Search Results

Abstract

Objective—To determine the effect of administration of commercially available sodium bicarbonate (NaHCO₃) on carbon 13 (¹³C) isotopic enrichment of carbon dioxide (CO₂) in serum of horses.

Animals—7 healthy Thoroughbreds.

Procedure—Sodium bicarbonate (450 g) was administered via nasogastric intubation to horses. Horses had been fed a diet obtained from the same source and had access to water from the same source for 3 months before the study. Blood samples were collected immediately before and at 2, 4, 6, and 24 hours after administration of NaHCO₃. The concentration of total CO₂ in serum was measured by use of a commercial analyzer. The ¹³C enrichment of bicarbonate in serum was estimated by measurement of ¹³C enrichment of CO₂ released by acidification of the serum. The ¹³C enrichment of commercially available NaHCO₃ was also determined and compared with that of CO₂ in serum of horses before administration of NaHCO₃.

Results—Commercially available NaHCO₃ had a ¹³C enrichment significantly different from that of carbon dioxide in serum of horses before treatment. Administration of NaHCO₃ increased the concentration of total CO₂ from pretreatment values. The ¹³C enrichment of CO₂ in serum was only transiently and minimally affected after administration of NaHCO₃.

Conclusions and Clinical Relevance—Administration of NaHCO₃ was not detected by measuring ¹³C enrichment of CO₂ in serum of horses. ( Am J Vet Res 2004;65:307–310)

Abstract

Objective—To determine components of the increase in oxygen consumption (O₂) 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 acidbase state (protein, electrolytes, and PCO₂).

Results—Increased O₂ 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⁻]_v 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 O₂ 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. (Am J Vet Res 2000;61:1325–1332)

Abstract

Objective—To evaluate plasma epinephrine and norepinephrine concentrations and serum cortisol concentration in horses with colic and assess the relationship of these variables with clinical signs, routinely measured clinicopathologic variables, and outcome in affected horses.

Design—Prospective observational study.

Animals—35 horses with colic.

Procedure—Blood samples were collected within 30 minutes of arrival at the veterinary hospital from horses referred because of colic. Plasma and serum samples were analyzed for cortisol, epinephrine, norepinephrine, lactate, and electrolyte concentrations and acid-base variables. Heart rate at admission and outcome (survival or nonsurvival) were recorded. Univariate logistic regression was used to calculate crude (unadjusted) odds ratios and 95% confidence intervals.

Results—Of the 35 horses with colic, 26 survived. Higher plasma epinephrine, plasma lactate, and serum cortisol concentrations were significantly associated with increased risk of nonsurvival, but plasma norepinephrine concentration was not associated with outcome. Plasma epinephrine concentration was significantly correlated with heart rate (r = 0.68), plasma lactate concentration (r = 0.87), blood pH (r = –0.83), anion gap (r = 0.74), and base excess (r = –0.81).

Conclusions and Clinical Relevance—The risk of death appears to be greater in colic-affected horses with high circulating concentrations of epinephrine and cortisol. The correlation of epinephrine with other biochemical markers of illness severity and with heart rate indicates that the degree of sympathetic activation in horses with colic can be inferred from routinely measured variables. (J Am Vet Med Assoc 2005;227:276–280)

Abstract

Objective—To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval.

Animals—100 sled dogs in Alaska.

Procedure—Dogs were examined in early September (before training) and late March (after training). During the interim, dogs trained by pulling a sled with a musher (mean, 20 km/d). Standard and signal-averaged ECG were obtained before and after training.

Results—Endurance training significantly increased mean QRS duration by 4.4 milliseconds for standard ECG (mean ± SEM; 62.3 ± 0.7 to 66.7 ± 0.6 milliseconds) and 4.3 milliseconds for signal-averaged ECG (51.5 ± 0.7 to 55.8 ± 0.6 milliseconds) without changing body weight. Increase in QRS duration corresponded to a calculated increase in heart weight (standard ECG, 23%; signal-averaged ECG, 27%). Signal-averaged QRS duration was correlated with echocardiographically determined left ventricular diastolic diameter for the X orthogonal lead (r = +0.41), Y orthogonal lead (r = +0.33), and vector (r = +0.35). Training also increased QT interval (234 ± 2 to 249 ± 2 milliseconds) and R-wave amplitude in leads II and rV₂, increased peak-to-peak voltage and S-wave amplitude in the Y orthogonal lead, and decreased Q-wave amplitude in the Y orthogonal lead.

