3 Cardiovascular disease

Perioperative acute myocardial infarction 52

Heart failure 54

Hypertension 58

Valvular heart disease 60

Prosthetic valves 61

Aortic stenosis 62

Aortic regurgitation 64

Mitral stenosis 66

Mitral regurgitation 68

The patient with an undiagnosed murmur 70

Pericardial disease 71

Cardiomyopathy 72

Patients with a transplanted heart 74

Peter Murphy

Congenital heart disease and non-cardiac surgery 76

Specific CHD lesions 78

Adults with CHD 80

Arrhythmias and cardiac conduction abnormalities require careful evaluation for underlying cardiopulmonary disease, drug toxicity, and metabolic abnormality.

Many patients with underlying IHD have a normal resting ECG.

Cardiopulmonary exercise testing: usually performed on a bicycle ergometer using respiratory gas analysis and an ECG. An arm ergometer is available for those patients who cannot cycle. When exercising aerobically there is a linear relationship between oxygen consumption and carbon dioxide production. When the anaerobic threshold is reached excess lactic acid produced by anaerobic metabolism is buffered by the bicarbonate system. This increases carbon dioxide production, producing an inflexion point in the graph which is the anaerobic threshold. A low anaerobic threshold (<∼11ml/min/kg), particularly if associated with ECG evidence of ischaemia, is associated with a high mortality in patients presenting for major intracavity surgery (see also p. 1053).

Dobutamine stress echocardiography: utilises an increasing dose of dobutamine (to a maximum of 40µg/kg/min) with simultaneous 2D precordial echocardiography to look for new or worsening wall motion abnormalities as an indicator of impaired perfusion. It is a complex, time-consuming test requiring expertise.

Recent evidence suggests that acute perioperative β-blockade may be detrimental. Although acute perioperative β-blockade reduces the risk of non-fatal perioperative MI, it is associated with increased rates of perioperative mortality and stroke.²

There is limited evidence to suggest that very high-risk patients who demonstrate inducible ischaemia on preoperative stress testing may benefit from carefully titrated β-blockade started at least one week prior to surgery.

Randomised trials have shown α₂ agonists to be beneficial and represent an alternative to β-blockers.³ Clonidine is the most widely available (up to 300µg daily).

Nitrates should be continued perioperatively—IV or transdermally if necessary. There is no evidence that prophylactic administration decreases the risk of perioperative cardiac complications.

Calcium channel blockers should be continued preoperatively and resumed as soon as possible postoperatively. They have never been shown to confer protection against perioperative cardiac complications. The dihydropyridine group (especially nifedipine SL) may add to the risk of acute MI.

ACE inhibitors improve survival in patients with left ventricular dysfunction and offer major benefits to patients with vascular disease or diabetes and normal left ventricular function. In the perioperative period they may increase the risk of hypotension (especially with thoracic epidurals or hypovolaemia), requiring more invasive haemodynamic monitoring for major surgery. Some anaesthetists routinely stop administration in the perioperative period—if stopped for several days restart at a reduced dose.

Perioperative statin administration has been shown to improve both short-term and long-term cardiac outcome following non-cardiac and coronary bypass surgery. Statins enhance plaque stability, making plaque rupture less likely.

All patients with documented ischaemic heart disease should continue to receive antiplatelet medication to protect against thromboembolic complications.

There is no evidence that any particular technique is superior. Avoid tachycardia and hypotension/hypertension to minimise myocardial ischaemia.

Good analgesia is important since uncontrolled pain is a potent cause of tachycardia: regional blocks can be very effective. Central neuraxial blocks ameliorate the hypercoagulable state seen following anaesthesia and surgery.

Haemoglobin levels should be kept >9g/dl.

Myocardial ischaemia may occur during emergence and extubation. Hypertension and tachycardia should be anticipated and avoided. The use of a short-acting β-blocker, e.g. esmolol, should be considered.

Consider admission to HDU postoperatively for close monitoring.

