Anesthesia for children with Congenital Heart Disease

CHILDREN WITH

CONGENITAL

HEART DISEASEGeorge Nicolaou, MD FRCPC

Department of Anesthesia

& Perioperative Medicine

University of Western Ontario

ANESTHESIA FOR

INTRODUCTION

• Number of children reaching adulthood with

CHD has increased over the last 5 decades

• D/T advances in diagnosis, medical, critical

and surgical care

• Therefore, not uncommon for adult patients

with CHD to present for non-cardiac surgery

INCIDENCE

• 7 to 10 per 1000 live births

• Premature infants 2-3X higher incidence

• Most common form of congenital disease

• Accounts for 30% of total incidence of all congenital diseases

• 10% -15% have associated congenital anomalies of skeletal, RT, GUT or GIT

• Only 15% survive to adulthood without treatment

ETIOLOGY

• 10% associated with chromosomal abnormalities

• Two thirds of these occur with Trisomy 21

• One third occur with karyotypic abnormalities such

as Trisomy 13, Trisomy 18 & Turner Syndrome

• Remaining 90% are multifactorial in origin

• Interaction of several genes with or without

external factors such as rubella, ethanol abuse,

lithium and maternal diabetes mellitus

FETAL CIRCULATION

• There are 4 shunts in

fetal circulation:

placenta, ductus

venosus, foramen ovale,

and ductus arteriosus

• In adult, gas exchange

occurs in lungs. In fetus,

the placenta provides

the exchange of gases

and nutrients

CARDIOPULMONARY CHANGES AT BIRTH

• Removal of placenta results in following:

• ↑ SVR (because the placenta has lowest

vascular resistance in the fetus)

• Cessation of blood flow in the umbilical vein

resulting in closure of the ductus venosus


• Lung expansion →

reduction of the

pulmonary vascular

resistance (PVR), an

increase in pulmonary

blood flow, & a fall in

PA pressure


• LUNG EXPANSION:

– Functional closure of the foramen ovale as a result

↑ LAP in excess RAP

– The LAP increases as a result of the ↑ PBF and ↑

pulmonary venous return to the LA

– RAP pressure falls as a result of closure of the

ductus venosus

– PDA closure D/T ↑ arterial oxygen saturation


• PVR high as SVR near or at

term

• High PVR maintained by ↑

amount of smooth muscle in

walls of pulmonary

arterioles & alveolar

hypoxia resulting from

collapsed lungs

• Lung expansion → ↑

alveolar oxygen tension →

↓ PVR

CLASSIFICATION OF CHD

• L – R SHUNTS

– Defects connecting arterial & venous circulation

– SVR > PVR → ↑ PBF

– ↑ pulmonary blood flow → pulmonary congestion

→ CHF → ↑ susceptibility to RTI

– Long standing L-R shunts → PHT

– PVR > SVR → R-L shunt → Eisenmenger’s

syndrome


• L - R SHUNTS INCLUDE :

– ASD →7.5% of CHD

– VSD → COMMONEST CHD – 25%

– PDA → 7.5% of CHD

• Common in premature infants

– ENDOCARDIAL CUSHION DEFECT - 3%

• Often seen with trisomy 21

– AORTOPULMONARY WINDOW

VENTRICULAR SEPTAL DEFECT

ATRIOVENTRICULAR CANAL DEFECT

L – R SHUNTS

• PERIOPERATIVE TREATMENT

– Indomethacin → PDA closure

– Digoxin, diuretics, ACE inhibitors → CHF

– Main PA band → ↑ PVR → ↓ L-R shunt

– Definitive open heart surgery

• POSTOPERATIVE PROBLEMS

– SVTs and conduction delays

– Valvular incompetence → most common after

canal defect repairs


• R – L SHUNTS

– Defect between R and L heart

– Resistance to pulmonary blood flow → ↓ PBF →

hypoxemia and cyanosis

• INCLUDE :

