Is There an Adverse Drug Reaction Between Renin-Angiotensin System Blockade and Inhaled Anesthetics

It is controversial whether or not patients whose Renin Angiotensin System is blocked for the treatment of hypertension suffer increased risk when undergoing surgery and anaesthesia. The investigators wish to test the hypothesis: Blockade of the Renin Angiotensin System causes altered dose response under general anaesthesia in a dose dependant manner. The investigators wish to look for altered responses across the usual anaesthetic dosing range as measured by blood pressure and heart responses.