- Email: [email protected]
Anaesthesia for paediatric diagnostic and interventional cardiological procedures
Anaesthesia for paediatric diagnostic and interventional cardiological procedures Matrix reference 2D02 3D00
Syed Mohsin Qureshi BSc MBBS MD FCARCSI Kuberan Pushparajah BMBS MRCPCH Dan Taylor MB ChB MRCPCH FRCA
Children presenting for cardiac catheterization may have complex pathophysiology and multiple co-morbidities. Maintaining haemodynamic stability during the procedure is crucial in obtaining meaningful diagnostic information. Therapeutic interventions in the catheter laboratory include occlusion of patent ductus arteriosus, closure of atrial septal defects, balloon dilatation for valvular stenosis and stenting of narrowed vessels. MRI is increasingly used for diagnostic imaging. Anaesthetized children must be rendered apnoeic during cardiac MRI, as breath holds are often required for good quality imaging. Syed Mohsin Qureshi BSc MBBS MD FCARCSI Specialist Trainee South East School of Anaesthesia King’s College Hospital, London, UK Kuberan Pushparajah BMBS MRCPCH Clinical Fellow Department of Congenital Cardiology Evelina London Children’s Hospital Guy’s and St Thomas’ NHS Foundation Trust, London, UK Dan Taylor MB ChB MRCPCH FRCA Consultant Paediatric Anaesthetist Evelina London Children’s Hospital Anaesthetic Department Guy’s and St Thomas’ NHS Foundation Trust Westminster Bridge Road London SE1 7EH, UK Tel: þ44 20 718 80654 Fax: þ44 20 7188 2284 E-mail: [email protected] (for correspondence)
1
Diagnostic cardiac catheterization was reported in the nineteenth century and interventional cardiac catheterization was first described by Rubio-Alvarez in 1954 for the treatment of pulmonary valve stenosis.1 In some centres, MRI is increasingly used for diagnostic imaging. To ensure safety and quality images, the majority of these procedures in children require general anaesthesia. Cardiac catheterization may be challenging when dealing with complex congenital cardiac lesions. Good communication between the team members is essential, so that cardiovascular changes can be anticipated and minimized as far as possible. This includes the full team: anaesthetist and assistant, cardiologist, scrub team, radiographer, and a cardiac physiologist. It is a challenging and high-risk field of anaesthetic practice and requires consultant-led care by specialists in paediatrics and congenital heart disease (CHD).
Diagnostic cardiac catheterization Diagnostic catheterization is becoming less popular with technological advances in non-invasive imaging such as cardiac CT and MRI allowing angiographic assessment. Paediatric cardiac catheter procedures are listed in Table 1.2,3 Invasive studies are still necessary to directly measure intracardiac and intravascular pressures and to allow direct measurement of arterial, mixed venous, pulmonary venous and pulmonary arterial saturations and derive shunt fraction, flows and resistance (Table 2).4,5 Dynamic investigations such as dobutamine stress testing and pulmonary vascular resistance studies (sometimes in conjunction with MRI) are also possible. Endomyocardial biopsies and coronary angiography (and endosonography) are performed as part of routine surveillance after cardiac transplantation. Myocardial biopsies are occasionally used to diagnose myocarditis and cardiomyopathy.
Interventional cardiac catheterization Interventional techniques Valvuloplasty A fluid-filled cardiac catheter is passed across the stenotic pulmonary or aortic valves and the pressure gradient assessed. This is exchanged over a guide wire for a balloon catheter, which is then inflated for a few seconds to split the fused valve leaflets. Balloon dilatation is repeated several times until an adequate reduction in gradient is achieved, ideally without severe valvular incompetence developing. Pulmonary valvuloplasty has successfully been performed for many years. It is the treatment of choice for isolated pulmonary stenosis with a gradient of more than 50 mm Hg. Neonates with critical pulmonary stenosis are cyanosed, often requiring ventilation and a prostaglandin infusion to maintain duct patency. Desaturation occurs during balloon dilatation, but cardiac output can be maintained by a patent ductus arteriosus. Critical aortic stenosis can be associated with severe cardiovascular collapse. Untreated severe aortic stenosis carries a high risk of sudden death. Aortic valvuloplasty presents a very high risk of haemodynamic instability and cardiac arrest from ischaemia and arrhythmias. Vasodilatation and hypovolaemia are poorly tolerated. Resuscitation drugs should be readily available to reverse haemodynamic compromise due to repeated occlusion of the aortic valve.
Septal defect closure Atrial septal defect closure is the most commonly performed procedure. Trans-oesophageal echocardiography (TOE) is used to assess the margins of the defect and to aid X-ray-guided device placement. It is generally well tolerated, but, dislodgement and embolization of the device, impingement on the surrounding structures and
doi:10.1093/bjaceaccp/mku002 Advance Access publication 24 February, 2014 Continuing Education in Anaesthesia, Critical Care & Pain | Volume 15 Number 1 2015 & The Author [2014]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
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Key points
Anaesthesia for paediatric cardiological procedures
perforation of the heart or great vessels may occur. Ventricular septal defect closure is usually performed surgically on cardiopulmonary bypass but they can sometimes be closed with a percutaneous device.
include arrhythmias, perforation of the myocardium, embolization, and structural damage to the valvular apparatus.
Angioplasty and placement of stents Atrial septostomy
Table 1 Paediatric cardiac catheter laboratory procedures Indications
Procedure
Diagnostic
Defining cardiac and vascular anatomy Measuring haemodynamic pressures and shunts Pulmonary hypertension studies using nitric oxide Coronary angiography and endosonography Myocardial and endomyocardial biopsy Valvuloplasty Septal defect closure Atrial septostomy Angioplasty and placement of stents Percutaneous valve placements Closure of systemic to pulmonary shunts, e.g. patent ductus arteriosus Hybrid procedure Conduction system mapping Radiofrequency and cryoablation Placement of pacemaker and ICD
Interventional
Electrophysiological studies
Percutaneous valve placement Severe pulmonary regurgitation or mixed pulmonary valve disease has traditionally required major surgery on bypass. The transcutaneous placement of pulmonary valves made from bovine jugular vein and titanium has transformed the management of these patients. Via a femoral venous sheath, the valve, mounted in a balloon-expandable stent, is threaded along a guide wire into the correct position under fluoroscopic and TOE guidance. The valve is then re-expanded to its final diameter to minimize any leaks or regurgitation.
