory disease abortion, neonatal foal death, myeloencephalopathy and chorioretinopathy. Despite intense scientific investigation, extensive use of vaccination, and established codes of practice for control of disease outbreaks, infection and disease remain common. While equine herpesvirus-1 infection remains a daunting challenge for immunoprophylaxis, many critical advances in equine immunology have resulted in studies of this virus, particularly related to MHC-restricted cytotoxicity in the horse. A workshop was convened in San Gimignano, Tuscany, Italy in June 2004, to bring together clinical and basic researchers in the field of equine herpesvirus-1 study to discuss the latest advances and future prospects for improving our understanding of these diseases, and equine immunity to herpesviral infection. This report highlights the new information that was the focus of this workshop, and is intended to summarize this material and identify the critical questions in the field.

Animals↗

PubMed2003

Parathyroid hormone (PTH) secretion, PTH mRNA and calcium-sensing receptor mRNA expression in equine parathyroid cells, and effects of interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha on equine parathyroid cell function.

Parathyroid hormone (PTH) is secreted by the chief cells of the parathyroid gland in response to changes in ionized calcium (Ca(2+)) concentrations. In this study, we measured PTH secretion, and PTH mRNA and calcium-sensing receptor (CaR) mRNA expression by equine parathyroid chief cells in vitro. We also evaluated the effects of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha on PTH secretion, and PTH and CaR mRNA expression. The relationship between PTH and Ca(2+) was inversely related. PTH secretion decreased from 100% (day 0) to 13% (day 30). PTH mRNA expression declined from 100% (day 0) to 25% (day 30). CaR mRNA decreased from 100% (day 0) to 16% (day 30). Chief cells exposed to high (2.0 mM) Ca(2+) concentrations had a lower PTH mRNA expression compared with low Ca(2+) concentrations. Ca(2+) concentrations had no effect on CaR mRNA expression. The inhibitory effect of high Ca(2+) concentrations on PTH secretion also declined over time. After day 10, there was no significant difference in PTH secretion between low and high Ca(2+ )concentrations. IL-1beta decreased both PTH secretion (75%) and PTH mRNA expression (73%), and resulted in a significant overexpression of CaR mRNA (up to 142%). The effects of IL-1beta were blocked by an IL-1 receptor antagonist. IL-1beta decreased the Ca(2+) set-point from 1.4 mM to 1.2 mM. IL-6 decreased PTH secretion (74%), but had no effect on PTH and CaR mRNA expression. TNF-alpha had no effect on PTH secretion, and PTH and CaR mRNA expression. In summary, the decreased responsiveness of parathyroid cells to Ca(2+) from 0 to 30 days can be explained, in part, by the reduced CaR expression. IL-1beta and IL-6 but not TNF-alpha affected parathyroid function in vitro and may be important in influencing PTH secretion in the septic horse.

Animals↗

PubMed2002

Chronic pulmonary disease with radiographic interstitial opacity (interstitial pneumonia) in foals.

Twelve foals, age 3-9 months, examined at The Ohio State University Veterinary Teaching Hospital between 1995 and 2000 were diagnosed with chronic pulmonary disease associated with marked interstitial opacity on radiographic examination. The most characteristic features were a history of respiratory disease of 1-3 months duration, marked clinical signs of respiratory disease, failure to yield a consistent pathogen from tracheobronchial aspirates and a predominantly interstitial pattern on thoracic radiographs. We attributed these signs to chronic interstitial pneumonia. Foals were treated with broad spectrum antimicrobial and corticosteroid drugs. All 12 foals were discharged alive from hospital and, of the 10 available for follow-up, all were disease-free and performing to expectation 5 months to 5 years after discharge. We conclude that chronic interstitial pneumonia, occuring in foals, is associated with a good prognosis and that corticosteroid therapy may be useful in its treatment.

Adrenal Cortex Hormones↗

PubMed2001

Intradermal testing in healthy horses and horses with chronic obstructive pulmonary disease, recurrent urticaria, or allergic dermatitis.

