Objective—To determine the cardiorespiratory effects of preemptive atropine administration in dogs sedated with medetomidine.
Design—Randomized crossover trial.
Animals—12 healthy adult dogs.
Procedures—Dogs underwent 6 treatments. Each treatment consisted of administration of atropine (0.04 mg/kg [0.018 mg/lb] of body weight, IM) or saline solution (0.9% NaCl, 1 ml, IM) and administration of medetomidine (10, 20, or 40 µg/kg [4.5, 9.1, or 18.2µg/lb], IM) 10 minutes later. Treatments were administered in random order, with a minimum of 1 week between treatments. Cardiorespiratory effects before and after atropine and medetomidine administration were assessed. Duration of lateral recumbency and quality of sedation and recovery were assessed.
Results—Bradycardia (heart rate < 60 beats/min) was seen in all dogs when saline solution was administered followed by medetomidine, and the dose of medetomidine was not associated with severity or frequency of bradycardia or second-degree heart block. However, a medetomidine dose-dependent increase in mean and diastolic blood pressures was observed, regardless of whether dogs received saline solution or atropine. Preemptive atropine administration effectively prevented bradycardia and seconddegree heart block but induced pulsus alternans and hypertension. The protective effects of atropine against bradycardia lasted 50 minutes. Blood gas values were within reference limits during all treatments and were not significantly different from baseline values. Higher doses of medetomidine resulted in a longer duration of lateral recumbency.
Conclusions and Clinical Relevance—Preemptive administration of atropine in dogs sedated with medetomidine effectively prevents bradycardia for 50 minutes but induces hypertension and pulsus alternans. ( J Am Vet Med Assoc 2001;218:52–58)
Objective—To determine sedative and cardiorespiratory
effects of IM administration of medetomidine
alone and in combination with butorphanol or ketamine
Design—Randomized, crossover study.
Animals—6 healthy adult dogs.
Procedure—Dogs were given medetomidine alone
(30 µg/kg [13.6 µg/lb] of body weight, IM), a combination
of medetomidine (30 µg/kg, IM) and butorphanol
(0.2 mg/kg [0.09 mg/lb], IM), or a combination of
medetomidine (30 µg/kg, IM) and ketamine (3 mg/kg
[1.36 mg/lb], IM). Treatments were administered in random
order with a minimum of 1 week between treatments.
Glycopyrrolate was given at the same time.
Atipamezole (150 µg/kg [68 µg/lb], IM) was given 40
minutes after administration of medetomidine.
Results—All but 1 dog (given medetomidine alone)
assumed lateral recumbency within 6 minutes after
drug administration. Endotracheal intubation was significantly
more difficult when dogs were given
medetomidine alone than when given medetomidine
and butorphanol. At all evaluation times, percentages
of dogs with positive responses to tail clamping or to
needle pricks in the cervical region, shoulder region,
abdominal region, or hindquarters were not significantly
different among drug treatments. The PaCO2
was significantly higher and the arterial pH and PaO2
were significantly lower when dogs were given
medetomidine and butorphanol or medetomidine and
ketamine than when they were given medetomidine
alone. Recovery quality following atipamezole administration
was unsatisfactory in 1 dog when given
medetomidine and ketamine.
Conclusion and Clinical Relevance—Results suggested
that a combination of medetomidine with
butorphanol or ketamine resulted in more reliable and
uniform sedation in dogs than did medetomidine
alone. (J Am Vet Med Assoc 2000;216:1578–1583)
Objective—To evaluate effects of medetomidine on
anesthetic dose requirements, cardiorespiratory
variables, plasma cortisol concentrations, and behavioral
pain scores in dogs undergoing ovariohysterectomy.
Design—Randomized, prospective study.
Animals—12 healthy Walker-type hound dogs.
Procedure—Dogs received medetomidine (40 µg/kg
[18.2 µg/lb] of body weight, IM; n = 6) or saline (0.9%
NaCl) solution (1 ml, IM; 6) prior to anesthesia induction
with thiopental; thiopental dose needed for endotracheal
intubation was compared between groups.
