Ebook Paediatric intensive care: Part 2

(BQ) Part 2 book Paediatric intensive care presents the following contents: Specific specialties (Cardiac disorders and postoperative care, respiratory disease, neurocritical care, trauma and burns,...), compassionate and family-orientated care.

27 Laboratory investigations for infectious disease 585

39 Paediatric intensive care medicine in

Cardiac disorders and

postoperative care

Chapter 20

Applied cardiovascular anatomy 348

Applied cardiovascular physiology 350

Bedside monitoring of the cardiovascular

system/circulation 350

Cardiac arrhythmias 350

Congestive heart failure 356

Pathophysiology of congenital heart disease 357

Pulmonary hypertension syndromes 361

Immediate postoperative care 369

Early postoperative problems 373

Late postoperative problems 382

Staged palliation of a univentricular heart 384

Common surgical procedures (A to Z) 385

Applied cardiovascular anatomy

This section describes salient features in a normal heart

Cardiac anatomy (see Fig 20.1)

Right heart

Deoxygenated blood from the systemic circulation returns to the

atrium (RA) through the superior and inferior caval veins (SVC and IVC)

Cardiac venous blood enters the heart through the

directly through the thebesian veins

During diastole, blood fl ows from the RA to the

ventricle (LV) It is heavily trabeculated, and it has a muscular sleeve

(infundibulum) separating the tricuspid valve from the pulmonary valve

The main

• pulmonary trunk arises to the left and anterior relative to the

aorta

It courses posteriorly before branching into the

arteries.

Left heart

Oxygenated blood from the lungs returns to the

through the right- and left-sided pulmonary veins

During diastole, blood enters the

• LV through the mitral valve, which is a

bicuspid valve (posterior/mural leafl et and anterior leafl et)

Each leafl et is secured at the base to the mitral annulus, and the free

coronary arteries, the 3rd leafl et being termed non-coronary

The left ventricular wall is 3 times thicker than the RV

•

Its fi bres are oriented in 3 layers; the inner (subendocardial) layer is the

•

most important in children, and young adults

The outermost oblique layer, along with the subendocardial layer,

twists towards the apex

The aorta ascends as a central structure from the heart, and usually

•

arches to the left curving over the heart to descend posteriorly to the left of the spine

Fig 20.1 a) Normal heart structures; b) normal O2 sat and pressure measurements.

Sequential segmental analysis

To evaluate patients with suspected congenital heart disease, it is tive to analyse the heart in a segmental pattern based on:

impera-Position of the heart, and other organs (thoracic and abdominal):

characteristics rather than its position, or relation to other structures

It is also important to understand that:

Connection

• is an anatomic term showing a direct link between 2

structures; drainage a haemodynamic one, referring to fl ow of blood Single

• refers to an absence of a corresponding contralateral

structure (single valve in tricuspid atresia); common refers to bilateral

components with an absent division (e.g common AV valve)

The endocardium is the inner layer of the heart, which is metabolically

active in contributing to cardiovascular function

The pericardium, a fi broserous sac consisting of visceral and parietal

layers, is a dynamic and adaptive structure which:

Protects the heart by acting as a barrier

The sinoatrial node (SA node) generates the electrical impulse which

spreads through the atrial chambers

SA node

• is situated at the SVC/right atrium junction

There is a single point of electrical connectivity between the atria and the

ventricles; the atrioventricular node (AV node)

AV node

• is situated in the triangle of Koch (near the coronary sinus)

The conduction system then proceeds as the bundle of His before dividing into the left and right bundles and then into various fascicles.

Circulation (see also b b Chapter 11)

There are 2 vascular beds in the circulation—the

systemic through which the blood is driven by the appropriate

ventricles (see Fig 20.1):

The pressure in the pulmonary circulation is signifi cantly lower than

•

that in the systemic circulation

The vessels become smaller and thinner as they get farther from the

•

great arteries, becoming arterioles, and fi nally capillaries which are the

units where gas and metabolic exchange takes place:

Arterioles are small arteries with relatively thick muscle and

Cardiac arrhythmias can be due to (Box 20.1):

Disturbances of rhythm (tachyarrhythmia):

Box 20.1 Cardiac arrhythmias in children can be due to:

Structural heart disease:

CARDIAC ARRHYTHMIAS

Substrates for the genesis of the arrhythmias are:

Re-entrant mechanisms: these require the presence of 2 electrical

•

pathways separated by an electrically inert tissue, having different

properties, setting up an electrical circuit

Automatic mechanisms: this is due to an abnormally active electrical

Re-entrant tachycardias are the commonest mechanism for arrhythmias

seen in children with normal hearts

P waves on corresponding surface ECG not identified

Fig 20.2 Atrial (V1) and surface (V2) ECGs in nodal rhythm Reproduced from

Mackay J and Arrow Smith, J (eds) (2004) Core topics in cardiac anaesthesia, with

permission from Cambridge University Press.

