Objective—To compare 3 dose levels of medetomidine
and dexmedetomidine for use as premedicants
in dogs undergoing propofol-isoflurane anesthesia.
Animals—6 healthy Beagles.
Procedure—Dogs received medetomidine or
dexmedetomidine intravenously at the following dose
levels: 0.4 µg of medetomidine or 0.2 µg of
dexmedetomidine/kg of body weight (M0.4/D0.2), 4.0
µg of medetomidine or 2.0 µg of dexmedetomidine/
kg (M4/D2), and 40 µg of medetomidine or 20 µg
of dexmedetomidine/kg (M40/D20). Sedation and
analgesia were scored before induction. Anesthesia
was induced with propofol and maintained with
isoflurane. End-tidal isoflurane concentration, heart
rate, and arterial blood pressures and gases were
Results—Degrees of sedation and analgesia were
significantly affected by dose level but not drug.
Combined mean end-tidal isoflurane concentration for
all dose levels was higher in dogs that received
medetomidine, compared with dexmedetomidine.
Recovery time was significantly prolonged in dogs
treated at the M40/D20 dose level, compared with
the other dose levels. After induction, blood pressure
decreased below reference range and heart rate
increased in dogs treated at the M0.4/D0.2 dose
level, whereas blood pressure was preserved in dogs
treated at the M40/D20 dose level. However, dogs in
these latter groups developed profound bradycardia
and mild metabolic acidosis during anesthesia.
Treatment at the M4/D2 dose level resulted in more
stable cardiovascular effects, compared with the
other dose levels. In addition, PaCO2 was similar
among dose levels.
Conclusions and Clinical Relevance—Dexmedetomidine
is at least as safe and effective as medetomidine
for use as a premedicant in dogs undergoing
propofol-isoflurane anesthesia. (Am J Vet Res
Objective—To identify behavioral alterations in client-owned cats recovering at home following elective ovariohysterectomy or castration and determine owner perceptions regarding severity of postoperative pain.
Animals—145 cats undergoing elective ovariohysterectomy (n = 80) or castration (65) at 4 veterinary clinics in Finland.
Procedures—Owners were asked to complete a questionnaire on their cats' behavior during the 3 days after surgery. Owners were also asked to indicate their perceptions of the severity of postoperative pain during these days by use of a 100-mm visual analog scale.
Results—Owners consistently indicated that there were changes in their cats' behavior, with the most commonly reported alterations being a decrease in overall activity level, an increase in the amount of time spent sleeping, a decrease in playfulness, and altered way of movement. Changes (ie, either an increase or decrease) in aggressive behavior were rare. Median pain score the day of surgery was 15.0 mm for male cats and 25.0 mm for female cats. Behavior score was significantly associated with day of observation, type of surgery (ovariohysterectomy vs castration), owner-assigned pain score, and veterinary clinic.
Conclusions and Clinical Relevance—Results suggested that behavioral alterations can be detected for several days after surgery in cats recovering at home following ovariohysterectomy or castration and emphasized owner concerns about the existence of postoperative pain.
Objective—To compare the perioperative stress
response in dogs administered medetomidine or acepromazine
as part of the preanesthetic medication.
Animals—42 client-owned dogs that underwent
Procedure—Each dog was randomly allocated to
receive medetomidine and butorphanol tartrate
(20 µg/kg and 0.2 mg/kg, respectively, IM) or acepromazine
maleate and butorphanol (0.05 and 0.2 mg/kg,
respectively, IM) for preanesthetic medication.
Approximately 80 minutes later, anesthesia was
induced by administration of propofol and maintained
by use of isoflurane in oxygen. Each dog was also
given carprofen before surgery and buprenorphine
after surgery. Plasma concentrations of epinephrine,
norepinephrine, cortisol, and β-endorphin were measured
at various stages during the perioperative period.
In addition, cardiovascular and clinical variables
Results—Concentrations of epinephrine, norepinephrine,
and cortisol were significantly lower for dogs
administered medetomidine. Concentrations of
β-endorphin did not differ between the 2 groups.
Heart rate was significantly lower and mean arterial
blood pressure significantly higher in dogs administered
medetomidine, compared with values for dogs
Conclusions and Clinical Relevance—Results indicate
that for preanesthetic medications, medetomidine
may offer some advantages over acepromazine
with respect to the ability to decrease perioperative
concentrations of stress-related hormones. In particular,
the ability to provide stable plasma catecholamine
concentrations may help to attenuate perioperative
activation of the sympathetic nervous system.
(Am J Vet Res 2002;63:969–975)
Objective—To investigate heart rate characteristics in dogs undergoing ovariohysterectomy following premedication with medetomidine or acepromazine.
Animals—43 client-owned dogs.
Procedure—24-hour ambulatory electrocardiography was performed beginning approximately 1 hour prior to administration of premedications. Dogs were premedicated with medetomidine and butorphanol (n = 21) or acepromazine and butorphanol (22) and, approximately 85 minutes later, were anesthetized with propofol and isoflurane. Electrocardiographic recordings were examined to determine heart rate, cardiac conduction disturbances (ventricular premature complexes and atrioventricular block), and indices of heart rate variability (HRV).
Results—Minimum heart rate during the 24-hour recording period was significantly lower among dogs given medetomidine than among dogs given acepromazine, but during the postoperative period, heart rate increased in all dogs as they became physically active. Intraoperative time domain HRV indices were lower and the low frequency-to-high frequency ratio was higher among dogs given acepromazine than among dogs given medetomidine; however, significant differences between groups were no longer seen by 6 hours after surgery. There was no significant difference between groups with regard to the number of ventricular premature complexes or to values of scaling exponent α2 (a nonlinear measure of HRV).
Conclusions and Clinical Relevance—Results suggest that there are greater enhancements in vagally related heart rate indices in medetomidine-treated dogs that may persist until 6 hours after surgery. Despite the low heart rates, dogs given medetomidine showed expected responses to surgery and positional stimuli, and the 2 preanesthetic protocols may not result in different prevalences of ventricular premature complexes. (J Am Vet Med Assoc 2005;226:738–745)