Objective—To measure cardiac output in healthy
female anesthetized dogs by use of lithium dilution
cardiac output and determine whether changes in
mean arterial pressure were caused by changes in
cardiac output or systemic vascular resistance.
Design—Prospective clinical study.
Animals—20 healthy female dogs.
Procedure—Dogs were anesthetized for ovariohysterectomy.
Ten dogs breathed spontaneously throughout
anesthesia, and 10 dogs received intermittent
positive-pressure ventilation. Cardiovascular and respiratory
measurements, including lithium dilution cardiac
output, were performed during anesthesia and
Results—Mean arterial pressure and systemic vascular
resistance index were low after induction of
anesthesia and just prior to surgery and increased
significantly after surgery began. Cardiac index (cardiac
output indexed to body surface area) did not
change significantly throughout anesthesia and
Conclusions and Clinical Relevance—Results provide
baseline data for cardiac output and cardiac index
measurements during clinical anesthesia and surgery
in dogs. Changes in mean arterial pressure do not
necessarily reflect corresponding changes in cardiac
index. (J Am Vet Med Assoc 2005;227:1419–1423)
Objective—To compare the disposition of lidocaine
administered IV in awake and anesthetized horses.
Procedure—After instrumentation and collection of
baseline data, lidocaine (loading infusion, 1.3 mg/kg
administered during 15 minutes (87 µg/kg/min); constant
rate infusion, 50 µg/kg/min) was administered IV
to awake or anesthetized horses for a total of 105 minutes.
Blood samples were collected at fixed times during
the loading and maintenance infusion periods and
after the infusion period for analysis of serum lidocaine
concentrations by use of liquid chromatography with
mass spectral detection. Selected cardiopulmonary
parameters including heart rate (HR), mean arterial
pressure (MAP), arterial pH, PaCO2, and PaO2 were also
recorded at fixed time points during lidocaine administration.
Serum lidocaine concentrations were evaluated
by use of standard noncompartmental analysis.
Results—Serum lidocaine concentrations were higher
in anesthetized than awake horses at all time points
during lidocaine administration. Serum lidocaine concentrations
reached peak values during the loading
infusion in both groups (1,849 ± 385 ng/mL and
3,348 ± 602 ng/mL in awake and anesthetized horses,
respectively). Most lidocaine pharmacokinetic variables
also differed between groups. Differences in cardiopulmonary
variables were predictable; for example,
HR and MAP were lower and PaO2 was higher in anesthetized
than awake horses but within reference
ranges reported for horses under similar conditions.
Conclusions and Clinical Relevance—Anesthesia
has an influence on the disposition of lidocaine in horses,
and a change in dosing during anesthesia should
be considered. (Am J Vet Res 2005;66:574–580)
Objective—To measure cardiac output and other hemodynamic variables in anesthetized dogs undergoing laparotomy because of abdominal neoplasia.
Design—Prospective case series.
Animals—8 dogs with splenic or hepatic tumors.
Procedures—Dogs were anesthetized and underwent abdominal laparotomy. End-tidal isoflurane concentration, heart rate, arterial blood pressures, cardiac output, arterial pH, blood gas partial pressures, PCV, and plasma total protein concentration were measured at set intervals before, during, and after surgery. Cardiac index, stroke index, and systemic vascular resistance index were calculated.
Results—End-tidal isoflurane concentration was lowest before and after surgery. Heart rate did not change significantly throughout the anesthetic period. Arterial blood pressures and systemic vascular resistance index were highest shortly after surgery began; cardiac index and stroke volume index did not change significantly during surgery but increased significantly after surgery ended.
Conclusions and Clinical Relevance—Results suggested that in dogs undergoing laparotomy because of abdominal neoplasia, changes in arterial blood pressures were not necessarily indicative of qualitatively similar changes in cardiac index.
Objective—To determine whether infusion of xylazine and ketamine or xylazine and propofol after sevoflurane administration in horses would improve the quality of recovery from anesthesia.
Animals—6 healthy adult horses.
Procedures—For each horse, anesthesia was induced by administration of xylazine, diazepam, and ketamine and maintained with sevoflurane for approximately 90 minutes (of which the last 60 minutes were under steady-state conditions) 3 times at 1-week intervals. For 1 anesthetic episode, each horse was allowed to recover from sevoflurane anesthesia; for the other 2 episodes, xylazine and ketamine or xylazine and propofol were infused for 30 or 15 minutes, respectively, after termination of sevoflurane administration. Selected cardiopulmonary variables were measured during anesthesia and recovery. Recovery events were monitored and subjectively scored.
Results—Cardiopulmonary variables differed minimally among treatments, although the xylazine-propofol infusion was associated with greater respiratory depression than was the xylazine-ketamine infusion. Interval from discontinuation of sevoflurane or infusion administration to standing did not differ significantly among treatments, but the number of attempts required to stand successfully was significantly lower after xylazine-propofol infusion, compared with the number of attempts after sevoflurane alone. Scores for recovery from anesthesia were significantly lower (ie, better recovery) after either infusion, compared with scores for sevoflurane administration alone.