Closure of systemic to pulmonary shunts This is commonly performed outside the neonatal period to limit excessive pulmonary blood flow, for example, in patent ductus arteriosus. Helical wires are used to close small vessels; more complex devices are needed to occlude large vessels. There is a risk of device dislodgement and embolization.
Hybrid procedure Surgical and endovascular techniques can be combined in certain circumstances, such as the first stage in palliation of hypoplastic left heart syndrome. It is usually performed soon after birth, with the aim of avoiding cardiopulmonary bypass in selected high-risk cases. This is a novel treatment performed in a few specialist centres. Hybrid procedures involve a sternotomy, followed by surgical
Table 2 Haemodynamic calculations performed during cardiac catheterization Flows Systemic flowðQs Þ ¼
VO2 (SaoO2 SmvO2 Þ Cm VO2 Pulmonary flowðQp Þ ¼ (SpvO2 SpaO2 Þ Cm
VO2, oxygen consumption; SaoO2 , aortic saturation; SmvO2 , mixed venous saturation; S pvO2 , pulmonary venous saturation; S paO2 , pulmonary artery saturation; Cm (oxygen content)¼S pO2 Hb (in g dl21)1.3410þ(PaO2 mm Hg0.003) Resistances PAP LAP Pulmonary vascular resistance (PVR) ¼ Qp Systemic vascular resistance (SVR) ¼
AoP RAP Qs
PAP, pulmonary artery pressure; LAP, left atrial pressure; AoP, aortic pressure; RAP, right atrial pressure Shunt fraction SaoO2 SmvO2 Pulmonary to systemic flow ratio (Qp :Qs ) ¼ S pvO2 S paO2
2
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This procedure is performed to allow mixing of blood to improve oxygen saturation in cardiac lesions such as transposition of great arteries or single-ventricle circulations dependent on adequate mixing at atrial level. These children are often very sick with hypoxaemia, systemic hypotension, and metabolic acidosis. They will usually be receiving a prostaglandin (PGE1) infusion to maintain a patent ductus arteriosus. A balloon-tipped catheter is passed from the right atrium through the foramen ovale and into the left atrium under trans-thoracic echocardiographic imaging. The balloon is then inflated and pulled across the septum to enlarge the septal communication. It is often performed several times until the atrial communication is large enough to allow free mixing of blood at atrial level. Complications
Angioplasty involves dilatation of narrowed blood vessels by a balloon-tipped catheter passed across the stenosed area. Occasionally, this is followed by endovascular stenting, for example in branch pulmonary artery stenosis, coarctation of aorta and superior vena cava obstruction. Stenting can involve passage of large catheters with risk of vascular damage, dislodgement and embolization of the stent.
Anaesthesia for paediatric cardiological procedures
as increased diastolic perfusion pressures, reducing the heart rate, removal of the catheter or administering coronary dilators like glyceryl trinitrate.
Anaesthesia for cardiac catheterization
Complications
Preoperative assessment
The overall incidence of complications in paediatric cardiac catheterization is quoted at 7.3%, of which the majority are vascular and related to femoral access. These include haemorrhage, retroperitoneal and local haematoma, pseudo-aneurysm, arterio-venous fistula, neuropathy and thrombosis leading to lower limb ischaemia.6 Mortality has been reported at 0.2%.6 Independent risk factors include younger patient age, low body weight and interventional procedures.
A comprehensive preoperative assessment of children with CHD is essential to understand the likely physiological consequences of anaesthesia and the planned intervention. In addition to standard preoperative assessment, particular attention should be paid to the cardiovascular system. Look for signs and symptoms of poor cardiac output and heart failure (difficulty feeding, poor growth, sweating in infants or reduced exercise tolerance in older children). Observations, especially baseline oxygen saturation, should be checked. Current medication should be reviewed and administered unless there are any contraindications on the day of surgery. Angiotensin-converting enzyme inhibitors are often omitted to avoid hypotension on induction but may be continued in some children with severe heart failure. Anticoagulants may also be omitted depending on risk– benefit, for example, children with shunt-dependent circulations are safer continuing anticoagulants even for catheterization procedures and accepting the slightly higher risk of bleeding rather than the problems arising from a blocked shunt. Children will often have had multiple cardiac investigations and operations. Previous anaesthetic charts are invaluable. The most recent echocardiography and MRI reports should be reviewed along with routine laboratory studies, including full blood count, creatinine, urea and electrolytes. Blood group and antibody screen should be performed for all and a cross-match of packed cells (one adult unit) for any interventional procedure. The ECG should be reviewed for any rhythm disturbances, ischaemic changes and chamber hypertrophy and pacemakers checked where present. A chest X-ray is helpful to assess the lung parenchyma, identify any areas of collapse, and confirm the position of previous pacemaker leads, devices, or stents. Premedication is not commonly used but may benefit anxious older children particularly who may have had multiple procedures. Clearly safety must be considered in the smaller, more cyanotic children or those with poor ventricular function. Midazolam up to 0.5 mg kg21 orally (up to a maximum 20 mg) is our choice when necessary. Parental presence, distraction techniques and assistance of play therapists are alternative means of reducing anxiety.
Arrhythmias These are most often caused by mechanical stimulation by catheters and are usually transient, resolving when the catheter is withdrawn. Persistence may indicate cardiac ischaemia or damage to the conducting system or myocardium. Trigger factors such as acidosis and electrolyte imbalance should be avoided. Anti-arrhythmics or pacing are rarely needed.
Vascular complications and cardiac perforation Large vascular sheaths may cause vascular damage, most commonly at the insertion site. This is usually managed conservatively. Other complications such as perforation of blood vessels, myocardium, or heart valves may cause cardiac tamponade occasionally requiring operative intervention.
Thrombosis and cerebrovascular accidents The presence of foreign bodies and damage to the endothelium will activate formation of thrombus, which may lead to embolic complications. To avoid this, heparin is given at a dose of 50 –100 units per kg after arterial cannulation aiming for an activated clotting time (ACT) of 200 s or above. High levels of ACT could cause haemorrhage and haematoma; hence, careful observation is required until heparin effect has dissipated.
Hypotension The causes are often multifactorial and include: anaesthetic agents, i.v. contrast, arrhythmias, hypovolaemia, and haemorrhage. In aortic and pulmonary valvuloplasty, balloon inflation will cause sudden decrease in the cardiac output and severe hypotension.
