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in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE

To increase acidic esophageal lumen pH in dogs that developed gastroesophageal reflux (GER) during anesthesia. We compared water and 2 different bicarbonate concentrations.

ANIMALS

112 healthy, nonbrachycephalic dogs presented for ovariectomy.

PROCEDURES

Following standard anesthesia and surgery protocols for ovariectomy in all dogs, esophageal lumen impedance and pH were monitored using a dedicated probe. Esophageal impedance indicates the presence of GER whereas pH indicates the acidity level. Dogs with strongly acidic GER and an esophageal lumen pH value < 4.0 were included in the study, and lavage was performed with either tap water, bicarbonate 1%, or bicarbonate 2% until the pH increased to > 4.0. The effect of lavage on esophageal pH was compared using the Kruskal–Wallis and Wilcoxon 2 sample tests. Associations between lavage and pH changes were determined.

RESULTS

Of 48/112 dogs with strongly acidic GER, 33% neutralized their esophageal pH during surgery. For the 32 dogs that maintained an esophageal lumen pH value < 4, esophageal lavage with water increased the lumen pH to > 4 in 78.6% of dogs, whereas both bicarbonate concentrations increased it in 100% of the dogs to a more neutral pH (P < .0001). The dogs in the water group were more likely to regurgitate after anesthesia (36% vs 0% in both bicarbonate groups, P = .028).

CLINICAL RELEVANCE

Bicarbonate 1% and 2% increased esophageal lumen pH to more than 4 after strongly acidic GER. Lavage with water was mildly effective, but required large volumes and predisposed to further regurgitation after anesthesia.

Open access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine the effects of morphine on histamine release from 2 canine mast cell tumor (MCT) cell lines and on plasma histamine concentrations in dogs with cutaneous MCTs.

ANIMALS

10 dogs with cutaneous MCT and 10 dogs with soft tissue sarcoma (STS).

PROCEDURES

The study consisted of 2 phases. First, 2 canine MCT cell lines were exposed to 3 pharmacologically relevant morphine concentrations, and histamine concentrations were determined by an ELISA. Second, dogs with MCT or STS received 0.5 mg of morphine/kg, IM, before surgery for tumor excision. Clinical signs, respiratory rate, heart rate, arterial blood pressure, rectal temperature, and plasma histamine concentrations were recorded before and 5, 15, 30, and 60 minutes after morphine administration but prior to surgery. Data were compared by use of a 2-way ANOVA with the Sidak multiple comparisons test.

RESULTS

In the first phase, canine MCT cell lines did not release histamine when exposed to pharmacologically relevant morphine concentrations. In the second phase, no differences were noted for heart rate, arterial blood pressure, and rectal temperature between MCT and STS groups. Plasma histamine concentrations did not significantly differ over time within groups and between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

No significant changes in histamine concentrations were noted for both in vitro and in vivo study phases, and no hemodynamic changes were noted for the in vivo study phase. These preliminary results suggested that morphine may be used safely in some dogs with MCT.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To characterize the effects of ketamine administration on the cardiovascular and respiratory systems and on acid-base balance and to record adverse effects of ketamine in isoflurane-anesthetized dogs.

Animals—6 healthy adult mongrel dogs.

Procedure—Dogs were anesthetized with isoflurane (1.25 times the individual minimum alveolar concentration) in oxygen, and ketamine was administered IV to target pseudo–steady-state plasma concentrations of 0, 0.5, 1, 2, 5, 8, and 11 µg/mL. Isoflurane concentration was reduced to an equipotent concentration. Cardiovascular, respiratory, and acid-base variables; body temperature; urine production; and adverse effects were recorded before and during noxious stimulation. Cardiac index, stroke index, rate-pressure product, systemic vascular resistance index, pulmonary vascular resistance index, left ventricular stroke work index, right ventricular stroke work index, arterial oxygen concentration, mixed-venous oxygen concentration, oxygen delivery, oxygen consumption, oxygen extraction ratio, alveolar-arterial oxygen partial pressure gradient, and venous admixture were calculated. Plasma ketamine and norketamine concentrations were measured.

Results—Overall, ketamine administration improved ventilation, oxygenation, hemodynamics, and oxygen delivery in isoflurane-anesthetized dogs in a dosedependent manner. With the addition of ketamine, core body temperature was maintained or increased and urine production was maintained at an acceptable amount. However, at the higher plasma ketamine concentrations, adverse effects such as spontaneous movement and profuse salivation were observed. Myoclonus and dysphoria were observed during recovery in most dogs.