Conclusions and Clinical Relevance—Xylazine-ketamine or xylazine-propofol infusion significantly improved quality of recovery from sevoflurane anesthesia in horses. Xylazine-ketamine or xylazine-propofol infusions may be of benefit during recovery from sevoflurane anesthesia in horses for which a smooth recovery is particularly critical. However, oxygenation and ventilation should be monitored carefully.
Objective—To evaluate the sedative and analgesic effects of subanesthetic doses of ketamine in horses sedated with xylazine, with or without butorphanol.
Design—Prospective, randomized, controlled study.
Animals—10 adult horses.
Procedures—Each horse was sedated multiple times by administration of xylazine (treatment X), xylazine and butorphanol (treatment XB), xylazine with 1 of 2 dosages of ketamine (treatment XK1 or XK2), or xylazine and butorphanol with 1 of 2 dosages of ketamine (treatment XBK1 or XBK2). Head height and various behaviors, including responses to noise, insertion of a dental float, needle prick on the flank, algometer pressure on the scapula, and bilateral carpal arthrocenteses, were evaluated.
Results—No significant differences were detected among sedation treatments for head height, response to noise, or response to arthrocenteses. Insertion of a dental float was easiest with treatment XBK2 and most difficult with treatments XK1 and XK2. Response to a needle prick on the flank was lowest with treatment XB and highest with treatment XK2. Tolerance to algometer pressure over the scapula was highest with treatment XBK2 and lowest with treatment X.
Conclusions and Clinical Relevance—Administration of a subanesthetic dosage of ketamine with xylazine and butorphanol may facilitate certain procedures, such as insertion of a dental float, in horses and enhance tolerance to pressure stimulation, but it may worsen responses to acute pain, such as that caused by a needle prick. Further evaluation is needed to determine whether subanesthetic dosages of ketamine might be useful when performing certain clinical procedures in horses.
Procedure—Dogs were anesthetized with glycopyrrolate,
morphine, propofol, and isoflurane. Thirteen
dogs were treated with ketamine IV, as follows: 0.5
mg/kg (0.23 mg/lb) as a bolus before surgery, 10
µg/kg/min (4.5 µg/lb/min) during surgery, and 2
µg/kg/min (0.9 µg/lb/min) for 18 hours after surgery.
Fourteen dogs received the same volume of saline
(0.9% NaCl) solution. All dogs received an infusion of
fentanyl (1 to 5 µg/kg/h [0.45 to 2.27 µg/lb/h]) for the
first 18 hours after surgery. Dogs were evaluated for
signs of pain before surgery, at the time of extubation,
and 1, 2, 3, 4, 12, and 18 hours after extubation.
Owners evaluated their dogs' appetite, activity, and
wound soreness on postoperative days 2, 3, and 4.
Results—Dogs that received ketamine infusions had
significantly lower pain scores 12 and 18 hours after
surgery and were significantly more active on postoperative
day 3 than dogs that received saline solution
Conclusions and Clinical Relevance—Results suggest
that perioperative administration of low doses of
ketamine to dogs may augment analgesia and comfort
in the postoperative surgical period. (J Am Vet
Med Assoc 2002;221:72–75)
Objective—To evaluate perioperative administration of gabapentin as an adjunct for analgesia in dogs undergoing amputation of a forelimb.
Design—Randomized, controlled trial.
Animals—30 client-owned dogs.
Procedures—On the day before surgery, a baseline pain evaluation was performed in each dog by use of multiple pain assessment methods. Dogs then received gabapentin (10 mg/kg [4.5 mg/lb], PO, once, followed by 5 mg/kg [2.3 mg/lb], PO, q 12 h for 3 additional days) or a placebo. On the day of surgery, dogs were anesthetized and forelimb amputation was performed. Fentanyl was infused after surgery for 18 to 24 hours; use of other analgesics was allowed. In-hospital pain evaluations were repeated at intervals for 18 hours after surgery, and owners were asked to evaluate daily their dog's activity, appetite, and wound soreness for the first 3 days after discharge from the hospital. Results were analyzed by use of a repeated-measures ANOVA.
Results—Pain evaluation scores did not differ significantly between gabapentin and placebo groups in the hospital or at home after discharge.
Conclusions and Clinical Relevance—As an adjunct to other analgesics and anesthetics, gabapentin, at the dose and frequency used in this study, did not provide a significant benefit for the management of acute perioperative pain in dogs undergoing forelimb amputation. The small sample size and number of other confounding factors, such as aggressive use of other analgesics, limited the likelihood of detecting a benefit of gabapentin. Other gabapentin doses or dosing regimens warrant further study.