Ischaemia Ischaemic ECG changes are common during coronary angiography and may occur in low cardiac output states. These can usually be reversed by measures to improve coronary perfusion pressure such
Induction Full standard monitoring should be applied before induction, if the child is co-operative. I.V. or inhalation induction depends on the child’s physiological condition, cooperation and personal preferences. Sevoflurane is our agent of choice for inhalation induction. Propofol or ketamine is used for i.v. induction. While choosing anaesthetic agents, consider the likely physiological consequences of
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banding of both pulmonary arteries and catheterization via direct cannulation of the pulmonary trunk to place a stent in the ductus arteriosus. Patients require full invasive monitoring and adequate venous access in preparation for possible deterioration that may require urgent surgery on cardiopulmonary bypass.
Anaesthesia for paediatric cardiological procedures
Positioning The patient is kept supine, arms above the head to expose the heart and great vessels for viewing by biplane X-ray imaging. Cables and ECG dots should be positioned to avoid artifacts during imaging. Once the procedure starts, access to the child will be limited, so a secure airway, reliable venous access, all monitoring displayed correctly and good thermoregulation measures are essential from the beginning. Ensure protection of eyes and pressure areas and minimize stretching on the brachial plexus.
Safety Radiation dose is monitored and minimized as far as possible. Lead gowns may cover areas of the body not being scanned. Attention should also be paid to staff safety in terms of protection from radiation exposure (lead gowns and thyroid protectors) and monitoring long-term exposure.
Maintenance During the procedure, it is essential to keep the patient immobile, haemodynamics as close to preprocedural values as possible, normothermia and normocapnia. Stable haemodynamics are required to generate meaningful baseline pressures and to allow interpretation of diagnostic interventions such as stress testing and nitric oxide not to be confounded by other factors. In vulnerable patients instability can quickly spiral out of control; careful monitoring and prompt intervention are essential. High inspired oxygen concentrations (above 30%) may give erroneous results in flow studies and may decrease pulmonary vascular
4
resistance, thereby increasing left-to-right shunt fraction. Oxygen and air with an inhalation agent is the preferred method for maintenance of anaesthesia. Increased inspired oxygen concentrations are used when attempting to reduce pulmonary vascular resistance in conjunction with inhaled nitric oxide, when investigating pulmonary hypertension. Intraoperatively only small doses of fentanyl (1–2 mg kg21) are required to blunt haemodynamic changes during stimuli such as insertion of femoral sheaths or TOE probes. Paracetamol and local anaesthetic infiltration are usually enough for post-procedural analgesia. An antiemetic (ondansetron 0.1 mg kg21) is usually given to avoid nausea and vomiting and unnecessary hospital overnight admission. Isotonic i.v. maintenance fluid will be required in the vast majority of cases, with attention to blood sugar monitoring in neonates. It is important to account for the volume and content of flushes and i.v. contrast used by the operator and also blood loss, both of which may be considerable. Iodinated contrast media have some nephrotoxic potential. Risk factors include pre-existing renal impairment, diabetes, heart failure and use of other nephrotoxic drugs, but problems can occur in patients with previously normal kidneys. Dehydration should be avoided, other nephrotoxic drugs omitted, and where risk is high, minimum volumes of iso-osmolar or low osmolar contrast medium used. The majority of patients are extubated at the end of the procedure and recovered in a routine fashion, with special attention to the femoral puncture sites and lower limb perfusion. Paediatric intensive care is reserved for ill or higher risk cases and those where serious complications have occurred.
Electrophysiological studies and pathway ablation The principle of electrophysiological (EP) studies is to identify the abnormal mechanism of arrhythmias, and localize abnormal pathways and foci responsible for the arrhythmias. Most of the children presenting for EP studies are otherwise healthy with a normal functioning heart and suffer from uncomplicated supraventricular tachycardia. Some may present with CHD, cardiomyopathy and life-threatening arrhythmias. Multiple arterial and venous accesses may be required. The technique involves passage of electrode catheters to the right heart and coronary sinus through femoral venous access. Occasionally, a trans-septal puncture is required. A previous CEACCP article gives a full account of anaesthesia for EP procedures for the adult patient.7 Destruction of abnormal pathways or foci is accomplished by delivering radiofrequency energy or cryoablation. The size of the lesion created is controlled by the temperature at the end of the catheter and duration of exposure. Thermal injury can occur if this is not carefully monitored. Repeat EP studies are conducted to ensure no additional or residual pathways remain. Principles of anaesthesia are similar to that of catheterization. Procedures are often very prolonged. Pressure areas should be well
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varying systemic and pulmonary vascular resistances on shunts and cardiac output. Tracheal intubation is required for the majority of cases and is facilitated with a neuromuscular blocking agent (e.g. atracurium 0.5 mg kg21). Older children having short procedures may occasionally be managed using a supraglottic airway device. The airway should be controlled during procedures associated with high risk of haemodynamic instability, procedures with high risk of complications, in patients in whom internal jugular venous access is required or who may require resuscitation. Avoid large leaks around the tracheal tubes to guarantee carbon dioxide clearance. Increased arterial CO2 tension or decreased pH may increase pulmonary vascular resistance with attendant effects on pulmonary blood flow and shunt direction. Antibiotic prophylaxis use varies but is required if any devices are being left in situ (e.g. flucloxacillin 50 mg kg21). Operator access is usually via femoral vessels, so it is easier to use neck and upper limb vessels for monitoring lines and access. Occasionally, procedures may be performed via upper limb vessels, so prior knowledge of this is essential. Reliable vascular access of adequate size is essential. Central access and arterial access is usually reserved for sicker children (e.g. critical aortic stenosis in neonates) but the need should be assessed on a case-by-case basis, as some children may be unwell enough to merit full monitoring for even minor procedures.
Anaesthesia for paediatric cardiological procedures
Implantation of pacemakers and defibrillators
Fig 1 Hybrid X-ray/MRI suite.
