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Abstract

Objective

To evaluate sedative effects of IM administration of a low dose of romifidine in dogs.

Animals

13 healthy adult Beagles.

Procedure

Physiologic saline solution (0.2 ml), 0.1% romifidine (10, 20, or 40 µg/kg), or 10% xylazine (1 mg/kg) was given IM in a crossover study design. Heart rate, respiratory rate, rectal temperature, hemoglobin saturation, and scores for sedation, muscle relaxation, posture, auditory response, and positioning response were recorded before and at regular intervals for up to 240 minutes after drug administration.

Results

Scores for sedation, muscle relaxation, posture, auditory response, and positioning response increased in a dose-dependent manner after romifidine administration. Sedation induced by the highest dose of romifidine (40 µg/kg) was comparable to that induced by xylazine (1 mg/kg). Heart rate, respiratory rate, and rectal temperature decreased in a dose-dependent manner after romifidine administration, but hemoglobin saturation did not change.

Conclusions and Clinical Implications

Romifidine (10, 20, or 40 µg/kg, IM) is an effective sedative in dogs, but causes a decrease in heart rate, respiratory rate, and rectal temperature. (Am J Vet Res 1999;60: 162-168)

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

SUMMARY

Objective

To determine the effects of medetomidine, administered IV, on serum insulin and plasma glucose concentrations in clinically normal dogs.

Animals

6 healthy adult Beagles.

Procedure

Dogs were randomly assigned to each of 3 treatments in a prospective cross-over study design. Serum insulin and plasma glucose concentrations were determined before and 20, 40, 60, 120, 180, 240, 300, 360, 420, and 480 minutes after IV administration of 0.9% NaCI solution (control) or medetomidine (10 or 20 μg/kg of body weight).

Results

Mean serum insulin concentration decreased after medetomidine administration and was significantly (P ≤ 0.05) lower than control values 20, 40, 60, and 120 minutes after drug administration. Mean plasma glucose concentration tended to increase after medetomidine administration, but did not differ significantly from control values.

Conclusions

In dogs, IV administration of medetomidine at dosages of 10 and 20 μg/kg transiently decreases serum insulin concentration, but plasma glucose concentration remains within the normal physiologic range.

Clinical Relevance

Medetomidine can be given at low, preanesthetic dosages without significantly altering plasma glucose concentration in clinically normal dogs. (Am J Vet Res 1997;58:1440–1442)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the pharmacokinetics and toxic effects associated with IV administration of lithium chloride (LiCl) to conscious healthy horses.

Animals—6 healthy Standardbred horses.

Procedure—Twenty 3-mmol boluses of LiCl (0.15 mmol/L) were injected IV at 3-minute intervals (total dose, 60 mmol) during a 1-hour period. Blood samples for measurement of serum lithium concentrations were collected before injection and up to 24 hours after injection. Behavioral and systemic toxic effects of LiCl were also assessed.

Results—Lithium elimination could best be described by a 3-compartment model for 5 of the 6 horses. Mean peak serum concentration was 0.561 mmol/L (range, 0.529 to 0.613 mmol/L), with actual measured mean serum value of 0.575 mmol/L (range, 0.52 to 0.67 mmol/L) at 2.5 minutes after administration of the last bolus. Half-life was 43.5 hours (range, 32 to 84 hours), and after 24 hours, mean serum lithium concentration was 0.13 ± 0.05 mmol/L (range, 0.07 to 0.21 mmol/L). The 60-mmol dose of LiCl did not produce significant differences in any measured hematologic or biochemical variables, gastrointestinal motility, or ECG variables evaluated during the study period.

Conclusions and Clinical Relevance—Distribution of lithium best fit a 3-compartment model, and clearance of the electrolyte was slow. Healthy horses remained unaffected by LiCl at doses that exceeded those required for determination of cardiac output. Peak serum concentrations were less than steadystate serum concentrations that reportedly cause toxic effects in other species. (Am J Vet Res 2001; 62:1387–1392)

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in American Journal of Veterinary Research

Abstract

Objective—To determine effects of preoperative administration of ketoprofen on whole blood platelet aggregation, buccal mucosal bleeding time, and hematologic indices in dogs after elective ovariohysterectomy.

Design—Randomized, masked clinical trial.

Animals—22 healthy dogs.

Procedure—60 minutes before induction of anesthesia, 11 dogs were given 0.9% NaCl solution (control), and 11 dogs were given ketoprofen (2 mg/kg [0.9 mg/lb], IM). Thirty minutes before induction of anesthesia, glycopyrrolate (0.01 mg/kg [0.005 mg/lb]), acepromazine (0.05 mg/kg [0.02 mg/lb]), and butorphanol (0.2 mg/kg [0.09 mg/lb]) were given IM to all dogs. Anesthesia was induced with thiopental (5 to 10 mg/kg [2.3 to 4.5 mg/lb], IV) and maintained with isoflurane (1 to 3%). Ovariohysterectomy was performed and butorphanol (0.1 mg/kg [0.05 mg/lb], IV) was given 15 minutes before completion of surgery. Blood samples for measurement of variables were collected at intervals before and after surgery.

