Cardiac anaesthesia: the last 10 years

In considering the progress and development of cardiac anaesthesia over the last 10 years, it is interesting to note both those things that have changed and also those which perhaps surprisingly have not. Any reflection over a 10-year period will inevitably be personal, and there is certainly enough practice variation in cardiac anaesthesia across the UK to render my observations inaccurate in the eyes of some. I have tried to be objective, but I expect that on occasion my interests and prejudices will have gained the upper hand and forced themselves through. The last 10 years have seen numerous structural changes within the NHS. Despite these changes, the provision of cardiac surgery has shown a modest increase, particularly during the early 1990s. Data from the United Kingdom Cardiac Surgery Register show that up to 2000, cardiac surgical activity increased progressively, this increase being largely accounted for by an increase in coronary revascularisation [1]. There is evidence that the rate of isolated CABG surgery may now have peaked, and recently waiting times for CABG surgery appear to be going down, although there will be some regional variation. In adult cardiac surgery, there is a trend to operate on older and sicker patients [2]. This has become particularly evident in those centres with good access to interventional cardiology. Coronary angioplasty, accompanied by intraluminal coronary stenting, has made an enormous impact on the treatment of ischaemic heart disease, and the introduction of drug eluting stents to inhibit coronary restenosis [3] will result in a much smaller percentage of patients undergoing coronary artery bypass graft surgery as their first intervention for IHD. There is also a trend to an increasing proportion of valve replacement procedures, particularly in elderly patients [4]. Of those patients who do undergo surgical coronary revascularisation, the last 10 years have seen an increase in the number of patients being revascularised without cardiopulmonary bypass support. Initially, MIDCAB (Minimally Invasive Coronary Artery Bypass – usually a single vessel procedure performed through an anterior mediastinotomy) and, more recently, OPCAB (Off Pump Coronary Artery Bypass – a procedure with multivessel access usually performed through a median sternotomy) have been performed. The uptake of these procedures has been variable; infrequent in some centres, commonplace or routine in others. The anaesthetic challenges are not complex but they may be demanding; to maintain good haemodynamic control throughout a procedure in which cardiac displacement may be severe, but mitigated in part by some of the new tissue stabilisation devices [5,6]. Cardiac surgery requires close teamwork between surgeons and anaesthetists, and OPCAB surgery is a perfect example of this. The technique is still controversial [7,8] but recent results have been more consistent [9–11]. OPCAB surgery will not replace PTCA and stent procedures, but I believe it will have a large impact on CABG surgery on-bypass, particularly in elderly or other high risk patients who are an increasing proportion of our workload. The development of newer procedures, such as heart port surgery and robotics, may have a significant future but my perception is that it is still too early to be sure. Heart and heart–lung transplantation has not increased over the 10-year period, and as ever the problem is access to donor organs [12,13]. The rate of paediatric cardiac surgery procedures has changed little overall [1], and with good public health and antenatal screening it is unlikely to change much in the future. The demands for paediatric cardiac surgery have been to deliver high quality outcomes against a background of increasing public expectation. Cardiac anaesthesia during the decade between 1984 and 1994 was transformed by the widespread use of beta blockers for patients undergoing CABG surgery. Recent data have confirmed their value [14]. Anaesthetists modified their anaesthetic techniques where necessary, and good cardiological control of angina, hypertension and to a lesser extent arrhythmias profoundly reduced the incidence of haemodynamic instability during induction of anaesthesia in the pre-revascularisation phase of surgery. Similarly, the last 10 years have seen the widespread use ACE inhibitors. Once again, anaesthetists have modified their peri-operative management where necessary. Despite evidence that discontinuing ACE inhibitors may be advisable [15] (in marked contrast to discontinuing beta blockers [16]) many anaesthetists continue these drugs up to the time of surgery, with no ill effect [17]. However, the postoperative management of patients may have been affected and certainly we have become more used to dealing with patients who are markedly vasodilated postoperatively [18]. Low dose vasoconstrictor infusions are now commonplace and the use of arginine-vasopressin or terlipressin has been recommended as specific therapy to counteract ACE-induced vasodilation post bypass [19]. The potassium channel openers (nicorandil) have also been accommodated with little change in practice. Many more patients are taking antiplatelet therapy than 10 years ago [2], but our attitude towards it is rather inconsistent. Initially, the