define the fitness of the patient for the proposed anaesthetic and surgery

 delineate the level of risk of the procedure

 decide on the most appropriate anaesthetic technique

 assess the requirement for preoperative therapy to be initiated, for example β-blockade or blood transfusion

 assess the level of perioperative monitoring required

 decide on the patient’s postoperative management, including where this should take place.

 high-risk surgery (defined as intraperitoneal, intrathoracic or suprainguinal vascular surgery)

 ischaemic heart disease diagnosed either from the history or investigation

 congestive heart failure

 cerebrovascular disease

 insulin-dependent diabetes mellitus

 renal impairment (creatinine >177 μmol L^− 1).

History: Symptoms of cardiovascular disease include chest pain, dyspnoea, palpitations, ankle swelling and intermittent claudication. Past medical history and medical records usually reveal the nature and severity of disease, as many patients with cardiovascular symptoms will already have undergone relevant investigations.

Examination: Preoperative cardiovascular examination should include measurement of heart rate, arterial pressure and assessment of peripheral pulses and perfusion. Signs of heart failure should be sought, including a third heart sound, elevated jugular venous pressure and fine basal crepitations on auscultation of the lung fields. The heart should be auscultated for murmurs indicative of valvular disease. In particular, it is vital to make the diagnosis of aortic stenosis pre-operatively.

Testing the patient’s exercise capacity in the ward or on a flight of stairs is a simple, but useful, assessment of functional reserve. The inability to climb two flights of stairs indicates a very high risk of cardiopulmonary complications after major high-risk surgery.

Risk Stratification: Assessment of the patient’s risk of a perioperative cardiac event provides prognostic information. These issues may be discussed with the patient and appropriate written information provided. Adequate provision of information and the opportunity to ask questions has been shown to allay preoperative anxiety. Assessment also guides perioperative investigation and management.

In patients with an active cardiac condition defined as unstable coronary syndrome, decompensated heart failure, significant arrhythmias or severe valvular disease (Table 18.3), only emergency procedures should be considered. Elective procedures should be postponed for evaluation, testing and optimization of the patient’s active cardiac condition to minimize perioperative risk. The need for evaluation and further testing depends on the risks associated with a particular surgical procedure, the patient’s physiological reserve or functional capacity, and whether testing would change management. Patients undergoing low-risk surgery, or those with proven good functional capacity undergoing intermediate or higher risk surgery, can usually proceed to surgery. They will only require further invasive cardiac investigations if it would change management (i.e. they would require medical optimization or be a candidate for coronary revascularization) (Fig. 18.1).

For example, patients who have sustained a myocardial infarction (MI) within the 30 days before proposed surgery are a high-risk group. As a result of increased sympathetic stimulation and the coagulation activation secondary to surgery, such patients have a very high risk (up to 28%) of perioperative MI, which carries a high (10–15%) mortality. A history of uncomplicated MI more than 30 days before surgery is no longer considered an absolute contraindication to elective surgery, provided that the patient is symptom-free and has a good exercise capacity (see Table 18.1).

If there is no urgency for surgery however, it is best to wait until 3 months after MI when, if patients are asymptomatic with a good exercise capacity, they rejoin the low-risk group.

Asymptomatic patients who have undergone successful coronary artery bypass grafting more than 6 weeks before surgery constitute a low-risk group. Indeed, the mortality in this group is less than in a matched group with well-controlled angina on medical therapy. However, the risk of coronary artery surgery itself negates this benefit. It is therefore recognized that major cardiac interventions such as bypass grafting are indicated before non-cardiac surgery only if the patient’s underlying cardiac condition merits intervention for its own sake. This is the case for patients with severe triple vessel disease or significant left main stem stenosis.