Conclusions and Clinical Relevance—Electrocardiographic changes reflected physiologic cardiac hypertrophy in these canine athletes in response to repetitive endurance exercise. The QRS duration increases in response to endurance exercise training and, therefore, may be of use in predicting performance in endurance activities. (Am J Vet Res 2000;61:582–588)

Abstract

Objective—To compare effects of low and high intensity warm-up exercise on oxygen consumption (O₂) and carbon dioxide production (CO₂ ) in horses. Animals—6 moderately conditioned adult Standardbreds.

Procedures—Horses ran for 2 minutes at 115% of maximum oxygen consumption (O₂max), 5 minutes after each of the following periods: no warm-up (NoWU); 10 minutes at 50% of O₂max (LoWU); or 7 minutes at 50% O₂max followed by 45-second intervals at 80, 90, and 100% O₂max (HiWU). Oxygen consumption and CO₂ were measured during exercise, and kinetics of O₂ and CO₂ were calculated. Accumulated O₂ deficit was also calculated.

Results—For both warm-up trials, the time constant for the rapid exponential increase in O₂ was 30% lower than for NoWU. Similarly, the rate of increase in CO₂ was 23% faster in LoWU and HiWU than in NoWU. Peak values for O₂ achieved during the highspeed test were not significantly different among trials (LoWU, 150.2 ± 3.2 ml/kg/min; HiWU, 151.2 ± 4.2 ml/kg/min; NoWU, 145.1 ± 4.1 ml/kg/min). However, accumulated O₂ deficit (ml of O₂ equivalents/kg) was significantly lower during LoWU (65.3 ± 5.1) and HiWU (63.4 ± 3.9) than during NoWU (82.1 ± 7.3).

Conclusions and Clinical Relevance—Both the lowand high-intensity warm-up, completed 5 minutes before the start of high-intensity exercise, accelerated the kinetics of O₂ and CO₂ and decreased accumulated O2 deficit during 2 minutes of intense exertion in horses that were moderately conditioned. (Am J Vet Res 2000;61:638–645)

Abstract

Objective—To determine the effect of a tongue-tie on upper airway mechanics in clinically normal horses exercising on a treadmill following sternothyrohyoid myectomy.

Animals—6 Standardbreds.

Procedure—Upper airway mechanics were measured with horses exercising on a treadmill at 5, 8, and 10 m/s 4 weeks after a sternothyrohyoid myectomy was performed. Pharyngeal and tracheal inspiratory and expiratory pressures were measured by use of transnasal pharyngeal and tracheal catheters connected to differential pressure transducers. Horses were fitted with a facemask and airflow was measured by use of a pneumotachograph. Horses underwent a standardized exercise protocol on a treadmill at 5, 8, and 10 m/s with and without a tongue-tie in a randomized cross-over design. Inspiratory and expiratory airflow, tracheal pressure, and pharyngeal pressure were measured, and inspiratory and expiratory resistances were calculated.

Results—We were unable to detect an effect of a tongue-tie on any of the respiratory variables measured.

Conclusions and Clinical Relevance—Results indicate that a tongue-tie does not alter upper airway mechanics following sternothyrohyoid myectomy in clinically normal horses during exercise. (Am J Vet Res 2001;62:779–782)

Abstract

Objective—To characterize insulin-sensitive glucose-transporter (GLUT-4) protein in equine tissues and determine effects of exercise and glucose administration on content of GLUT-4 protein in equine skeletal muscle.

Sample Population—Tissue samples from 9 horses.

Procedure—Western blot analyses were performed on crude membrane preparations of equine tissues to characterize GLUT-4. In a crossover, randomized study, horses were strenuously exercised for 3 consecutive days and then administered 13.5% glucose or isotonic saline (0.9% NaCl; control) solution, IV, at similar infusion rates for 12.1 hours. Samples were collected from the middle gluteal muscle before and after exercise and 10.1 hours after completion of an infusion and used for measurements of glycogen concentration and total content of GLUT-4 protein.

Results—Immunoblot analyses detected specifically immunoreactive bands for GLUT-4 in insulin-sensitive tissues. Content of GLUT-4 protein in skeletal muscle increased significantly by 27.3 and 12.3% 22.2 hours after exercise for control and glucose groups, respectively. Intravenous infusion of glucose resulted in a significantly higher rate of glycogenesis, compared with results for the control group (mean ± SD, 3.98 ± 0.61 and 1.47 ± 0.20 mmol/kg/h, respectively). Despite enhanced glycogenesis, we did not detect an increase in content of GLUT-4 protein after glucose infusion, compared with values after exercise.

Conclusions and Clinical Relevance—GLUT-4 protein was expressed in equine skeletal and cardiac muscles. Exercise increased total content of GLUT-4 protein in skeletal muscle, and replenishment of muscle glycogen stores after glucose infusion attenuated the exercise-induced increase in the content of GLUT-4 protein in equine skeletal muscle. (Am J Vet Res 2003;64:1500–1506)

Abstract

Objective—To evaluate the efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage (EIPH) in Thoroughbred racehorses under typical racing conditions.

