Inhibitors of the renin angiotensin system: implications for the anaesthesiologist.
The major long-term benefits of angiotensin-converting enzyme (ACE) inhibitors have now clearly been demonstrated in patients with arterial hypertension, cardiac insufficiency, coronary artery disease and several renal diseases. Such long-term treatment markedly alters the cardiovascular response to anaesthesia and surgery, whereas preliminary data suggest that short-term renin angiotensin system blockade might provide perioperative organ protection and improved circulatory conditions. Besides the classic view that the conversion of angiotensin I to angiotensin II is mainly due to ACE, alternative pathways have recently been identified, including cathepsin G as well as chymostatin- and aprotinin-sensitive serine proteases that are released from mastocytes and endothelial cells and which are insensitive to the effects of ACE inhibitors. These proteases are thought to contribute to tissue perfusion under hypoxic conditions and to structural remodelling. In clinical practice, ACE inhibitors may be preferred to angiotensin II receptor antagonists since the former, besides reducing angiotensin II synthesis, also lead to an accumulation of kinins (e.g. bradykinin), which have important cardio- and renal protective effects through liberation of prostacyclin and nitric oxide in endothelial cells and through stimulation of guanylate cyclase to form cyclic GMP.
Licker
M
M
Department of Anaesthesiology, Pharmacology and Surgical Intensive Care, University Hospital, Geneva, Switzerland.
Morel
D R
DR