Treatment

Based on presentation and identifi cation of the mechanism Acute agement will usually involve IV adenosine or synchronized cardioversion Specifi c treatment depends on the mechanism:

man-Vagal manoeuvres: Valsalva, diving refl ex

automaticity (more common in VT)

Ventricular fi brillation (VF) is a series of uncoordinated ventricular

•

depolarizations associated with an absence of cardiac output

Important clues on ECG to help identifi cation (Fig 20.3):

ECG, and identifi cation for a cause should be the primary aim

ECG monitoring (Holter, loop recorders)

•

Specifi c investigations: genetic testing (long QT syndrome,

•

cardiomyopathy) or cardiac MRI (arrhythmogenic RV dysplasia)

Invasive EP study will help to map the focus, and ablate it

•

Acute management of VT depends upon hemodynamic status:

If the patient is stable, amiodarone can be considered

Specifi c management of ventricular arrhythmias includes:

Individuals at risk (previous history, family history):

These are due to abnormalities in the generation of an electrical impulse

or conduction defects They can be seen in children with structurally normal hearts (complete congenital heart block) or with structural heart disease (ventricular inversion, post surgical)

They can be classifi ed as:

• rd degree: complete AV block

Sinus node dysfunction: bradycardia

•

Chronotropic incompetence

2nd-degree AV blocks with Wenkebach phenomenon (Type I) is a gressive prolongation of PR interval leading to a blocked impulse Type II

pro-is an abrupt block of an impulse without prolongation of PR interval

Presentation and coexisting conditions

In children, overt symptoms due to bradycardia are relatively uncommon

Neonates and infants

Heart failure (fetal hydrops)

ECG, and identifi cation for a cause should be the primary aim

ECG monitoring (Holter, loop recorders) may identify a long pause,

but are poorly tolerated by mothers

Acute management of a compromised child

Chronotropic agents (isoprenaline)

upgraded to a dual chambered system (DDD) to maintain AV

synchrony in older children

Congestive heart failure

Congestive cardiac failure develops when systemic oxygen supply is equate for oxygen demands, or is maintained at the expense of higher atrial fi lling pressures In paediatric practice, the cause is frequently a large L-to-R shunt (LlR) (large VSD) with ‘preserved myocardial function’ as opposed to ‘pump failure’ as commonly seen in adults

inad-A range of compensatory mechanisms, initially benefi cial, contribute to the pathophysiology These include:

Salt and water retention:

• pulmonary blood fl ow (in LlR shunts)

Lower oncotic pressures (low albumin concentrations)

• cardiac output (‘high output’ states):

Sepsis (‘warm shock’)

PATHOPHYSIOLOGY OF CONGENITAL HEART DISEASE

Impaired myocardial contractility:

• effort tolerance, chest pain

Failure to thrive, breathless on feeding

Box 20.3 Treatment of congestive heart failure

Specifi c management of treatable causes, e.g structural heart disease,

— respiratory support: CPAP, ventilation

Impaired myocardial contractility:

Clinical manifestations are related to:

Size of the defect

• volume and pressure of pulmonary vasculature

Large shunts can result in pulmonary vascular disease if not

•

corrected in the 1st year of life

Airway obstruction with hyperinfl ation

Hypercyanotic spells in tetralogy of Fallot

Characterized by a pronounced fall in O2 saturation often associated with

a manoeuvre causing an increase in intrathoracic pressure, whilst dropping the SVR Treatment consists of:

Calm the child

the atrial communication to maintain adequate oxygen levels.