Results—In dogs given ketoprofen, platelet aggregation was decreased 95 ± 10% and 80 ± 35% (mean ± SD) immediately after surgery and 24 hours after surgery, respectively, compared with preoperative values. At both times, mean values in dogs given ketoprofen differed significantly from those in control dogs. Significant differences between groups were not observed for mucosal bleeding time or hematologic indices.

Conclusions and Clinical Relevance—Preoperative administration of ketoprofen inhibited platelet aggregation but did not alter bleeding time. Ketoprofen can be given before surgery to healthy dogs undergoing elective ovariohysterectomy, provided that dogs are screened for potential bleeding problems before surgery and monitored closely after surgery. (J Am Vet Med Assoc 2002;220:1818–1822)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effects of preoperative administration of ketoprofen on anesthetic requirements and signs of postoperative pain in dogs undergoing elective ovariohysterectomy.

Design—Randomized, controlled clinical trial.

Animals—22 clinically normal client-owned dogs.

Procedure—60 minutes before induction of anesthesia, 11 dogs were given ketoprofen (2 mg/kg [0.9 mg/lb], IM), and the other 11 were given saline (0.9% NaCl) solution. Dogs were premedicated with glycopyrrolate, acepromazine, and butorphanol and anesthetized with thiopental; anesthesia was maintained with isoflurane. Ovariohysterectomy was performed by an experienced surgeon, and butorphanol was given 15 minutes before completion of the procedure. Objective behavioral scores and numerical pain scores at rest and with movement were recorded every 2 hours for 12 hours after surgery and then every 4 hours for an additional 12 hours.

Results—Preoperative administration of ketoprofen did not reduce the dose of thiopental required to induce anesthesia or the end-tidal concentration of isoflurane required to maintain anesthesia. Activity levels and median objective behavioral scores were significantly higher 4 and 6 hours after surgery in dogs given ketoprofen than in dogs given saline solution. However, mean numerical pain scores in dogs given ketoprofen were not significantly different from scores for dogs given saline solution at any time.

Conclusions and Clinical Relevance—Results suggest that preoperative administration of ketoprofen does not reduce anesthetic requirements in dogs undergoing elective ovariohysterectomy but may reduce signs of pain after surgery. Results also suggest that the objective behavioral score may be a more sensitive measure of acute postoperative pain than traditional numerical pain scores. (J Am Vet Med Assoc 2002;221:1268–1275)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine effects of IV medetomidine administration on selected clinicopathologic variables in dogs.

Animals

6 healthy adult Beagles.

Procedure

Dogs were randomly assigned to each of 3 treatments in a crossover study design. Serum osmolality, urine osmolality, urine pH, and fractional clearances of sodium, chloride, potassium, and glucose were determined before and 20, 40, 60, 120, 180, 240, 300, 360, 420, and 480 minutes after IV administration of 0.9% NaCl (saline) solution (control) or medetomidine (10 or 20 μg/kg of body weight). The urinary bladder was emptied prior to saline or medetomidine administration, and urine volume was determined at the same posttreatment times as those described previously. Free water clearance was calculated for all posttreatment times.

Results

After medetomidine administration, serum osmolality, urine volume, free water clearance, and fractional clearance of potassium and glucose increased; urine osmolality decreased. Initially, urine pH and fractional clearance of chloride decreased, then subsequently increased. Fractional clearance of sodium did not change.

Conclusions and Clinical Relevance

Because IV administration of medetomidine to dogs at dosages of 10 and 20 μg/kg induces a diuretic effect that lasts up to 4 hours, the drug should be used with discretion in hypovolemic or dehydrated dogs, and its use should be avoided in those with urinary tract obstruction. (Am J Vet Res 1998;59:756-761)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To compare the effects of xylazine bolus versus medetomidine constant rate infusion (MCRI) on cardiopulmonary function and depth of anesthesia in dorsally recumbent, spontaneously breathing, isoflurane-anesthetized horses.

Design—Prospective, randomized crossover study.

Animals—10 healthy adult Standardbreds.

Procedures—Horses were premedicated with xylazine or medetomidine IV. Anesthesia was induced with diazepam and ketamine and maintained with isoflurane for 150 minutes. For the xylazine treatment, end-tidal isoflurane concentration was maintained at 1.7%, and xylazine (0.2 mg/kg [0.09 mg/lb], IV) was administered as a bolus at the end of anesthesia. For the MCRI treatment, end-tidal isoflurane concentration was maintained at 1.4%, and medetomidine (0.005 mg/kg/h [0.0023 mg/lb/h], IV) was infused throughout anesthesia. Physiologic data (ie, heart rate, respiratory rate, rectal temperature, bispectral index, and electromyographic values) were compared between treatments with xylazine bolus versus MCRI.