Following major surgery, all patients at risk should have supplemental oxygen for 3–4days.⁴

All patients should receive supplemental oxygen.

Patients should be given SL glyceryl trinitrate and IV morphine to relieve any chest pain.

If the patient is not taking an antiplatelet drug they should receive aspirin (75–300mg) or clopidogrel (75–600mg) if aspirin intolerant.

β-blockade should be used to control heart rate and to decrease myocardial oxygen demand (metoprolol 1–5mg boluses or esmolol 50–200 micrograms/kg/min loading dose, then 0.05–0.2µ/kg/min). Aim for a rate of 60–90bpm.

Pulmonary oedema if present should be treated with upright posture, IV furosemide (40mg), and IV nitrates. CPAP should be considered.

Other therapeutic options are reduced postoperatively. Acute thrombolysis is relatively contraindicated by recent surgery. If available, acute angioplasty of the ‘culprit lesion’ should be considered—close liaison with a cardiologist is essential.

Exercise intolerance

Orthopnoea

Exertional dyspnoea

High incidence of ventricular arrhythmias

Shortened life expectancy

Vasodilators decrease preload and afterload. ACE inhibitors, and to a lesser extent angiotensin-II receptor antagonists, improve survival. Nitrates are also used.

b-blockers (carvedilol, bisoprolol) are indicated to reduce heart rate and myocardial oxygen demand. Studies show improved survival, but cardiological input is required.

Inotropes: digoxin improves symptoms and may be used to control the ventricular rate in atrial fibrillation and in patients in sinus rhythm with severe or worsening heart failure.

Anticoagulation: indicated for atrial fibrillation and for those with a history of thromboembolism, left ventricular aneurysm, or with evidence of intracardiac thrombus on echocardiography.

Some patients with intractable heart failure may have atrial synchronous biventricular pacing devices inserted in an attempt to improve functional capacity and quality of life.

Some patients with severely impaired ventricular performance and a history of ventricular tachycardia/ventricular fibrillation will have biventricular automatic implantable cardioverter defibrillators (AICDs) inserted for secondary prevention of arrhythmic death—see p. 94.

Optimise medical therapy to minimise symptoms of left ventricular dysfunction and maximise functional capacity.

Continue antifailure therapy in the preoperative period.

Consider a period of preoperative ‘optimisation’ in ICU/HDU.

Treat metabolic abnormalities.

Treat symptomatic arrhythmias and attempt to optimise heart rate to around 80bpm. Rhythms other than sinus are poorly tolerated (especially AF), as properly timed atrial contractions contribute up to 30% of ventricular filling.

Pleural effusions, cardiomegaly.

Alternatives include transoesophageal echocardiography, radionuclide imaging, and cardiac magnetic resonance imaging.

Modern echocardiography machines generate values for ejection fraction (normal range 60–80%) and fractional shortening (normal range 28–44%) which define the degree of LV impairment.

Use local or regional techniques for peripheral procedures.

There is little conclusive evidence of the benefits of general versus regional anaesthesia for more major surgery.

Patients should receive all their antifailure medications on the morning of surgery.

Digoxin should be given IV postoperatively if the patient is in AF but if in sinus rhythm it can usually be omitted until eating resumes. Nitrates can be given transdermally while nil by mouth.

ACE inhibitors should be resumed as soon as possible postoperatively. If omitted for 3d or more they should be reintroduced at a low dose to minimise first-dose hypotension.

Whichever anaesthetic technique is chosen, minimise negative inotropy, tachycardia, diastolic hypotension, and systolic hypertension. Careful monitoring of fluid balance is essential. Invasive cardiovascular monitoring, including measurement of cardiac output should be considered for all major surgery.

Patients who decompensate in the perioperative period may require treatment with inotropes such as dobutamine and phosphodiesterase inhibitors.