Increasing numbers of patients now present for non-cardiac surgery having undergone percutaneous coronary interventions (PCI), particularly intracoronary stenting (ICS). Guidelines for the optimal perioperative management of these patients have been produced (Fig. 18.2). There are a number of important points. Firstly, it is beneficial to discuss the patient’s management with an experienced cardiologist. The risk of non-cardiac surgery in patients with intracoronary stents depends on the timing of surgery related to insertion of the stent and the type of stent used. Bare metal stents have been largely superseded by drug-eluting stents, which contain a cytotoxic agent. This is slowly released from the ICS to limit endothelialization, which reduces the incidence of thrombosis and stenosis within the stent itself. However, more prolonged and intensive antiplatelet therapy is required for drug-eluting stents because they are at increased risk of thrombosis until re-endothelialization has occurred. Following insertion of any ICS, there is an initial requirement for dual antiplatelet therapy (e.g. aspirin and clopidogrel). Non-cardiac surgery should be avoided during this time if possible. If antiplatelet therapy is stopped, the risk of stent thrombosis (which carries a 7% mortality) is high, while continuing therapy increases the risk of perioperative bleeding. The duration of dual antiplatelet therapy should be a minimum of one month after bare metal stents and up to 12 months for drug-eluting stents. It is recommended that even urgent surgery should be postponed for at least 4–6 weeks after ICS insertion, and elective surgery deferred for 3 months after bare metal stent, and for 12 months after drug-eluting stent insertion. If possible, even beyond these times, aspirin should be continued throughout the perioperative period, particularly because abrupt cessation of aspirin increases thrombogenicity. In the future, the possibility of bridging therapy with short-acting glycoprotein IIb/IIa inhibitors such as tirofiban may be considered.

As with coronary revascularization procedures, and due to the risks outlined, there is no place for prophylactic coronary stenting before surgery unless this is independently indicated for the cardiac condition.

Investigations: Standard investigations including haematology, biochemistry, an ECG and chest X-ray are necessary in all patients with proven or suspected cardiovascular disease. A coagulation screen may be indicated.

Subsequent investigations depend on the assessed risk for the patient and the clinical findings.

All patients found to have a murmur should have preoperative echocardiography. Significant aortic stenosis, for example, is associated with an increased risk of perioperative cardiovascular events and may be difficult to confirm and grade on clinical grounds alone. Echocardiography also provides useful information on left ventricular function.

Additional cardiovascular investigations are indicated only if they influence management. The incidence of asymptomatic coronary artery disease in the population is approximately 4%, and screening tests are unlikely to be helpful in patients with no cardiac symptoms. Patients with active cardiac conditions, in whom specific management of cardiovascular disease is indicated independent of the need for non-cardiac surgery, should undergo non-invasive cardiac testing, with or without coronary angiography and further treatment as indicated.

Between these two extremes lies a group of patients at increased risk of perioperative cardiovascular events in whom further assessment is indicated because perioperative care is influenced by the results. Moreover, accurate determination of risk to the patient may help decision-making with regard to the need for surgery and/or the type of operation and anaesthetic (Fig. 18.1).

Patients who should be considered for further pre-operative testing include:

The choice of preoperative test is dictated by local and patient factors, but commonly it includes exercise stress testing, dobutamine stress echocardiography and dipyridamole thallium scanning. Cardiological advice should be sought for both the test required and interpretation of the results with regard to predicting the perioperative risk of a serious cardiovascular event.

Pre-Existing Cardiovascular Disease: Ischaemic heart disease. Medical therapy should be reviewed and optimized if symptoms are poorly controlled.

Hypertension. Raised arterial pressure is a major cause of morbidity and mortality in the general population because of the detrimental effects on the myocardial, cerebrovascular and renal circulations. It is now recognized that both hypertension and isolated systolic hypertension should be treated because effective control of arterial pressure reduces the incidence of complications from target organ damage. The British Hypertension Society guidelines recommend starting antihypertensive therapy for sustained pressures above 140/90 mmHg. However, in the perioperative setting, there is little evidence that patients with isolated hypertension of less than 180/110 mmHg have a significantly increased risk of cardiovascular complications and isolated hypertension below this level is classified as a low-risk factor. If hypertension is identified preoperatively, evidence of target organ damage should be sought. If target organ damage is found, then the risks of anaesthesia and surgery are dependent on this. Subsequent investigation and management should be based on target organ function rather than on the hypertension per se. Postoperative follow-up and treatment are indicated.