– TOF – 10% of CHD, commonest R-L shunt

– PULMONARY ATRESIA

– TRICUSPID ATRESIA

– EBSTEIN’S ANOMALY

R – L SHUNTS

• GOAL → ↑ PBF to improve oxygenation

– Neonatal PGE1 (0.03 – 0.10mcg/kg/min)

maintains PDA → ↑ PBF

– PGE1 complications → vasodilatation,

hypotension, bradycardia, arrhythmias, apnea or

hypoventilation, seizures, hyperthermia

– Palliative shunts → ↑ PBF, improve hypoxemia

and stimulate growth in PA → aids technical

feasibility of future repair

GLENN SHUNT

MODIFIED BLALOCK-TAUSSIG

SHUNT

TETRALOGY OF FALLOT

• 10% of all CHD

• Most common R – L shunt

• 4 anomalies:

– RVOT obstruction ( infundibular, pulmonic or

supravalvular stenosis )

– Subaortic VSD

– Overriding aorta

– RVH

TETRALOGY OF FALLOT

TETRALOGY OF FALLOT

• Hypercyanotic ( “tet” ) spells occur D/T

infundibular spasm, low pH or low PaO2

• In awake patient manifests as acute cyanosis &

hyperventilation

• May occur with feeding, crying, defecation or

stress

• During anesthesia D/T acute dynamic

infundibular spasm

TETRALOGY OF FALLOT

• Treatment of Hypercyanotic Spells

– High FiO2 → pulmonary vasodilator → ↓ PVR

– Hydration (fluid bolus) → opens RVOT

– Morphine (0.1mg/kg/dose) → sedation,↓ PVR

– Ketamine → ↑ SVR, sedation, analgesia → ↑ PBF

– Phenylephrine (1mcg/kg/dose) → ↑ SVR

– β-blockers (Esmolol 100-200mcg/kg/min)

→ ↓HR,-ve inotropy → improves flow across

obstructed valve &↓ infundibular spasm

TETRALOGY OF FALLOT

• Halothane → ↓ HR & -ve inotropy

– Rapidly tuned on and off

– Careful in severe RVF

• Thiopental → -ve inotropy

• Squatting, abdominal compression→↑ SVR

EBSTEIN’S ANOMALY


• COMPLEX SHUNTS (MIXING LESIONS)

– Continuous mixing of venous and arterial blood –

blood saturation 70% - 80%

– May or may not be obstruction to flow

– Produce both cyanosis and CHF

– Overzealous improvement in PBF steals

circulation from aorta → systemic hypotension →

coronary ischemia


• COMPLEX SHUNTS INCLUDE :

– TRUNCUS ARTERIOSUS

– TRANSPOSITION OF GREAT VESSELS – 5%

• Arterial switch procedure > 95% survival

– TOTAL ANOMALOUS PV RETURN

– DOUBLE OUTLET RIGHT VENTRICLE

– HYPOPLASTIC LEFT HEART SYNDROME

• Most common CHD presenting 1st week of life

• Most common cause of death in 1st month of life

TOTAL ANOMALOUS PULMONARY

VENOUS RETURN

TOTAL ANOMALOUS PULMONARY

VENOUS RETURN

HYPOPLASTIC LEFT HEART SYNDROME

TRANSPOSITION OF GREAT VESSELS

TRUNCUS ARTERIOSUS

DOUBLE OUTLET RIGHT VENTRICLE

FONTAN PROCEDURE

NORWOOD PROCEDURE

JATENE PROCEDURE


• OBSTRUCTIVE LESIONS

– Either valvular stenosis or vascular bands

– ↓ perfusion & pressure overload of corresponding ventricle

– CHF common

– Right sided obstructions PBF hypoxemia and cyanosis

– Left sided obstructions systemic blood flow tissue hypoperfusion, metabolic acidosis and shock


• OBSTRUCTIVE LESIONS INCLUDE :

– AORTIC STENOSIS

– MITRAL STENOSIS

– PULMONIC STENOSIS

– COARCTATION OF AORTA – 8% of CHD

• 80% have bicuspid aortic valve

– COR TRIATRIATUM

– INTERRUPTED AORTIC ARCH

COARCTATION OF AORTA

COARCTATION OF AORTA

INTERUPTION OF AORTIC ARCH

COR TRIATIATUM



ANESTHETIC MANAGEMENT

• Perioperative management requires a team

approach

• Most important consideration is necessity for

individualized care

• CHD is polymorphic and may clinically

manifest across a broad clinical spectrum


• Unpalliated

• Partially palliated

• Completely palliated

– ASD and PDA only congenital lesions that

can be truly “corrected”

Anesthesiologists will encounter children with

CHD for elective non-cardiac surgery at one of

three stages:


• 50% Dx by 1st week of life; rest by 5 years

• Child’s diagnosis & current medical condition will determine preoperative evaluation

• Understand the anatomic and hemodynamic function of child’s heart

• Discuss case with pediatrician and cardiologist

• Review diagnostic & therapeutic interventions

• Above will estimate disease severity and help formulate anesthetic plan

HISTORY & PHYSICAL

• Assess functional status – daily activities & exercise tolerance

• Infants - ↓ cardiac reserve → cyanosis, diaphoresis & respiratory distress during feeding

• Palpitations, syncope, chest pain

• Heart murmur (s)

• Congestive heart failure

• Hypertension

HISTORY & PHYSICAL

• Tachypnea, dyspnea, cyanosis

• Squatting

• Clubbing of digits

• FTT d/t limited cardiac output and increased

oxygen consumption

• Medications – diuretics, afterload reduction

agents, antiplatelet, anticoagulants

• Immunosuppressants – heart transplant

LABORATORY EVALUATION

• BLOODWORK

• Electrolyte disturbances 2° to chronic diuretic therapy

or renal dysfunction

• Hemoglobin level best indicator of R-L shunting

magnitude & chronicity

• Hematocrit to evaluate severity of polycythemia or

iron deficiency anemia

• Screening coagulation tests

• Baseline ABG & pulse oximetry

• Calcium & glucose - newborns, critically ill children


• 12 LEAD EKG

– Chamber enlargement/hypertrophy

– Axis deviation

– Conduction defects

– Arrhythmias

– Myocardial ischemia


• CHEST X - RAY

– Heart size and shape

– Prominence of pulmonary vascularity

– Lateral film if previous cardiac surgery for

position of major vessels in relation to sternum


• ECHOCARDIOGRAPHY

– Anatomic defects/shunts

– Ventricular function

– Valve function

– Doppler & color flow imaging direction of

flow through defect/valves, velocities and

pressure gradients


• CARDIAC CATHERIZATION

– Size & location of defects

– Degree of stenosis & shunt

– Pressure gradients & O2 saturation in each

chamber and great vessel

– Mixed venous O2 saturation obtained in SVC or

proximal to area where shunt occurs

– Low saturations in LA and LV = R – L shunt

– High saturations in RA & RV = L – R shunt


• CARDIAC CATHERIZATION

– Determine shunt direction: ratio of pulmonary to

systemic blood flow : Qp / Qs

– Qp / Qs ratio < 1= R – L shunt

– Qp / Qs ratio > 1= L – R shunt

PREMEDICATION

a) Omit for infants < six months of age

b) Administer under direct supervision of Anesthesiologist in preoperative facility