Renal perfusion is easily compromised due to markedly impaired glomerular filtration rates and patients are susceptible to renal failure perioperatively. If urine output falls, hypovolaemia should be excluded and adequate perfusion pressure and cardiac output ensured before diuretics are used. NSAIDs are a potent renal insult in these patients and their use requires care.

All patients should have supplemental oxygen following surgery.

Good postoperative analgesia is essential to minimise detrimental effects of catecholamine release in response to pain.

Have a low threshold for admission to ICU/HDU in the postoperative period.

Is the hypertension severe? Patients with Stage 3 hypertension (systolic >180mmHg, diastolic >110mmHg) should ideally have this treated prior to elective surgery.

Is there evidence of end-organ involvement? The presence of coronary or cerebrovascular disease, impairment of renal function, signs of left ventricular hypertrophy, and heart failure puts patients in a high-risk category. These conditions may require further investigation and/or treatment in addition to control of elevated blood pressure.

Continue preoperative antihypertensive treatment during the perioperative period.

Stage 1 (systolic 140–159mmHg, diastolic 90–99mmHg) and Stage 2 (systolic 160–179mmHg, diastolic 100–109mmHg) hypertension are not independent risk factor for perioperative cardiovascular complications. Surgery should normally proceed in these patients.

If a patient has Stage 3 hypertension (systolic >180mmHg, diastolic >110mmHg), with evidence of damage to the heart or kidneys, defer surgery to allow blood pressure to be controlled and the aetiology investigated. There is, however, no level-one evidence as to how long the operation should be delayed (>4wk is often recommended) or that this strategy reduces perioperative risk.

Patients with Stage 3 hypertension considered fit for surgery in other respects and with no evidence of end-organ involvement should not be deferred simply on the grounds of elevated blood pressure. Attempt to ensure cardiovascular stability, using invasive monitoring where indicated, and actively control excursions in mean arterial pressure greater than 20% from baseline.

Patients undergoing major surgery or who are unstable perioperatively should be monitored closely in ICU/HDU.

Sympatholytic therapies such as α₂ agonists (clonidine) and thoracic epidural blockade may have a role but also carry risks of hypotension postoperatively.

Relate perioperative BP readings to the underlying norm—a systolic <100mmHg may represent hypotension in a normally hypertensive patient.¹

Plan anaesthesia according to the haemodynamic picture.

Tissue valves do not require anticoagulation. Mechanical valve replacements require lifetime anticoagulation.

The risk of thromboembolism if anticoagulation is stopped depends on the site and type of valve replacement.

Modern bi-leaflet aortic valve replacements have a low (<4% per annum) risk of thromboembolism and are best managed by withholding warfarin for 5d preoperatively and administering a prophylactic dose of low molecular weight heparin.

Older aortic valve replacements and mechanical mitral valve replacements have a much greater propensity to embolise (>4% per annum). They are best managed by stopping warfarin 5d preoperatively. Bridging therapy with either an intravenous infusion of unfractionated heparin or therapeutic subcutaneous low molecular weight heparin is recommended when the INR <2. Unfractionated heparin infusions should be stopped 6hr prior to surgery and therapeutic low molecular weight heparin stopped the night before surgery.

IV heparin/therapeutic LMWH can be restarted postoperatively and warfarin reinstituted when it is safe to do so.

Elevated filling pressures and sinus rhythm are required to fill the non-compliant left ventricle. ‘Normal’ left ventricular end diastolic pressure may reflect hypovolaemia.

Properly timed atrial contractions contribute as much as 40% to left ventricular preload in patients with aortic stenosis (normal = 20–30%). Arrhythmia may produce a critical reduction in cardiac output.

High risk of myocardial ischaemia due to increased oxygen demand and wall tension in the hypertrophied left ventricle. Thirty percent of patients who have aortic stenosis with normal coronary arteries have angina. Subendocardial ischaemia may exist as coronary blood supply does not increase in proportion to the muscular hypertrophy. Tachycardia is detrimental as it may produce ischaemia. Maintenance of diastolic blood pressure is crucial to maintain coronary perfusion.

