Asian Cardiovasc Thorac Ann 2004;12:346-349
© 2004 Asia Publishing EXchange Ltd
Preoperative Angiotensin-Converting Enzyme Inhibition Can Cause Severe Post CPB Vasodilation – Current UK Opinion
Mohan P Devbhandari, FRCS,
Sendhil K Balasubramanian, FRCS,
Max Codispoti, FRCS,
Onyekwelu C Nzewi, FRCS,
Sai U Prasad, FRCS
Department of Cardiothoracic Surgery Royal Infirmary of Edinburgh Edinburgh, UK
For reprint information contact: Mohan P Devbhandari, FRCS Tel: 44 125 365 5833 Fax: 44 125 330 3669 Email: sdevbhandari{at}aol.com Department of Cardiothoracic Surgery, Blackpool Victoria Hospital, Whinney Heys Road, Blackpool FY3 8NR, UK.
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ABSTRACT
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Preoperative use of angiotensin-converting enzyme inhibitors in cardiac surgery patients is thought to cause extreme vasodilatation in post cardiopulmonary bypass period. Opinions are divided as to whether it is beneficial or not to stop it prior to operation. A national survey in the UK was carried out on this issue. Questionnaires were sent to 167 currently practicing UK cardiac surgeons, out of which 105 (62%) replied back. Their responses were analyzed. Among the surgeons who replied to the questionnaires, the majority (63%) were of the opinion that the use of angiotensin-converting enzyme inhibitors leads to vasodilatation resulting in increased usage of fluids, inotropes and vasoconstrictors. However, there was no agreement on the issue of stopping it prior to surgery. Forty one (39%) felt it was beneficial to stop the angiotensin-converting enzyme inhibitors prior to surgery whereas 40 (38%) of them thought it was harmful to stop it. Twenty one (20%) were of the opinion that it made no difference. 39% of respondents practiced stopping the drug prior to planned operation. This national survey revealed differences in management of patients on angiotensin-converting enzyme inhibitors undergoing cardiac surgery. Recommendations from available literature are equally varied, highlighting the need for multicenter randomized trials to address this clinical problem.
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INTRODUCTION
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Since description of the first angiotensin-converting enzyme inhibitor (ACEI) captopril in 1977, a wide variety of drugs of this group have come into clinical use. They are increasingly being used for a widening group of cardiac and vascular indications. Consequently a significant proportion of patients are on chronic ACEI therapy when they come for cardiac surgery. There are three classes of ACEI represented by captopril (class I), enalapril (class II) and lisinopril (class III). Despite intense pharmaceutical promotion of the specific virtues of individual drugs, they, as a group, have very similar mechanism of action and side effects.
The therapeutic effect of vasodilatation becomes disadvantageous at the time of surgery. The continued administration of ACEI in cardiac surgical patients up until the time of their operation is thought to cause extreme vasodilatation in the intra- and early post-operative period. This situation often results in the need for alpha-adrenergic drugs and increased amounts of intravenous fluids. Conflicting results have been reported on whether it is beneficial or not to stop the administration of ACEI prior to cardiac surgery. This survey was designed to obtain an overview of current practices adopted by consultant cardiac surgeons in the UK relating to the use of ACEI in the period preceding cardiac operations.
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METHODS
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Questionnaires consisting of six questions were sent to 167 currently practicing UK cardiac surgeons (Figure 1
). Their responses were collected and analyzed.
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RESULTS
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One hundred and five surgeons out of 167 (62%) replied to the questionnaire, the results of which are summarized in Figure 2. There was no agreement on the issue of stopping ACEI prior to surgery and its effects. Approximately two thirds (65%) of the surgeons who replied do not stop administration of ACEI in the preoperative period (Question 1). Among those who do have a policy of stopping ACEI, the majority (85%) stop their administration less than 1 week before surgery, with the remainder (15%) stopping ACEI one week before surgery (Question 2).