c) Oxygen, ventilation bag, mask and pulse oximetry immediately available

d) Oral Premedication

• Midazolam 0.25 -1.0 mg/kg

• Ketamine 2 - 4 mg/kg

• Atropine 0.02 mg/kg

PREMEDICATION

e) IV Premedication

• Midazolam 0.02 - 0.05 mg/kg titrated in small

increments

f) IM Premedication

• Uncooperative or unable to take orally

• Ketamine 1-2 mg/kg

• Midazolam 0.2 mg/kg

• Glycopyrrolate or Atropine 0.02 mg/kg

MONITORING

• Routine CAS monitoring

• Precordial or esophageal stethoscope

• Continuous airway manometry

• Multiple - site temperature measurement

• Volumetric urine collection

• Pulse oximetry on two different limbs

• TEE

MONITORING

• PDA

– Pulse oximetry right hand to measure pre-ductal

oxygenation

– 2nd probe on toe to measure post-ductal

oxygenation

• COARCTATION OF AORTA

– Pulse oximeter on right upper limb

– Pre and post - coarctation blood pressure cuffs

should be placed

ANESTHETIC AGENTS

• INHALATIONAL AGENTS

– Safe in children with minor cardiac defects

– Most common agents used are halothane and

sevoflurane in oxygen

– Monitor EKG for changes in P wave retrograde

P wave or junctional rhythm may indicate too deep

anesthesia

INHALATIONAL ANESTHETICS

• HALOTHANE

– Depresses myocardial function, alters sinus

node function, sensitizes myocardium to

catecholamines

– MAP + HR

– CI + EF

• Relax infundibular spasm in TOF

• Agent of choice for HCOM


SEVOFLURANE

• No HR

• Less myocardial depression than Halothane

• Mild SVR → improves systemic flow in L-R

shunts

• Can produce diastolic dysfunction


ISOFLURANE

• Pungent not good for induction

• Incidence of laryngospasm > 20%


• Vasodilatation leads to SVR → MAP

• HR which can lead to CI


DESFLURANE

• Pungent not good for induction; highest

incidence of laryngospasm

• SNS activation → with fentanyl

• HR + SVR



NITROUS OXIDE

• Enlarge intravascular air emboli

• May cause microbubbles and macrobubbles to

expand obstruction to blood flow in

arteries and capillaries

• In shunts, potential for bubbles to be shunted

into systemic circulation


NITROUS OXIDE

• At 50% concentration does not affect PVR and

PAP in children

• Mildly CO at 50% concentration

• Avoid in children with limited pulmonary

blood flow, PHT or myocardial function

IM & IV ANESTHETICS

KETAMINE

• No change in PVR in children when airway maintained & ventilation supported

• Sympathomimetic effects help maintain HR, SVR, MAP and contractility

• Greater hemodynamic stability in hypovolemic patients

• Copious secretions → laryngospasm → atropine or glycopyrrolate

IM & IV ANESTHETICS

KETAMINE

• Relative contraindications may be coronary insufficiency caused by:

– anomalous coronary artery

– severe critical AS

– hypoplastic left heart syndrome with aortic atresia

– hypoplasia of the ascending aorta

• Above patients prone to VF d/t coronary insufficiency d/t catecholamine release from ketamine

IM & IV ANESTHETICS

IM Induction with Ketamine:

• Ketamine 5 mg/kg

• Succinylcholine 5 mg/kg or Rocuronium 1.5 – 2.0 mg/kg

• Atropine or Glycopyrrolate 0.02 mg/kg

IV Induction with Ketamine:

• Ketamine 1-2 mg/kg

• Succinylcholine 1-2 mg/kg or Rocuronium 0.6-1.2 mg/kg

• Atropine or Glycopyrrolate 0.01 mg/kg

IM & IV ANESTHETICS

OPIOIDS• Excellent induction agents in very sick children

• No cardiodepressant effects if bradycardia avoided

• If used with N2O - negative inotropic effects of

N2O may appear

• Fentanyl 25-100 µg/kg IV

• Sufentanil 5-20 µg/kg IV

• Pancuronium 0.05 - 0.1 mg/kg IV offset

vagotonic effects of high dose opioids

IM & IV ANESTHETICS

ETOMIDATE• CV stability

• 0.3 mg/kg IV

THIOPENTAL & PROPOFOL• Not recommended in patients with severe cardiac

defects

• In moderate cardiac defects:– Thiopental 1-2 mg/kg IV or Propofol 1-1.5 mg/kg IV

– Patient euvolemic


• GENERAL PRINCIPLES

Where:

Q = Blood flow (CO)

P = Pressure within a chamber or vessel

R = Vascular resistance of pulmonary or

systemic vasculature

Ability to alter above relationship is the basic tenet of

anesthetic management in children with CHD

R

PQ


P manipulate with positive or negative

inotropic agents

Q hydration + preload and inotropes

However, the anesthesiologist’s principal focus

is an attempt to manipulate resistance, by dilators

and constrictors


• GENERAL CONSIDERATIONS

– De-air intravenous lines air bubble in a R-L shunt

can cross into systemic circulation and cause a

stroke

– L-R shunt air bubbles pass into lungs and are

absorbed

– Endocarditis prophylaxis

– Tracheal narrowing d/t subglottic stenosis or

associated vascular malformations


– Tracheal shortening or stenosis esp. in children

with trisomy 21

– Strokes from embolic phenomena in R-L shunts

and polycythemia

– Chronic hypoxemia compensated by polycythemia

→ ↑ O2 carrying capacity

– HCT ≥ 65% → ↑ blood viscosity → tissue hypoxia

& ↑ SVR & PVR → venous thrombosis → strokes

& cardiac ischemia


– Normal or low HCT D/T iron deficiency → less

deformable RBCs → ↑ blood viscosity

– Therefore adequate hydration & decrease RBC

mass if HCT > 65%

– Diuretics → hypochloremic, hypokalemic

metabolic alkalosis


ANESTHESIA INDUCTION

• Myocardial function preserved IV or

inhalational techniques suitable

• Severe cardiac defects IV induction

• Modify dosages in patients with severe

failure

ANESTHESIC MANAGEMENT

ANESTHESIA MAINTENANCE

• Depends on preoperative status

• Response to induction & tolerance of

individual patient

• Midazolam 0.15-0.2 mg/IV for amnesia


• L - R SHUNTS :