Ejection systolic murmur maximal at the 2nd intercostal space, right sternal edge radiating to the neck.

CXR: normal until the left ventricle begins to fail, post-stenotic dilatation of the aorta, calcified aortic annulus.

Cardiac catheterisation is also used to estimate the gradient across the valve and to quantify any concurrent coronary artery disease.

Asymptomatic patients for major elective surgery associated with marked fluid shifts (thoracic, abdominal, major orthopaedic) with gradients across the valve >50mmHg should have valve replacement considered prior to surgery.

Asymptomatic patients for intermediate or minor surgery generally do well if managed carefully.

Maintain sinus rhythm.

Adequate volume loading.

High normal systemic vascular resistance.

Meticulous attention must be paid to fluid balance and postoperative pain management.

Infusions of vasoconstrictors may be required to maintain haemodynamic stability.

Aortic dissection and connective tissue disorders that dilate the aortic root (tertiary syphilis, Marfan's syndrome p. 317, ankylosing spondylitis p. 195) result in secondary aortic incompetence.

Valvular regurgitation usually develops over many years, allowing the heart to adapt to increased volume.

Acute regurgitation secondary to endocarditis or aortic dissection presents with acute left heart failure and pulmonary oedema. Such patients require emergency valve surgery.

Vasodilators increase forward flow by lowering afterload, decrease left ventricular size, and enhance ejection fraction.

Heart rates greater than 90bpm reduce diastolic ‘regurgitation’ time and degree of regurgitation.

Aortic diastolic pressure is dependent on the aortic valve and decreases when the valve becomes incompetent.

Palpitations.

Collapsing (‘waterhammer’) pulse. Corrigan's sign—visible neck pulsation. De Musset's sign—head nodding. Quincke's sign—visible capillary pulsations in the nail beds.

Diastolic murmur 2nd intercostal space right sternal edge.

ECG: non-specific LVH.

Echocardiography gives qualitative analysis of the degree of regurgitation.

Adequate volume loading.

Low systemic vascular resistance.

Maintain contractility.

The left ventricle functions normally but is small and poorly filled.

Initially the left atrium dilates, keeping the pulmonary artery pressure low. As disease progresses pulmonary artery pressure increases and medial hypertrophy develops, resulting in chronic reactive pulmonary hypertension. The right heart hypertrophies to pump against a pressure overload, then fails. Secondary pulmonary/tricuspid regurgitation develops.

The pressure gradient across the narrow mitral orifice increases with the square of cardiac output (NB pregnancy). Rapid heart rates, especially with atrial fibrillation, decrease diastolic filling time and markedly decrease cardiac output.

LV filling is optimised by a slow heart rate.

Fatigue.

Palpitations.

Peripheral cyanosis.

Signs of right heart failure (elevated JVP, hepatomegaly, peripheral oedema, ascites).

Tapping apex beat. Loud first heart sound, opening snap (if in sinus rhythm), and low-pitched diastolic murmur heard best at the apex (with the bell of the stethoscope).

CXR: valve calcification. Large left atrium (lateral film). Double shadow behind heart on PA film. Splaying of the carina. Kerley B lines indicating pulmonary congestion.

Echocardiography: measures the gradient and valve area—see table.

Maintain sinus rhythm if possible. Immediate cardioversion if AF occurs perioperatively.

Adequate preload.

High normal systemic vascular resistance.

Avoid hypercarbia, acidosis, and hypoxia, which may exacerbate pulmonary hypertension.

Leaflet MR is a complication of endocarditis, rheumatic fever, and mitral valve prolapse.

Chordal MR follows chordae rupture after acute myocardial infarction or after bacterial endocarditis.

Papillary muscle MR results from ischaemic posterior papillary muscle dysfunction.

Left ventricular failure leads to varying amounts of MR when the mitral annulus dilates.

As much as 50% of the left ventricular volume flows into a massively dilated left atrium through the incompetent mitral valve before the aortic valve opens. Left ventricular ejection fraction is therefore supranormal.