For non-urgent surgery, patients with severe hypertension, i.e. > 180/110 mmHg, should be treated to lower the arterial pressure in a controlled manner before embarking on surgery. In the case of urgent surgery, more rapid control may be achieved. In light of their beneficial effects in high-risk cardiovascular patients, β-blockers are probably the agents of choice. Care must be taken, however, because rapid decreases in arterial pressure may be detrimental.

Antihypertensive therapy should be continued as far as possible throughout the perioperative period.

Many patients seen at preadmission clinic or admitted to hospital have hypertension which subsequently settles or which is not in keeping with the recordings made by their general practitioner. There is no evidence that so called ‘white coat hypertension’ carries an increased perioperative risk. Often, these patients benefit from a benzodiazepine premedication.

Heart failure. A history of treated heart failure and low left ventricular ejection fraction are intermediate clinical risk factors. Treatment should be optimized as far as possible pre-operatively and investigation of underlying coronary artery disease undertaken as appropriate, as outlined above.

Treatment and Additional Interventions: β-Blockers. Established β-blocker therapy should be maintained throughout the perioperative period either orally or intravenously if necessary. Sudden preoperative cessation may be associated with rebound effects such as angina, myocardial infarction, arrhythmias and hypertension. The dose of β-blocker may be reduced if there is undue bradycardia preoperatively (< 50 beat min⁻¹). Intraoperative bradycardia usually responds to intravenous atropine or glycopyrrolate. Some studies have shown that institution of perioperative β-blockade reduces short and long term cardiovascular morbidity and mortality in patients with definite evidence of ischaemic heart disease undergoing high-risk surgery.

These advantages are not seen in patients receiving chronic therapy and do not appear to be restricted to any particular β-blocker. Beta blockade should therefore be considered for these patients but the optimal time to begin therapy and the optimal duration of β-blockade are uncertain. In a non-urgent situation, it may be preferable to introduce β-blockade cautiously over several weeks, particularly if there is evidence of left ventricular dysfunction. It should be noted that several studies in lower risk patients (e.g. those with risk factors for ischaemic heart disease but no symptoms) have shown no overall benefit from perioperative β-blockade. In the POISE study, perioperative β-blockade actually increased the overall mortality and the incidences of stroke, bradycardia and hypotension.

Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers. These agents have disease-modifying effects in patients with vascular disease, cardiac failure and diabetes, with a reduction in cardiac morbidity and mortality. They may predispose to renal failure and hyperkalaemia and may be associated with intractable intraoperative hypotension. There is currently no consensus as to whether or not these agents should be continued intraoperatively.

Antiplatelet agents. Aspirin and clopidogrel are used increasingly in combination to maintain vessel patency following percutaneous coronary intervention (PCI) and to reduce thrombosis in patients with unstable angina or recent MI. Both agents have irreversible effects on platelet action and their effect therefore continues for the life of the platelet. Aspirin inhibits cyclo-oxygenase-mediated production of thromboxane. Clopidogrel is a non-competitive antagonist of platelet ADP receptors. They have a synergistic effect in inhibiting platelet aggregation. Both agents need to be stopped for at least 7 days to see these effects reversed by new platelet production. Whether or not these agents are continued perioperatively depends on the perceived risk of bleeding against the increased risk of cardiovascular events. If the drugs are continued, both the surgeon and anaesthetist must be aware of the increased risk of haemorrhage and take appropriate anticipatory measures. Platelet transfusion is the only effective therapy for uncontrolled haemorrhage secondary to these agents.

In general, if a patient is anticoagulated (see below) or receiving clopidogrel, neuraxial blockade is contraindicated because of the increased risk of haematoma and neurological damage. Aspirin alone is not considered a significant risk factor.