As expected, all surgeons who stop ACEI before surgery (35% of respondents) think this action is beneficial. Among the surgeons who do not stop ACEI before surgery, 40 (61.5%) think that stopping ACEI is not beneficial, whereas 23 (35.4%) believe that it makes no difference (Question 3). However, 36.1% of respondents think that stopping ACEI before surgery is harmful, with 46.6% believing the contrary. Interestingly, 16.2% of respondents are of the opinion that stopping ACEI makes no difference (Question 4). The majority (62%) of respondents are of the opinion that the continued administration of ACEI until the time of surgery leads to vasodilatation in the early postoperative period resulting in increased use of fluids, inotropes and vasoconstrictors. Conversely, 19% think that this is not the case and 13.3% believe that it makes no difference (Question 5).
In the comment section of the last question most of the surgeons who do not stop ACEI administration expressed their concern regarding deleterious effects of stopping the drug especially in patients with reduced left ventricular function. They felt the problem could be easily managed by use of vasoconstrictors in the postoperative period.
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DISCUSSION
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This survey highlights a striking lack of consensus amongst cardiac surgeons on the use or non-use of ACEI in the short period preceding cardiac surgical procedure. It also shows contrasting opinions on the observed effects of ACEI in the early postoperative period. Even though the response rate of the questionnaire was moderate it covers all the cardiac centers (40 out of 40) in the United Kingdom and is fairly representative of the existing practice in this country. ACEI are regarded as the mainstay of treatment in patients with left ventricular failure.1 It has been demonstrated that long-term therapy with ACEI facilitates regression of left ventricular hypertrophy as well as remodelling of vascular smooth muscle and cardiac myocytes.2 These structural changes explain the diminished adrenergic responsiveness of the cardiovascular system after treatment with ACEI.3,4
It has been suggested that patients receiving long-term ACEI therapy experience marked vasodilatation in the early postoperative period, often requiring administration of large volumes of intravenous vasoconstrictors.5 Ruiz Ros and colleagues investigated the effect of preoperative administration of captopril by a prospective randomized controlled trial in a group of patients undergoing valve surgery and concluded that it increased the incidence of stunning.6 In a non-randomized prospective study Argenziano and associates also found a significant increase in the incidence of vasodilatory shock after cardiac surgery in patients on chronic ACEI therapy.7 There is a further concern that in patients undergoing coronary revascularization with arterial conduits, the use of vasoconstrictors could potentially lead to spasm of these grafts, reflecting unfavorable clinical outcomes.8
In contrast to these studies a number of non-randomized10,11 and randomized11 studies have reported that there was no difference in outcome whether or not the ACEI were in use prior to surgery. This issue was further investigated in patients with good left ventricular function by Pigott and colleagues in a prospective randomized trial which showed that stopping this drug preoperatively achieved a greater mean arterial pressure and decreased the need of vasoconstrictors during cardiopulmonary bypass (CPB), but did not make any difference after separation from CPB.12 Because of the small number of patients studied and the fact that stopping the drug just 12 to 24 hours prior to surgery did decrease the incidence of vasodilation on CPB, this practice has not been widely adopted by the surgical community. An opposite view was seen within the same institution where this work was carried out.8 Webb and associates also reported a similar finding in a randomized study.11
This study was not designed to recommend any change in practice but rather to assess the general opinion and approaches to this clinical problem. This confirms that there is still a large body of opinion amongst surgeons that these drugs should be discontinued at least a week prior to surgery, if possible. In view of the contrasting evidence available in the literature to date,5–11 there is a need for carefully conducted prospective studies on the effects of ACEI in the early period following cardiac surgery to provide conclusive evidence to guide clinical practice. This survey provides evidence of contrasting practices amongst cardiac surgeons in the UK on the management of patients treated with ACEI prior to cardiac surgery. This reflects contrasting evidence in the literature and highlights the need for large randomized trials to provide conclusive data that can guide clinical practice.
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REFERENCES
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ABSTRACT
INTRODUCTION