Pulmonary vascular congestion develops, followed by pulmonary hypertension.

The degree of regurgitation is determined by the afterload, size of the regurgitant orifice, and the heart rate. A moderately increased heart rate (>90bpm) decreases the time for regurgitation in systole and decreases the time for diastolic filling, reducing LV overload.

Dyspnoea.

Soft S₁, apical pansystolic murmur radiating to the axilla, loud S₃.

Atrial fibrillation.

CXR: left atrial and left ventricular enlargement. Mitral annular calcification.

Echocardiography assesses the degree of regurgitation. (Transoesophageal echo particularly useful as mitral valve close to the oesophagus.)

Adequate preload.

Low systemic vascular resistance.

Low pulmonary vascular resistance.

Usually asymptomatic, but may be associated with atypical chest pain, palpitations, syncope, and emboli.

Mid-systolic click and late diastolic murmur.

Echocardiography shows enlarged redundant mitral valve leaflets prolapsing into the left atrium during mid- to late-systole causing arrhythmias and regurgitation.

Antiarrhythmics must be continued perioperatively.

No history of angina/breathlessness/syncope

Absence of slow rising pulse (normal pulse pressure)

Absence of LVH/LV strain on ECG.

Frequently occurs with myocarditis which may increase the likelihood of arrhythmia and sudden death.

Elective surgery should be postponed for at least 6wk.

Pulsus paradoxus may be evident—a fall in systolic blood pressure with inspiration. The normal maximum fall is 10mmHg.

Systolic function of the myocardium is well maintained but diastolic function is severely impaired. When exercise tolerance is reduced general anaesthesia carries a significant risk.

Bradycardia and reduced cardiac filling are poorly tolerated.

Elevations in intrathoracic pressure, as occur during IPPV, can result in profound hypotension.

If anaesthesia is unavoidable and regional block is not possible then a spontaneously breathing technique is preferable to IPPV. Preload should be maintained and tachycardia avoided.

Main feature is asymmetric hypertrophy of the interventricular septum, which obstructs the outflow tract when it contracts.

Ventricular systole is associated with movement of the anterior mitral valve leaflet towards the septum (‘systolic anterior motion’—SAM) and the outflow tract is further obstructed. In some patients this causes mitral regurgitation.

As with aortic stenosis, HOCM results in a pressure overload of the left ventricle. Diastolic dysfunction is evident on echo.

Sinus rhythm is crucial to maintain ventricular filling.

Maintain sinus rhythm.

Adequate volume loading.

High normal systemic vascular resistance.

Low ventricular contractility.

Peripheral vasodilatation, myocardial depression, and reduced venous return may cause catastrophic cardiovascular decompensation and may precipitate cardiac arrest.

Venous return may be further compromised by positive pressure ventilation. Wherever possible maintain spontaneous respiration.

Ketamine may be useful as it increases myocardial contractility and peripheral resistance.

Fluids should be given to maintain elevated right heart pressures.

Adequate volume loading.

High normal systemic vascular resistance.

Avoid myocardial depression.

Commonest problems are heart failure, arrhythmias, and embolic phenomena.

Heart failure is treated with diuretics, ACE inhibitors, and vasodilators. Amiodarone is the drug of choice for arrhythmias as it has least myocardial depressant effect. Patients are frequently anticoagulated. Synchronised dual chamber pacing may be used. Some patients may have a biventricular pacing/defibrillator (AICD) in place (see p. 94).

Invasive cardiovascular monitoring is required during anaesthesia (arterial and pulmonary arterial catheters and non-invasive methods of cardiac output estimation, e.g. oesophageal Doppler, PiCCO, LiDCO).

Adequate volume loading.

Normal systemic vascular resistance.

Avoid myocardial depression: inotropic support is frequently required with dobutamine or phosphodiesterase inhibitors.

Effects of immunosuppression

Medications

Associated risk factors.

