1. The anaesthetic, cardiovascular, respiratory and adverse effects produced by the
intravenous injection of
CT 1341,
thiopentone,
methohexitone,
pentobarbitone,
propanidid and
ketamine have been compared in unrestrained cats prepared with chronically implanted venous and arterial
cannulae. Aortic blood pressure and heart rates were monitored before, during and after
loss of consciousness.2.
CT 1341 produced rapid induction of anaesthesia followed by moderately rapid recovery, was active over a wide range of doses and caused minimal
respiratory depression and few adverse effects. It caused an initial short-lasting
tachycardia and fall in aortic blood pressure succeeded by a secondary depressor response.3. The safety margin was narrower with the
barbiturate drugs than with
CT 1341, and large doses induced apnoea and
respiratory depression. Small doses of
methohexitone elicited excitatory effects and large doses caused severe respiratory and circulatory depression, and recovery from anaesthesia was protracted.4.
Propanidid induced short-lasting light anaesthesia. The safety margin was narrowest with this
drug and induction was associated with adverse circulatory, respiratory and other effects.5.
Ketamine was active over a wide range of doses but exhibited qualitatively different properties from the other anaesthetics. Induction was slower after small doses and these produced circulatory stimulation,
catatonia and bizarre behavioural effects. Large doses caused respiratory and circulatory depression and recovery was protracted.6. It is concluded that
CT 1341 has a wider therapeutic latitude, produces less
respiratory depression and has other advantages over the currently used intravenous anaesthetics.