and clinical cardiac disease is common in older dogs, and impaired cardiovascular
function should be expected in elderly patients.
Baroreceptor function may be impaired, particularly in
patients with chronic congestive heart failure, and the cardiovascular system's ability
to compensate for surgical haemorrhage, or for the vasodilatory effects of anaesthetic
agents may be inadequate resulting in severe hypotension.
Existing cardiovascular conditions such as congestive
heart failure, cor pulmonale, sick sinus syndrome and the cardiac signs associated
with hyperthyroidism in cats should be stabilised before general anaesthesia.
Anaesthetic agents depress cardiac function and cardiac
arrest can be precipitated if cardiac arrhythmias are present, particularly ventricular
arrhythmias that are refractory to therapy, right bundle branch block and bradycardia
(heart rate below 60 in dogs; below 80 in cats).
Monitoring heart rate and systolic and diastolic blood
pressures by direct or indirect methods is desirable throughout anaesthesia as is
ECG recording, monitoring pulse character and regular examination of visible mucous
membranes for capillary refill time.