Preoperative cardiovascular assessment for noncardiac surgery: update of the guidelines

Transcription

1 04RC1- de Hert Preoperative cardiovascular assessment for noncardiac surgery: update of the guidelines Stefan De Hert Department of Anesthesiology, Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium Introduction Worldwide more than 230 million major surgical operations are performed annually and this number continues to increase [1]. The reported 30-day mortality in moderate to high risk noncardiac surgery ranges from 2% to more than 5% [2-5] and cardiac complications are the most important cause of perioperative morbidity and mortality. These include cardiac death, nonfatal myocardial infarction and nonfatal cardiac arrest [6,7]. Perioperative myocardial infarction Historically, according to the World Health Organization definition, the diagnosis of myocardial infarction requires the presence of two of the following three features: symptoms of myocardial ischaemia, elevation of concentrations of markers of cardiac damage, and a typical electrocardiographic pattern involving the development of Q waves or persistent T wave changes [8]. With the availability of specific and highly sensitive immunoassays for myocardial proteins, such as cardiac troponins T and I, it has become possible to identify the presence of small areas of myocardial injury. This has led to a redefinition of the diagnosis of myocardial infarction including a characteristic rise and fall in blood concentrations of cardiac troponins and/or creatine kinase (CK) MB in the context of ischaemic symptoms or a coronary intervention [9-11]. Defining perioperative myocardial infarction (PMI), however, is less straightforward because the classical clinical symptoms may be blunted in anaesthetised and sedated patients, electrocardiographic changes may be subtle and transient and CKMB assessment has limited sensitivity and specificity because of the potential for skeletal muscle injury associated with surgery. As a consequence, the diagnosis of PMI was often delayed until the third to fifth postoperative day and was associated with a high mortality ranging from 30 to 70% related to the absence of prompt treatment of the perioperative ischemic event [12]. The use of serial troponin assessments has indicated that most PMIs occur within 24 to 48 hours of surgery [13,14]. Interestingly, two distinct types of postoperative troponin release have been observed: an early peak occurring within the first 24 hours and a late peak occurring after 24 hours [15]. Although approximately 90% of the troponin elevations seem to occur within the first 24 hours, the different time profiles of postoperative troponin release are suggestive of distinct pathophysiological mechanisms associated with perioperative myocardial infarction. Indeed, two types of PMI have been defined that are caused by distinct pathophysiological mechanisms [12,16]. These are the acute coronary syndrome (type 1 PMI) and the myocardial oxygen supply-demand imbalance (type 2 PMI). The pathophysiological mechanisms involved are schematically represented in Figure 1. Figure 1: Schematic representation of the pathophysiological mechanisms involved in the two types of perioperative myocardial infarction (PMI): the acute coronary syndrome (type 1 PMI) and the myocardial oxygen supply-demand imbalance (type 2 PMI)

2 Cardiac risk indices The goal of cardiac risk stratification is to identify those patients who are at increased risk for developing perioperative cardiac complications in order to do as much as possible to prevent such events occurring. In addition, identification of such risks may guide perioperative management, including the choice of surgical and anaesthetic techniques and the type and intensity of postoperative care and surveillance. Ultimately, cardiac risk stratification may also facilitate informed patient consent and physician decision making. There are two types of clinical risk indices. The different generic cardiac risk indices (e.g. Lee and Goldman score) estimate a patient s risk by estimating the number of predictors of risk in a patient [17,18]. The Bayesian risk indices (e.g. Detsky index) include an estimate of the cardiac event rate for a specific surgical procedure, and thus the probability for cardiac events. Combining this pre-test probability with the patient s individual risk index (predictors of risk such as, history of angina, diabetes, etc.) or likelihood index for cardiac events, will result in the post-test probability for the individual patient to develop perioperative adverse cardiac events [19,20]. Several studies have assessed the predictive accuracy of both the generic and the Bayesian risk indices. However their predictive accuracy remains uncertain mostly because complication rates for individual surgical procedures in different institutions remain ill-defined. Therefore, the ultimate determination of the optimal risk index to predict major perioperative cardiac events will require a multicentre approach including several university and non-university hospitals [6]. Until such information is available, the revised cardiac risk index (RCRI) is the best validated and most accurate predictive generic risk index, which is, in addition, simple to use in daily clinical practice [18]. This index consists of 6 equally weighted cardiovascular risk factors, assigning one point for the presence of one of the following variables: high risk surgical procedure, history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular accident, preoperative treatment with insulin, or a serum creatinine greater than 2.0 mg.dl -1. The estimated risks of major cardiac complications associated with indices of 0, 1, 2, and 3 or higher are 0.4 ( ) %, 1.0 ( ) %, 2.4 ( ) % and 5.4 ( ) % respectively. Preoperative cardiovascular assessment Cardiac risk indices may help in the decision making whether or not further strategies for diagnosis and perioperative management need to be applied. However, such risk estimates do not clearly define the specific needs of each individual patient with regard to further testing and perioperative strategies. This necessitates information on the extent and stability of the patient s individual cardiovascular disease. Such information is usually obtained from clinical assessment and potentially from additional technical testing [21]. Recently, task forces both in the United States and in Europe have addressed the problem of pre-operative assessment and perioperative management of the patient undergoing non-cardiac surgery, and provided recommendations and guidelines [22-24]. However, it is important to note that such recommendations are based on the best available evidence at the moment of the writing of the guidelines and that this best available evidence may change with the publication of studies providing new information or new insights that may challenge previous results [24,25]. Clinical assessment If there is no need for emergency surgery further clinical assessment is indicated. The occurrence of cardiac complications after noncardiac surgery depend not only on specific patient-related risk factors but also on the type of surgery and the circumstances under which the surgery takes place [26]. Surgical factors that influence cardiac risk are related to the urgency, magnitude, type, and duration of the procedure, as well as its impact on temperature regulation, blood loss and fluid shifts. Therefore preoperative clinical assessment will include an evaluation of patient specific variables as well as an evaluation of a surgical risk estimate. There are a number of active cardiac conditions that are considered to indicate a major clinical risk for perioperative complications. The presence of one or more of these conditions, summarized in table 1, is an indication for further assessment and an adapted management strategy, including possible postponement of elective surgery should additional treatment be necessary