Design—Randomized, placebo-controlled, blinded, crossover field trial.

Animals—167 Thoroughbred racehorses.

Procedures—Horses were allocated to race fields of 9 to 16 horses each and raced twice, 1 week apart, with each of the 2 races consisting of the same race field and distance. Each horse received furosemide (500 mg, IV) before one race and a placebo (saline solution) before the other, with the order of treatments randomly determined. Severity of EIPH was scored on a scale from 0 to 4 after each race by means of tracheobronchoscopy. Data were analyzed by means of various methods of multivariable logistic regression.

Results—Horses were substantially more likely to develop EIPH (severity score ≥ 1; odds ratio, 3.3 to 4.4) or moderate to severe EIPH (severity score ≥ 2; odds ratio, 6.9 to 11.0) following administration of saline solution than following administration of furosemide. In addition, 81 of the 120 (67.5%) horses that had EIPH after administration of saline solution had a reduction in EIPH severity score of at least 1 when treated with furosemide.

Conclusions and Clinical Relevance—Results indicated that prerace administration of furosemide decreased the incidence and severity of EIPH in Thoroughbreds racing under typical conditions in South Africa.

Abstract

Objective—To determine clinical and clinicopathologic abnormalities in horses administered a blood transfusion and evaluate effects of blood transfusion on these variables.

Design—Retrospective case series.

Animals—31 adult horses that received ≥ 1 blood transfusion.

Procedures—Medical records of horses receiving a blood transfusion were reviewed to obtain clinical findings, laboratory test results before and after transfusion, adjunctive treatments, transfusion type and volume, response to transfusion, results of donor-recipient compatibility testing, adverse reactions, and outcome.

Results—31 horses received 44 transfusions for hemorrhagic anemia (HG; n = 18 horses), hemolytic anemia (HL; 8), or anemia attributable to erythropoietic failure (EF; 5). Tachycardia and tachypnea were detected in 31 of 31 (100%) and 22 of 31 (71%) horses, respectively, before transfusion. The PCV and hemoglobin concentration were less than the reference range in 11 of 18 horses with HG, 8 of 8 horses with HL, and 5 of 5 horses with EF. Hyperlactatemia was detected in 16 of 17 recorded values before transfusion. Heart rate, respiratory rate, and PCV improved after transfusion, with differences among the types of anemia. Seventeen (54%) horses were discharged, 9 (29%) were euthanized, and 5 (16%) died of natural causes. Adverse reactions were evident during 7 of 44 (16%) transfusions, varying from urticarial reactions to anaphylactic shock.

Conclusions and Clinical Relevance—Abnormalities in clinical and clinicopathologic variables differed depending on the type of anemia. Colic, cold extremities, signs of depression, lethargy, tachycardia, tachypnea, low PCV, low hemoglobin concentration, and hyperlactatemia were commonly detected before transfusion and resolved after transfusion.

Abstract

Objective—To determine serum antibody titers against canine distemper virus (CDV), canine adenovirus type II (CAV-2), and canine parvovirus (CPV) in trained sled dogs prior to and after completion of a long-distance race.

Design—Prospective cohort study.

Animals—195 Alaskan sled dogs (from 18 kennels) that participated in the 2006 Iditarod Trail Race.

Procedures—All 1,323 dogs participating in the race had been vaccinated against the 3 viruses at 19 to 286 days prior to initial blood sample collection (obtained within the month preceding the race). Within 12 hours of race completion, blood samples were collected from 195 dogs (convenience sample) and matched with each dog's prerace sample. Serum antibody titers (90% confidence intervals [CIs]) were determined via serum neutralization assays.

Results—After racing, geometric mean titers against CDV and CPV were significantly higher (2,495 [90% CI, 321 to 16,384] and 6,323 [90% CI, 512 to 32,768], respectively) than prerace values (82 [90% CI, 11 to 362] and 166 [90% CI, 32 to 1,024], respectively). Sixty-one of 194 (31.4%) dogs had t 4-fold increases in anti-CPV antibody titers after racing. Prerace serum antibody titers against CDV, CPV, and CAV-2 varied significantly by sled team but were not associated with time since vaccination.

Conclusions and Clinical Relevance—Postrace increases in serum anti-CDV and anti-CPV antibody titer might reflect exposure of dogs to these agents immediately before or during racing. Dogs had no clinical signs of CDV-, CAV-2-, or CPV-associated disease; therefore, the clinical importance of these titer changes is uncertain.