Conclusions and Clinical Relevance—Infusion of ketamine appears to be a suitable technique for balanced anesthesia with isoflurane in dogs. Plasma ketamine concentrations between 2 to 3 µg/mL elicited the most benefits with minimal adverse effects. (Am J Vet Res 2005;66:2122–2129)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of 6 plasma ketamine concentrations on the minimum alveolar concentration (MAC) of isoflurane in dogs.

Animals—6 dogs.

Procedure—In experiment 1, the MAC of isoflurane was measured in each dog and the pharmacokinetics of ketamine were determined in isoflurane-anesthetized dogs after IV administration of a bolus (3 mg/kg) of ketamine. In experiment 2, the same dogs were anesthetized with isoflurane in oxygen. A target-controlled IV infusion device was used to administer ketamine and to achieve plasma ketamine concentrations of 0.5, 1, 2, 5, 8, and 11 μg/mL by use of parameters obtained from experiment 1. The MAC of isoflurane was determined at each plasma ketamine concentration, and blood samples were collected for ketamine and norketamine concentration determination.

Results—Actual mean ± SD plasma ketamine concentrations were 1.07 ± 0.42 μg/mL, 1.62 ± 0.98 μg/mL, 3.32 ± 0.59 μg/mL, 4.92 ± 2.64 μg/mL, 13.03 ± 10.49 μg/mL, and 22.80 ± 25.56 μg/mL for target plasma concentrations of 0.5, 1, 2, 5, 8, and 11 μg/mL, respectively. At these plasma concentrations, isoflurane MAC was reduced by 10.89% to 39.48%, 26.77% to 43.74%, 25.24% to 84.89%, 44.34% to 78.16%, 69.62% to 92.31%, and 71.97% to 95.42%, respectively. The reduction in isoflurane MAC was significant, and the response had a linear and quadratic component. Salivation, regurgitation, mydriasis, increased body temperature, and spontaneous movements were some of the adverse effects associated with the high plasma ketamine concentrations.

Conclusions and Clinical Relevance—Ketamine appears to have a potential role for balanced anesthesia in dogs. (Am J Vet Res 2006;67:21–25)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of morphine administration for 6 days on gastrointestinal tract function in healthy adult horses.

Animals—5 horses.

Procedures—Horses were randomly allocated into 2 groups in a crossover study. Horses in the treatment group received morphine sulfate at a dosage of 0.5 mg/kg, IV, every 12 hours for 6 days. Horses in the control group received saline (0.9% NaCl) solution at a dosage of 10 mL, IV, every 12 hours for 6 days. Variables assessed included defecation frequency, weight of feces produced, intestinal transit time (evaluated by use of barium-filled spheres and radiographic detection in feces), fecal moisture content, borborygmus score, and signs of CNS excitement and colic.

Results—Administration of morphine resulted in gastrointestinal tract dysfunction for 6 hours after each injection. During those 6 hours, mean ± SD defecation frequency decreased from 3.1 ± 1 bowel movements in control horses to 0.9 ± 0.5 bowel movements in treated horses, weight of feces decreased from 4.1 ± 0.7 kg to 1.1 ± 0.7 kg, fecal moisture content decreased from 76 ± 2.7% to 73.5 ± 2.9%, and borborygmus score decreased from 13.2 ± 2.9 to 6.3 ± 3.9. Mean gastrointestinal transit time was also increased, compared with transit times in control horses.

Conclusions and Clinical Relevance—Morphine administered at 0.5 mg/kg twice daily decreased propulsive motility and moisture content in the gastrointestinal tract lumen. These effects may predispose treated horses to development of ileus and constipation.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate degree of sedation and cardiovascular, respiratory, acid-base excess, and electrolyte variables in response to IM administration of dexmedetomidine or dexmedetomidine with atropine.

Design—Randomized crossover study.

Animals—5 healthy 1- to 2-year-old sexually intact male Treeing Walker Coonhounds.

Procedures—Dogs were instrumented with catheters placed in the dorsal pedal artery and lateral saphenous vein. All dogs received dexmedetomidine (10 μg/kg [4.5 μg/lb], IM) or dexmedetomidine with atropine (0.02 mg/kg [0.009 mg/lb], IM). Variables were measured at baseline (time 0) and 5, 15, 30, and 60 minutes after drug administration.

Results—In all dogs, lithium dilution cardiac output decreased from a mean ± SD baseline value of 5.07 ± 1.0 L/min to 2.1 ± 0.9 L/min. Cardiac output was not different between dexmedetomidine group dogs and dexmedetomidine-atropine group dogs. Mean arterial pressure increased from baseline in both groups but was significantly higher in dexmedetomidine-atropine group dogs, compared with dexmedetomidine group dogs. Heart rate in dexmedetomidine group dogs decreased from 110 ± 14.2 beats/min to 49.4 ± 10.4 beats/min by 15 minutes. No differences were seen in blood gas values, electrolyte concentration, or hemoglobin values over time or between groups. Arrhythmias were detected in dexmedetomidine-atropine group dogs and included atrioventricular block, ventricular premature contractions, and ventricular bigeminy.