3 unstable coronary syndromes decompensated heart failure significant arrhythmias severe valvular disease unstable or severe angina recent myocardial infarction (within 30 days) high-grade atrioventricular block symptomatic ventricular arrhythmias supraventricular arrhythmias with uncontrolled ventricular rate (> 100 bpm at rest) symptomatic bradycardia newly recognized ventricular tachycardia severe aortic stenosis (mean pressure gradient > 40 mm Hg, area < 1 cm 2 or symptomatic) symptomatic mitral stenosis Table 1: active cardiac conditions that necessitate further evaluation and treatment before non-cardiac surgery If no active cardiac conditions are present, the next step is to assess the risk of surgery (Table 2) [27]. Many surgical procedures are associated with a low risk of perioperative complications even in high-risk patients. In such case it is recommended to proceed with planned surgery. In the case of intermediate or high risk surgery, further assessment of the patient s physical status is indicated. This evaluation considers whether the patient can sustain a functional capacity equal or greater than 4 metabolic equivalents without symptoms. If so, there should be no problem proceeding with surgery. If, however, the patient is symptomatic or the functional capacity of the patient is unknown, further assessment is necessary. high risk (cardiac risk > 5%) aortic surgery major vascular surgery peripheral vascular surgery intermediate risk (cardiac risk 1 5%) intraperitoneal and intrathoracic surgery carotid endarterectomy head and neck surgery orthopaedic surgery prostate surgery low risk (cardiac risk < 1%) endoscopic procedures superficial procedures cataract surgery breast surgery ambulatory surgery Table 2: risk of cardiac death and non-fatal myocardial infarction for non-cardiac operations This assessment will determine the need for further evaluation and potential treatment prior to surgery based on the presence of a number of clinical risk factors. These include history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular disease, diabetes mellitus and a pre-operative creatinine level > 2.0mg.dl -1. If there are no clinical risk factors, surgery can be planned. If the patient has 1 or 2 risk factors then it is recommended to proceed to planned surgery but with adequate heart rate control. Alternatively, further assessment of cardiac status by non-invasive testing can be considered, but only if it will change management. In high risk surgery patients with 3 or more risk factors, it is suggested that testing should only be considered if the results of such tests will change management. For intermediate risk surgery patients, there are insufficient data to date to determine the best strategy (proceed to surgery with heart rate control or perform further testing). Of note, the European guidelines [23] (more than the American guidelines [22]) place emphasis on the use of a titrated preoperative pharmacological treatment with β- blockers and statins. As discussed later on, this strategy may be challenged following some recent evidence

