Objective—To compare the effects of lactated
Ringer's solution (LRS) with those of a physiologically
balanced 6% hetastarch plasma expander administered
to isoflurane-anesthetized dogs with hypotension
induced by blood withdrawal.
Animals—12 healthy Beagles.
Procedure—Blood was withdrawn from isofluraneanesthetized
dogs (volume withdrawn measured) to a
systolic arterial blood pressure (SAP) of 80 mm Hg.
Six dogs each received either LRS or hetastarch solution
(90 mL/kg/h, IV). Hemodynamic variables, pH,
blood gas concentrations, PCV, serum electrolyte and
total protein concentrations, and colloid osmotic pressure
(COP) were determined at baseline, while SAP
was 80 mm Hg, and after fluid treatment. The volume
of fluid administered and rate of return of SAP to within
10% of baseline values were recorded.
Results—Mean ± SD volume of blood withdrawn to
decrease SAP to 80 mm Hg was 173 ± 38 mL.
Hemodynamic variables decreased after blood withdrawal
but returned to baseline values more rapidly
after infusion of a smaller volume of hetastarch solution,
compared with the response to LRS infusion.
Whereas PCV and serum total protein concentration
decreased after administration of either solution, COP
decreased only after administration of LRS. The total
volume of hetastarch solution and LRS required to
restore and maintain SAP to within 10% of baseline
values was 1.1 ± 0.9 and 4.4 ± 1.7 times greater than
the volume of blood removed, respectively.
Conclusions and Clinical Relevance—Compared
with LRS infusion, smaller volumes of hetastarch
solution normalized and maintained SAP without lowering
COP in isoflurane-anesthetized dogs after blood
withdrawal. (Am J Vet Res 2004;65:1189–1194)
Objective–To determine prevalence of pain among
dogs and cats examined as outpatients at a veterinary
teaching hospital and characteristics of pain in dogs
and cats with evidence of pain.
Animals–1,153 dogs and 652 cats examined as outpatients
at The Ohio State University during 2002.
Procedure–A questionnaire was administered to
owners of all dogs and cats. For dogs and cats with
evidence of pain, the cause, signs, anatomic location,
type (superficial somatic, deep somatic, or visceral),
duration, and severity of the pain and the principle
mechanism (inflammatory, neuropathic, both, or
unknown) responsible for the pain were determined
on the basis of questionnaire responses and results
of physical examination. The presence of primary
hyperalgesia, secondary hyperalgesia, allodynia, and
hyposensitivity was recorded.
Results–231 (20%) dogs and 92 (14%) cats had evidence
of pain. Dogs with evidence of pain were significantly
older and heavier than dogs without. Cats
with evidence of pain were significantly older than
cats without. In most dogs and cats with evidence of
pain, the pain was determined to be of short duration
(< 7 days), of mild or moderate severity, somatic,
associated with primary hyperalgesia, and inflammatory.
Analgesic drugs were frequently administered to
dogs with chronic pain, but were not always considered
Conclusions and Clinical Relevance–Results suggest
that mild or moderate pain associated with
inflammation may be seen in dogs and cats examined
as outpatients. Older, heavier dogs and older cats
were more likely to have evidence of pain. (J Am Vet
Med Assoc 2004;224:1459–1463)
Objective—To estimate the prevalence and characteristics
of pain in dogs and cats examined by an
emergency service at a veterinary teaching hospital
and evaluate the response of dogs and cats with
signs of pain to analgesic treatment.
Animals—317 dogs and 112 cats.
Procedure—A questionnaire was used to categorize
the characteristics of pain. The location, cause, and
signs of pain were determined by obtaining a thorough
history and conducting a physical examination.
Pain was categorized by type (superficial somatic,
deep somatic, or visceral), mechanism (inflammatory,
neuropathic, or both), severity (mild, moderate, or
severe), and duration. Evidence for primary or secondary
hypersensitivity and hyposensitivity to manipulation
was determined. The response to single or
multiple analgesic drug administration was assessed.