belief was that aspirin should be stopped before surgery in order to reduce peri-operative blood loss [20,21], although this has been questioned [22]. Certainly, there is evidence that postoperative aspirin therapy improves peri-operative outcomes from CABG [23]. The position regarding clopidogrel is more clear cut. When platelets become activated by various mechanisms they release adenosine-5′-diphosphate, which acts in a positive feedback mechanism on two different G-protein coupled receptors' platelets. This released adenosine-5′-diphosphate is critical for sustained aggregation and stabilisation of thrombi, and one of the receptors is the target of the antithrombotic drug clopidogrel. Clopidogrel use in the cardiac surgery patient has been associated with increased bleeding [24,25] and whereas the effects of aspirin may be counteracted by treatment with either aprotinin or tranexamic acid [26–28], no similar effective treatment exists with clopidogrel, and many surgical teams would heed the recommendation that it be discontinued days in advance of surgery. However, this is not always possible, particularly in the urgent or emergency setting. Over the period in question the UK has seen the clinical introduction of sevoflurane and remifentanil. Both drugs had a bumpy introduction to clinical practice. In the case of sevoflurane, the issue of toxic metabolites delayed clinical introduction and use for some years [29,30], whilst in the case of remifentanil the commercial decision of Glaxo Welcome to curtail research and development in anaesthetic products was certainly influential. Sevoflurane has been taken up by paediatric anaesthetists, and colleagues in paediatric cardiac anaesthesia now use it routinely. Remifentanil use in cardiac anaesthesia is still patchy. The initial promise of being able to control haemodynamic responses to stimuli such as sternotomy and sternal spread has been validated [31], and is clinically useful. Managing the change from intra-operative to postoperative analgesia has proved more difficult, sometimes alarmingly so, and many anaesthetists have resorted to the use of more conventional longer-acting opioids for postoperative analgesia. Very high dose opioid anaesthesia for cardiac surgery never became well established in clinical practice in the UK, and has started to fade elsewhere. Sufentanil, probably the most popular opioid in Europe and the USA for cardiac anaesthesia, has never been available in the UK as a consequence of marketing decisions taken 20 years ago. Sometimes the delays in introducing new compounds are inevitable but they are often frustrating for clinicians. A good example is the continued unavailability of dexmedetomidine. The potential value of central alpha-2 receptor mediated sympatholysis and analgesia without undue sedation is clear, and yet commercial release appears to be indefinitely delayed. The value of opioid analgesia in cardiac patients has stood the test of time but there is nonetheless interest in other compounds. The use of NSAIDs has increased, and their limitations better understood. The introduction of COX-2 inhibitors in cardiac anaesthesia has been associated with proven efficacy but has raised safety concerns [32] and it will be interesting to see the results of current trials regarding their use. One technique that continues to be controversial is that of epidural anaesthesia in cardiac surgery [33,34]. The controversy is straightforward; do the analgesic and physiological benefits outweigh the potential complications of using such techniques in patients who will be fully anticoagulated? Assuming that all the modern coagulation tests are fully available and best practice is followed, the safety argument appears to be moving the epiduralists' way [35,36]. It will be interesting to see whether the physiological and short-term clinical benefits are reproducibly transformed into better clinical outcomes, because at the moment many clinicians remain unconvinced. The introduction of ‘fast track’ cardiac surgery has universally been recognised as a useful development [37]. This term usually means early return to consciousness, self ventilation and extubation; transfer to a step down unit or reduction in nursing care intensity, perhaps facilitating more operations per day. Initially, clinicians were keen to recommend that the key to successful practice lay in the anaesthetic recipe − avoid high doses of opioids or benzodiazepines, use vasodilators, forced air re-warming, propofol infusions, volatile agents, epidural techniques and many other recommendations [38–40]. Many of these are theoretically and practically sound recommendations for good practice, however quickly one desired patient recovery to proceed. Thus we accepted that attention to detail, and using a range of drugs and techniques to get the patient into good clinical shape, was important. The totality of the approach – or ‘philosophy’– was important, not the recipe. The acceptance of this ‘philosophy’, and an understanding of its limitations, is now so widespread in the UK and elsewhere that I believe we can be confident of a paradigm shift; adult cardiac surgery is no longer a surgery-specific indication for prolonged intubation and intensive care. Indeed, given the generally low provision of intensive care beds in the