4 Noninvasive testing Additional preoperative testing is performed in order to provide an objective measure of functional capacity, and to identify the importance of pre-operative myocardial ischemia and rhythm disturbances. While most currently applied tests seem to have a satisfying sensitivity and specificity, dobutamine stress echocardiography has been shown to have a positive trend towards better diagnostic performance, especially in situations of valvular or left ventricular dysfunction [28]. However some caution is warranted with the interpretation of these results because a number of methodological issues have been identified in the studies included in this meta-analysis such as a retrospective design, absence of blinding and the low event rate. Therefore, it has been claimed that such methodological limitations leave a considerable uncertainty with regard to the ability of these non-invasive tests to predict perioperative cardiac events in noncardiac surgery [6]. Another application of some of these non-invasive techniques is to evaluate the extent of viable myocardium in patients with coronary artery disease and hence identify those patients that may benefit from revascularization [29]. Preoperative treatment The potential benefits of preoperative coronary revascularization remain a point of debate. It seems that only a selected patient population may benefit from such intervention [30,31]. Overall, it seems that the indications for preoperative coronary revascularization are similar to those in the non-operative setting. Once the decision for preoperative coronary revascularization has been taken, a choice should be made between surgery or a percutaneous coronary intervention (PCI). A recent study in patients receiving multivessel coronary artery revascularization as prophylaxis for elective vascular surgery indicated that patients having coronary surgery had fewer myocardial infarctions after the vascular surgery than those having had a PCI. This difference between groups was attributed to a more complete revascularization [32]. Percutaneous coronary revascularization with the use of stents has been introduced to reduce the incidence of restenosis. To prevent early in-stent thrombosis dual antiplatelet therapy is indicated, the duration of which depends on the type of stent used. Interruption of antiplatelet therapy has been associated with late in-stent thrombosis [33]. Approximately 5% of patients who had coronary stenting require some form of non-cardiac surgery within 1 year after stenting [34]. Since antiplatelet therapy may increase the risk of perioperative bleeding, there has been a tendency to discontinue these drugs at the time of surgery. However such action may have disastrous consequences for the surgical patient [35] and therefore specific guidelines have been developed for the management of such patients [36,37,38]. With respect to potential preoperative revascularization by percutaneous coronary angioplasty, a strategy of balloon angioplasty or bare-metal stent placement followed by 4 to 6 weeks of dual-antiplatelet therapy is recommended. In patients who have received drug-eluting coronary stents and who need an urgent surgical procedure, necessitating the discontinuation of thienopyridine therapy, it is suggested that aspirin therapy is continued and the thienopyridine is restarted as soon as possible. Elective noncardiac surgery is not recommended within 4 to 6 weeks of bare-metal coronary stent implantation or within 12 months of drug-eluting coronary stent implantation in patients in whom thienopyridine therapy, or the dual therapy aspirin thienopyridine will need to be discontinued perioperatively. Finally, elective noncardiac surgery is also not recommended within 4 weeks of balloon angioplasty. With regard to the indications of valve repair before noncardiac surgery, only limited data are available, that do not allow for recommendations to be defined. Based on clinical experience it seems logical to have those patients with valvular disease, that is severe enough to constitute an indication for surgical correction in its own right, treated before the noncardiac surgery. It has been suggested that a less invasive approach using balloon valvuloplasty might constitute an intermediate step in reducing the operative risk of noncardiac surgery in these patients [38] but no controlled studies on the subject are available

5 Issues in perioperative management A substantial part of the existing guidelines on preoperative evaluation and perioperative management of the noncardiac surgery patient [22,23] deal with perioperative management strategies that aim to reduce perioperative cardiac risk. Since their initial publication, a number of new data have become available that merit some considerations with regard to their potential impact on some of the recommendations. Perioperative β-blocking therapy Both the American and the European guidelines have put emphasis on an assumed beneficial effect of perioperatively initiating β-blocking medication. Especially in the European guidelines, well-titrated β-blocking therapy is involved at different steps of the flowchart. The safety of perioperative β-blockade has recently been questioned by a recent meta-analysis [39] and sometimes later the publication of the results of the POISE trial [40]. This study showed a beneficial effect of a high-dose metoprolol controlled-release therapy on the risk of perioperative myocardial infarction but this was at the expense of an increased risk of stroke and overall mortality. Although it was indicated that the initiation time and dose of β-blocker therapy with tight dose adjustments for heart rate control, and a correct estimation of the underlying cardiac risk of the individual patient are important factors determining the effectiveness and safety of the therapy [41,42], there seems now to be sufficient evidence to refrain from routinely initiating perioperative β-blocking treatment for noncardiac surgery [43,44]. Consequently, the American guidelines have revised their recommendations with regard to perioperative β-blocking therapy, leaving only continuation of current β-blocking therapy as an indication [45]. Perioperative statin therapy Statins are commonly prescribed for primary and secondary prevention of cardiovascular events in patients with hypercholesterolaemia and more recently also in patients with normal plasma cholesterol levels, who are at risk for or are known to have coronary artery disease. A number of these studies have suggested that statins may also decrease the incidence of adverse cardiovascular outcome after cardiac and non-cardiac surgery. These protective effects have been related to the lipid lowering and the pleiotropic effects of statins. Two recent systematic reviews with meta-analysis of the available studies have been conducted looking at the available evidence for the protective effects of statins in the perioperative period [46,47]. It appeared that the majority of the studies on the topic were retrospective and observational and confounded by prescribing bias, inability to control for a steady evolution of statin use over time, and inability to control for preoperative risk other than through propensity scoring. Most of the evidence seems to indicate that perioperative statin therapy is associated with a survival benefit, however with a variable effect on postoperative cardiovascular morbidity. There is a need for larger prospective, randomized clinical trials to confirm this observation and to determine the optimal timing and duration of statin therapy in the surgical setting. Perioperative anaesthetic management Increasing evidence has indicated that volatile anaesthetic agents may have cardioprotective properties. In the setting of coronary artery surgery, the use of these drugs was shown to be associated with a better preservation of postoperative myocardial function and less evidence of postoperative myocardial damage, though the real clinical impact of these protective effects on postoperative outcome remain to be definitively established [48-51]. Based on this circumstantial evidence the American guidelines have suggested the use of volatile anaesthetic agents during noncardiac surgery in haemodynamically stable patients at risk for myocardial ischemia [22]. Because of the lack of any evidence in noncardiac surgery, no such recommendation has been made in the European guidelines [23]. Recently, two small randomized controlled trials have compared a volatile anaesthetic regimen to an intravenous anaesthetic regimen in noncardiac surgery, one suggesting a lower cardiac event rate with a volatile anaesthetic regimen [52] while the other found no evidence for a cardioprotective effect [53]. It is obvious that further research on the topic is needed before recommendations can be made [54]

