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 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 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 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.
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.
Objective—To evaluate the degree of postoperative pain in dogs undergoing elective castration or ovariohysterectomy (OHE); determine whether an association exists between surgeon experience, incision length, or surgery duration and degree of postoperative pain; and determine whether analgesic treatment decreases expression of postoperative pain behaviors.
Design—Randomized controlled clinical trial.
Animals—426 client-owned dogs undergoing OHE or castration.
Procedures—Dogs underwent OHE or castration performed by an experienced veterinarian or a fourth-year veterinary student. Dogs were randomly assigned to 1 of 4 treatment groups: no perioperative analgesic treatment (n = 44), preoperative administration of morphine (144), preoperative administration of nalbuphine (119), and postoperative administration of ketoprofen (119). Dogs were evaluated while in the hospital before anesthesia and for 4 hours after surgery and once a day at home for 3 days after surgery.
Results—Dogs in all 4 groups had significant increases in overall pain scores after surgery, compared with baseline scores. There were significant differences among groups, with control dogs having significantly higher increases in overall pain scores than dogs in the other groups. Factors that did not influence the frequency or severity of pain-related behaviors included breed, individual hospital, anesthetic induction protocol, surgeon experience, and duration of surgery.
Conclusions and Clinical Relevance—Results suggested that dogs expressed behaviors suggestive of pain following OHE and castration, that analgesic treatment mitigated the expression of pain-related behaviors, and that surgeon experience and surgery duration did not have any effect on expression of pain-related behaviors.
Objective—To compare cardiovascular effects of sevoflurane alone and sevoflurane plus an IV infusion of lidocaine in horses.
Animals—8 adult horses.
Procedures—Each horse was anesthetized twice via IV administration of xylazine, diazepam, and ketamine. During 1 anesthetic episode, anesthesia was maintained by administration of sevoflurane in oxygen at 1.0 and 1.5 times the minimum alveolar concentration (MAC). During the other episode, anesthesia was maintained at the same MAC multiples via a reduced concentration of sevoflurane plus an IV infusion of lidocaine. Heart rate, arterial blood pressures, blood gas analyses, and cardiac output were measured during mechanical (controlled) ventilation at both 1.0 and 1.5 MAC for each anesthetic protocol and during spontaneous ventilation at 1 of the 2 MAC multiples.
Results—Cardiorespiratory variables did not differ significantly between anesthetic protocols. Blood pressures were highest at 1.0 MAC during spontaneous ventilation and lowest at 1.5 MAC during controlled ventilation for either anesthetic protocol. Cardiac output was significantly higher during 1.0 MAC than during 1.5 MAC for sevoflurane plus lidocaine but was not affected by anesthetic protocol or mode of ventilation. Clinically important hypotension was detected at 1.5 MAC for both anesthetic protocols.
Conclusions and Clinical Relevance—Lidocaine infusion did not alter cardiorespiratory variables during anesthesia in horses, provided anesthetic depth was maintained constant. The IV administration of lidocaine to anesthetized nonstimulated horses should be used for reasons other than to improve cardiovascular performance. Severe hypotension can be expected in nonstimulated horses at 1.5 MAC sevoflurane, regardless of whether lidocaine is administered.