Immediate management consists of a prostaglandin E infusion and a balloon atrial septostomy

pulmonary venous return relative to systemic venous return

Manipulation of PVR and SVR can be useful in manipulating the Qp:Qs

•

which will infl uence O2 saturation

Obstruction to systemic output

Can be broadly divided into obstruction to the LV outfl ow and infl ow

LV outfl ow tract obstruction

During fetal development systemic perfusion is not compromised, due

to ductal patency, but LV hypertrophy and compromise to LV ment can occur to an extent that it is not able to maintain adequate inde-pendent systemic circulation (hypoplastic left heart syndrome)

develop-In the postnatal period, ductal patency is essential to maintain systemic

fl ow The systemic perfusion may be dependent entirely on the ductal

fl ow and right ventricular function (hypoplastic left heart syndrome/ aortic Atresia), or partially (aortic coarctation) where reasonable systemic per-fusion can be maintained as long as the aortic end of the ductal patency

is maintained

•

‘Back pressure’ changes related to elevated LA pressure:

•

i

• pulmonary venous pressures

Pulmonary and RV hypertension

•

Systemic venous congestion (if RV dysfunction)

•

Regurgitant lesions

Valvar regurgitation is usually associated with other cardiac abnormalities

It can be congenital or acquired—due to an infection or secondary to ventricular dilatation Symptoms are related to the duration, and severity

of the lesions; chronic lesions are better tolerated

Mitral valve regurgitation (MR) can be due to:

Haemodynamic derangements cause:

Left atrial and ventricular volume overload

Once there is progressive LA dilation, the mitral annulus stretches leading

to further i in mitral regurgitation (progressive)

Tricuspid valve regurgitation (TR) can be due to:

Dysplastic tricuspid valve

i

• RA pressures

R

• lL shunts l hypoxaemia

Potential for lung hypoplasia

• l lung function compromise

Aortic valve regurgitation (AR) is rarely an isolated anomaly Haemodynamic

• l diastolic runoff l dcoronary blood fl ow.

Pulmonary valve regurgitation (PR) can be due to:

Absent pulmonary valve syndrome

Pulmonary hypertension syndromes

Pulmonary hypertension (PH) is defi ned as a mean pulmonary artery sures of 25mmHg

pres-It can be classifi ed according to aetiology (Box 20.4)

Box 20.4 Aetiology of PH syndromes

Pulmonary arterial hypertension:

Blade atrial septostomy—to allow R

• lL shunt and preserve cardiac output at the expense of cyanosis

SYSTEMIC HYPERTENSION

Systemic hypertension

Hypertension is uncommon in childhood, but often goes unrecognized for

a long time It is defi ned as systolic and/or diastolic BP being >95 tile for age on 3 occasions

percen-Cardiac sequelae of childhood hypertension are uncommon, but acute, severe forms (malignant hypertension) can result in ventricular dys-function and congestive heart failure Long standing hypertension can result in:

Diastolic dysfunction with

• ilate fi lling (prominent ‘A’ contribution

Hypertensive crisis: after initial resuscitation, aim should be to reduce

BP but to avoid a precipitous drop to maintain organ perfusion Rule of thumb is to reduce BP by no more than 25% in fi rst 12–24H A quicker reduction is safe if the BP rise is of very recent onset

• -adrenergic receptor blockers (propranolol, atenolol)

Diuretics (frusemide, thiazide)

Myocarditis is an acute process characterized by infl ammatory infi ltration

of the myocardium along with cellular necrosis, and is caused by infectious agents (e.g enterovirus, coxsacchie), or can be an autoimmune process (e.g lupus)

Incidence and prevalence are low in children; however there is some dence of an increasing trend It is likely that a number of less severe cases

evi-of myocarditis associated with a viral infection go undetected

performed due to associated high risk

Cardiomyopathy screen to identify cause—details are available from

Induction of anaesthesia is high risk if ventricular function is severely compromised:

Summon expert assistance

Once stable, management should be aimed towards:

Identifi cation and treatment of cause

Myocarditis therapy: unproven but used in some centres.

Immunomodulatory therapy—IV immunoglobulin (IVIG)

•

Immunosuppressive therapy—steroids, cyclosporine, azathioprine

•

Continuing cardiac instability

Mechanical support—LV assist device (LVAD), e.g Berlin Heart Excor

Poor prognostic factors

Infective endocarditis

Infection of the endocardium, heart valves, or related structures is known

as infective endocarditis Risk factors include:

Structural heart disease

in the presence of fi bronectin at the local site (Box 20.7)

Infection can damage cardiac structures, vegetations may obstruct blood

fl ow, and occasionally will embolize to other areas, most commonly the lungs (or brain)

Immunological mechanisms are central to pathogenesis, and sequelae of this process, and involves cell-mediated and humoral mediated pathways.Hypergammaglobulinaemia:

Box 20.7 Commonest organisms include:

Streptococcus viridians (~40%; commonest)

