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The influence of suxamethonium on cardiovascular and respiratory function in the anaesthetized horse
Author(s) -
LEES P.,
TAVERNOR W. D.
Publication year - 1969
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1969.tb08309.x
Subject(s) - blood pressure , anesthesia , medicine , respiratory system , tachyphylaxis , heart rate , halothane , respiratory rate , depressant , pharmacology
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 P co 2 levels and in plasma concentrations of bicarbonate, sodium and potassium ions, and reductions in arterial blood pH and P o 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.