Date post: | 11-May-2015 |
Category: |
Health & Medicine |
Upload: | cairo1957 |
View: | 1,154 times |
Download: | 4 times |
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
CARDIOPULMONARY CHANGES AT BIRTH
• Lung expansion →
reduction of the
pulmonary vascular
resistance (PVR), an
increase in pulmonary
blood flow, & a fall in
PA pressure
CARDIOPULMONARY CHANGES AT BIRTH
• 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
CARDIOPULMONARY CHANGES AT BIRTH
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
• 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
CLASSIFICATION OF CHD
CLASSIFICATION OF CHD
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
ANESTHETIC MANAGEMENT
• 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:
ANESTHETIC MANAGEMENT
• 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
LABORATORY EVALUATION
• 12 LEAD EKG
– Chamber enlargement/hypertrophy
– Axis deviation
– Conduction defects
– Arrhythmias
– Myocardial ischemia
LABORATORY EVALUATION
• 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
LABORATORY EVALUATION
• ECHOCARDIOGRAPHY
– Anatomic defects/shunts
– Ventricular function
– Valve function
– Doppler & color flow imaging direction of
flow through defect/valves, velocities and
pressure gradients
LABORATORY EVALUATION
• 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
LABORATORY EVALUATION
• 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
INHALATIONAL ANESTHETICS
SEVOFLURANE
• No HR
• Less myocardial depression than Halothane
• Mild SVR → improves systemic flow in L-R
shunts
• Can produce diastolic dysfunction
INHALATIONAL ANESTHETICS
ISOFLURANE
• Pungent not good for induction
• Incidence of laryngospasm > 20%
• Less myocardial depression than Halothane
• Vasodilatation leads to SVR → MAP
• HR which can lead to CI
INHALATIONAL ANESTHETICS
DESFLURANE
• Pungent not good for induction; highest
incidence of laryngospasm
• SNS activation → with fentanyl
• HR + SVR
• Less myocardial depression than Halothane
INHALATIONAL ANESTHETICS
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
INHALATIONAL ANESTHETICS
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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
– 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
ANESTHETIC MANAGEMENT
– 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
ANESTHETIC MANAGEMENT
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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
• L-R SHUNTS :
– GOAL = SVR and ↑ PVR → L-R shunt
• PPV & PEEP increases PVR
• Ketamine increases SVR
• Inhalation agents decrease SVR
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
• ↓ 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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
• 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
ANESTHETIC MANAGEMENT
• 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