Peds Congenital Hearts and Things Flashcards
causes of congenital heart defects
- chromosome abnormalities
- single-gene abnormalities
- conditions during pregnancy that affect the baby
- combination of genetic and environment problems
- unknown causes (idiopathic)
diagnosis of congenital heart defect
- in utero
- found with newborn physical
- ECHO, EKG, CXR
- cardiac cath, cMRI, CT, TEE, Holter recording
preoperative eval for congenital heart defect
- heart murmur
- functional status, growth and development (are they meeting milestones?)
- review most recent echo/labs/tests
- children with history of CHF, cyanosis, pulmonary HTN, and young age are at a potentially higher risk
characteristics of fetal circulation
- high PVR
- low SVR
- most oxygenated blood from umbilical vein shunts across the ductus venosis and foramen ovale to perfuse the heart and brain
- Hgb F has P50 of 19 mmHg and greater affinity for oxygen than Hgb A
- fetal pH is 7.25-7.35 (slightly acidic)
L to R shunts
- connects arterial and venous circulation resulting in increased pulmonary blood flow
- pulmonary overcirculation
- leads to an increase in RV preload because a large amount of LV output bypasses the systemic circulation, enters the lungs and rapidly returns to the L side of the heart
- pink lesions
- PDA, ASD, VSD
R to L shunts
- venous blood ejected systemically
- decreased pulmonary blood flow and patients are cyanotic
- blue lesions
- ASD or VSD with pulm HTN, TET during TET spell
obstructive lesions
- prevent ventricular flow from either side of the heart
- decrease cardiac output
- coarctation of the aorta, aortic stenosis
mixed or cyanotic lesions
- mixing of venous and arterial blood
- HLHS
- these lesions can also lead to pulmonary over-circulation and CHR
- occur when a functional single ventricle ejects the mixed systemic and pulmonary venous return
- the patients are cyanotic and often dependent on the PDA at birth
Eisenmenger’s syndrome
- when large VSDs are uncorrected, the resulting pulmonary HTN can reverse the shunting of blood across the defect
- the previously L to R shunt becomes R to L because of Pulm HTN
Qp
- total pulmonary blood flow
- sum of effective pulmonary blood flow and recirculated pulmonary blood flow
Qs
- total systemic blood flow
- sum of effective systemic blood flow and recirculated systemic blood flow
single ventricle physiology
- complete mixing of pulmonary and systemic venous blood at the atrial or ventricle level
- blood then equally distributed out to both the systemic and pulmonary beds
three things are true in single-ventricle physiology
- ventricular output is the sum of pulmonary blood flow (Qp) and systemic blood flow (Qs)
- distribution of systemic and pulmonary blood flow is dependent on the relative resistances to flow (both intra and extracardiac) into the two parallel circuits
- oxygen saturations are the same in the aorta and the pulmonary artery
what is normal Qp/Qs?
- 1:1 which has equal RV and LV output
- pulmonary blood flow is equal to systemic blood flow
what is Qp/Qs?
-a ratio of estimated pulmonary to systemic blood flow that is useful in determining over circulation to the pulmonary system or LV workload
formula for Qp/Qs
Qp/Qs = SaO2 - SvO2/SpvO2 - SpaO2
- SaO2 = aortic O2 sat
- SvO2 = SVC O2 sat
- SpvO2 = pulmonary vein O2 sat
- SpaO2 = pulmonary artery O2 sat
- derivation of Fick’s law
how is Qp/Qs measured
cardiac cath, measure oxygen saturations in all four of these areas to calculate
shortcut for Qp/Qs + four assumptions made
- the patient is breathing room air and pulmonary venous blood is fully saturated
- oxygen consumption is normal, resulting in a SvO2 of 25-30% less than SaO2
- the patient is NOT severely anemic (has a normal SVC O2 saturation)
- complete mixing results in aortic and pulmonary artery O2 saturations being equal
- most cases = assumptions valid and allow a rapid determination of Qp/Qs based on SpO2 alone
Qp/Qs <1
- shunt is right to left
- patient will be cyanotic
Qp/Qs 1-2
- shunt is minimally L to R
- patient will be asymptomatic
Qp/Qs 2-3
- shut is moderate L to R
- mild symptoms of CHF
Qp/Qs >3
- shunt is LARGE L to R
- severe symptoms of CHF
ASD
- atrial septal defect
- as many as 1 in 5 healthy adults still have a PFO
- often asymptomatic and discovered incidentally (murmur)
- large defect left untreated can cause R sided volume overload (Qp/Qs >2) with RA and RV dilation and increased pulmonary blood flow
- repair can be closure device in cath lab or surgery
VSD
- ventricular septal defect
- most common congential defect in children
- leads to pulmonary overcirculation due to L to R shunting in isolated lesion
- large defect –> equal pressure in both ventricles –> PVR 1/6 SVR –> so more pulmonary blood flow –> CHF –> damage to pulm vascular bed