Ovariohysterectomy was performed during halothane
anesthesia. Blood samples were obtained at various
times before drug administration until 300 minutes
after extubation. Various physiologic measurements
and end-tidal halothane concentrations were recorded.
Results—In medetomidine-treated dogs, heart rate
was significantly lower than in controls, and blood
pressure did not change significantly from baseline.
Plasma cortisol concentrations did not increase significantly
until 60 minutes after extubation in medetomidine-treated dogs, whereas values in control dogs
were increased from time of surgery until the end of
the recording period. Control dogs had higher pain
scores than treated dogs from extubation until the
end of the recording period.
Conclusion and Clinical Relevance—Administration
of medetomidine reduced dose requirements for
thiopental and halothane and provided postoperative
analgesia up to 90 minutes after extubation. Dogs
undergoing ovariohysterectomy by use of thiopental
induction and halothane anesthesia benefit from analgesia
induced by medetomidine administered prior to
anesthesia induction. Additional analgesia is appropriate
60 minutes after extubation. (J Am Vet Med Assoc
Objective—To identify factors associated with gastrointestinal
tract perforation in dogs being treated
with a selective cyclooxygenase-2 (COX-2) inhibitor
Procedure—The Novartis Animal Health pharmacovigilance
database was searched for records of
dogs treated with deracoxib in which gastrointestinal
tract perforation was documented.
Results—16 of the 29 (55%) dogs had received deracoxib
at a dosage higher than that approved by the
FDA for the particular indication being treated, with 25
(86%) dogs having received deracoxib at a dosage > 2
mg/kg/d (0.9 mg/lb/d). Seventeen (59%) dogs had
received at least 1 other nonsteroidal anti-inflammatory
drug (NSAID) or a corticosteroid in close temporal
association (within 24 hours) with deracoxib administration
(ie, immediately before or following). In all, 26
(90%) dogs had received deracoxib at a higher-than-approved
dosage or had received at least 1 other
NSAID or corticosteroid in close temporal association
with deracoxib administration. Twenty dogs died or
were euthanatized, and 9 survived.
Conclusions and Clinical Relevance—In dogs with
gastrointestinal tract perforation and that had been
treated with deracoxib, perforation was most likely
attributable to a number of factors. Deracoxib should
only be used at approved dosages. Cortico-steroids
and other less selective NSAIDs should not be administered
in close temporal association with selective
COX-2 inhibitors, including deracoxib. Further study is
required to define this problem. (J Am Vet Med Assoc 2005;227:1112–1117)
Animals—124 dogs with compensated mitral valve regurgitation (MR).
Procedures—Dogs randomly assigned to receive enalapril or placebo were monitored for the primary endpoint of onset of CHF for ≤ 58 months. Secondary endpoints included time from study entry to the combined endpoint of CHF-all-cause death; number of dogs free of CHF at 500, 1,000, and 1,500 days; and mean number of CHF-free days.
Results—Kaplan-Meier estimates of the effect of enalapril on the primary endpoint did not reveal a significant treatment benefit. Chronic enalapril administration did have a significant benefit on the combined endpoint of CHF-all-cause death (benefit was 317 days [10.6 months]). Dogs receiving enalapril remained free of CHF for a significantly longer time than those receiving placebo and were significantly more likely to be free of CHF at day 500 and at study end.
Conclusions and Clinical Relevance—Chronic enalapril treatment of dogs with naturally occurring, moderate to severe MR significantly delayed onset of CHF, compared with placebo, on the basis of number of CHF-free days, number of dogs free of CHF at days 500 and study end, and increased time to a combined secondary endpoint of CHF-all-cause death. Improvement in the primary endpoint, CHF-free survival, was not significant. Results suggest that enalapril modestly delays the onset of CHF in dogs with moderate to severe MR.