UK, this is not before time. Filling ITU beds with relatively fit patients recovering from routine cardiac surgery is a poor use of a scarce critical care resource. PA catheter use has always been patchy in the UK. Some places use them routinely, others virtually never. This variation in practice is not unique to the UK. I believe most clinicians use PA catheters when they believe there is a specific indication, for example pulmonary hypertension and/or very poor left ventricular function. There has been much criticism of the routine use of PA catheters in the literature [41,42], much of it probably justified. I believe that cardiac anaesthetists have long recognised two important facts; firstly, the PA catheter is a monitor, not a therapy. The data it produces are valueless unless effective therapeutic decisions can be based upon them. Secondly, we have long realised that cardiac pressure measurements are only an estimate of cardiac volume measurements, and there are circumstances where the relationship is poor. Despite the development of different types of PA catheter, I personally doubt that the take up rate will alter much over the next 10 years. However, we have seen the introduction of ultrasound devices designed to facilitate the location and successful cannulation of central veins [43], and these will become more widely available. They are clearly useful, and should be used particularly in those patients in whom inadvertent arterial puncture, pneumothorax or failure to cannulate is either more likely or carries a high adverse impact. Currently, we are encouraged to consider their routine use through the recommendations of the National Institute of Clinical Excellence [44], who are clearly persuaded of their value. If you wish to measure cardiac output, there are now a number of technologies to choose from. Cold thermodilution, warm thermodilution, tracheal or thoracic bio-impedance, lithium dilution, pulse contour analysis, PiCCo, oesophageal Doppler, echocardiography, expired gas analysis and no doubt others, many of which have been introduced in the last 10 years. It will be interesting to see how many of these will stand the test of the next 10 years. Cardiac surgery has been associated with a measurable incidence of both awareness and neurological or neuropsychiatric damage [45]. Ten years ago we had no effective method for the routine detection of these important events, and sadly, despite a number of research avenues, we still do not. For many cardiac anaesthetists, the development and use of transoesophageal echocardiography (TOE) has been the most important development of the last 10 years. It is interesting to recall the speed with which events have taken place. Guidelines for the use of and clinical accreditation in transthoracic and/or transoesophageal echocardiography in the UK, USA and Europe have all appeared and perhaps been updated within the last 10 years [46–48], as has structured training in TOE in the UK. Many UK anaesthetists have taken the ASE/SCA accreditation exam, which itself has been evaluated [49]. Details of a comprehensive accreditation process for UK cardiac anaesthetists and cardiologists are available [48,50], and a similar process for European practitioners is envisaged. It is beyond the scope of this article to review the indications for peri-operative TOE. However, TOE is now established as a routine tool for a range of intra-operative diagnostic and monitoring purposes and as a contributor to the process of intra-operative decision making. If current trends continue, cardiac surgery over the next 10 years will become more complex and be performed on a sicker and older population. If we are to provide the best possible service to these patients, I am confident that competence in TOE will become an essential requirement for cardiac anaesthetists in the next 10 years, and that every UK cardiac centre will need to make peri-operative TOE available. Bleeding during and after cardiac surgery has always been a concern. The use of cardiopulmonary bypass necessitates full anticoagulation. The bleeding points themselves are often large vessels and bleeding reduces cardiac output by hypovolaemia, cardiac tamponade and myocardial hypoxaemia. Many of the techniques that are used to minimise blood loss predate the last decade. Autologous intra-operative donation is almost as old as cardiac surgery, and the landmark studies on aprotinin are certainly more than 10 years old [51]. The use of pharmacological agents to reduce bleeding, principally aprotinin and tranexamic acid, was criticised early on, but the last 10 years have seen a systematic review of their effects [52]. We can now be confident that these agents are useful at reducing peri-operative bleeding in the majority of cardiac surgery patients without specific adverse events, although some issues still remain unresolved. Cell saver technology has also been available for some years, but it is now economically feasible as a result of the ever increasing cost of allogeneic red cells. The technology is effective, but not without effect on the salvaged blood [53]. Nonetheless, many now use pharmacological agents and on every cardiac is that the use of blood techniques will for cardiac surgery patients in the and we should to an of routine cardiac surgery without