Pacemaker implantation is indicated in symptomatic bradycardia due to sinoatrial node dysfunction and complete heart block. Transvenous pacing leads are usually inserted through the subclavian vein and the subcutaneous generator is fixed below the left sternum. In infants and neonates device size is disproportionate to the size of the patient; therefore surgical placement of epicardial wires via a sternotomy may be necessary. Patients will require general anaesthesia with tracheal intubation. Insertion of an implantable cardiovertor-defibrillator (ICD) is indicated in children who suffer from life-threatening ventricular arrhythmias. This will include patients with channelopathies and forms of cardiomyopathy associated with sustained VT/VF in the absence of a reversible cause. These patients can have a family history of life-threatening arrhythmias or sudden cardiac death in the family. Once an ICD is inserted it is usual to test its function by inducing ventricular fibrillation. It is essential to have an external defibrillator attached to the patient should the ICD fail. Anaesthesia is similar to that for cardiac catheterization but may be challenging in children with impaired ventricular function. Careful titration of anaesthetic agents to avoid hypotension, excessive bradycardia, or tachycardia is essential. Invasive monitoring may be required. Local anaesthetic infiltration at the site of pacemaker insertion and paracetamol with or without a small dose of a suitable opioid will usually provide adequate postoperative analgesia. A prophylactic dose of antibiotic (e.g. flucloxacillin and gentamicin) at the time of induction is routine practice in our unit.
Cardiac MRI Cardiac MRI (CMR) is increasingly used due to its advantages over cardiac catheterization techniques. CMR provides high-quality information on cardiovascular anatomy, function and tissue characterization. It is non-invasive and avoids exposure to ionizing radiation. Disadvantages include need for MR-compatible equipment and long examination times. A checklist must be undertaken to ensure no
contra-indications such as MRI-incompatible pacemakers or ferromagnetic implants exist. With preparation and play therapy, children as young as 7 yr may have CMR awake. Small babies are occasionally imaged using a ‘feed and wrap’ regimen. However, general anaesthesia is often required, especially as breath holds are desirable for detailed images. Occasionally catheterization is combined with CMR for accurate assessment of anatomy and haemodynamics with lower radiation exposure than purely fluoroscopy-guided procedures.8 This is ideally performed under general anaesthesia in specifically designed environment (Fig. 1). The patient trolley can easily be moved on rollers in and out of the MR scanner for catheter interventions outside the 5 Gauss line, inside which the magnetic field is increasingly intense. It is essential for all members of the team working in an MRI environment to work within the standard operating procedures of the facility with a particular attention to safety. Attention should be paid to all equipment being MRI safe. All staff should be safety checked, be aware of emergency drills and how to safely enter the scanning room if required. The detailed principles of anaesthesia for MRI have been discussed previously in this journal.9 All children are intubated and ventilated to allow control of PCO2 and facilitate breath holding. Induction is generally in an adjacent anaesthetic room and the patient then transferred into the MR/ Catheter room. An additional set of MRI-compatible ECG leads are placed to get data from R wave signals and ears covered to protect from acoustic damage. A coil is positioned over the heart to serve as a receiver and images are taken in different planes to delineate the anatomy of the heart and vascular structures. Flow patterns, cardiac index, ejection fraction and regional wall motion abnormalities can also be assessed accurately. Maintenance is usually with a volatile agent and apnoea can be achieved with controlled ventilation using neuromuscular blocking agents or a remifentanil infusion (0.05–0.10 mg kg21min21). Remifentanil has the advantage of controlling heart rate, which helps with image quality, especially when multiple breath holds are required and PCO2 may climb. A long-length circle breathing system
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padded to prevent pressure and nerve injury from firm surfaces. Antiarrhythmic medication is stopped preprocedure except in malignant arrhythmias and agents that may affect the ability to generate the arrhythmia and identify arrythmogenic foci (e.g. clonidine, high-dose opioid) should be avoided. Deep planes of anaesthesia may also suppress abnormal pathways and arrhythmic foci. Some centres prefer i.v. anaesthesia with propofol but volatile agents are not contra-indicated. Analgesia requirements are minimal (though femoral sheath access and ablation of the posterior wall of the atrium can be briefly stimulating). Ablation of abnormal pathway may cause severe bradycardia, transient, or even permanent heart block. If severe bradycardia is not responding to atropine, isoprenaline may be a useful alternative.
Anaesthesia for paediatric cardiological procedures
that extends into the control room (where it can be intermittently opened) or other method of providing a pause in ventilation should be set up and tested preprocedure.
Cardiac CT
Declaration of interest None declared.
References 1. Rubio-Alvarez V, Limon R, Soni J. Intracardiac valvulotomy by means of a catheter. Arch Inst Cardiol Mex 1953; 23: 183– 92 2. Feltes TF, Bacha E, Beekman RH et al. Indications for cardiac catheterization and intervention in pediatric cardiac disease: a scientific
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3. James I, Wilmshurst S. Anaesthesia for cardiac catheterisation and other investigative procedures in children. In: James I, Walker I, eds. Core Topics in Paediatric Anaesthesia. Cambridge: Cambridge University Press, 2013; 314–21 4. Wilkinson JL. Haemodynamic calculations in the catheter laboratory. Heart 2001; 85: 113–20 5. Arnold PD, Holtby HM. Andropoulos DB. Anesthesia for cardiac catheter laboratory. In: Andropoulos DB, Stayer SA, Russell IA, Mossad EB, eds. Anesthesia for Congenital Heart Disease. Chichester: Blackwell Publishing Ltd, 2010; 521– 45 6. Mehta R, Lee KJ, Chaturvedi R et al. Complications of pediatric cardiac catheterization: a review in the current era. Catheter Cardiovasc Interv 2008; 72: 278–85 7. Ashley EM. Anaesthesia for elecrophysiology procedures in the cardiac catheter laboratory. Contin Educ Anaesth Crit Care Pain 2012; 12: 230–6 8. Razavi R, Hill DLG, Keevil SF et al. Cardiac catheterisation guided by MRI in children and adults with congenital heart disease. Lancet 2003; 362: 1877– 82 9. Reddy U, White MJ, Wilson SR. Anaesthesia for magnetic resonance imaging. Contin Educ Anaesth Crit Care Pain 2012; 12: 140– 4
Please see multiple choice questions 1–4.
