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)
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
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)
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)
Objective—To determine the effect of endurance
training on QRS duration, QRS-wave amplitude, and
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
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)
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)
Objective—To determine the effect of a tongue-tie on
upper airway mechanics in clinically normal horses
exercising on a treadmill following sternothyrohyoid
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
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
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)
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.
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.
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.