Anticoagulants. Where long-term therapy is indicated, perioperative control must be monitored closely. Warfarin should be stopped at least 48 h preoperatively and the prothrombin time monitored daily. The prothrombin time should be less than 1.5 times control at the time of surgery. If prolonged, the use of vitamin K may be considered; however, this takes 6–12 h to act and may compromise subsequent anticoagulation, so its use depends on the reasons for anticoagulation. In an emergency or where excessive haemorrhage occurs, fresh frozen plasma should be given to supply coagulation factors. For patients at high risk from thrombosis, e.g. with a prosthetic heart valve, an intravenous heparin infusion should be started when the prothrombin time decreases and continued until 2 h preoperatively. After minor surgery with low risk of haemorrhage, warfarin may be restarted postoperatively. After major surgery, an infusion of unfractionated heparin should be used to maintain anticoagulation until warfarin therapy is reinstituted safely. The heparin infusion may be titrated to activated partial thromboplastin time (aPTT) to maintain good control and if necessary may be reversed rapidly with intravenous protamine. Protamine should be given slowly to avoid hypotension and if given in excessive dose is itself an anticoagulant.

Statins. Statins reduce morbidity and mortality in patients with vascular disease even in the presence of a normal cholesterol concentration. This is thought to result from stabilization of atheromatous plaques. There is also increasing evidence in patients undergoing high-risk vascular surgery that initiating statin therapy may reduce cardiovascular complications. The introduction of a statin preoperatively should therefore be considered in this group. Again, the optimal timing of this intervention is unknown but it has been suggested that therapy should be started 1 month before surgery.

α₂-Agonists. Drugs such as clonidine reduce sympathetic activity, reduce arterial pressure and heart rate and have analgesic properties. There is some evidence to suggest they may be of benefit in patients at high risk of perioperative cardiovascular events, but this is insufficient to recommend their routine use.

Continued administration mandates a greater degree of cardiovascular monitoring, particularly with regard to maintenance of intravascular volume. Vasoactive agents may be required to maintain an adequate arterial pressure.

Preoptimization. Measures to improve cardiac output and oxygen delivery have been shown to improve outcome in some high-risk patients with limited physiological reserve undergoing major surgery. These measures include monitored fluid therapy, vasoactive support, blood transfusion and mechanical ventilation, and are aimed at improving tissue oxygen delivery and hence oxygen delivery/consumption balance. The level of monitoring required, patient selection and the risk/benefit balance of increasing myocardial oxygen demand in the face of ischaemic heart disease, versus improving cardiac output and hence oxygen delivery, need to be considered on an individual basis.

This management strategy may be undertaken in a critical care area or in the anaesthetic room and requires close cooperation between relevant medical staff.

It is not known yet if combining preoptimization with preoperative therapy with agents such as β-blockers is helpful. However, the two approaches are not necessarily mutually exclusive.

Premedication: Anxiety is a cause of sympathetic nervous system activation which may be detrimental in patients with cardiovascular disease. While not all patients require anxiolytic premedication, there should be a low threshold for use in these patients. A benzodiazepine such as temazepam is usually satisfactory. In patients with low or fixed cardiac output states, e.g. mitral or aortic stenosis, constrictive pericarditis or congestive cardiac failure, and other high-risk patients, it is important to avoid hypotension or excessive sedation, respiratory depression and hypoxaemia which could result from premedication, and in these situations it may be preferable to omit sedative premedication.

The patient’s usual cardiac medications and any additional therapy started preoperatively should be continued and included in the premedication.

High-risk patients benefit from oxygen therapy before transfer to the anaesthetic room, especially if sedative premedication has been given.

 Anaesthesia should comprise a balanced technique aimed at maintaining cardiovascular stability. A variety of options may be suitable, including both general and regional anaesthesia or a combination.

 Tachycardia should be avoided and an adequate arterial pressure maintained (there should not be a sustained reduction in arterial pressure of more than 20% of the patient’s normal pressure). Coronary perfusion and myocardial oxygen delivery are thus maintained without increasing myocardial work and oxygen requirements.

 For patients identified as high risk, consideration should be given to stress reduction. Measures to achieve this are dictated by the patient and operative factors. These include the following:

 The level of intraoperative monitoring should be dictated by risk assessment. The following should be considered in addition to standard monitoring.

 Patients should be well oxygenated and normocapnic.

 Close attention to fluid balance is mandatory. This begins preoperatively when fluid depletion secondary to factors such as excessive fasting times and bowel preparation should be corrected. As far as possible, normovolaemia should be maintained. Intravascular volume depletion is known to compromise organ perfusion and oxygen delivery but there is increasing evidence that postoperative recovery is also compromised by excessive volume and sodium loading in the immediate perioperative period.