OBJECTIVE: To compare responses to a variety of intradermally injected allergens among healthy horses and horses with chronic obstructive pulmonary disease (COPD), recurrent urticaria (RU), and atopic dermatitis-insect hypersensitivity (allergic dermatitis [AD]). DESIGN: Case-control study. ANIMALS: 86 horses. PROCEDURE: Results of intradermal testing for horses with COPD, RU, or AD were compared with results for healthy horses. RESULTS: Compared with healthy horses, horses with COPD, RU, and AD were significantly more likely to have positive (> or = 3+) reactions to intradermal allergens (molds, weeds, trees, grasses-crops, and insects) 30 minutes (immediate reaction), 4 hours (late-phase reactions), and 24 hours (delayed-phase reactions) after exposure. In addition, diseased horses reacted to a significantly higher number of allergens in each allergen group than did healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE: Reactions to individual allergens should not be used to determine that horses have hypersensitivity. Overall patterns of reactivity to intradermal allergens may be helpful in management when used in conjunction with a compatible history and evidence of potential exposure to allergens in horses with conditions associated with hypersensitivity to environmental allergens.

Allergens↗

PubMed2001

Comparison of immediate intradermal test reactivity with serum IgE quantitation by use of a radioallergosorbent test and two ELISA in horses with and without atopy.

OBJECTIVE: To compare a radioallergosorbent test and 2 ELISA with intradermal testing for the determination of environmental allergen hypersensitivity in horses with and without atopic diseases. DESIGN: Prospective clinical study. ANIMALS: 10 horses with recurrent urticaria, 7 with atopic dermatitis, 16 with chronic obstructive pulmonary disease, and 22 without atopy. PROCEDURE: History, physical examination, hemogram, serum biochemical analyses, bronchoalveolar lavage, and an intradermal test (used as the criterion standard) with a regional panel of 73 allergens were performed in all horses. Serum was analyzed by use of the 3 in vitro assays of allergen-specific IgE. RESULTS: An ELISA based on the alpha chain of the high-affinity IgE receptor, the Fcepsilon receptor immunoglobin epsilon chain (FcepsilonRIalpha) for IgE, had the overall highest kappa statistic (0.238), positive predictive value (49%), and negative predictive value (78%). Overall agreement between the FcepsilonRIalpha-based ELISA and the intradermal test was fair. The highest kappa statistic was obtained by the FcepsilonRIalpha-based ELISA in horses with atopic dermatitis (0.330). Kappa statistics for the radioallergosorbent test and a polyclonal antibody-based ELISA agreed slightly with that of the intradermal test at best. CONCLUSIONS AND CLINICAL RELEVANCE: None of the 3 serum allergy tests reliably detected allergen hypersensitivity, compared with the intradermal test. The FcepsilonRIalpha-based ELISA performed significantly better overall than the other 2 tests. Low sensitivity of all 3 assays indicates the need for continued study to elucidate a more sensitive test for the determination of potentially pathogenic allergens in horses.

Animals↗

PubMed2001

Results of intradermal tests in horses without atopy and horses with chronic obstructive pulmonary disease.

OBJECTIVE: To compare results of intradermal tests (IDT), conducted using environmental allergens, in horses without atopy and horses with chronic obstructive pulmonary disease (COPD). ANIMALS: 38 horses (22 horses without atopy and 16 horses with COPD). PROCEDURE: All horses were examined (physical examination, hematologic examination, serum biochemical analyses, examination of bronchoalveolar lavage fluid). An IDT was conducted, using a full panel of 73 allergens consisting of grasses, weeds, trees, molds, and insects. Results of the IDT were evaluated 30 minutes and 4, 6, and 24 hours after injection of allergens. Horses without atopy were euthanatized, and gross and histologic changes of lung parenchyma were assessed. RESULTS: Horses without atopy had a greater number of positive immediate and late-phase reactions than did horses with COPD. Horses with COPD did not have a significantly greater number of positive reactions than horses without atopy at any time period for any allergen group (grasses, weeds, trees, molds, and insects). CONCLUSIONS AND CLINICAL RELEVANCE: Positive results of IDT document allergen-specific hypersensitivity but do not necessarily distinguish clinically relevant reactions from subclinical reactivity in horses with COPD. Interpreting the clinical relevance of results of IDT requires a thorough knowledge of the medical history, physical examination findings, and environment of each animal.

Allergens↗

PubMed2001

Comparison of serum parathyroid hormone and ionized calcium and magnesium concentrations and fractional urinary clearance of calcium and phosphorus in healthy horses and horses with enterocolitis.

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.

Animals↗

PubMed2000

Analysis of risk factors for the development of equine protozoal myeloencephalitis in horses.

