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  • Author or Editor: Charles E. Short x
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SUMMARY

We compared the anesthetic combination of detomidine, ketamine, and halothane in control horses not undergoing apparently painful procedures with that in horses during arthroscopic surgery. The effectiveness of this regimen in suppressing neurologic response to surgery was, thus, evaluated. In this study, significant differences were not observed in electroencephalographic total amplitude, spectral edge, or beta-to-delta frequency ratio between surgically treated and nonsurgically treated (control) horses. On the basis of its attenuation of encephalographic responses, we conclude that detomidine (20 μg/kg of body weight, iv) and ketamine (2.2 mg/kg, iv) induction of anesthesia followed by maintenance with halothane is an effective regimen for control of pain in horses during arthroscopic surgery.

The insignificant frequency changes observed without any other signs of inadequate anesthesia or pain may indicate a surgical stress response. We hypothesize that brain activity monitoring may give an earlier index to initiation of surgically induced stress than do hormonal responses, because endocrine alterations are not as rapidly perceived as is the electroencephalogram. Analysis of spectral edge frequency changes could be used to evaluate anesthetic regimens to find those that cause the least stress to the cns during surgery in horses. Differences in species responses to an anesthetic agent or the regimen’s effectiveness in prevention of pain during surgery may be identified by adoption of the study model. Evaluation of cardiopulmonary variables during anesthesia, with and without surgery, did not reveal any alterations that would be relevant to cns responses. Blood pressure, heart rate, Pa O 2 , Pa CO 2 , and pH were stabilized by use of intermittent positive-pressure ventilation in all horses, and dobutamine was administered, as needed, to avoid bias of electroencephalogram data.

Free access
in American Journal of Veterinary Research

SUMMARY

The isoflurane-sparing effect of the α2-adrenergic agonist medetomidine (30 μg/kg of body weight, IV) was tested in 7 dogs, using a blinded, randomized-block study design. The baseline minimal alveolar concentration (mac) of isoflurane was 1.18 vol% (95% confidence interval [097,1.39])- Medetomidine significantly (P < 0.003) reduced isoflurane mac by 47.2%. Atipamezolc (0.3 mg/kg, iv), an α2-adrenergic antagonist, completely reversed the effect of mcdetomidine on isoflurane mac. Atipamezole alone did not significantly alter isoflurane mac.

After medetomidine administration, marked bradycardia developed in all dogs and persisted for more than 2 hours Mean arterial blood pressure increased acutely, but later decreased, and hypotension persisted for more than 2 hours. Atipamezole reversed the bradycardic and hypotensive effects of medetomidine.

Results of this study indicate that medetomidine mav be useful in clinical cases in which isoflurane mac-reduction is desirable and that atipamezole might be used to reverse desirable and undesirable effects of medetomidine during isoflurane anesthesia.

Free access
in American Journal of Veterinary Research

SUMMARY

Gentamicin sulfate, equivalent to 4 mg of gentamicin base/kg of body weight, was administered iv to 6 Thoroughbred foals on day 1 (12 to 24 hours of age) and at 5, 10, 15, and 30 days after birth. On day 40 after parturition, gentamicin was given to the mares at a dosage similar to that used in foals. Decay of serum gentamicin concentrations was best described by a 2-compartment model. Among foals, the overall elimination rate constant at 30 days of age was significantly (P < 0.05) greater than at days 1, 10, and 15. There was, however, no difference in the overall elimination rate constant between foals and mares. The volume of distribution (Vd), determined on the basis of total area under the disposition curve, did not change between day 1 and day 30. Mean values of Vd of foals were between 1.5 and 2.5 times higher than the mean Vd of the mares; however, only values from the foals at days 5 and 10 were significantly greater. Both age and interindividual differences were reflected in the total body clearance (ClB) of gentamicin. Total body clearance of gentamicin of foals on day 1 was less than that of foals on days 5, 10, and 30. Additionally, ClB of gentamicin on day 15 was less than that on day 30. There was no significant difference between ClB of foals and mares except for the day-30 group, which had a higher clearance rate than did the adults. Protein binding of gentamicin was < 30% in all groups, and there were no apparent age-related differences.

