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Home / Equine Research Bank / Br J Pharmacol / Influence of halothane and catecholamines on heart rate and ...
British journal of pharmacology1970; 39(1); 149-159; doi: 10.1111/j.1476-5381.1970.tb09564.x

Influence of halothane and catecholamines on heart rate and rhythm in the horse.

Abstract: 1. Ventricular ectopic beats were recorded in eight of thirteen conscious horses following the intravenous administration of adrenaline in doses of 3 mug/kg. Following pre-treatment with either atropine sulphate (0.1 mg/kg) or propranolol hydrochloride (0.1 mg/kg), the same dose level of adrenaline failed to produce ventricular ectopic beats.2. Halothane anaesthesia sensitized the equine heart to the arrhythmogenic actions of adrenaline; the incidence and duration of ventricular arrhythmias being greater than in conscious animals. In comparison with the findings in conscious horses, ether anaesthesia appeared to protect the heart against adrenaline-induced arrhythmias.3. From a comparison of the arrhythmogenic, chronotropic and pressor actions of adrenaline, noradrenaline and isoprenaline during halothane anaesthesia, it was concluded that sensitization to the arrhythmogenic actions of catecholamines resulted primarily from the action of halothane on the ventricle. The results also indicated that the pressor responses to catecholamines during halothane anaesthesia probably played some part in the genesis of arrhythmias.4. No "spontaneous" ventricular arrhythmias were recorded in twenty-four horses anaesthetized with halothane or in sixteen animals under ether anaesthesia.5. The available evidence indicates that a moderate to fairly severe degree of hypercapnia produced little increase in sympathetic control of the myocardium during halothane anaesthesia; the absence of irregularities in ventricular rhythm during halothane anaesthesia were attributed to this factor.
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Publication Date: 1970-05-01 PubMed ID: 5420092PubMed Central: PMC1703061DOI: 10.1111/j.1476-5381.1970.tb09564.xGoogle Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigates how the anesthetic drug halothane and substances known as catecholamines such as adrenaline, impact the heart rate and rhythm in horses, determining that halothane can make the heart more responsive to the irregular rhythm-causing effects of adrenaline.

Procedure and Findings

  • The study recorded abnormal heartbeats called ventricular ectopic beats in eight out of thirteen awake horses that were given adrenaline through the vein. However, once these horses had been pre-treated with other drugs (atropine sulphate or propranolol hydrochloride), the same amount of adrenaline did not cause these ectopic beats.
  • The study found that under halothane anesthesia, the horse’s heart became more prone to irregular rhythms caused by adrenaline. The presence and duration of these irregular heart rhythms were greater than in horses that were not under anesthesia. Comparatively, anesthesia with ether appeared to provide some heart protection against these adrenaline-induced arrhythmias.

Comparison of Adrenaline, Noradrenaline, and Isoprenaline effects under Halothane Anesthesia

  • The effects of the adrenaline, noradrenaline, and isoprenaline on the heart rate, rhythm, and blood pressure were compared under halothane anesthesia. The researchers concluded that the increased susceptibility to abnormal heart rhythms caused by these chemicals was largely due to the halothane’s impact on the ventricles of the heart. The study also suggested that the changes in blood pressure response to these chemicals during halothane anaesthesia may play a role in the development of these irregularities.

Spontaneous Ventricular Arrhythmias and Hypercapnia

  • No spontaneous ventricular arrhythmias were recorded in twenty-four horses anaesthetized with halothane or in sixteen animals under ether anesthesia.
  • They also found that moderate to fairly severe hypercapnia – elevated carbon dioxide levels in the blood – led to little increase in sympathetic control of the myocardium (the middle layer of heart muscle) during halothane anaesthesia. The researchers attributed the absence of irregular heartbeats during halothane anaesthesia to this.

Cite This Article

APA
Lees P, Tavernor WD. (1970). Influence of halothane and catecholamines on heart rate and rhythm in the horse. Br J Pharmacol, 39(1), 149-159. https://doi.org/10.1111/j.1476-5381.1970.tb09564.x

Publication

British journal of pharmacology
ISSN: 0007-1188
NlmUniqueID: 7502536
Country: England
Language: English
Volume: 39
Issue: 1
Pages: 149-159

Researcher Affiliations

Lees, P
    Tavernor, W D

      MeSH Terms

      • Anesthesia, Inhalation
      • Animals
      • Arrhythmias, Cardiac / chemically induced
      • Atropine / pharmacology
      • Catecholamines / pharmacology
      • Consciousness
      • Epinephrine / administration & dosage
      • Ethers
      • Female
      • Halothane / pharmacology
      • Heart Rate / drug effects
      • Horses
      • Hypercapnia / physiopathology
      • Isoproterenol / pharmacology
      • Male
      • Norepinephrine / pharmacology
      • Propranolol / pharmacology

      References

      This article includes 17 references
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      Citations

      This article has been cited 3 times.
      1. Coudry V, Jean D, Desbois C, Tnibar A, Laugier C, George C. Myocardial fibrosis in a horse with polymorphic ventricular tachycardia observed during general anesthesia. Can Vet J 2007 Jun;48(6):623-6.
        pubmed: 17616061
      2. Blaze CA, Robinson NE. Apneic oxygenation in anesthetized ponies and horses. Vet Res Commun 1987;11(3):281-91.
        doi: 10.1007/BF00570926pubmed: 3114941google scholar: lookup
      3. Rezakhani A, Edjtehadi M, Szabuniewicz M. Prevention of thiopental and thiopental/halothane cardiac sensitization to epinephrine in the sheep. Can J Comp Med 1977 Oct;41(4):389-95.
        pubmed: 922556
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