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CT angiography is valuable for defining extra-cardiac vascular structures (e.g. aorto-pulmonary collaterals) and the relationship of vessels and airways (e.g. vascular rings). It may also be an alternative in the occasional patient with an MRI non-compatible pacemaker. Scanning takes just a few seconds to acquire images, but a breath hold is required usually requiring general anaesthesia and controlled ventilation in children unable to cooperate.
statement from the American Heart Association. Circulation 2011; 123: 2607– 52
Syed Mohsin Qureshi BSc MBBS MD FCARCSI Kuberan Pushparajah BMBS MRCPCH Dan Taylor MB ChB MRCPCH FRCA
Children presenting for cardiac catheterization may have complex pathophysiology and multiple co-morbidities. Maintaining haemodynamic stability during the procedure is crucial in obtaining meaningful diagnostic information. Therapeutic interventions in the catheter laboratory include occlusion of patent ductus arteriosus, closure of atrial septal defects, balloon dilatation for valvular stenosis and stenting of narrowed vessels. MRI is increasingly used for diagnostic imaging. Anaesthetized children must be rendered apnoeic during cardiac MRI, as breath holds are often required for good quality imaging. Syed Mohsin Qureshi BSc MBBS MD FCARCSI Specialist Trainee South East School of Anaesthesia King’s College Hospital, London, UK Kuberan Pushparajah BMBS MRCPCH Clinical Fellow Department of Congenital Cardiology Evelina London Children’s Hospital Guy’s and St Thomas’ NHS Foundation Trust, London, UK Dan Taylor MB ChB MRCPCH FRCA Consultant Paediatric Anaesthetist Evelina London Children’s Hospital Anaesthetic Department Guy’s and St Thomas’ NHS Foundation Trust Westminster Bridge Road London SE1 7EH, UK Tel: þ44 20 718 80654 Fax: þ44 20 7188 2284 E-mail: [email protected] (for correspondence)
1
Diagnostic cardiac catheterization was reported in the nineteenth century and interventional cardiac catheterization was first described by Rubio-Alvarez in 1954 for the treatment of pulmonary valve stenosis.1 In some centres, MRI is increasingly used for diagnostic imaging. To ensure safety and quality images, the majority of these procedures in children require general anaesthesia. Cardiac catheterization may be challenging when dealing with complex congenital cardiac lesions. Good communication between the team members is essential, so that cardiovascular changes can be anticipated and minimized as far as possible. This includes the full team: anaesthetist and assistant, cardiologist, scrub team, radiographer, and a cardiac physiologist. It is a challenging and high-risk field of anaesthetic practice and requires consultant-led care by specialists in paediatrics and congenital heart disease (CHD).
Diagnostic cardiac catheterization Diagnostic catheterization is becoming less popular with technological advances in non-invasive imaging such as cardiac CT and MRI allowing angiographic assessment. Paediatric cardiac catheter procedures are listed in Table 1.2,3 Invasive studies are still necessary to directly measure intracardiac and intravascular pressures and to allow direct measurement of arterial, mixed venous, pulmonary venous and pulmonary arterial saturations and derive shunt fraction, flows and resistance (Table 2).4,5 Dynamic investigations such as dobutamine stress testing and pulmonary vascular resistance studies (sometimes in conjunction with MRI) are also possible. Endomyocardial biopsies and coronary angiography (and endosonography) are performed as part of routine surveillance after cardiac transplantation. Myocardial biopsies are occasionally used to diagnose myocarditis and cardiomyopathy.
Interventional cardiac catheterization Interventional techniques Valvuloplasty A fluid-filled cardiac catheter is passed across the stenotic pulmonary or aortic valves and the pressure gradient assessed. This is exchanged over a guide wire for a balloon catheter, which is then inflated for a few seconds to split the fused valve leaflets. Balloon dilatation is repeated several times until an adequate reduction in gradient is achieved, ideally without severe valvular incompetence developing. Pulmonary valvuloplasty has successfully been performed for many years. It is the treatment of choice for isolated pulmonary stenosis with a gradient of more than 50 mm Hg. Neonates with critical pulmonary stenosis are cyanosed, often requiring ventilation and a prostaglandin infusion to maintain duct patency. Desaturation occurs during balloon dilatation, but cardiac output can be maintained by a patent ductus arteriosus. Critical aortic stenosis can be associated with severe cardiovascular collapse. Untreated severe aortic stenosis carries a high risk of sudden death. Aortic valvuloplasty presents a very high risk of haemodynamic instability and cardiac arrest from ischaemia and arrhythmias. Vasodilatation and hypovolaemia are poorly tolerated. Resuscitation drugs should be readily available to reverse haemodynamic compromise due to repeated occlusion of the aortic valve.
Septal defect closure Atrial septal defect closure is the most commonly performed procedure. Trans-oesophageal echocardiography (TOE) is used to assess the margins of the defect and to aid X-ray-guided device placement. It is generally well tolerated, but, dislodgement and embolization of the device, impingement on the surrounding structures and
doi:10.1093/bjaceaccp/mku002 Advance Access publication 24 February, 2014 Continuing Education in Anaesthesia, Critical Care & Pain | Volume 15 Number 1 2015 & The Author [2014]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://ceaccp.oxfordjournals.org/ at McMaster University Library on January 9, 2015
Key points
Anaesthesia for paediatric cardiological procedures
perforation of the heart or great vessels may occur. Ventricular septal defect closure is usually performed surgically on cardiopulmonary bypass but they can sometimes be closed with a percutaneous device.
include arrhythmias, perforation of the myocardium, embolization, and structural damage to the valvular apparatus.
Angioplasty and placement of stents Atrial septostomy
Table 1 Paediatric cardiac catheter laboratory procedures Indications
Procedure
Diagnostic
Defining cardiac and vascular anatomy Measuring haemodynamic pressures and shunts Pulmonary hypertension studies using nitric oxide Coronary angiography and endosonography Myocardial and endomyocardial biopsy Valvuloplasty Septal defect closure Atrial septostomy Angioplasty and placement of stents Percutaneous valve placements Closure of systemic to pulmonary shunts, e.g. patent ductus arteriosus Hybrid procedure Conduction system mapping Radiofrequency and cryoablation Placement of pacemaker and ICD
Interventional
Electrophysiological studies
Percutaneous valve placement Severe pulmonary regurgitation or mixed pulmonary valve disease has traditionally required major surgery on bypass. The transcutaneous placement of pulmonary valves made from bovine jugular vein and titanium has transformed the management of these patients. Via a femoral venous sheath, the valve, mounted in a balloon-expandable stent, is threaded along a guide wire into the correct position under fluoroscopic and TOE guidance. The valve is then re-expanded to its final diameter to minimize any leaks or regurgitation.