OBJECTIVE: To investigate risk factors for development of equine protozoal myeloencephalitis (EPM) in horses. DESIGN: Case-control study. ANIMALS: 251 horses admitted to The Ohio State University Veterinary Teaching Hospital from 1992 to 1995. PROCEDURE: On the basis of clinical signs of neurologic disease and detection of antibody to Sarcocystis neurona or S neurona DNA in cerebrospinal fluid, a diagnosis of EPM was made for 251 horses. Two contemporaneous series of control horses were selected from horses admitted to the hospital. One control series (n = 225) consisted of horses with diseases of the neurologic system other than EPM (neurologic control horses), and the other consisted of 251 horses admitted for reasons other than nervous system diseases (nonneurologic control horses). Data were obtained from hospital records and telephone conversations. Risk factors associated with disease status were analyzed, using multivariable logistic regression. RESULTS: Horses ranged from 1 day to 30 years old (mean +/- SD, 5.7 +/- 5.2 years). Risk factors associated with an increased risk of developing EPM included age, season of admission, prior diagnosis of EPM on the premises, opossums on premises, health events prior to admission, and racing or showing as a primary use. Factors associated with a reduced risk of developing EPM included protection of feed from wildlife and proximity of a creek or river to the premises where the horse resided. CONCLUSIONS AND CLINICAL RELEVANCE: Development of EPM was associated with a number of management-related factors that can be altered to decrease the risk for the disease.

Animals↗

PubMed2000

Evaluation of risk factors associated with clinical improvement and survival of horses with equine protozoal myeloencephalitis.

OBJECTIVE: To investigate risk factors for use in predicting clinical improvement and survival of horses with equine protozoal myeloencephalitis (EPM). DESIGN: Longitudinal epidemiologic study. ANIMALS: 251 horses with EPM. PROCEDURE: Between 1992 and 1995, 251 horses with EPM were admitted to our facility. A diagnosis of EPM was made on the basis of neurologic abnormalities and detection of antibody to Sarcocystis neurona or S neurona DNA in CSF. Data were obtained from hospital records and through telephone follow-up interviews. Factors associated with clinical improvement and survival were analyzed, using multivariable logistic regression. RESULTS: The likelihood of clinical improvement after diagnosis of EPM was lower in horses used for breeding and pleasure activities. Treatment for EPM increased the probability that a horse would have clinical improvement. The likelihood of survival among horses with EPM was lower among horses with more severe clinical signs and higher among horses that improved after EPM was diagnosed. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of horses with EPM is indicated in most situations; however, severity of clinical signs should be taken into consideration when making treatment decisions. Response to treatment is an important indicator of survival.

Animals↗

PubMed2000

Determinants of oxygen delivery and hemoglobin saturation during incremental exercise in horses.

OBJECTIVE: To determine components of the increase in oxygen consumption (VO2) and evaluate determinants of hemoglobin saturation (SO2) during incremental treadmill exercise in unfit horses. ANIMALS: 7 unfit adult mares. PROCEDURES: Horses performed 1 preliminary exercise test (EXT) and 2 experimental EXT. Arterial and mixed venous blood samples and hemodynamic measurements were taken during the last 30 seconds of each step of the GXT to measure PO2, hemoglobin concentration ([Hb]), SO2, and determinants of acid-base state (protein, electrolytes, and PCO2). RESULTS: Increased VO2 during exercise was facilitated by significant increases in cardiac output (CO), [Hb], and widening of the arteriovenous difference in O2. Arterial and venous pH, PaO2, and PvO2 decreased during exercise. Arterial PCO2, bicarbonate ([HCO3-])a, and [HCO3-] decreased significantly, whereas PVCO2 and increased. Arterial and venous sodium concentration, potassium concentration, strong ion difference, and venous lactate concentration all increased significantly during exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in CO, [Hb], and O2 extraction contributed equally to increased VO2 during exercise. Higher PCO2 did not provide an independent contribution to shift in the oxyhemoglobin dissociation curve (OCD) in venous blood. However, lower PaCO2 shifted the curve leftward, facilitating O2 loading. The shift of ODC resulted in minimal effect on O2 extraction because of convergence of the ODC at lower values of PO2. Decreased pH appeared responsible for the rightward shift of the ODC, which may be necessary to allow maximal O2 extraction at high blood flows achieved during exercise.