Free access
in American Journal of Veterinary Research

SUMMARY

Objectives

To compare the dose-sparing effect of medetomidine on the propofol induction dose and concentration of halothane for maintenance of anesthesia during laparoscopy and to provide guidelines for effective and safe use of these anesthetics in dogs to ensure desirable perioperative analgesia.

Animals

14 purpose-bred dogs.

Procedure

Cardiopulmonary and electroencephalographic responses were determined during 2 anesthesia protocols in dogs scheduled for laparoscopy. Fifteen minutes before anesthesia induction, all dogs received atropine sulfate (0.02 mg/kg of body weight, IM). Seven dogs were then given propofol (6.6 mg/kg, IV); anesthesia was maintained with halothane in oxygen. The other dogs were given medetomidine hydrochloride (10 μg/kg, IM) 5 minutes after administration of atropine sulfate; anesthesia was then induced by administration of propofol (2.8 mg/kg, IV) and was maintained with halothane in oxygen.

Results

The halothane concentration required for laparoscopy was lower in dogs given medetomidine. Anesthetic requirements were significantly increased during abdominal manipulation in both groups. Total amplitude of the electroencephalograph in medetomidine-treated dogs was not significantly lower than that in dogs not given medetomidine. Pulmonary responses were stable throughout all procedures. The primary cardiovascular response was an increase in blood pressure associated with the medetomidine-atropine preanesthetic combination. Significant differences in total amplitude or frequency shifts (spectral edge) of brain wave activity were not associated with surgical stimulation.

Conclusion

Lack of neurologic changes during laparoscopy supports the efficacy of either medetomidine-propofol-halothane or propofol-halothane combinations at higher concentrations to provide desirable analgesia and anesthesia in this group of dogs. (Am J Vet Res 1997;58:1443–1450)

Free access
in American Journal of Veterinary Research

SUMMARY

Intracranial pressure and cardiovascular variables after iv administration of medetomidine (0.03 mg/kg of body weight) were evaluated in 6 healthy, mixed-breed dogs anesthetized with 1.3% end-tidal isoflurane concentration and mechanically ventilated to normocapnia (PaCO2 , 35 to 45 mm of Hg). Baseline values were determined for intracranial pressure, heart rate, arterial blood pressure, cardiac output, mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, end-tidal CO2 tension and isoflurane concentration, arterial pH and CO2 and O2 tensions, and core body temperature. Cerebral perfusion pressure, cardiac index, systemic and pulmonary vascular resistances, plasma HCO3- concentration, and base excess were calculated. Intracranial pressure was measured, using a calibrated, fiberoptic transducer placed within the brain parenchyma and secured to the calvarium by means of a subarachnoid bolt. Cardiac output was determined by thermodilution. End-tidal CO2 tension and isoflurane concentration were determined, using an infrared gas analyzer. Administration of medetomidine did not change intracranial pressure, but was associated with significant (P < 0.05) decreases in values for heart rate, cardiac index, end-tidal CO2, and HCO3- and with significant increases in systolic, mean, and diastolic pressure; pulmonary artery pressure; systemic vascular resistance; central venous pressure; and pulmonary capillary wedge pressure.

Free access
in American Journal of Veterinary Research

SUMMARY

Sodium salicylate was administered to cattle and goats iv and po according to a crossover design. Total urinary excretion of sa and its metabolites was measured for 3 days after dosing. Salicyluric acid (sua) was the only metabolite detected in urine of either species. Recovery of sodium salicylate and sua in goats amounted to 67.9 and 34.6% of the dose, respectively, after iv administration. After oral dosing, total recoveries were 30.2% (sodium salicylate) and 71.7%(sua) of dose. By comparison, cattle excreted significantly (P < 0.05) less sodium salicylate (54.0%) and more sua (49.9%) after iv dosing. The same pattern was observed after oral administration, wherein cattle excreted < 12% as sodium salicylate and more than 99% as sua. In both species, almost 90% of the drug excreted as sodium salicylate was found in urine within the first 12 hours after an iv dose and within 24 hours after oral dosing. The excretion of sua was somewhat slower in both species, especially after oral administration. The data suggested that there were only quantitative differences in the metabolism and elimination of sodium salicylate between the 2 species, with cattle excreting a higher proportion of the drug as the glycine conjugate sua.

Free access
in American Journal of Veterinary Research