6 Surveillance and diagnosis of myocardial damage Perioperative myocardial damage can be documented by assessing clinical symptoms, serial electrocardiograms, cardiac-specific biomarkers, comparative ventriculographic studies, and radioisotopic or magnetic resonance studies. Measurements of troponin T or I have been shown to indicate myocardial damage with smaller amounts of injury [55]. Recently, high sensitive assays for troponin measurements have been introduced, that are expected to allow for the diagnosis of subtle limited myocardial damage [56,57]. Ongoing studies are evaluating the possible surplus value of such measurement in the detection of perioperative cardiac damage. Conclusions Noncardiac surgery is associated with substantial cardiac morbidity and mortality. Guidelines have been developed in order to improve care of these patients. Guidelines intend to propose recommendations based on the relevant available evidence on a particular subject. These recommendations aim to help physicians to select the best possible management strategies for the individual patient suffering from a specific condition. Ideally, such recommendations should not only take into account the potential effect of a particular strategy on outcome but also assess the risk-benefit ratio of that particular strategy. Best available evidence may change over time, either because newly performed studies provide newer information and insights when results of previous studies used to grade the recommendations have been contested for one reason or another. Recently, the Erasmus Medical Centre Rotterdam (the Netherlands) announced that they have dismissed Prof. dr. Poldermans, the chair of the European Guidelines Task Force, because of violation of scientific integrity, mainly related to the lack of informed consent for certain examinations and the inaccuracy and carelessness in data management in some of his ongoing and recent studies ( Poldermans has an impressive track record of publications in the field of perioperative evaluation and management of non-cardiac surgery patients, especially with regard to the perioperative use of β-blocking therapy and statins. Consequently, some of the contributions of his group have - among other studies been used to assess the level of evidence of some of the recommendations made in the guidelines for preoperative cardiac risk assessment and perioperative cardiac management in noncardiac surgery. Poldermans has resigned from the European Society of Cardiology (ESC) Committee for Practice Guidelines and this Committee is looking into the Guidelines for preoperative cardiac risk assessment and preoperative cardiac management in non-cardiac surgery, in order to decide if these need to be re-examined in the light of recent events. A new statement will be issued by the ESC once a decision has been reached. ( It will become clear in the upcoming months whether the evidence provided by the studies of the Poldermans group on perioperative management with β-blockers and statins do indeed require a re-evaluation and rewriting of the guidelines. Independently from this issue, ultimately the production and writing of guidelines on clinical practice strategies is a dynamic process, in which participants involved need to question themselves and the available evidence continuously. Only then can medicine, and especially evidence-based medicine, evolve and improve. Key learning points Noncardiac surgery is associated with a substantial perioperative cardiac morbidity and mortality Two types of PMI have been defined that are caused by distinct pathophysiological mechanisms: the acute coronary syndrome (type 1 PMI) and the myocardial oxygen supply-demand imbalance (type 2 PMI) Guidelines provide recommendations based on the best available evidence According to the best available evidence β-blocking and statin therapy should be continued perioperatively in those patients currently taking this medication

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