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Abstract

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 surgery.

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 surgery.

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)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare the disposition of lidocaine administered IV in awake and anesthetized horses.

Animals—16 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)

Full access
in American Journal of Veterinary Research

Abstract

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.

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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

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.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare indicators of postoperative pain and behavior in dogs with and without a lowdose ketamine infusion added to usual perioperative management.

Design—Prospective, randomized, blinded clinical study.

Animals—27 dogs undergoing forelimb amputation.

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 infusions.

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)

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in Journal of the American Veterinary Medical Association

Abstract

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.

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in Journal of the American Veterinary Medical Association