- as PVR falls in firth months of life, flow across the VSD can increase GREATLY (Qp/Qs >3, meaning the L heart has to pump 3xs normal volume to meet the usual systemic demands)
restrictive VSD
small size and limited pulmonary over circulation
unrestrictive VSD
large flow across the septum with balance between SVR and PVR
indications for surgery with VSD
- poor feeding
- reduced weight gain
- increased in incidence of respiratory infection
what is at risk during a VSD repair
-conduction system because it runs along the ventricular septum
PDA
- patent ductus arteriosus
- leftover fetal artery connection between the aorta and pulmonary artery
- unrestricted PDA will have significant L to R shunting
- significant diastolic runoff into pulmonary circulation lowers systemic DBP, which compromises distal and coronary perfusion
- closure - commonly done with cardiac cath (coil)
- surgical closure = L thoracic approach, closed by suture tie or metal clip
CAVC
- complete atrio-ventricular canal
- free communication between all four chambers of the heart
- located where the atrial septum joints the ventricular septum; involves atria, ventricles, tricuspid and mitral valves
- result is formation of a single large valve; the common AV valve; often regurgitant
greatest percentage of kids with CAVC
down syndrome
surgical repair of CAVC
- septum patch and new valves
- usually done < 6 months of age before pulmonary vascular changes develop
- problems can be residual septal defects, AV valve regurg, post-op pulmonary reactivity (esp if high Qp/Qs prior to surgery) and conduction system damage
Coarctation
- narrowing in the aorta commonly occurring immediately distal to the origin of the L subclavian artery
- most often located near ductus arteriosus
- proximal to ductus = pre ductal; distal to the ductas = post ductal
- frequently associated with bicuspid aortic valve
critical coarc
- circulatory collapse
- shock
- acidosis
- because POOR distal perfusion
- PGE1 (prostin) started to reopen ductus and distal perfusion remains ductal dependent until surgery
coarc surgical repairs
- resection and end to end anastamosis
- suclavian flap = subclavian artery used as a flap to enlarge the constricted part of the aorta; bad thing = lose the subclavian to the L arm so needs to be perfused by collaterals
- balloon angioplasty (cath lab)
coarc presentation
- upper extremity HTN
- decreased lower extremity pulses
- LVH
where is BP measured in coarc
- R arm
- this is because the aortic cross clamp will be proximal to the L subclavian
pulmonary valve stenosis
- narrowing of pulmonary valve that causes the RV to work harder to pump blood past the blockage
- symptoms depend on the severity of obstruction
- often treated with balloon dilation
- usually part of other complex lesions
aortic valve stenosis
- narrowing of aortic valve that causes LV to work harder to pump blood past the blockage
- severe AS in utero may impair LV development
- balloon dilation is an option
- valve replacement at young age may require revisions over time
Ross Procedure
- performed on patients with aortic stenosis as alternative to prosthetic valve replacement
- diseased aortic root resected and the patient’s own pulmonary valve root is excised and implanted into the aortic position
- coronary arteries re-implanted into the neo-aortic root
- RV to PA conduit and valve made with cadaveric tissue
- RV to PA connection may require revision over time but provides better long term solution to the aortic valve
advantages of Ross procedure
- freedom from long-term anticoagulation
- valve grows as the patient grows
disadvantages of Ross procedure
-single valve disease (aortic) is treated with two valve procedure
BTT shunt (formerly BT shunt)
- Blalock-Taussig-Thomas Shunt [Helen Taussig peds cardiologist, Alfred Blalock peds surg, and Vivien Thomas surgical assistant]
- operation to create a type of systemic to pulmonary shunt
- important uses in certain types of cyanotic lesions to get some blood flow to the lungs
- crucial palliation prior to complete repair later in life
classic BTS
- subclavian artery is divided and directely anastomosed to the ipsilateral pulmonary artery
- allows patient’s own subclavian artery to grow so no need for revision
- pulses in ipsilateral arm will be decreased or non-palpable
- prudent to expect classic BTS in older adult survivors of CHD
modified BTS (MBTS)
- synthetic shunt between the subclavian artery and PA
- ipsilateral arm reflects true pressure and available for art-line placement
- artifical material will not grow with the patient
- hypotension leads to SLUGGISH flow and possible thrombosis which can be critical
when was tetralogy of fallot first described
1888
what are the four key features of tetralogy of fallot
- VSD
- RVOT (r ventricular outflow tract obstruction)
- overriding aorta (aorta lies directly over VSD)
- RV hypertrophy (secondary to pressure overload)
when is TOF repair done?