 Patients at high risk from cardiovascular disease do not tolerate anaemia. The optimal level of haemoglobin is the subject of much discussion but is probably around 10 g L⁻¹.

 Patients should be actively warmed to avoid hypothermia, which activates the stress response, predisposes to arrhythmias and increases oxygen consumption postoperatively as a result of shivering.

 Effective perioperative analgesia is essential. Pain is a potent stimulator of the stress response and uncontrolled sympathetic activation increases myocardial work and oxygen demand, predisposing to myocardial ischaemia or infarction.

 Before embarking on anaesthesia and surgery, consideration needs to be given to the patient’s management and destination postoperatively, e.g. would benefit be derived from a period of artificial ventilation or continued close monitoring in a high dependency or intensive care area postoperatively?

 Good communication between all of the relevant carers, including cardiology, critical care and the surgical team, is important.

Anaesthetic Agents: Most intravenous anaesthetic induction agents are cardiovascular depressants, causing both vasodilatation and myocardial depression. This is exaggerated in patients with low fixed cardiac output states and by concurrent hypovolaemia. Of the agents in regular use, etomidate is the least cardiac depressant. Care with dosing and rate of administration limits the hypotension caused by drugs such as propofol or thiopental. Co-induction with more than one agent may be beneficial in reducing the dose requirements of each and limiting hypotension. Concurrent administration of midazolam and a short-acting opioid (alfentanil or fentanyl) is often used. Remifentanil may be useful in these patients, in a low-dose infusion of 0.1–0.2 μg kg⁻¹ min⁻¹. It limits the dose of induction agent required and blunts the cardiovascular response to laryngoscopy and tracheal intubation. However, used in high doses, it may induce respiratory muscle stiffness and make bag and mask ventilation difficult before the onset of neuromuscular blockade.

For patients naive to β-blockers, esmolol (a short- acting i.v. β-blocker) may be used to obtund the cardiovascular response to airway manoeuvres.

Of the neuromuscular blocking agents, rocuronium and vecuronium are the most cardiostable.

Brief periods of cardiac ischaemia provide protection against the damaging effects of subsequent more prolonged episodes; this is known as ischaemic preconditioning. Much is now known about the physiology of this in experimental situations, including the fact that volatile anaesthetic agents and opioids help to induce ischaemic preconditioning, while other agents, e.g. the sulphonylureas, inhibit it.

There is clinical evidence of its relevance, e.g. patients with pre-infarct angina generally have a better prognosis than those who are asymptomatic, and this may be a result of preconditioning. The clinical application of these findings is as yet unknown, but may favour the use of volatile agents in this high-risk group.

 bradyarrhythmia unresponsive to atropine if associated with syncope, hypotension or ventricular arrhythmias

 risk of asystole

 complete heart block

 second-degree heart block (Mobitz 2)

 first-degree heart block associated with bifascicular block

 sick sinus syndrome.

Intraoperative Arrhythmias: Arrhythmias are common in the perioperative period and are often self-limiting and require no specific treatment. However, precipitants of these arrhythmias should be sought and corrected if possible as they are more likely to occur and cause cardiovascular compromise in patients with underlying heart disease.

Factors predisposing to intraoperative arrhythmias include the following.

Patient factors:

Autonomic effects:

Direct stimulation:

Drugs:

Management: This depends on the nature of the arrhythmia, likely causes and the degree of haemodynamic compromise.

Intraoperative Bradyarrhythmias: Bradyarrhythmias may often be prevented and may be treated using an intravenous anticholinergic, e.g. atropine or glycopyrrolate.

External pacing defibrillators are now widely available and can be used for temporary cardiac pacing for patients unresponsive to anticholinergics pending insertion of a transvenous pacemaker.

Intraoperative Tachyarrhythmias: These are either supraventricular or ventricular in origin. Generally, but not exclusively, supraventricular arrhythmias are narrow-complex, in distinction to broad-complex ventricular arrhythmias.