Box 20.8 Learning point

Infective endocarditis is a clinical diagnosis confi rmed by presence of positive blood cultures Presence of an echogenic focus (vegetation)

on echocardiography supports the diagnosis; however a negative result does not rule out the diagnosis

Pericarditis and cardiac tamponade

Pericarditis can occur due to:

— S aureus (1/3 cases; 3/4 of those who die)

— Haemophilus infl uenza, type b

— Streptococcus

Tamponade occurs when there is suffi cient fl uid in the pericardial cavity

to cause compromise to cardiac fi lling or contractility, and is not sarily related to the amount of fl uid in the cavity (or size of cardiac silhou-ette on CXR)

neces-It can be seen as a result of acute pericarditis or in the postoperative period following cardiac (thoracic) surgery

hypertension is much less common

Changes in inotrope and vasodilator therapy

•

Greater use of ultrafi ltration following bypass and ECLS for children in

•

a low cardiac output state

Fast-tracking of suitable patients to achieve short PICU and hospital

•

stays

Cardiac surgical patients epitomize the importance of a multidisciplinary approach in a specialized paediatric or cardiac ICU

Immediate postoperative care

The major goal is to establish adequate cardiac output to ensure tissue oxygen delivery and end-organ function This is best addressed with a sys-tematic approach

Cardiovascular

Anaesthetic and surgical handovers provide vital information from the

•

operating room whilst the patient was on and off CPB

It is important that both occur as they will provide different

•

information

Note CPB, aortic cross clamp, and circulatory arrest durations

•

Note invasive monitoring lines such as atrial and pulmonary artery lines

•

over and above standard arterial and central venous lines

If rhythm disturbance is anticipated, attach the temporary epicardial

•

pacing wires to a pacemaker

Clinical examination on arrival to the PICU is imperative

Assess pulses and perfusion and markers of adequate cardiac output

•

including lactate and urine output

High lactate persistently >5mmol/L is associated with a poor outcome

Box 20.9 Criteria for extubation

Patient is warm, awake, and calm with intact airway refl exes

Routine post operative CXR to confi rm

Appropriate ETT position

IMMEDIATE POSTOPERATIVE CARE

Box 20.10 Principles of ventilation

Avoid a high mean airway pressures which will impede systemic

•

venous return, iPVR, and reduce cardiac output—especially

important after BCPS or Fontan procedure

Set PEEP ~5cmH

• 2O unless lung pathology demands a higher

PEEP—too high PEEP will i PVR but too low PEEP will result in

atelectasis, which will also i PVR

Use a volume mode with TV ~10mL.kg, limit further if

fl ow occurs during expiratory phase of ventilation

Ventilate to a normal PaCO

Avoid hyperventilation as it causes

• i SVR and dcardiac output

Tolerate mild hypercapnia and mild respiratory acidosis

to 48h (penicillins/cephalosporins) The optimum antibiotic regimen and duration is unclear for patients with delayed sternal closure and practice varies widely

Strict aseptic central venous catheter management is essential with

•

early line removal when possible

Regular mouth care and oral toilet

Fever should be avoided as it causes

• iO2 demand and may exacerbate brain injury

Consider fungal infection in the chronic patient

•

Renal

Fluid and electrolyte imbalance is common after CPB:

CPB is associated with a large positive sodium and water balance

•

Secondary capillary leak and sodium and water retention following

•

CPB will further augment a positive fl uid balance

Reduced cardiac output will compromise renal blood fl ow and urine

•

output; secondary release of renin, angiotensin, and antidiuretic

hormone will exacerbate fl uid overload

Secondary capillary leak and sodium and water retention following

•

CPB will further augment a positive fl uid balance

Consider diastolic dysfunction and sepsis if oedema persists

•

Close attention to strict hourly fl uid balance is paramount Assess patient volume status with clinical examination and pre-load estimates (CVP, atrial pressures)

Box 20.11 Principles of postoperative fl uid and electrolyte management

Restrict fl uid therapy to 25–50% maintenance in the initial 24–48h

if hyperkalaemia persists (see b p.257)

associated osmotic diuresis

Avoid causing hypoglycaemia

Nutrition is an essential part of postoperative management:

Aim for early enteral feeding in uncomplicated cases

Exercise caution in patients who had prolonged CPB and DHCA times or low cardiac output state pre- and postoperatively as gut perfusion may

be affected In these patients, consider complete bowel rest and institute TPN early to optimize caloric and protein intake Consult dietician.Feeding is routinely stopped for 4h prior to extubation

In some centres these drugs are given continuously by infusion, others give intermittent doses as required.

