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)