Results—Heart rate was lower, but mean arterial blood pressure was higher from 20 to 40 minutes with MCRI treatment, compared with conventional treatment with xylazine. Respiratory rate and rectal temperature were greater with MCRI treatment. Bispectral index was lower with MCRI treatment from 80 to 150 minutes, and electromyographic values were lower with MCRI treatment from 30 to 150 minutes.

Conclusions and Clinical Relevance—In isoflurane-anesthetized horses, premedication with medetomidine followed by administration of medetomidine as a constant rate infusion resulted in decreased heart rate, higher arterial blood pressure from 20 through 40 minutes after induction of anesthesia, and better preserved body temperature, compared with conventional treatment with xylazine. Greater depth of anesthesia and muscle relaxation were seen with MCRI treatment, despite the lower isoflurane concentration.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare the effect of xylazine bolus versus medetomidine constant rate infusion (MCRI) on serum cortisol and glucose concentrations, urine production, and anesthetic recovery characteristics in dorsally recumbent, spontaneously breathing, isoflurane-anesthetized horses.

Design—Prospective, randomized crossover study.

Animals—10 healthy Standardbreds.

Procedures—Horses were premedicated with xylazine or medetomidine IV. Anesthesia was induced with diazepam and ketamine and maintained with isoflurane for 150 minutes. For the xylazine treatment, end-tidal isoflurane concentration was maintained at 1.7% and xylazine (0.2 mg/kg [0.09 mg/lb]), IV) was administered as a bolus at the end of anesthesia. For the MCRI treatment, end-tidal isoflurane concentration was maintained at 1.4% and medetomidine (0.005 mg/kg/h [0.0023 mg/lb/h], IV) was infused throughout anesthesia. Serum cortisol and glucose concentrations were measured before, during, and after anesthesia. Urine specific gravity and volume were measured during anesthesia. Unassisted anesthetic recoveries were recorded by a digital video camera for later evaluation by 2 observers who were blinded to treatment.

Results—Serum cortisol concentration was lower and serum glucose concentration was higher with MCRI treatment, compared with xylazine treatment. Time to sternal recumbency was longer with MCRI treatment, but no difference was seen between treatments for times to extubation, first movement, or standing. Objective (mean attempt interval) and subjective (visual analog score) recovery scores were significantly better with MCRI treatment, compared with xylazine treatment.

Conclusions and Clinical Relevance—In isoflurane-anesthetized horses, premedication and administration of medetomidine as a constant rate infusion resulted in decreased serum cortisol concentration, increased serum glucose concentration, and superior anesthetic recovery characteristics, compared with conventional treatment with xylazine.

Full access
in Journal of the American Veterinary Medical Association

Summary

Eight dogs (body weight, 12.5 to 21.5 kg) were assigned at random to each of 3 treatment groups (is, ix, im) that were not given glycopyrrolate and to each of 3 groups that were given glycopyrrolate (igs, igx, igm). Dogs were anesthetized with isoflurane (1.95% end-tidal concentration), and ventilation was controlled (PCO2 , 35 to 40 mm of Hg end-tidal concentration). Glycopyrrolate was administered iv and im at a dosage of 11 μg/kg of body weight, each. Saline solution, xylazine (1.1 mg/kg, im), or medetomidine (15 μg/kg, im) was administered 10 minutes after baseline ade determination. Redetermination of the ade at the same infusion rate was started 10 minutes after drug administration. Arrhythmogenic dose was determined by constant infusion of epinephrine at rates of 1.0, 2.5, and 5.0 μg/kg/min. The ade was defined as the total dose of epinephrine that induced at least 4 ectopic ventricular depolarizations within 15 seconds during a 3-minute infusion, or within 1 minute after the end of the infusion. Total dose was calculated as the product of infusion rate and time to arrhythmia. Statistical analysis of the differences between baseline and treatment ade values was performed by use of one-way anova. Mean ± sem baseline ade values for groups is, ix, and im were 1.55 ± 0.23, 161 ± 0.28, and 1.95 ± 0.65 μg/kg, respectively. Differences for groups is, ix, and im were – 0.12 ± 0.05, – O.31 ± 0.40, and – 0.17 ± 0.26, respectively. Differences for groups igs, igx, and igm could not be calculated because arrhythmias satisfying the ade criteria were not observed at the maximal infusion rate of 5.0 μg/kg/min. Differences among groups is, ix, and im were not significant. We conclude that in isoflurane-anesthetized dogs: preanesthetic dosages of xylazine (1.1 mg/kg, im) or medetomidine (15 μg/kg, im) do not enhance arrhythmogenicity, and at these dosages, there is no difference in the arrhythmogenic potential of either α2-adrenergic receptor agonist.

Free access
in American Journal of Veterinary Research