Supraventricular tachycardia. If there is haemodynamic compromise, the treatment of choice is synchronized DC cardioversion, particularly as the patient is already anaesthetized. This applies to all supraventricular tachyarrhythmias. If cardioversion fails, amiodarone 300 mg be given i.v. over 10–20 min and electrical cardioversion re-attempted.

If the patient is not severely compromised, management depends on the individual arrhythmia:

Permanent Pacemakers: Many patients with these devices have underlying heart disease which should be managed accordingly.

Permanent pacemakers are inserted in an increasing number of patients and are becoming increasingly complex. Pacemakers are classified by a series of 5 letters relating to the functions they possess (Table 18.4).

Specific Issues in Anaesthetic Management:

Implantable Cardioverter Defibrillators (ICDs): Increasingly, these devices are used for the management of patients with recurrent life-threatening episodes of VF and VT. ICDs may also have a pacemaker function. As with permanent pacemakers, they may be subject to electromagnetic interference and the same precautions apply.

The antitachycardia and defibrillator actions should be switched off before surgery involving diathermy. Diathermy could be interpreted as VF and a shock delivered unnecessarily. An external defibrillator must be available and the patient should be in a high-dependency area postoperatively until the ICD is checked and reactivated.

 The patient’s functional reserve is a good indicator of the severity of a valve lesion

 Routine antibiotic prophylaxis is no longer recommended for all patients with valvular heart disease

 Patients with valvular heart disease may be receiving anticoagulants; perioperative heparinization is necessary

 No specific anaesthetic technique is preferred for valvular heart disease. The aim is to maintain cardiovascular stability. In severe disease, this is often best achieved using a general anaesthetic technique with opioids and controlled ventilation

 Invasive monitoring is often required in these patients.

 Acute changes in volume status cause severe haemodynamic consequences and hypovolaemia should be avoided

 Outflow obstruction is exacerbated by catecholamines so that inotropic agents should be avoided

 Patients are usually receiving a β-blocker which should be continued perioperatively

 Patients with previous malignant ventricular arrhythmias are likely to have an ICD in situ.

Chest X-ray: The preoperative chest X-ray is a poor indicator of functional impairment but may be indicated in certain situations:

ECG: This may indicate right atrial enlargement or right ventricular hypertrophy (P pulmonale in II; dominant R wave in III, V_1–3). Associated ischaemic heart disease is common, and ECG abnormalities may confirm this (Fig. 18.1).

Haematology: Polycythaemia occurs secondary to chronic hypoxaemia, while anaemia aggravates tissue hypoxia. Leucocytosis may indicate active infection.

Sputum Culture: Sputum culture is essential in patients with chronic lung disease or suspected acute infection.

Pulmonary Function Tests: Peak expiratory flow rate, forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) can be measured easily at the bedside. The FEV₁:FVC ratio is decreased in obstructive lung disease and normal in restrictive disease. In the presence of obstructive disease, the test should be repeated 5–10 min after administration of a bronchodilator aerosol to provide an indication of reversibility. An FVC < 1–1.5 L is indicative of limited ability to take large sigh breaths, expand lung bases and clear secretions by coughing.

Fuller investigation involves measurement of functional residual capacity (FRC), residual volume and total lung capacity, but these are rarely of value in determining clinical management.

Blood Gas Measurement: Arterial blood gas measurement is indicated in patients with chronic respiratory disease scheduled to undergo significant surgery and also if there is suspected acute hypoxaemia. It is also advisable when pulmonary function tests are markedly abnormal, e.g. in obstructive disease where the FEV₁ is less than 1.5 L. A raised PaCO₂ with normal pH indicates chronic hypercapnia with renal compensation; a combined raised PaCO₂ and acidosis indicates an acute event. Hypercapnia, particularly if acute, associated with acidosis, is likely to be associated with postoperative pulmonary complications. With a PaCO₂ of 6.7 kPa (50 mmHg) or greater, elective controlled ventilation may be required after major surgery. The combination of a low preoperative arterial oxygen tension (PaO₂) and dyspnoea at rest is also associated with a high likelihood of the need for planned ventilation after abdominal surgery.