- usually in first 6 months of life
- however if neonate too small can palliate with BTS
what determines the degree of cyanosis in TOF?
- limitation of pulmonary blood flow
- magnitude of ventricular level R to L shunting
hypercyanotic spell or TET spell
-acute dynamic increase in pulmonary outflow tract obstruction (spasm) may result in intensely cyanotic episode due to R to L shunting
causes of TET spell
- crying
- feeding
- acidosis
- catecholamines
- surgical stimulation
treatment TET spell
- increase SVR to relax the spasm
- child will squat to increase afterload (the position increases SVR, reduces HR, and reduces R to L shunt across the VSD)
- anesthetic treatment includes 100% FiO2, sedation, fluid, beta blocker, alpha agonist (to increase afterload and slow down the HR)
TOF repair
- closure of VSD with patch
- removal of some thickened muscle to relieve RVOTO
- eliminates intracardiac shunting at the ventricular level (so no more cyanosis) and addresses the RVOTO
- may also include enlarging the L and R pulmonary arteries
anesthesia for TOF repair
- avoid Tet spell
- generous premedication
- sufficient anesthesia/analgesia
- avoid reductions in SVR
- RV output is limiting factor on overall CO
- treat tet spell quickly with phenyl if necessary
treatment for TET spell intraoperatively
- 100% oxygen
- knees to chest
- fluid bolus
- hyperventilation
- sedation
- esmolol (0.5 mg/kg IV) or propranolol (0.1-0.3 mg/kg IV)
- phenylephrine 1-10 mcg/kg IV
Post TOF repair
- hypertrophied RV has poor compliance which is worse in immediate post op period due to R ventriculotomy (must maintain adequate filling)
- PFO or small ASD created that becomes a pop off if R sided pressures increase; so CO is maintained at expense of modest systemic desat
- over time, tricuspid valve may become incompetnet leading to RV overload and ventricular ectopy
- conduction system may be damaged in the repair
- RV decompensation over time due to free pulmonary insufficiency in trans-annular patch repair
HLHS
- Hypoplastic Left Heart Syndrome
- multitude of defects with the common denominator being under development of the L side of the heart
- results in single ventricle physiology AND complete mixing of systemic and pulmonary circulation
- expected oxygen saturation 75-80%
HLHS at birth
- RV provides pulmonary blood flow
- systemic blood flow is from the PA via the PDA (ductal dependent)
- if the PDA closes the neonate will present in shock due to severely reduced systemic perfusion
- most are diagnosed in utero and PGE1 is started to maintain ductal patency
three surgical palliative operations for HLHS
- stage 1 = norwood (soon after birth)
- stage 2 = bidirectional glenn (4-12 months)
- stage 3 = fontan (1.5-3 years old)
what is the goal of palliation for HLHS
to separate the pulmonary and systemic circulations
norwood with shunt
- connection between systemic to pulmonary circulation
- atrial septectomy and creation of ONE common atrium
- reconstruction of PA to aortic arch (neo-aorta)
- ligation of PDA
- establish pathway for blood flow to the lungs with BTS/MBTS/Sano shunt
what oxygen sats will the patient have after a norwood?
