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British journal of pharmacology1969; 36(1); 116-131; doi: 10.1111/j.1476-5381.1969.tb08309.x

The influence of suxamethonium on cardiovascular and respiratory function in the anaesthetized horse.

Abstract: 1. In horses anaesthetized with halothane the intravenous administration of suxamethonium chloride, at a dose level of 0.2 mg/kg, produced a short-lived period of hypoventilation, which was associated with increases in arterial blood PCO(2) levels and in plasma concentrations of bicarbonate, sodium and potassium ions, and reductions in arterial blood pH and PO(2) values.2. The respiratory depressant action of suxamethonium chloride 0.2 mg/kg was accompanied by increases in blood pressure and heart rate. Doses of suxamethonium chloride 0.4 mg/kg produced similar but quantitatively greater changes in cardiovascular and respiratory function. These effects were not accompanied by cardiac arrhythmias, with the exception of one animal, in which an unusually prolonged period of apnoea occurred.3. The cardiovascular effects of suxamethonium during halothane anaesthesia were diminished but not abolished when the respiratory depressant action of suxamethonium was prevented by applying positive pressure ventilation.4. The cardiovascular effects of suxamethonium in horses anaesthetized with halothane were partially antagonized by propranolol and completely antagonized by hexamethonium. It is suggested that the cardiovascular effects of suxamethonium are mediated by two distinct mechanisms: reflexly mediated increases in heart rate and sympathetic vasoconstrictor tone due to the respiratory depression, and a direct stimulant action of suxamethonium on peripheral, autonomic ganglia.5. Much less pronounced changes in cardiovascular function, but not in respiratory function, were recorded when suxamethonium was administered to horses anaesthetized with ether.6. A slight degree of tachyphylaxis to the cardiovascular and respiratory effects of suxamethonium was recorded in horses anaesthetized with halothane.7. Some atypical effects of suxamethonium on respiration are described.
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Publication Date: 1969-05-01 PubMed ID: 5768082PubMed Central: PMC1703571DOI: 10.1111/j.1476-5381.1969.tb08309.xGoogle Scholar: Lookup
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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.

The research investigates the impact of suxamethonium chloride on the cardiovascular and respiratory functions in horses anesthetized with halothane and ether. Findings demonstrated that the drug led to hypoventilation and changes in blood composition, but these effects could be mitigated by certain interventions.

Effects of Suxamethonium Chloride in Halothane-anesthetized Horses

  • The administration of suxamethonium chloride in horses led to a brief period of weak or shallow breathing (hypoventilation). This was evidenced by increased levels of bicarbonate, sodium, and potassium ions in plasma, and a rise in arterial blood CO2 levels. Additionally, it resulted in decreased pH levels and oxygen (PO2) values in arterial blood.
  • This period of hypoventilation was associated with heightened blood pressure and heart rate. Larger doses of suxamethonium chloride amplified these respiratory and cardiovascular changes, with one instance of an unusually long period of stopped breathing (apnoea) occurring, but no indications of cardiac arrhythmias.

Respiratory and Cardiovascular Impact of Suxamethonium Chloride

  • When horses were aided with positive pressure ventilation, the overall impact of suxamethonium on cardiovascular functions during halothane anaesthesia was reduced, but not entirely eliminated.
  • The cardiovascular effects of suxamethonium in horses under halothane anaesthesia could be partially offset with propranolol and entirely counteracted with hexamethonium. This suggests that the drug’s cardiovascular impacts stem from two separate mechanisms: reflex reactions leading to increased heart rate and tightened blood vessels due to respiratory depression, and a direct stimulatory effect of suxamethonium on peripheral, automatic ganglia.
  • Significantly less drastic changes in cardiovascular function, yet no change in respiratory function, were observed when suxamethonium was given to horses anesthetized with ether.

Tolerance and Atypical Effects of Suxamethonium

  • The research also recorded a minor degree of tachyphylaxis (decreased responsiveness to a drug after repeated doses) to the cardiovascular and respiratory effects of suxamethonium in horses under halothane anaesthesia.
  • The study also describes some unusual effects of suxamethonium on the respiration of the horses.

Cite This Article

APA
Lees P, Tavernor WD. (1969). The influence of suxamethonium on cardiovascular and respiratory function in the anaesthetized horse. Br J Pharmacol, 36(1), 116-131. https://doi.org/10.1111/j.1476-5381.1969.tb08309.x

Publication

British journal of pharmacology
ISSN: 0007-1188
NlmUniqueID: 7502536
Country: England
Language: English
Volume: 36
Issue: 1
Pages: 116-131

Researcher Affiliations

Lees, P
    Tavernor, W D

      MeSH Terms

      • Anesthesia, Inhalation / veterinary
      • Animals
      • Blood Pressure / drug effects
      • Carbon Dioxide / blood
      • Cardiovascular System / drug effects
      • Heart Rate / drug effects
      • Hexamethonium Compounds / pharmacology
      • Horses
      • Oxygen / blood
      • Propranolol / pharmacology
      • Respiration / drug effects
      • Succinylcholine / pharmacology

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      Citations

      This article has been cited 1 times.
      1. Lees P, Tavernor WD. Influence of halothane and catecholamines on heart rate and rhythm in the horse. Br J Pharmacol 1970 May;39(1):149-59.
        doi: 10.1111/j.1476-5381.1970.tb09564.xpubmed: 5420092google scholar: lookup
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