Acid-Base Equilibrium↗

PubMed1999

Thoracic and abdominal blastomycosis in a horse.

A 5-year-old Quarter Horse mare was examined because of lethargy, fever, and weight loss of 1 month's duration. Thoracic auscultation revealed decreased lung sounds cranioventrally. Thoracic ultrasonography revealed bilateral anechoic areas with hyperechoic strands, consistent with pleural effusion and fibrin tags. A large amount of free fluid was evident during abdominal ultrasonography. Abnormalities included anemia, hyperproteinemia, hyperglobulinemia, hyperfibrinogenemia, and hypoalbuminemia. Thoracic radiography revealed alveolar infiltrates in the cranial and caudoventral lung fields. A cavitary mass, consistent with an abscess, could be seen caudodorsal to the crura of the diaphragm. Ultrasonographic evaluation of this area revealed a hypoechoic mass with septations. Bilateral thoracocentesis was performed. Bacterial culture of the pleural fluid did not yield growth, but Blastomyces dermatitidis was isolated from pleural fluid, abdominal fluid, and an aspirate of the abscess. The mare was euthanatized, and a diagnosis of thoracic and abdominal blastomycosis was confirmed at necropsy.

Animals↗

PubMed1999

Contributions of equine exercise physiology research to the success of the 1996 Equestrian Olympic Games: a review.

Following public concern about the weather conditions for the 1996 Olympic Games in Atlanta an international research programme was initiated. The primary objective of this effort was to identify strategies for ensuring welfare of horses competing in the heat. Field observations of horses during the endurance test of 3-day events in Europe, Canada, and the USA characterised the work effort of this form of competition; laboratory treadmill studies assessed limitations to performance of heat and humidity, explored the relationships of thermoregulatory demands to the phases of the competition and documented fluid and electrolyte losses. Estimates of energy expenditure and heat production during the endurance test were made. Strategies for facilitating heat dissipation were also studied in depth. Assessment of the effect of environmental conditions was based upon intensive climate monitoring using a modification of the Wet Bulb Globe Temperature index. Studies of heat acclimation provided a basis for recommendation of acclimatization times for horses before the Games. The results of all these studies guided the management of equine athletes at the 1996 Olympic Games and significantly advanced knowledge of thermoregulation in competitive horses.

Animals↗

PubMed1999

Effect of ambient temperature and humidity on pulmonary artery temperature of exercising horses.

Six healthy Thoroughbred mares were trained to run on a high-speed treadmill and were conditioned for approximately 5 weeks. Each horse performed 6 identical standardised exercise tests (SET) 5 to 7 days apart. Each SET was performed under different ambient laboratory conditions: low temperature/low humidity (LL) 20.2 degrees +/- 0.6 degree C, 53.6 +/- 4.1%; low temperature/high humidity (LH) 19.7 +/- 0.6 degrees C, 86.7 +/- 4.2%; medium temperature/low humidity (ML) 24.6 +/- 0.2 degrees C, 58.7 +/- 3.7%; medium temperature/high humidity (MH) 24.7 +/- 0.3 degrees C, 87.5 +/- 1.4%; high temperature/low humidity (HL) 31.1 +/- 0.6 degrees C, 41.6 +/- 3.5%; and high temperature/high humidity (HH) 30.6 +/- 0.2 degrees C, 84.4 +/- 3.6%. Horses completed the 46 min SET, became fatigued or exercise was terminated when a pulmonary artery temperature (PAT) of 41.5 degrees C was reached. During a 30 min recovery period, horses stood quietly on the treadmill. Only one trial was terminated due to fatigue; in all other trials horses completed the 46 min SET or the trial was terminated when PAT = 41.5 degrees C. The relationships among run time (min) or PAT (degree C), ambient temperature and % relative humidity were defined by multiple linear regression analysis. Run time (min) = 90.9 - (1.39 x ambient temperature degree C) - (0.236 x relative humidity %). Approximately 54% of the variation in run times was explained by variation in environmental conditions, indicating that ambient temperature and humidity contribute substantially to the rate of rise in PAT. Run times to a PAT of 41.5 degrees C were significantly shorter (P < 0.000001) in HH than in other groups during the SET. Approximately 63% of the variation in PAT at the end of exercise was due to ambient temperature and humidity. In general, the longer the exercise time, the better the correlation among PAT, ambient temperature and relative humidity. Rectal temperature increased significantly (P < 0.0001) during the recovery period only in horses in the HH group, indicating that heat dissipation during recovery may have been impaired by environmental conditions. This study demonstrates that hot humid conditions result in more rapid rate of rise in PAT for horses undertaking identical exercise tests.