Results—179 (56%) dogs and 60 (54%) cats had
signs of pain. In most of these dogs and cats, pain
was classified as acute (< 24 hours' duration) and of
moderate severity and was associated with primary
hypersensitivity. Most dogs had deep somatic pain;
most cats had visceral pain. Inflammation was the
most common mechanism. One hundred nineteen
(66%) dogs and 41 (68%) cats were treated with analgesic
drugs. Analgesic treatment was considered
effective in 73 (61%) dogs and 31 (76%) cats.
Conclusions and Clinical Relevance—Results suggest
that moderate to severe acute somatic pain
caused by inflammation is common in dogs and cats
examined by an emergency service and that a combination
of multiple analgesic drugs is more effective
than any single analgesic drug in the treatment of pain
in these dogs and cats. (J Am Vet Med Assoc 2005;226:2004–2009)
Objective—To determine the effects of constant rate
infusion of morphine, lidocaine, ketamine, and morphine-
lidocaine-ketamine (MLK) combination on endtidal
isoflurane concentration (ET-Iso) and minimum
alveolar concentration (MAC) in dogs anesthetized
with isoflurane and monitor depth of anesthesia by
use of the bispectral index (BIS).
Animals—6 adult dogs.
Procedure—Each dog was anesthetized with isoflurane
on 5 occasions, separated by a minimum of 7 to
10 days. Individual isoflurane MAC values were determined
for each dog. Reduction in isoflurane MAC,
induced by administration of morphine (3.3
µg/kg/min), lidocaine (50 µg/kg/min), ketamine (10
µg/kg/min), and MLK, was determined. Heart rate,
mean arterial blood pressure, oxygen saturation as
measured by pulse oximetry (SpO2), core body temperature,
and BIS were monitored.
Results—Mean ± SD isoflurane MAC was 1.38 ±
0.08%. Morphine, lidocaine, ketamine, and MLK significantly
lowered isoflurane MAC by 48, 29, 25, and 45%,
respectively. The percentage reductions in isoflurane
MAC for morphine and MLK were not significantly different
but were significantly greater than for lidocaine
and ketamine. The SpO2, mean arterial pressure, and
core body temperature were not different among
groups. Heart rate was significantly decreased at isoflurane
MAC during infusion of morphine and MLK. The BIS
was inversely related to the ET-Iso and was significantly
increased at isoflurane MAC during infusions of morphine
and ketamine, compared with isoflurane alone.
Conclusions and Clinical Relevance—Low infusion
doses of morphine, lidocaine, ketamine, and MLK
decreased isoflurane MAC in dogs and were not associated
with adverse hemodynamic effects. The BIS
can be used to monitor depth of anesthesia. (Am J Vet Res 2003;64:1155–1160)
Objective—To compare effects of 2 acetylcholinesterase inhibitors on recovery quality of horses anesthetized with isoflurane.
Animals—6 horses in phase 1, 7 horses in phase 2A, and 14 horses in phase 2B.
Procedures—The study comprised 3 phases (2 randomized, blinded crossover phases in horses undergoing orthopedic procedures and 1 prospective dose-determining phase). In phase 1, horses were anesthetized with isoflurane and received neostigmine or saline (0.9% NaCl) solution prior to anesthetic recovery. Phase 2A was a physostigmine dose-determining phase. In phase 2B, horses were anesthetized with isoflurane and received neostigmine or physostigmine prior to recovery. Objective recovery events were recorded and subjective visual analogue scale scores of recovery quality were assigned from video recordings.
Results—Recovery measures in phase 1 were not different between horses receiving neostigmine or saline solution. In phase 2A, 0.04 mg of physostigmine/kg was the highest cumulative dose that did not cause clinically relevant adverse behavioral or gastrointestinal effects. Horses receiving physostigmine had higher mean ± SD visual analogue scale recovery scores (70.8 ± 13.3 mm) than did horses receiving neostigmine (62.4 ± 12.8 mm) in phase 2B, with fewer attempts until sternal and standing recovery. Incidence of colic behavior did not differ among groups.
