ANAESTHETICS

Isoflurane or Halothane

Halothane and Isoflurane are the two types of inhalational anaesthetic agents that we offer.  These types of anaesthetics are used for longer surgeries because they are more advantageous than intravenous injectable agents.

Halothane

Halothane has been used in human and veterinary medicine since the 1950s.  It is the most commonly used inhalational anaesthetic agent used in veterinary practices.

Cardiovascular effects:

v      Cardiovascular depressionàblood pressure, cardiac output, stroke volume left ventricular work, total peripheral resistance are all reduced.

v      Decreased myocardial contractility

v      Increases potential for arrhythmias

Respiratory effects:

v      Depresses ventilation (dose dependent)

v      Mild bronchodilation

Hepatic and Renal system effects:

v      Decreased function through decreased blood flow

v      Metabolised 20% in liver

v      Decreased urine production

Other effects:

v      Maybe excitement in recovery

v      Increased cerebral blood flow

v      Depressed GIT motility

Isoflurane

Isoflurane is the most recently discovered inhalational anaesthetic agent that has been used since 1980.

Cardiovascular effects:

v      Depression similar to that of halothane

v      Cardiac output is preserved more than in halothane

v      Myocardial function is maintained better than with halothane, in fact blood flow to the myocardium is improved

v      Does not cause arrhythmias

Respiratory effects:

v      More depressant than halothane

Renal and hepatic system effects:

v      Blood flow to these well maintained

v      Minimal metabolism in the body (less than 1%)

Other effects:

v      Increase in cerebral blood flow less than with halothane

The solubility of the two drugs affects the speed of induction and recovery from anaesthesia, ie the more soluble the drug the longer the induction and recovery times.  Halothane is much more soluble than isoflurane so induction is slower and recovery is prolonged compared with isoflurane.