American journal of veterinary research
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The arrhythmogenic dose of epinephrine (ADE) was determined in 6 pigs during steady-state anesthesia (1.5% halothane in O2) and steady-state anesthesia plus xylazine (1.1 mg X kg-1 X hr-1; IV infusion) and after either prazosin (alpha 1) or metoprolol (beta 1) adrenergic blockade during halothane-xylazine (H-X) anesthesia. A constant infusion (1, 2, 3, 5, and 10 micrograms X kg-1 X min-1) of freshly mixed epinephrine (100 micrograms X ml-1 in saline solution) was used to determine ADE. The ADE was defined as the total dose of epinephrine which produced 4 or more continuous or intermittent, premature, ventricular contractions within a 15-s period. ⋯ Xylazine administration did not significantly decrease ADE, although mean arterial pressure significantly increased. Prazosin administration significantly increased ADE and was associated with an increased heart rate and a decreased mean arterial pressure. We conclude that alpha 1-blockade with prazosin is more protective to epinephrine-induced arrhythmias in H-X-anesthetized pigs than is beta 1-blockade with metoprolol.
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Comparative Study
Barbiturate anesthesia in greyhound and mixed-breed dogs: comparative cardiopulmonary effects, anesthetic effects, and recovery rates.
The cardiovascular effects, anesthetic effects, and recovery rates were evaluated in racing Greyhounds under barbiturate anesthesia. Greyhounds and mixed-breed dogs of similar body weights were given (by IV route) thiopental (15 mg/kg), thiamylal (15 mg/kg), methohexital (10 mg/kg), and pentobarbital (20 mg/kg). The anesthesia lasted longer in Greyhound than in non-Greyhound mixed-breed dogs given thiopental, thiamylal, and methohexital. ⋯ Packed cell volumes in Greyhounds were significantly higher than those in non-Greyhound mixed-breed dogs after the thiobarbiturates and methohexital were administered. Total plasma protein concentrations were significantly lower in Greyhounds, compared with those in the other dogs before and during barbiturate anesthesia. Methohexital is a useful alternative to thiobarbiturates for short-duration barbiturate anesthesia in Greyhounds.
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Warfarin-induced anticoagulation and reversal of the induced anticoagulation by vitamin K1 were evaluated in 4 mature horses. Each horse was given warfarin IV until the prothrombin (PT) time was prolonged by approximately 1.5 times the predosing base-line value. In experiment 1, we evaluated the time required for PT to return to the predosing value (PT reversal time) after warfarin administration was discontinued. ⋯ Therapeutic response time was designated as the time required for the mean PT time of treated horses to reach the midpoint between the longest mean PT time achieved during anticoagulation and the mean base-line PT time. The therapeutic response time, without supportive therapy, after discontinuation of warfarin administration was 30 hours, and there was a PT reversal time of approximately 5 days from the last dose of warfarin. The 100-mg dose of vitamin K1 shortened the therapeutic response time to 12 hours and the PT reversal time to 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)