Conclusions and Clinical Relevance—Inhibition with physostigmine improved anesthetic recovery quality in horses anesthetized with isoflurane, compared with recovery quality for horses receiving neostigmine. Inhibition of central muscarinic receptors by inhalation anesthetics may underlie emergence delirium in horses recovering from anesthesia.
Objective—To determine the effect of IV administration of perzinfotel on the minimum alveolar concentration (MAC) of isoflurane in dogs.
Animals—6 healthy sexually intact male Beagles.
Procedures—Dogs were instrumented with a telemetry device that permitted continuous monitoring of heart rate, arterial blood pressure, and body temperature. Dogs were anesthetized with propofol (4 to 6 mg/kg, IV) and isoflurane for 30 minutes before determination of MAC of isoflurane. Isoflurane MAC values were determined 4 times, separated by a minimum of 7 days, before and after IV administration of perzinfotel (0 [control], 5, 10, and 20 mg/kg). Bispectral index and percentage hemoglobin saturation with oxygen (SpO2) were monitored throughout anesthesia.
Results—Isoflurane MAC was 1.32 ± 0.14%. Intravenous administration of perzinfotel at 0, 5, 10, and 20 mg/kg decreased isoflurane MAC by 0%, 24%, 30%, and 47%, respectively. Perzinfotel significantly decreased isoflurane MAC values, compared with baseline and control values. The bispectral index typically increased with higher doses of perzinfotel and lower isoflurane concentrations, but not significantly. Heart rate, body temperature, and SpO2 did not change, but systolic, mean, and diastolic arterial blood pressures significantly increased with decreases in isoflurane MAC after administration of perzinfotel at 10 and 20 mg/kg, compared with 0 and 5 mg/kg.
Conclusions and Clinical Relevance—IV administration of perzinfotel decreased isoflurane MAC values. Improved hemodynamics were associated with decreases in isoflurane concentration.
Objective—To determine cardiopulmonary effects of incremental doses of dopamine and phenylephrine during isoflurane-induced hypotension in cats with hypertrophic cardiomyopathy (HCM).
Animals—6 adult cats with severe naturally occurring HCM.
Procedures—Each cat was anesthetized twice (once for dopamine treatment and once for phenylephrine treatment; treatment order was randomized). Hypotension was induced by increasing isoflurane concentration. Cardiopulmonary data, including measurement of plasma concentration of cardiac troponin I (cTnI), were obtained before anesthesia, 20 minutes after onset of hypotension, and 20 minutes after each incremental infusion of dopamine (2.5, 5, and 10 μg/kg/min) or phenylephrine (0.25, 0.5, and 1 μg/kg/min).
Results—Mean ± SD end-tidal isoflurane concentration for dopamine and phenylephrine was 2.44 ± 0.05% and 2.48 ± 0.04%, respectively. Cardiac index and tissue oxygen delivery were significantly increased after administration of dopamine, compared with results after administration of phenylephrine. Systemic vascular resistance index was significantly increased after administration of phenylephrine, compared with results after administration of dopamine. Oxygen consumption remained unchanged for both treatments. Systemic and pulmonary arterial blood pressures were increased after administration of both dopamine and phenylephrine. Acid-base status and blood lactate concentration did not change and were not different between treatments. The cTnI concentration increased during anesthesia and infusion of dopamine and phenylephrine but did not differ significantly between treatments.
Conclusions and Clinical Relevance—Dopamine and phenylephrine induced dose-dependent increases in systemic and pulmonary blood pressure, but only dopamine resulted in increased cardiac output. Hypotension and infusions of dopamine and phenylephrine caused significant increases in cTnI concentrations.