• Continuous dilution in pulmonary

circulation may onset time of IV

agents

• Speed of induction with inhalation

agents not affected unless CO is

significantly reduced

• Degree of RV overload and/or failure

underappreciated – careful induction


• L-R SHUNTS :

– GOAL = SVR and ↑ PVR → L-R shunt

• PPV & PEEP increases PVR

• Ketamine increases SVR

• Inhalation agents decrease SVR


• R-L SHUNTS :

– GOAL : PBF by SVR and ↓ PVR

• PVR & ↓ SVR → ↓ PBF

– Hypoxemia/atelectasis/PEEP

– Acidosis/hypercapnia

– HCT

– Sympathetic stimulation & surgical stimulation

– Vasodilators & inhalation agents → ↓ SVR


• ↓ PVR & SVR → PBF

– Hyperoxia/Normal FRC

– Alkalosis/hypocapnia

– Low HCT

– Low mean airway pressure

– Blunted stress response

– Nitric oxide/ pulmonary vasodilators

– Vasoconstrictors & direct manipulation→ SVR


• R –L SHUNTS :

– Continue PE1 infusions

– Adequate hydration esp. if HCT > 50%

– Inhalation induction prolonged by limited

pulmonary blood flow

– IV induction times are more rapid d/t bypassing

pulmonary circulation dilution

– PEEP and PPV increase PVR


• COMPLEX SHUNTS :

• Manipulating PVR or SVR to PBF will:

• Not improve oxygenation

• Worsen biventricular failure

• Steal circulation from aorta and cause

coronary ischemia

• Maintain “status” quo with high dose opioids

that do not significantly affect heart rate,

contractibility, or resistance is recommended


• COMPLEX SHUNTS :

– Short procedures slow gradual induction with low

dose Halothane least effect on +ve chronotropy &

SVR

– Nitrous Oxide limits FiO2 & helps prevent

coronary steal & ↓ Halothane requirements


• OBSTRUCTIVE LESIONS

• Lesions with > 50 mmHg pressure gradient +

CHF opioid technique

• Optimize preload improves flow beyond

lesion

• Avoid tachycardia ↑ myocardial demand & ↓

flow beyond obstruction

• Inhalation agents -ve inotropy & decrease

SVR worsens gradient & flow past obstruction

REGIONAL ANESTHESIA &ANALGESIA

• CONSIDERATIONS

– Coarctation of aorta dilated tortuous intercostal

collateral arteries risk for arterial puncture

and absorption of local anesthetic during

intercostal blockade

– Lungs may absorb up to 80% of local anesthetic on

first passage. Therefore risk of local anesthetic

toxicity in R-L shunts

• Central axis blockade may cause

vasodilation which can:i. Be hazardous in patients with significant AS or

left-sided obstructive lesions

ii. Cause oxyhemoglobin saturation in R-L shunts

iii. Improve microcirculation flow and venous

thrombosis in patients with polycythemia

• Children with chronic cyanosis are at risk

for coagulation abnormalities

REGIONAL ANESTHESIA &ANALGESIA

POSTOPERATIVE MANAGEMENT

• Children with CHD are very susceptible to:i. Deleterious effects of hypoventilation

ii. Mild decreases in oxyhemoglobin saturation

Therefore, give supplemental O2 and

maintain patent airway

• In patients with single ventricle titrate SaO2

to 85%. Higher oxygen saturations can

PVR PBF systemic blood flow

• Pain catecholamines which can affect

vascular resistance and shunt direction

• Anticipate conduction disturbances in septal

defects

• Pain infundibular spasm in TOF

RVOT obstruction cyanosis, hypoxia,

syncope, seizures, acidosis and death

POSTOPERATIVE MANAGEMENT

Health & Medicine

Anesthesia for children with Congenital Heart Disease