Normal autonomic system responses are lost (beat-to-beat variation in heart rate, response to Valsalva manoeuvre/carotid sinus massage).

Contractility of the heart is close to normal, unless rejection is developing. In the absence of sympathetic innervation the age- predicted maximal heart rate is reduced.

Despite some evidence that reinnervation can occur some years after transplantation the heart should be viewed as permanently denervated. This results in poor tolerance of acute hypovolaemia.

If pharmacological manipulation is required then direct-acting agents should be used: atropine has no effect on the denervated heart, the effect of ephedrine is reduced and unpredictable, and hydralazine and phenylephrine produce no reflex tachy- or bradycardia in response to their primary action. Adrenaline, noradrenaline, isoprenaline, and β- and α-blockers act as expected.

Nucleic acid synthesis inhibitors (azathioprine) block lymphocyte proliferation.

Steroids block the production of inflammatory cytokines, lyse T lymphocytes, and alter the function of the remaining lymphocytes.

Cough may be impaired due to a combination of phrenic and recurrent laryngeal nerve palsies. This increases the risks of sputum retention and postoperative chest infection.

Heart–lung recipients will have a tracheal anastomosis. It is desirable to avoid unnecessary intubation, but if it is necessary use a short tube and carefully monitor tracheal cuff pressure. Disrupted lung lymphatic drainage increases the risk of pulmonary oedema.

The transplanted heart develops coronary artery disease.

Subarachnoid/epidural block may result in marked falls in blood pressure because of absent cardiac innervation.

Corrective procedures: the patient's haemodynamic status is markedly improved but life expectancy may not be normal (e.g. tetralogy of Fallot repair see also p. 79).

Palliative procedures: these patients may have abnormal circulations and physiology but avoid the consequences of untreated CHD. Life expectancy is not normal but many survive to adulthood (e.g. Fontan procedures see also p. 79).

Examination: check for cyanosis, peripheral oedema, hepatosplenomegaly, murmurs, and signs of infection/failure. Check peripheral pulses. Neurological examination for cyanotic patients.

Investigations: CXR/ECG. Record baseline SpO₂ on air. Laboratory tests depend on the proposed surgery, but most will require FBC, clotting screen, LFTs, and electrolytes. Some patients will need pulmonary function tests.

Consult the patient's cardiologist—recent echocardiography report and catheter data should be available. Potential risk factors should be considered, along with potential treatment regimes, e.g. inotropes and vasodilators.

Consider whether the proposed surgery is necessary, with regard to the potential risks, whether admission to ICU/HDU will be required, and whether the patient can or should be moved to a cardiac centre.

Severe hypoxaemia with SpO₂ <75% on air.

Polycythaemia (haematocrit >60%).

Unexplained dizziness/syncope/fever or recent CVE.

Severe aortic/pulmonary valve stenosis.

Uncorrected tetralogy of Fallot or Eisenmenger's syndrome.

Patients with hypoplastic left heart syndrome (HLHS).

Recent onset of arrhythmias.

Air emboli: all CHD patients are at risk from air embolism. Intravascular lines should be free of air.

Cyanosis has many causes, e.g. shunting of blood from the right to left side of the heart (tetralogy of Fallot, Eisenmenger's syndrome) and intracardiac mixing (complete atrioventricular septal defect). Cyanosis results in polycythaemia and increased blood volume. Blood viscosity is increased, impairing tissue perfusion. There is often thrombocytopenia and fibrinogen deficiency leading to a bleeding tendency. An increase in tissue vascularity worsens bleeding problems. Cyanosis can also lead to renal/cerebral thrombosis and renal tubular atrophy.

Anticoagulant treatment (aspirin or warfarin) is common in CHD patients.

Antibiotic prophylaxis—see p. 1254.

Myocardial ischaemia developing in a patient with CHD is significant and should be investigated.

Usually results in a left-to-right shunt.

Can be closed surgically or transcatheter.

Danger of paradoxical emboli.

