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Abstract

Objective—To evaluate the effects of ketamine, magnesium sulfate, and their combination on the minimum alveolar concentration (MAC) of isoflurane (ISO-MAC) in goats.

Animals—8 adult goats.

Procedures—Anesthesia was induced with isoflurane delivered via face mask. Goats were intubated and ventilated to maintain normocapnia. After an appropriate equilibration period, baseline MAC (MACB) was determined and the following 4 treatments were administered IV: saline (0.9% NaCl) solution (loading dose [LD], 30 mL/20 min; constant rate infusion [CRI], 60 mL/h), magnesium sulfate (LD, 50 mg/kg; CRI, 10 mg/kg/h), ketamine (LD, 1 mg/kg; CRI, 25 μg/kg/min), and magnesium sulfate (LD, 50 mg/kg; CRI, 10 mg/kg/h) combined with ketamine (LD, 1 mg/kg; CRI, 25 μg/kg/min); then MAC was redetermined.

Results—Ketamine significantly decreased ISOMAC by 28.7 ± 3.7%, and ketamine combined with magnesium sulfate significantly decreased ISOMAC by 21.1 ± 4.1%. Saline solution or magnesium sulfate alone did not significantly change ISOMAC.

Conclusions and Clinical Relevance—Ketamine and ketamine combined with magnesium sulfate, at doses used in the study, decreased the end-tidal isoflurane concentration needed to maintain anesthesia, verifying the clinical impression that ketamine decreases the end-tidal isoflurane concentration needed to maintain surgical anesthesia. Magnesium, at doses used in the study, did not decrease ISOMAC or augment ketamine's effects on ISOMAC.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate antinociceptive and selected effects associated with IM administration of xylazine hydrochloride in combination with tiletamine-zolazepam in llamas.

Animals—8 adult male llamas.

Procedures—Each llama received tiletamine-zolazepam (2 mg/kg) combined with either xylazine (0.1, 0.2, or 0.4 mg/kg) or saline (0.9% NaCl) solution IM (treatments designated as TZ-Xy0.1, TZ-Xy0.2, TZ-Xy0.4, and TZ-Sal, respectively) at 1-week intervals. Selected cardiorespiratory variables were assessed during lateral recumbency and anesthesia, and recovery characteristics were recorded. Duration of antinociception was evaluated by clamping a claw every 5 minutes.

Results—Interval between treatment administration and lateral recumbency for TZ-Xy0.4 was shorter than that for TZ-Xy0.1 or TZ-Sal. Mean ± SEM duration of antinociception was longer for TZ-Xy0.4 (51.3 ± 7. 0 minutes), compared with findings for TZ-Xy0.2 (31.9 ± 6.0 minutes), TZ-Xy0.1 (8.1 ± 4.0 minutes), and TZ-Sal (0.6 ± 0.6 minutes). Interval between treatment administration and standing was longer for TZ-Xy0.4 (112 ± 9 minutes) than it was for TZ-Xy0.2 (77 ± 9 minutes) or TZ-Sal (68 ± 9 minutes). Mean heart and respiratory rates during the first 30 minutes for TZ-Sal exceeded values for the other treatments. Administration of TZ-Xy0.2 and TZ-Xy0.4 resulted in Pao 2 < 60 mm Hg at 5 minutes after llamas attained lateral recumbency, and values differed from TZ-Sal findings at 5, 10, and 15 minutes; Paco 2 was greater for TZ-Xy0.2 and TZ-Xy0.4 than for TZ-Sal at 5, 10, 15, and 20 minutes.

Conclusions and Clinical Relevance—Xylazine (0.2 and 0.4 mg/kg) increased the duration of antinociception in llamas anesthetized with tiletamine-zolazepam.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate sedative, antinociceptive, and physiologic effects of acepromazine and butorphanol during tiletamine-zolazepam (TZ) anesthesia in llamas.

Animals—5 young adult llamas.

Procedures—Llamas received each of 5 treatments IM (1-week intervals): A (acepromazine, 0.05 mg/kg), B1 (butorphanol, 0.1 mg/kg), AB (acepromazine, 0.05 mg/kg, and butorphanol, 0.1 mg/kg), B2 (butorphanol, 0.2 mg/kg), or C (saline [0.9% NaCl] solution). Sedation was evaluated during a 30-minute period prior to anesthesia with TZ (2 mg/kg, IM). Anesthesia and recovery characteristics and selected cardiorespiratory variables were recorded at intervals. Antinociception was assessed via a toe-clamp technique.

Results—Sedation was not evident following any treatment. Times to sternal and lateral recumbency did not differ among treatments. Duration of lateral recumbency was significantly longer for treatment AB than for treatment C. Duration of antinociception was significantly longer for treatments A and AB, compared with treatment C, and longer for treatment AB, compared with treatment B2. Treatment B1 resulted in a significant decrease in respiratory rate, compared with treatment C. Compared with treatment C, diastolic and mean blood pressures were lower after treatment A. Heart rate was increased with treatment A, compared with treatment B1 or treatment C. Although severe hypoxemia developed in llamas anesthetized with TZ alone and with each treatment-TZ combination, hemoglobin saturation remained high and the hypoxemia was not considered clinically important.

Conclusions and Clinical Relevance—Sedation or changes in heart and respiratory rates were not detected with any treatment before administration of TZ. Acepromazine alone and acepromazine with butorphanol (0.1 mg/kg) prolonged the duration of antinociception in TZ-treated llamas.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effectiveness of preinduction hyperbaric oxygen treatment (HBOT) in ameliorating signs of experimentally induced endotoxemia in horses.

Animals—18 healthy adult horses.

Procedures—Horses were randomly assigned to 1 of 3 equal-sized treatment groups to receive normobaric ambient air and lipopolysaccharide (LPS), HBOT and LPS, or HBOT and physiologic saline (0.9% NaCl) solution. Horses were physically examined, and blood was obtained for a CBC and to determine concentration or activity of plasma tissue necrosis factor-α, blood lactate, and blood glucose before the horses were treated with HBOT and then intermittently for 6 hours after administration of LPS or physiologic saline solution.

Results—All LPS-treated horses developed signs and biochemical and hematologic changes consistent with endotoxemia. Treatment with HBOT significantly ameliorated the effect of LPS on clinical endotoxemia score but did not significantly improve other abnormalities associated with endotoxemia.

Conclusions and Clinical Relevance—The protective effect of HBOT was minimal, and results did not support its use as a treatment for horses prior to development of endotoxemia.

Full access
in American Journal of Veterinary Research