75-80%
SpO2 > 85% excessive pulmonary blood flow
SpO2 < 70% inadequate pulmonary blood flow
sano shunt
- gore-tex graft from RV to pulmonary artery
- provides for better pulmonary perfusion
- downside = leaves scar tissue in the RV
bidirectional glenn
- direct anastomosis of SVC and a pulmonary artery branch
- ligation of shunt
- bidirectional = blood flow to both the R and L pulmonary arteries
- requires LOW PVR and blood flow is passive
- maintain adequate volume and low PVR
- expected arterial oxygen sat is 75-85% (IVC venous blood continues to flow into the heart and therefore systemic circulation hence the lower sat)
fontan procedure
- inferior vena cava connected to the pulmonary vaculature
- allows for passive blood flow from IVC to lungs while bypassing the heart
- completes the separation of the pulmonary and systemic circulations
- expected art oxygen sat = 88-93% (coronary sinus is NOT included in fontan anastomosis)
extra-cardiac fontan
conduit sutured from IVC to pulmonary circulation
lateral tunnel fontan
baffle within the RA directs IVC blood into the pulmonary circulation
fenestrated fontan
allows for a pop-off hole in the RA from the conduit or tunnel
HLHS additional considerations
- prior to stage 1, ductal dependent (PDA must be kept open with prostin)
- restrict excessive pulmonary blood flow
- higher than expected O2 sat may mean inadequate systemic perfusion and pulmonary overload (consider NIRS)
- patient may need inotropes (dopa, epi)
- minimize myocardial depression
- prevent and treat pulmonary HTN crisis
how can you restrict excessive pulmonary blood flow in HLHS?
- allow mild hypercarbia (PCO2 45-55 mmHg)
- allow low oxygen concentrations
- use PEEP
chronic fontan complications
- dysrhytmias (frequent due to elevated atrial pressure and atrial suture lines)
- protein losing enteropathy (poorly understood development of hypoalbuminemia despite normal renal and hepatic fxn)
- thrombosis (dysrhythmias that cause venous stasis or sluggish flow)
s/s of phtn crisis
- desaturation
- bradycardia
- systemic hypotension
known factors to increase pulmonary vascular tone
- hypoxemia and use of <30% FiO2
- hypercarbia and acidosis
- hypothermia
- atelectasis
- transmitted positive pressure & PEEP
- stress response/stimulation/light anesthesia
known factors to decrease pulmonary vascular resistance
- increasing oxygen to 100%
- hyperventilation
- potent inhalation agents reduce SVR more than PVR
- nitric oxide
nitric oxide
- powerful smooth muscle vasodilator with a short half life
- currently used in neonates to promote capillary and pulmonary dilation to treat pulmonary HTN
- available in concentrations 100 ppm and 800 ppm
- over dose = methemoglobin and pulmonary toxicity
MOA of nitric oxide
- stimulates guanylate cyclase which leads to formation of cyclic-GMP
- cyclic GMP activates protein kinase G, which causes reuptake of calcium
- fall in concentration of calcium stops the MLCK cross bridge cycle and leads to relaxation of smooth muscle
Subacute bacterial endocarditis (SBE)
- infection caused by bacteria that enter the bloodstream and settle in the heart lining, a heart valve, or blood vessel
- IE is uncommon, but children with uncorrected CHD are at increased risk
- certain procedures performed on these patients require antibiotic prophylaxis
most common cause of SBE
stphylococcus aureus
most commonly used antibiotics for SBE prophylaxis
- cefazolin 50 mg/kg IV
- cetriaxone 50 mg/kg IV
what agent is recommended if penicillin allergy
- has to be a true allergy
- doxycycline 4.4 mg/kg
- NOT clindamycin (associated with higher complications like death from c-diff infection)
when should abx for SBE prophylaxis be administered?
30-60 minutes prior to the procedure
what HIGH risk patients is SBE prophylaxis suggested for?
