anesthesia for children with congenital heart disease1

CHILDREN WITH CONGENITAL

HEART DISEASEGeorge Nicolaou, MD FRCPC

Department of Anesthesia

& Perioperative Medicine

University of Western Ontario

http://www.childrensheartinstitute.org

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 :5– ASDASD →7.5% of CHD

– VSDVSD → COMMONEST CHD – 25%

– PDA PDA → 7.5% of CHD• Common in premature infants

– ENDOCARDIAL CUSHION DEFECT - 3%ENDOCARDIAL CUSHION DEFECT - 3%• Often seen with trisomy 21( Common atrioventricular canal,

Atrioventricular septal defect)[single Av annulus that drains boths atria] 3 components [Ostium primum+interventricular communication+abnormal AV valves}

– AORTOPULMONARY WINDOW[vascular communication between the ascending aorta and main pulm artery]

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

• A subset of associated cardiac anomalies—so-called ductal-dependent lesions—depend on flow through the PDA to maintain systemic blood flow. Premature closure of the ductus without concurrent repair of the following defects is contraindicated and may be fatal:

• Pulmonary artery hypoplasia• Pulmonary atresia• Tricuspid atresia• Transposition of the great arteries• Aortic valve atresia• Mitral valve atresia with hypoplastic left ventricle• Severe coarctation of the aorta/Interrupted aortic arch


• R – L SHUNTS– Resistance to pulmonary blood flow → ↓ PBF →

hypoxemia and cyanosis– Defect between R and L heart

• INCLUDE :– TOF – 10% of CHD, commonest R-L shuntTOF – 10% of CHD, commonest R-L shunt– PULMONARY ATRESIA PULMONARY ATRESIA – TRICUSPID ATRESIATRICUSPID ATRESIA

– EBSTEIN’S ANOMALYEBSTEIN’S ANOMALY(atrialized Rt Ventricle, proximal inlet portion of RV is above the displaced Tricuspid valve, also is stenosed usually.Associated with ASD, PS, or pulm atresia ,PDA and corrected TGA. Inc incidence of prexcitation syndrome[WPW]

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(single arterial trunk arising from both ventricles,failure of

the truncus to divide into aorta nd pulmonary artery)Always VSD

– TRANSPOSITION OF GREAT VESSELS – 5%

• Arterial switch procedure > 95% survival (d-type)

• L-type where both the 2 ventricles and the 2 great vessels are swaped(corrected TGA)

– TOTAL ANOMALOUS PV RETURN(all pulm viens drain into sys circ. Rather than lt atrium. Vertical vien then SVC, Supracardiac ,intracardiac in rt atrium ,or infracardiac in portal vien or IVC)

– DOUBLE OUTLET RIGHT VENTRICLE(4 Types depending on the relation of the conotruncal VSD with the great vessels.

– HYPOPLASTIC LEFT HEART SYNDROME

• Most common CHD presenting 1st week of life

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

• 4 types of DORV1.Subaortic VSD with or without pulmonary stenosis(like Fallots)

• 2Subpulmonary VSD with or without subaortic stenosis and or arch obstruction (like TGA

• 3Doubly comitted VSD

• 4.Remote VSD

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 STENOSISAORTIC STENOSIS– MITRAL STENOSISMITRAL STENOSIS– PULMONIC STENOSISPULMONIC STENOSIS– COARCTATION OF AORTA – 8% of CHDCOARCTATION OF AORTA – 8% of CHD

• 80% have bicuspid aortic valve80% have bicuspid aortic valve

– COR TRIATRIATUMCOR TRIATRIATUM– INTERRUPTED AORTIC ARCHINTERRUPTED AORTIC ARCH

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 ageb) Administer under direct supervision of

Anesthesiologist in preoperative facilityc) Oxygen, ventilation bag, mask and pulse

oximetry immediately availabled) 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

RP

Q


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

anesthesia for children with congenital heart disease1

Health & Medicine

common r

classification of chd

chd common

r shunts defects

r shunts pht pvr svr

commonest r

pulmonary blood flow

chd vsd commonest chd