Letter to the Editor: In Response
We thank Whalley and Maurer for their interest in our investigations [1,2], and their comments deserve explanations.
Although mean changes in arterial blood pressure after induction of anesthesia (using a similar technique) are broadly similar in patients treated with angiotension-converting enzyme inhibitors (ACEIs) for hypertension or cardiac failure, two major differences are noticeable between these two pathologies.
First, the mechanisms involved in anesthesia-induced hemodynamic changes are not similar. In hypertensive patients, a dramatic reduction in ventricular preload may explain the reduction in cardiac index. In patients with cardiac failure, a negative inotropic effect of anesthesia combined with ACEIs may explain the decreased cardiac index. In hypertensive patients, ACEIs induce a volume-dependent state of arterial blood pressure regulation, and our major concern during surgery should be to maintain a normovolemia. In patients with cardiac failure, the negative inotropic effect of the combination of the ACEIs and anesthesia suggest that the anesthesia dose should be reduced.
Second, ACEIs increase the incidence of serious adverse hypotension in hypertensive patients but not in patients with cardiac failure. In both studies, mean changes in arterial blood pressure are similar, but mean values, even with standard deviation, may mask the extremes, and it is clinically relevant to consider patients who experience severe hypotension because they are at a higher risk of complications. It seems therefore that changes in a series of hypertensive patients are wider than those in a series of patients with cardiac failure. ACEIs increase the risk of hypotension in hypertensive patients but not in congestive patients.
In conclusion, the recent study  suggests that the risk of severe hypotension is not increased by ACEIs in patients with cardiac failure. Conversely, there are no data to justify maintenance of treatment up to the day of surgery. At the present time, Whalley and Maurer have no reason to alter their preoperative policy with regard to ACEI treatment.
Department of Anaesthesiology and Intensive Care; University of Montpellier; Montpellier, France
1. Ryckwaert F, Colson P. Hemodynamic effects of anesthesia in patients with ischemic heart failure chronically treated with angiotensin-converting enzyme. Anesth Analg 1997;84:945-9.
2. Colson P, Saussine M, Seguin J, et al. Hemodynamic effects of anesthesia in patients chronically treated with angiotensin converting enzyme inhibitors. Anesth Analg 1992;74:805-8