Animals↗

PubMed1999

Evaluation of washing with cold water to facilitate heat dissipation in horses exercised in hot, humid conditions.

OBJECTIVE: To determine whether body temperature of horses exercised in hot, humid conditions and then repetitively washed with cold water will decrease more rapidly than that of horses that are not washed, and to determine whether washing with cold water has deleterious effects on horses. ANIMALS: 5 physically fit Thoroughbred mares, 3 to 10 years old. PROCEDURES: Horses were exercised on a high-speed treadmill in hot (31.1+/-0.3 C), humid (relative humidity, 77.7+/-2%) conditions. Exercise was terminated when pulmonary artery temperature reached 41.5 C. Values for pulmonary artery, rectal, and left gluteal muscle temperatures were compared throughout a 30-minute recovery period after exercise during which horses stood quietly (passive cooling) or were cooled (active cooling) by repeated applications of cold (1 5.6+/-0.6 C) water. RESULTS: Pulmonary artery temperature was significantly less for actively cooled horses, compared with passively cooled horses 4 minutes into the recovery period. Left gluteal muscle temperature decreased significantly in actively cooled, but not passively cooled, horses during the recovery period. Heart rate and rectal temperature were significantly less for actively cooled horses by 15 minutes of the recovery period. Cooling technique did not effect hydration status, muscle health, or serum electrolyte concentrations. Active cooling did not cause obvious adverse effects. CONCLUSION AND CLINICAL RELEVANCE: Active cooling by washing with cold water is a safe, effective means for facilitating heat dissipation of horses after exercise in a hot, humid environment.

Animals↗

PubMed1999

In vitro dose-dependent effects of enrofloxacin on equine articular cartilage.

OBJECTIVE: To determine whether enrofloxacin has detrimental, dose-dependent effects on equine articular cartilage in vitro. ANIMALS: Cartilage explants were developed from 6 healthy horses between 0 and 96 months old. PROCEDURE: Patellar cartilage explants were incubated in 5 concentrations of enrofloxacin (2 microg/ml, 10 microg/ml, 1,000 microg/ml, 10,000 microg/ml, and 50,000 microg/ml) for 72 hours. Proteoglycan synthesis (Na35SO4 incorporation for 24 hours), proteoglycan degradation (Na35SO4 release for 72 hours), endogenous proteoglycan content (dimethylmethlene blue assay), and total protein content were determined. Cartilage explants were evaluated by use of histomorphologic and histomorphometric techniques (toluidine blue stain) for cytologic and matrix characteristics. Quantitative data were analyzed with a one-way ANOVA to compare results among various enrofloxacin concentration groups and the control group. A general linear model was used to determine whether age had an effect. RESULT: Proteoglycan synthesis was excellent in control specimens and in specimens incubated in low concentrations of enrofloxacin (2 microg/ml and 10 microg/ml). High concentrations of enrofloxacin (> 1,000 microg/ml) effectively eliminated proteoglycan synthesis regardless of horse age. Proteoglycan degradation at low concentrations (2 microg/ml and 10 microg/ml) was not different than control. High concentrations of enrofloxacin (> 1,000 microg/ml) caused significant degradation. Different concentrations of enrofloxacin did not affect endogenous proteoglycan. High concentrations of enrofloxacin were associated with a significant increase in number of pyknotic nuclei. CONCLUSION: Concentrations of enrofloxacin that might be achieved following systemic administration did not suppress chondrocyte metabolism in vitro. High concentrations of enrofloxacin (> 1,000 microg/ml) were toxic to chondrocytes.

Analysis of Variance↗

PubMed1997

Seroprevalence of antibodies to Sarcocystis neurona in horses residing in Ohio.