- prosthetic cardiac valve or material
- previous or recurrent infective endocarditis
- congenital heart disease (unrepaired, cyanotic, palliative shunts; within 6 months following a complete repair; repair with residual defect at site of prosthetic material; certain types of conduit/valve placements)
- heart transplant with developed valvopathy
procedures requiring prophylaxis if patient is in the HIGH RISK category
- dental procedures that involve manipulation of gingival tissue, perforation of oral mucosa, or teeth extractions/drainage of an abscess
- respiratory tract procedures involving biopsy/incision
- procedures on infected skin and msk tissue
- cardiac surgery
prophylaxis NOT recommended for these procedures even if HIGH risk
- GI (if not ongoing GI infection)
- GU
- routine dental cleaning
- brochoscopy without biopsies
Down Syndrome
- trisomy 21
- chromosomal disease with distinct facies, significant airway and cardiac findings with varying degrees of intellectual disability
Down Syndrome HEENT/airway
- brushfield spots on iris
- upslanting eyes
- narrow nasopharynx
- small ears
- macroglossia
- pharyngeal hypotonia
- high-arched palate
- tonsil and adenoid hypertrophy
- micrognathia
- short broad neck
- small trachea
Down Syndrome chest
- chronic upper airway obstruction with hypoventilation and OSA
- recurrent pulmonary infections
Down Syndrome CV
- 1/2 have CHD –> ASD, VSD, AV canal, PDA, TOF
- L to R shunting may lead to pulm HTN and pulm vascular disease
Down Syndrome neuromuscular
- hypotonia
- dementia + parkinson’s in older adults
- intellectual decline may occur with age
Down Syndrome ortho
- joint laxity
- alantoaxial cervical instability (7-36%)
- short stubby hands
- single horizontal palmar crease
Down Syndrome GI/GU
- congenital duodenal atresia
- increased incidence of Hirschsprung
Down Syndrome other
-increased incidence of leukemias, hypothyroidism, and antithyroid antibodies
anesthesia for patients with Down Syndrome
- assess airway CV and ROS
- assess for alantoaxial instability
- assess for OSA
- CHD - SBE prophylaxis
- prone to bradycardia on induction
- challenging vascular access
- downsize ETT because subglottic stenosis
- DD varies
- hypothyroid
- postop stridor and respiratory complications common
DiGeorge Syndrome
- 22q11 micro deletion
- gene involved in the developmental process and includes defects in the development of the thymus, parathyroid, and great vessels
- has been associated with prenatal exposure to alcohol and accutane
- M&M associated with cardiac defects, T cell immunodeficiency, and seizures r/t hypocalcemia
DiGeorge Syndrome S/S
- micrognathia
- small mouth opening
- short trachea
- conotruncal cardiac defects
- hypocalcemia
how can immune disorder with DiGeorge be treated?
thymus transplant
anesthesia for DiGeorge
- micrognathia may mean difficult intubation
- short trachea may lead to endobronchial intubation
- choanal atresia precludes nasal trumpets or nasal intubation
- all blood products must be irradiated to kill leukocytes which can cause GVHD
- careful asepsis
- calcium level MUST be evaluated
- parathyroid dysfunction –> SIGNIFICANT hypocalcemia
- CHD = SBE prophylaxis
williams syndrome
- deletion of chromosome 7
- first described in 1961
williams syndrome clinical features
- elfin facies
- small teeth
- vocal cord paralysis
- mild mental disability
- cerebral artery stenosis with ischemic events
- HTN
- abdominal aortic coarc
- cocktail party personality
williams syndrome CV
- stenotic lesions at multiple levels possible –> valvar pulmonary stenosis, branch pulmonary stenosis, aortic stenosis, supravalvular aortic stenosis with coronary artery stenosis (impeded flow to coronaries)
- RISK OF SUDDEN DEATH due to severe myocardial ischemia, LV dysfunction, ventricular arrhythmias
williams syndrome anesthetic considerations
- risk of sudden death outside of hospital as well as during cardiac cath and during anesthesia (thought to be due to severity of vascular stenosis and valve stenosis)
- baseline EKG and ECHO
- prepare for ECMO
- SBE prophylaxis
noonan syndrome
- autosomal dominant
- characterized by…
- hypertelorism (increased distance between orbits)
- mircognathia
- short stature
- pectus excavatum/carinatum
- bleeding diasthesis
- CHD
noonan syndrome anesthetic considerations
- possible difficult intubation, usually less marked with age
- difficult PIV placement if there is significant edema
- chest deformities may lead to decreased lung function
- bleeding diathesis may increase amt of periop bleeding
- renal impairment may affect metabolism of renally excreted drugs
- spinal abnormalities may make epidural catheter placement difficult
- SBE prophylaxis and HOCM considerations
marfan syndrome
- multisystem disorder resulting from a mutation in connective tissue protein
- fibrillin which is a major element of extracellular microfibrils in the elastic and non-elastic connective tissues
- involves CV, skeletal and ocular systems
- high degree of incomplete expressivity so MUCH individual variation
marfan syndrome clinical features
- narrow facies with high arched palate and crowded teeth
- pectus excavatum
- lower FVC due to early airway closure from not enough elastic tissue
- OSA
- aortic or pulmonary artery dilation
- mitral valve prolapse
- wide lumbosacral canal and spinal arachnoid cysts
marfan syndrome anesthetic considerations
- avoid HTN for those at risk for aortic dissection
- preop ECHO
- beta blockers
- SBE prophylaxis esp with mitral valve prolapse and insufficiency
- increased risk for pneumothorax so careful with PPV
- careful with positioning due to joint laxity
- may require larger than normal doses of spinal/epidural meds due to increased length and increased CSF