Conclusions and Clinical Relevance—Administration of atropine at 0.02 mg/kg, IM, with dexmedetomidine at 10 μg/kg, IM, resulted in an increase in mean arterial blood pressure and heart rate; deleterious cardiac arrhythmias were also observed. Use of atropine with dexmedetomidine is not recommended in dogs.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether number of instrument cannulas is associated with surgical time or severity of postoperative pain in dogs undergoing laparoscopic ovariectomy.

Design—Randomized clinical trial.

Animals—18 healthy dogs.

Procedures—Dogs were randomly assigned to undergo laparoscopic ovariectomy with 1, 2, or 3 instrument cannulas. Surgical time and intraoperative and postoperative complications were recorded. Severity of pain was monitored 2, 4, 8, 12, and 24 hours after surgery by means of pain scoring with a modified Melbourne Pain Scale and palpation of surgical sites with variably sized von Frey filaments. Owner-assessed postoperative comfort was also evaluated.

Results—Surgical time was significantly longer with 1 cannula (mean ± SD, 29.7 ± 5.6 minutes) than with 2 cannulas (18.2 ± 4.4 minutes) or 3 cannulas (19.3 ± 3.4 minutes). Intraoperative complications included splenic puncture (2 dogs), pedicle hemorrhage (1 dog), and SC emphysema (1 dog); complication rates were not significantly different among groups. Total pain score was significantly lower for dogs with 2 cannulas than for dogs with 3 cannulas; total pain score for dogs with 1 cannula did not differ significantly from scores for dogs with 2 cannulas or 3 cannulas. Owner assessments of postoperative comfort and number of days pain medications were administered did not differ among groups.

Conclusions and Clinical Relevance—Results suggested that laparoscopic ovariectomy with 2 instrument cannulas, rather than with 1, resulted in shorter surgical times without increasing severity of postoperative pain.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the anesthetic-sparing effect of maropitant, a neurokinin 1 receptor antagonist, during noxious visceral stimulation of the ovary and ovarian ligament in dogs.

Animals—Eight 1-year-old female dogs.

Procedures—Dogs were anesthetized with sevoflurane. Following instrumentation and stabilization, the right ovary and ovarian ligament were accessed by use of laparoscopy. The ovary was stimulated with a traction force of 6.61 N. The minimum alveolar concentration (MAC) was determined before and after 2 doses of maropitant.

Results—The sevoflurane MAC value was 2.12 ± 0.4% during stimulation without treatment (control). Administration of maropitant (1 mg/kg, IV, followed by 30 μg/kg/h, IV) decreased the sevoflurane MAC to 1.61 ± 0.4% (24% decrease). A higher maropitant dose (5 mg/kg, IV, followed by 150 μg/kg/h, IV) decreased the MAC to 1.48 ± 0.4% (30% decrease).

Conclusions and Clinical Relevance—Maropitant decreased the anesthetic requirements during visceral stimulation of the ovary and ovarian ligament in dogs. Results suggest the potential role for neurokinin 1 receptor antagonists to manage ovarian and visceral pain.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine fluid retention, glomerular filtration rate, and urine output in dogs anesthetized for a surgical orthopedic procedure.

Animals—23 dogs treated with a tibial plateau leveling osteotomy.

Procedures—12 dogs were used as a control group. Cardiac output was measured in 5 dogs, and 6 dogs received carprofen for at least 14 days. Dogs received oxymorphone, atropine, propofol, and isoflurane for anesthesia (duration, 4 hours). Urine and blood samples were obtained for analysis every 30 minutes. Lactated Ringer's solution was administered at 10 mL/kg/h. Urine output was measured and glomerular filtration rate was estimated. Fluid retention was measured by use of body weight, fluid balance, and bioimpedance spectroscopy.

Results—No difference was found among control, cardiac output, or carprofen groups, so data were combined. Median urine output and glomerular filtration rate were 0.46 mL/kg/h and 1.84 mL/kg/min. Dogs retained a large amount of fluids during anesthesia, as indicated by increased body weight, positive fluid balance, increased total body water volume, and increased extracellular fluid volume. The PCV, total protein concentration, and esophageal temperature decreased in a linear manner.

Conclusions and Clinical Relevance—Dogs anesthetized for a tibial plateau leveling osteotomy retained a large amount of fluids, had low urinary output, and had decreased PCV, total protein concentration, and esophageal temperature. Evaluation of urine output alone in anesthetized dogs may not be an adequate indicator of fluid balance.

Full access
in American Journal of Veterinary Research