Oral sedation allows use of lower doses of benzodiazepines

intermit-NMB should be discontinued as soon as possible

also to allow neurological evaluation

In circumstances where patients require heavy sedation and prolonged

•

NMB, EEG may be of benefi t

Drug accumulation is common in the postoperative paediatric cardiac population so drugs need to be weaned as soon as allowed This will facili-tate regular neurological examination required to elicit the possible CNS complications of surgery and CPB Neurological injury is uncommon, but the risk is i when DHCA is required (see b p.225)

Early postoperative problems

Low cardiac output state (LCOS) (Box 20.12)

Inadequate cardiac output usually indicates abnormal recovery and signs

of this need to be monitored vigilantly Clinical manifestations include: Poor perfusion and haemodynamic instability

Rising lactate implies inadequate DO

• 2 and predicts a poor outcome

Box 20.12 LCOS may be caused by:

Low preload (atrial or central venous pressure)

Atrial pressures are directly related to intravascular blood volume

•

status but also related to ventricular compliance

Fluid administration is guided by LAP and RAP, and the haemodynamic

•

response to a fl uid bolus

Right-sided procedures, such as TOF, often need higher RAP to

•

maintain cardiac output; RV compliance is poor

Certain left-sided procedures, such as TAPVC, are associated with a

•

higher LAP

Impaired myocardial contractility

Measures are taken to protect the myocardium during CPB However, the systemic infl ammatory response to CPB induces a spectrum of patho-physiological changes ranging from mild organ dysfunction to multisystem organ failure

Factors that will depress myocardial performance include:

Need to perform a ventriculotomy (RV–PA conduits)

Inotropic support (see b Chapter 11)

Most patients require inotropic support in the postoperative period Choice of agent will depend on vascular tone of the pulmonary and sys-temic circulations and the degree of myocardial dysfunction (see Table 20.1) Commonly used agents are dopamine, dobutamine, adrenaline but PDEIs (milrinone, enoximone) are increasingly popular for their inodilatory properties norepinephrine is used for its combined inotropic and vaso-constricting properties Occasionally vasopressin is used in catecholamine resistant shock Newer agents are being developed, e.g levosimenden, but require careful evaluation

Table 20.1 Vasoactive agents

Drug Effects Dose range Side effects

A effect at doses

>20mcg/kg/h

than adrenaline but chronotrophy

iarrhythmias

EARLY POSTOPERATIVE PROBLEMS

Table 20.1 (Continued)

Drug Effects Dose range Side effects

iSVR, moderate intropy Milrinone Phosphodiesterase

inhibitor

0.1–1.0mcg/kg/min Lusitrophy,

inodilation, minimal iHR

Rhythm disorders (see b p.350)

Sinus rhythm at normal rate is optimum

of P wave to the QRS complex in tachycardias

Attach one or both atrial wires to V1 whilst performing a

retrograde conduction from a junctional ectopic focus is more likely

If dissociation of P and QRS complexes is found the tachycardia is

Atrial ECG taken by connecting atrial pacing wires to V1

P wave precedes every QRS

P waves on corresponding surface ECG are too small to be identified

Fig 20.4 Atrial (V1) and surface (V2) ECGs in NSR—P waves are amplifi ed by

atrial ECG Reproduced from Mackey J and Arrowsmith J (eds) (2004) Core topics in

cardiac anaesthesia with permission from Cambridge University Press.

• fl utter often responds to overdrive pacing but may require

electrical cardioversion and digoxin

• are rare in paediatric practice, but VT or

VF needs immediate DC cardioversion

EARLY POSTOPERATIVE PROBLEMS

Pacing modes are described by a standard nomenclature: this describes

Emergency mode DOO

Both chambers are paced

Rapid atrial pacing

Can be used to overdrive pace an SVT

Pace above the SVT rate until capture is achieved

lost; this may result in loss of ventricular output

Do the same with the atrial output

threshold are commonly used approaches)

Bleeding and cardiac tamponade (see b p.381)

Residual anatomic defect

Needs to be considered when LCOS persists

•

Consider TOE if TTE inconclusive (better visualization, in particular

•

venous pathways and atrial anatomy)