OBJECTIVE: To determine the seroprevalence of serum antibodies to Sarcocystis neurona in horses residing in Ohio. DESIGN: Prevalence survey. SAMPLE POPULATION: Serum from samples from 1,056 horses. Serum was collected on every 36th sample submitted to the Ohio State Diagnostic Laboratory for testing for equine infectious anemia. PROCEDURE: Serum was frozen at -80 C and analyzed for antibodies to S neurona, using a western blot. Information regarding blood sample collection, age, breed, sex, and geographic location was recorded for each horse. Data were analyzed, using multivariable logistic regression. RESULTS: Horses of 37 breeds from 81 of Ohio's 88 counties were included in the study population. There were 481 females, 133 males, and 442 geldings ranging in age from 3 months to 27 years; > 48% were < 5.6 years old. More than 53% of samples were seropositive for antibodies to S neurona. A gender or breed effect on seroprevalence was not identified. There was a significant effect of age (P < or = 0.0001; with older horses more likely to be affected), and of location (statistical and extension districts; P = 0.02 and P = 0.03, respectively) on seroprevalence. Location effects appeared to be correlated to the number of days with temperatures below freezing (P < 0.05). CLINICAL IMPLICATIONS: The high seroprevalence of antibodies to S neurona found in the sample population emphasizes the importance of examining CSF for S neurona-specific antibodies when establishing a diagnosis of equn protozoal myeloencephalitis.

Age Distribution↗

PubMed1997

Effect of sodium bicarbonate administration on blood constituents of horses.

OBJECTIVE: To describe changes in blood constituents of horses after oral and i.v. administration of sodium bicarbonate (NaHCO3), and to determine whether the changes are dose dependent. ANIMALS: 6 adult Standardbred mares. PROCEDURE: 3 oral doses (1,500, 1,000, and 250 mg/kg of body weight) or 1 intravenous dose (250 mg/kg, 5% solution) of NaHCO3 in 3 L of water, or water (3 L orally), were given to the mares; then changes in blood constituents were measured. Access to food and water was denied during the experiment. Blood samples were collected immediately before treatment and at hourly intervals for 12 hours after treatment, and were analyzed for blood gas tensions; serum osmolality; serum sodium, potassium, chloride, and creatinine concentrations; PCV; and total solids concentration in plasma. RESULTS: All NaHCO3 treatments induced significant (P < 0.05) metabolic alkalosis, hypernatremia, hypokalemia, and hyperosmolality for at least 8 hours. In mares given the 1,500- and 1,000-mg doses of NaHCO3 orally, hypercapnia persisted for at least 12 hours, whereas hypercapnia lasted 2 hours in mares given the 250-mg dose orally or i.v. (P < 0.05). A tendency for reduction in PCV, proteins in plasma concentration, and serum concentration of chloride was observed 1 hour after i.v. administered doses of NaHCO3. CONCLUSIONS: Oral or i.v. administration of NaHCO3 (> or = 250 mg/kg) to resting horses without ad libitum access to water induces significant and persistent acid-base and electrolyte changes.

Acid-Base Equilibrium↗

PubMed1997

Effect of sodium bicarbonate administration on renal function of horses.

OBJECTIVE: To describe changes in renal function of horses after oral and i.v. administration of sodium bicarbonate (NaHCO3) and to determine whether changes are dose dependent. ANIMALS: 6 Standardbred mares. PROCEDURE: Blood and urine samples for determination of renal function were collected immediately before and at hourly intervals for 12 hours after administration of each of 3 oral doses (1,500, 1,000 and 250 mg/kg of body weight, in 3 L of water) and 1 i.v. dose (250 mg/kg, 5% solution) of NaHCO3, or water (3 L orally). RESULTS: NaHCO3 induced increases in urine flow; electrolyte-free water reabsorption; urine concentrations of sodium and bicarbonate; fractional excretion of sodium, potassium, chloride, and bicarbonate; urinary excretion and clearance of sodium and bicarbonate; urine pH and anion gap; and mean plasma concentration of antidiuretic hormone. NaHCO3 induced attenuation in reduction with time of urine excretion and clearance of potassium, chloride, and osmoles, and induced reduction in urine osmolality. Plasma aldosterone and atrial natriuretic peptide concentrations and glomerular filtration rate were not modified. CONCLUSIONS: Renal responses to NaHCO3 load emphasize conservation of plasma volume and reestablishment of acid-base balance over control of hyperosmolality by diuresis, natriuresis, and increased bicarbonaturia. These responses imply a large fluid shift from the extravascular space to the vascular compartment, which was eliminated via diuresis, thus preventing hypervolemia.

Acid-Base Equilibrium↗