More severe form, atrioventricular septal defect (AVSD), is associated with Down's syndrome and results in severe pulmonary hypertension (see p. 305).

Surgical repair of these lesions may result in complete heart block.

Clinical effects depend on size and number of VSDs.

A small, single VSD may be asymptomatic with a small left-to-right shunt (pulmonary:systemic flow ratio <1.5:1). In patients who have not had corrective surgery, prevent air emboli and fluid overload.

Patients with a moderate sized, single VSD often present with mild CCF. They have increased pulmonary blood flow (pulmonary:systemic flow ratio 3:1). If the lesion is not treated they are at risk of pulmonary hypertension and shunt reversal.

Patients with a large VSD have equal pressures in their right and left ventricles and present at around 2 months of age with severe CCF. They require early operations. However, if they need anaesthesia for another procedure prior to definitive cardiac surgery they present severe problems. They should be intubated, for all but the most minor procedures, and increases in left-to-right shunt should be avoided (e.g. avoid hyperventilation and high FiO₂). Care should be taken with fluid administration, and inotropic support is often required.

Patients with multiple VSDs often require pulmonary artery banding to protect the pulmonary circulation. This band tightens as the child grows, leading to cyanosis. VSDs often close spontaneously and then the band may be removed.

Can be closed surgically or transcatheter.

Prior to complete repair, TOF may be treated medically with β-blockade or surgically via a Blalock–Taussig (BT) shunt (subclavian to pulmonary artery).

In patients without a BT shunt, and prior to definitive surgery, the ratio of SVR:PVR determines both the systemic blood flow and blood oxygen saturation. If they require anaesthesia at this stage they should be intubated and ventilated in order to maintain a low PVR. Cyanosis should be treated with hyperventilation, IV fluid, and systemic vasopressors such as phenylephrine.

Total repair of TOF is undertaken at around 2–6 months of age.

Abnormal and irreversible elevation in PVR resulting in cyanosis and right-to-left shunting. The degree of shunting depends on the PVR:SVR ratio. Increasing the SVR or decreasing the PVR leads to better arterial SpO₂, as in patients with TOF.

Avoid reductions in SVR (epidural/spinal anaesthesia) and rises in PVR (hypoxia/hypercarbia/acidosis/cold).

Desaturation episodes can be treated as for TOF above.

Inotropic support may be required for the shortest of procedures and an ITU bed should be available.

Manage patient in a specialist centre whenever possible.

Leads to elevated systemic venous pressures, liver congestion, protein-losing enteropathy, tendency for fluid overload, ascites, and pleural and pericardial effusions. Hypovolaemia can lead to hypoxia and cardiovascular collapse. Patients are anticoagulated with warfarin.

In these patients intermittent positive pressure ventilation results in a fall in cardiac output and high ventilatory pressures result in poor pulmonary perfusion. Fluid overload is poorly tolerated, as is hypovolaemia.

Central venous pressure monitoring is helpful and is best instituted via the femoral venous route.

Lesions resulting in large left-to-right shunts will cause progressive pulmonary hypertension and eventual shunt reversal (Eisenmenger's syndrome). Once irreversible pulmonary hypertension has developed surgical correction is not possible. These patients are high risk. If surgery is absolutely necessary it should be performed in a specialist centre.

Best assessment of cardiovascular function is generally the exercise tolerance.

Exclude surgical sequelae/continuing disease.

Exclude any associated congenital abnormalities.

An understanding of the underlying physiology is required to avoid disaster when anaesthetising these patients. At present, management is best provided in specialist cardiac centres.

In patients with a Fontan circulation, blood leaves a single ventricle, passes through the systemic circulation and then through the pulmonary circulation, before returning to the heart. The consequences of this are that the CVP is high, providing a pressure gradient across the pulmonary circulation. Any pulmonary hypertension is poorly tolerated and results in reduced ventricular filling. The high venous pressure can result in life-threatening haemorrhage from mucosal procedures such as adenoidectomy (or nasal intubation!).