Closure of systemic to pulmonary shunts This is commonly performed outside the neonatal period to limit excessive pulmonary blood flow, for example, in patent ductus arteriosus. Helical wires are used to close small vessels; more complex devices are needed to occlude large vessels. There is a risk of device dislodgement and embolization.
Hybrid procedure Surgical and endovascular techniques can be combined in certain circumstances, such as the first stage in palliation of hypoplastic left heart syndrome. It is usually performed soon after birth, with the aim of avoiding cardiopulmonary bypass in selected high-risk cases. This is a novel treatment performed in a few specialist centres. Hybrid procedures involve a sternotomy, followed by surgical
Table 2 Haemodynamic calculations performed during cardiac catheterization Flows Systemic flowðQs Þ ¼
VO2 (SaoO2 SmvO2 Þ Cm VO2 Pulmonary flowðQp Þ ¼ (SpvO2 SpaO2 Þ Cm
VO2, oxygen consumption; SaoO2 , aortic saturation; SmvO2 , mixed venous saturation; S pvO2 , pulmonary venous saturation; S paO2 , pulmonary artery saturation; Cm (oxygen content)¼S pO2 Hb (in g dl21)1.3410þ(PaO2 mm Hg0.003) Resistances PAP LAP Pulmonary vascular resistance (PVR) ¼ Qp Systemic vascular resistance (SVR) ¼
AoP RAP Qs
PAP, pulmonary artery pressure; LAP, left atrial pressure; AoP, aortic pressure; RAP, right atrial pressure Shunt fraction SaoO2 SmvO2 Pulmonary to systemic flow ratio (Qp :Qs ) ¼ S pvO2 S paO2
2
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This procedure is performed to allow mixing of blood to improve oxygen saturation in cardiac lesions such as transposition of great arteries or single-ventricle circulations dependent on adequate mixing at atrial level. These children are often very sick with hypoxaemia, systemic hypotension, and metabolic acidosis. They will usually be receiving a prostaglandin (PGE1) infusion to maintain a patent ductus arteriosus. A balloon-tipped catheter is passed from the right atrium through the foramen ovale and into the left atrium under trans-thoracic echocardiographic imaging. The balloon is then inflated and pulled across the septum to enlarge the septal communication. It is often performed several times until the atrial communication is large enough to allow free mixing of blood at atrial level. Complications
Angioplasty involves dilatation of narrowed blood vessels by a balloon-tipped catheter passed across the stenosed area. Occasionally, this is followed by endovascular stenting, for example in branch pulmonary artery stenosis, coarctation of aorta and superior vena cava obstruction. Stenting can involve passage of large catheters with risk of vascular damage, dislodgement and embolization of the stent.
Anaesthesia for paediatric cardiological procedures
as increased diastolic perfusion pressures, reducing the heart rate, removal of the catheter or administering coronary dilators like glyceryl trinitrate.
Anaesthesia for cardiac catheterization
Complications
Preoperative assessment
The overall incidence of complications in paediatric cardiac catheterization is quoted at 7.3%, of which the majority are vascular and related to femoral access. These include haemorrhage, retroperitoneal and local haematoma, pseudo-aneurysm, arterio-venous fistula, neuropathy and thrombosis leading to lower limb ischaemia.6 Mortality has been reported at 0.2%.6 Independent risk factors include younger patient age, low body weight and interventional procedures.
A comprehensive preoperative assessment of children with CHD is essential to understand the likely physiological consequences of anaesthesia and the planned intervention. In addition to standard preoperative assessment, particular attention should be paid to the cardiovascular system. Look for signs and symptoms of poor cardiac output and heart failure (difficulty feeding, poor growth, sweating in infants or reduced exercise tolerance in older children). Observations, especially baseline oxygen saturation, should be checked. Current medication should be reviewed and administered unless there are any contraindications on the day of surgery. Angiotensin-converting enzyme inhibitors are often omitted to avoid hypotension on induction but may be continued in some children with severe heart failure. Anticoagulants may also be omitted depending on risk– benefit, for example, children with shunt-dependent circulations are safer continuing anticoagulants even for catheterization procedures and accepting the slightly higher risk of bleeding rather than the problems arising from a blocked shunt. Children will often have had multiple cardiac investigations and operations. Previous anaesthetic charts are invaluable. The most recent echocardiography and MRI reports should be reviewed along with routine laboratory studies, including full blood count, creatinine, urea and electrolytes. Blood group and antibody screen should be performed for all and a cross-match of packed cells (one adult unit) for any interventional procedure. The ECG should be reviewed for any rhythm disturbances, ischaemic changes and chamber hypertrophy and pacemakers checked where present. A chest X-ray is helpful to assess the lung parenchyma, identify any areas of collapse, and confirm the position of previous pacemaker leads, devices, or stents. Premedication is not commonly used but may benefit anxious older children particularly who may have had multiple procedures. Clearly safety must be considered in the smaller, more cyanotic children or those with poor ventricular function. Midazolam up to 0.5 mg kg21 orally (up to a maximum 20 mg) is our choice when necessary. Parental presence, distraction techniques and assistance of play therapists are alternative means of reducing anxiety.
Arrhythmias These are most often caused by mechanical stimulation by catheters and are usually transient, resolving when the catheter is withdrawn. Persistence may indicate cardiac ischaemia or damage to the conducting system or myocardium. Trigger factors such as acidosis and electrolyte imbalance should be avoided. Anti-arrhythmics or pacing are rarely needed.
Vascular complications and cardiac perforation Large vascular sheaths may cause vascular damage, most commonly at the insertion site. This is usually managed conservatively. Other complications such as perforation of blood vessels, myocardium, or heart valves may cause cardiac tamponade occasionally requiring operative intervention.
Thrombosis and cerebrovascular accidents The presence of foreign bodies and damage to the endothelium will activate formation of thrombus, which may lead to embolic complications. To avoid this, heparin is given at a dose of 50 –100 units per kg after arterial cannulation aiming for an activated clotting time (ACT) of 200 s or above. High levels of ACT could cause haemorrhage and haematoma; hence, careful observation is required until heparin effect has dissipated.
Hypotension The causes are often multifactorial and include: anaesthetic agents, i.v. contrast, arrhythmias, hypovolaemia, and haemorrhage. In aortic and pulmonary valvuloplasty, balloon inflation will cause sudden decrease in the cardiac output and severe hypotension.