Early cardiac catheterization if no progress

•

Surgical or catheter intervention correction of residual defect

•

Other options in LCOS

The sternum may be left open to allow myocardial oedema to subside

Seen in lesions with large L

• lR shunts with chronic high pulmonary

blood fl ow (AVSD, truncus); muscular hypertrophy of PAs

Pulmonary pressures also increase from any condition that impedes

•

pulmonary venous drainage (obstructed TAPVC)

i

• PVR may be reactive or fi xed

Assessment of PVR and reactivity to O

• 2, iNO at cardiac catheterization

can identify a high-risk group for postoperative PH

Postoperative

• iPA and RV pressures may result in RV failure

Diagnosis of postoperative pulmonary hypertension

A PA line is inserted via the RVOT in cases judged to be at risk

degree of PH; ratio <50% seldom results in RV dysfunction

Echo can be used to estimate RV pressure if no PA line:

towards or above systemic level

Pulmonary hypertensive events are often accompanied by a sudden

•

reduction in lung compliance, which may mimic a blocked ETT

iiPAP

RV dysfunctioniCVP

RV pump failuredLAPdsystemic BP

Treatment (see Box 20.13)

Is aimed at

• dPVR and supporting RV function

No treatment may be required if

• iPA pressure is well tolerated

Keep patient well sedated with opiates and benzodiazepines

sustained high FiO2 (pulmonary toxicity)

Avoid hypercapnia, do not use hyperventilation to

iSVR and dCO

Inhaled NO (5–20ppm) is a potent selective pulmonary vasodilator and

•

the treatment of choice

Acute

• dPAP should be evident immediately

Discontinue if no benefi cial response within 30min

Consider other pulmonary vasodilators

Box 20.13 Treatment of a pulmonary hypertensive crisis

Sedate and paralyse

•

FiO

• 2 1.0, ventilate to low/normal PaCO2

Correct acidosis with bicarbonate therapy

Box 20.14 The oliguric patient

Assess cardiac output/oxygen delivery—increase inotropic and

•

vasodilator support if LCOS

Try volume bolus—assess haemodynamic response and urine output

infusion may be needed

Introduce renal replacement therapy if no response to furosemide

•

infusion or if hyperkalaemia, acidosis

Box 20.15 Indications for dialysis

peritoneal fl uid and PD to be easily instituted if needed

Commonly used in neonates and infants undergoing complex repairs

•

Techniques are intermittent (‘in and out’) PD, automated cycling PD,

•

and ‘cross fl ow’ PD (requires 2 catheters)

Limited clearances achieved

• not exclude a pericardial collection

Do not delay chest exploration of you suspect tamponade

Necrotizing enterocolitis (NEC)

The risk of NEC in the neonatal cardiac population is substantial Associated risk factors include prematurity, HLHS, truncus arteriosus, and episodes of low cardiac output and shock

Clinical presentation varies and diagnosis is often diffi cult:

Pneumoperitoneum is a late sign and an absolute indication for laparotomy Most cases are managed conservatively:

IV antibiotics (cephalosporin/aminoglycoside/metronidazole) for 7–10

Accumulation of chyle in the pleural cavity:

2% incidence after CHD surgery

wean from mechanical ventilation.

Bilateral diaphragmatic paralysis

Box 20.17 Aetiology of brain injury

Clinical presentation varies from seizures, encephalopathy, and

chorei-form movements in the acute setting, to cerebral palsy and learning orders later on

dis-Diagnosis

MRI is the imaging modality of choice; CT is useful but cerebral USS is

•

of limited value in detecting hypoxic-ischaemic injury

EEG may detect sub-clinical seizure activity

•

Staged palliation of a univentricular heart

A number of lesions are not suitable for a 2-ventricle repair and are managed with a series of 2 or 3 palliative procedures Examples include mitral atresia, tricuspid atresia, some forms of pulmonary atresia, DILV, and HLHS

In the neonatal period surgery may be required to optimize pulmonary blood fl ow

Too little blood fl ow requires an arterial–pulmonary artery shunt

•

Too much blood fl ow requires a PA band to reduce blood fl ow

•

PVR is high in the newborn period and falls over the fi rst few months

of life Creation of a bidirectional cavopulmonary (‘venous’) shunt in the newborn period would result in very high SVC pressure and low PBF—hence an arterial shunt is initially needed

Univentricular heart

Assessment

of pulmonary

blood flow

Too much blood flow to lungs

Balanced pulmonary blood flow

Too little blood flow

until 6 months old

Modified BT shunt

Age 6

months Cavopulmonaryshunt

Age 2–4

years operationFontan

Fig 20.5 Pathways of palliative operations.