allogeneic red The current of inhibitors was introduced into cardiac surgery practice over 10 years ago with the of and they are often by a dose and this practice has recently been and many use the dose drugs have being for a low cardiac output in the cardiac surgery patient this is associated with vasodilation is a effect of for many the in have the drugs of as they output and more However, the of inhibitors and appears the most effective therapy The effects of inhibitors may be counteracted by an of a such as more This drug and its have shown much promise in cardiac surgery patients particularly for the management of vasodilation by or was introduced in the as a treatment for low output heart although interest in its use to be on its effects on the value as a in cardiac surgery is controversial the use of low dose as a to have been in the intensive care although there are data specific to the early period cardiopulmonary There are numerous of drugs that have not been introduced into the UK, despite their proven efficacy and elsewhere. and the of channel with the of the One drug that is on the of introduction is an drug effect is to the to and to the of Both also some of and the inhibitors themselves are a of interest in the for the management of heart The use of agents for heart failure was in the but a understanding of mediated mechanisms has interest in these agents It will be to see how they Over the last 10 years, our understanding of the myocardial effects of has increased particularly of those anaesthetic that may the against ischaemic damage and mechanisms by peri-operative beta It is my belief that of the has not increased markedly over the last 10 years. have become more both in of of the and and of the and many modern devices can better with use is still infrequent and generally associated with much risk patients and adverse the is for ventricular devices A number have been and introduced in the last some of which are relatively whereas others can only be used as a to A review of such devices is beyond the scope of this It is my belief whilst the number of will increase very other for heart failure will increase However, will not change A number of changes of have in the of The for to has made some and a better understanding of the to cardiopulmonary bypass has much interest in and the bypass have with as have pharmacological techniques designed to the effects of However, the from to has been virtually and there is more interest in and use of as to the positive displacement particularly for prolonged of the use of has been all but but of the observations may be One important development has been the of cardiac anaesthetists and cardiac surgeons in the UK to of monitoring during cardiopulmonary bypass recommendations have to changes in and the process of cardiopulmonary bypass should become as a I believe our have changed over the last 10 years. The has become well but some cardiac anaesthetists now themselves in clinical from their other anaesthetic often to and cardiac surgery. I have no of and I can that it may make particularly for cardiac anaesthetists of practice is in cardiac anaesthesia and postoperative care. However, are and not clinical or and we of in a where clinical service and particularly and are of as an activity and This may become anaesthesia within an and appears to have little activity is well established in cardiac In the European of and the European of of and this activity not be to be The changes by have affected but cardiac anaesthetists have these changes particularly The effect of on the of training has been to the training period, which has in the of anaesthetic in cardiac surgery. It is now and in many for anaesthetic to for cardiac surgery unless and an increasing percentage of cardiac anaesthetists and see themselves so more in the future of of in This has raised anaesthetic and during cardiopulmonary The UK is unique in Europe in both a structured anaesthetic training and that all training in cardiac anaesthesia before the of a in It is my that this will In the early the of Anaesthetists as of the with the to and designed to outcomes in cardiac surgery. interest and to risk and as a at the was to initial was to for adult cardiac surgery, but it was in the of paediatric cardiac surgery and in that issues which The as they is The practice of in the UK has changed as a result – changed in which are still and down is still we and how well we do is a and the essential to and our practice. It is a for all of and particularly for the and surgeons that such a had such a future is made of the as the We should expect to with older and sicker patients, and both more complex procedures and more surgery where The of cardiac intervention will continue but this will have a on interventional than on cardiac surgery, and only a would against yet more structural changes cardiac within the NHS. I believe that pharmacological in important myocardial and management are but the of the may be upon and this will be to more than the of The future of training in cardiac anaesthesia in the UK will be profoundly affected on the requirement into and accreditation may in TOE is in the UK and and these two in may make future practice in cardiac anaesthesia only for those who are able to themselves fully to unlikely but who have the last 10