Ischaemia Ischaemic ECG changes are common during coronary angiography and may occur in low cardiac output states. These can usually be reversed by measures to improve coronary perfusion pressure such
Induction Full standard monitoring should be applied before induction, if the child is co-operative. I.V. or inhalation induction depends on the child’s physiological condition, cooperation and personal preferences. Sevoflurane is our agent of choice for inhalation induction. Propofol or ketamine is used for i.v. induction. While choosing anaesthetic agents, consider the likely physiological consequences of
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banding of both pulmonary arteries and catheterization via direct cannulation of the pulmonary trunk to place a stent in the ductus arteriosus. Patients require full invasive monitoring and adequate venous access in preparation for possible deterioration that may require urgent surgery on cardiopulmonary bypass.
Anaesthesia for paediatric cardiological procedures
Positioning The patient is kept supine, arms above the head to expose the heart and great vessels for viewing by biplane X-ray imaging. Cables and ECG dots should be positioned to avoid artifacts during imaging. Once the procedure starts, access to the child will be limited, so a secure airway, reliable venous access, all monitoring displayed correctly and good thermoregulation measures are essential from the beginning. Ensure protection of eyes and pressure areas and minimize stretching on the brachial plexus.
Safety Radiation dose is monitored and minimized as far as possible. Lead gowns may cover areas of the body not being scanned. Attention should also be paid to staff safety in terms of protection from radiation exposure (lead gowns and thyroid protectors) and monitoring long-term exposure.
Maintenance During the procedure, it is essential to keep the patient immobile, haemodynamics as close to preprocedural values as possible, normothermia and normocapnia. Stable haemodynamics are required to generate meaningful baseline pressures and to allow interpretation of diagnostic interventions such as stress testing and nitric oxide not to be confounded by other factors. In vulnerable patients instability can quickly spiral out of control; careful monitoring and prompt intervention are essential. High inspired oxygen concentrations (above 30%) may give erroneous results in flow studies and may decrease pulmonary vascular
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resistance, thereby increasing left-to-right shunt fraction. Oxygen and air with an inhalation agent is the preferred method for maintenance of anaesthesia. Increased inspired oxygen concentrations are used when attempting to reduce pulmonary vascular resistance in conjunction with inhaled nitric oxide, when investigating pulmonary hypertension. Intraoperatively only small doses of fentanyl (1–2 mg kg21) are required to blunt haemodynamic changes during stimuli such as insertion of femoral sheaths or TOE probes. Paracetamol and local anaesthetic infiltration are usually enough for post-procedural analgesia. An antiemetic (ondansetron 0.1 mg kg21) is usually given to avoid nausea and vomiting and unnecessary hospital overnight admission. Isotonic i.v. maintenance fluid will be required in the vast majority of cases, with attention to blood sugar monitoring in neonates. It is important to account for the volume and content of flushes and i.v. contrast used by the operator and also blood loss, both of which may be considerable. Iodinated contrast media have some nephrotoxic potential. Risk factors include pre-existing renal impairment, diabetes, heart failure and use of other nephrotoxic drugs, but problems can occur in patients with previously normal kidneys. Dehydration should be avoided, other nephrotoxic drugs omitted, and where risk is high, minimum volumes of iso-osmolar or low osmolar contrast medium used. The majority of patients are extubated at the end of the procedure and recovered in a routine fashion, with special attention to the femoral puncture sites and lower limb perfusion. Paediatric intensive care is reserved for ill or higher risk cases and those where serious complications have occurred.
Electrophysiological studies and pathway ablation The principle of electrophysiological (EP) studies is to identify the abnormal mechanism of arrhythmias, and localize abnormal pathways and foci responsible for the arrhythmias. Most of the children presenting for EP studies are otherwise healthy with a normal functioning heart and suffer from uncomplicated supraventricular tachycardia. Some may present with CHD, cardiomyopathy and life-threatening arrhythmias. Multiple arterial and venous accesses may be required. The technique involves passage of electrode catheters to the right heart and coronary sinus through femoral venous access. Occasionally, a trans-septal puncture is required. A previous CEACCP article gives a full account of anaesthesia for EP procedures for the adult patient.7 Destruction of abnormal pathways or foci is accomplished by delivering radiofrequency energy or cryoablation. The size of the lesion created is controlled by the temperature at the end of the catheter and duration of exposure. Thermal injury can occur if this is not carefully monitored. Repeat EP studies are conducted to ensure no additional or residual pathways remain. Principles of anaesthesia are similar to that of catheterization. Procedures are often very prolonged. Pressure areas should be well
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varying systemic and pulmonary vascular resistances on shunts and cardiac output. Tracheal intubation is required for the majority of cases and is facilitated with a neuromuscular blocking agent (e.g. atracurium 0.5 mg kg21). Older children having short procedures may occasionally be managed using a supraglottic airway device. The airway should be controlled during procedures associated with high risk of haemodynamic instability, procedures with high risk of complications, in patients in whom internal jugular venous access is required or who may require resuscitation. Avoid large leaks around the tracheal tubes to guarantee carbon dioxide clearance. Increased arterial CO2 tension or decreased pH may increase pulmonary vascular resistance with attendant effects on pulmonary blood flow and shunt direction. Antibiotic prophylaxis use varies but is required if any devices are being left in situ (e.g. flucloxacillin 50 mg kg21). Operator access is usually via femoral vessels, so it is easier to use neck and upper limb vessels for monitoring lines and access. Occasionally, procedures may be performed via upper limb vessels, so prior knowledge of this is essential. Reliable vascular access of adequate size is essential. Central access and arterial access is usually reserved for sicker children (e.g. critical aortic stenosis in neonates) but the need should be assessed on a case-by-case basis, as some children may be unwell enough to merit full monitoring for even minor procedures.
Anaesthesia for paediatric cardiological procedures
Implantation of pacemakers and defibrillators
Fig 1 Hybrid X-ray/MRI suite.
Pacemaker implantation is indicated in symptomatic bradycardia due to sinoatrial node dysfunction and complete heart block. Transvenous pacing leads are usually inserted through the subclavian vein and the subcutaneous generator is fixed below the left sternum. In infants and neonates device size is disproportionate to the size of the patient; therefore surgical placement of epicardial wires via a sternotomy may be necessary. Patients will require general anaesthesia with tracheal intubation. Insertion of an implantable cardiovertor-defibrillator (ICD) is indicated in children who suffer from life-threatening ventricular arrhythmias. This will include patients with channelopathies and forms of cardiomyopathy associated with sustained VT/VF in the absence of a reversible cause. These patients can have a family history of life-threatening arrhythmias or sudden cardiac death in the family. Once an ICD is inserted it is usual to test its function by inducing ventricular fibrillation. It is essential to have an external defibrillator attached to the patient should the ICD fail. Anaesthesia is similar to that for cardiac catheterization but may be challenging in children with impaired ventricular function. Careful titration of anaesthetic agents to avoid hypotension, excessive bradycardia, or tachycardia is essential. Invasive monitoring may be required. Local anaesthetic infiltration at the site of pacemaker insertion and paracetamol with or without a small dose of a suitable opioid will usually provide adequate postoperative analgesia. A prophylactic dose of antibiotic (e.g. flucloxacillin and gentamicin) at the time of induction is routine practice in our unit.
Cardiac MRI Cardiac MRI (CMR) is increasingly used due to its advantages over cardiac catheterization techniques. CMR provides high-quality information on cardiovascular anatomy, function and tissue characterization. It is non-invasive and avoids exposure to ionizing radiation. Disadvantages include need for MR-compatible equipment and long examination times. A checklist must be undertaken to ensure no
contra-indications such as MRI-incompatible pacemakers or ferromagnetic implants exist. With preparation and play therapy, children as young as 7 yr may have CMR awake. Small babies are occasionally imaged using a ‘feed and wrap’ regimen. However, general anaesthesia is often required, especially as breath holds are desirable for detailed images. Occasionally catheterization is combined with CMR for accurate assessment of anatomy and haemodynamics with lower radiation exposure than purely fluoroscopy-guided procedures.8 This is ideally performed under general anaesthesia in specifically designed environment (Fig. 1). The patient trolley can easily be moved on rollers in and out of the MR scanner for catheter interventions outside the 5 Gauss line, inside which the magnetic field is increasingly intense. It is essential for all members of the team working in an MRI environment to work within the standard operating procedures of the facility with a particular attention to safety. Attention should be paid to all equipment being MRI safe. All staff should be safety checked, be aware of emergency drills and how to safely enter the scanning room if required. The detailed principles of anaesthesia for MRI have been discussed previously in this journal.9 All children are intubated and ventilated to allow control of PCO2 and facilitate breath holding. Induction is generally in an adjacent anaesthetic room and the patient then transferred into the MR/ Catheter room. An additional set of MRI-compatible ECG leads are placed to get data from R wave signals and ears covered to protect from acoustic damage. A coil is positioned over the heart to serve as a receiver and images are taken in different planes to delineate the anatomy of the heart and vascular structures. Flow patterns, cardiac index, ejection fraction and regional wall motion abnormalities can also be assessed accurately. Maintenance is usually with a volatile agent and apnoea can be achieved with controlled ventilation using neuromuscular blocking agents or a remifentanil infusion (0.05–0.10 mg kg21min21). Remifentanil has the advantage of controlling heart rate, which helps with image quality, especially when multiple breath holds are required and PCO2 may climb. A long-length circle breathing system
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padded to prevent pressure and nerve injury from firm surfaces. Antiarrhythmic medication is stopped preprocedure except in malignant arrhythmias and agents that may affect the ability to generate the arrhythmia and identify arrythmogenic foci (e.g. clonidine, high-dose opioid) should be avoided. Deep planes of anaesthesia may also suppress abnormal pathways and arrhythmic foci. Some centres prefer i.v. anaesthesia with propofol but volatile agents are not contra-indicated. Analgesia requirements are minimal (though femoral sheath access and ablation of the posterior wall of the atrium can be briefly stimulating). Ablation of abnormal pathway may cause severe bradycardia, transient, or even permanent heart block. If severe bradycardia is not responding to atropine, isoprenaline may be a useful alternative.
Anaesthesia for paediatric cardiological procedures
that extends into the control room (where it can be intermittently opened) or other method of providing a pause in ventilation should be set up and tested preprocedure.
Cardiac CT
Declaration of interest None declared.
References 1. Rubio-Alvarez V, Limon R, Soni J. Intracardiac valvulotomy by means of a catheter. Arch Inst Cardiol Mex 1953; 23: 183– 92 2. Feltes TF, Bacha E, Beekman RH et al. Indications for cardiac catheterization and intervention in pediatric cardiac disease: a scientific
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3. James I, Wilmshurst S. Anaesthesia for cardiac catheterisation and other investigative procedures in children. In: James I, Walker I, eds. Core Topics in Paediatric Anaesthesia. Cambridge: Cambridge University Press, 2013; 314–21 4. Wilkinson JL. Haemodynamic calculations in the catheter laboratory. Heart 2001; 85: 113–20 5. Arnold PD, Holtby HM. Andropoulos DB. Anesthesia for cardiac catheter laboratory. In: Andropoulos DB, Stayer SA, Russell IA, Mossad EB, eds. Anesthesia for Congenital Heart Disease. Chichester: Blackwell Publishing Ltd, 2010; 521– 45 6. Mehta R, Lee KJ, Chaturvedi R et al. Complications of pediatric cardiac catheterization: a review in the current era. Catheter Cardiovasc Interv 2008; 72: 278–85 7. Ashley EM. Anaesthesia for elecrophysiology procedures in the cardiac catheter laboratory. Contin Educ Anaesth Crit Care Pain 2012; 12: 230–6 8. Razavi R, Hill DLG, Keevil SF et al. Cardiac catheterisation guided by MRI in children and adults with congenital heart disease. Lancet 2003; 362: 1877– 82 9. Reddy U, White MJ, Wilson SR. Anaesthesia for magnetic resonance imaging. Contin Educ Anaesth Crit Care Pain 2012; 12: 140– 4
Please see multiple choice questions 1–4.
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CT angiography is valuable for defining extra-cardiac vascular structures (e.g. aorto-pulmonary collaterals) and the relationship of vessels and airways (e.g. vascular rings). It may also be an alternative in the occasional patient with an MRI non-compatible pacemaker. Scanning takes just a few seconds to acquire images, but a breath hold is required usually requiring general anaesthesia and controlled ventilation in children unable to cooperate.
statement from the American Heart Association. Circulation 2011; 123: 2607– 52