Hypoplastic Left Heart syndrome Flashcards
Hypoplastic left heart syndrome is a term used to describe a spectrum of defects with the common denominator being
under development of the heart’s left side
-aorta, aortic valve, LV, and MV
Hypoplastic left heart syndrome results in
single ventricle physiology & complete mixing of systemic and pulmonary circulation
The expected oxygen saturation for a patient with HLHS is
75-80%
Describe surgical palliation for HLHS.
- this defect is not correctable and definitive treatment is a heart transplant
The three palliative operations for HLHS include:
Stage 1: Norwood- soon after birth
Stage 2: Bidirectional Glenn at 4-12 months old
Stage 3: Fontan at 1.5-3 years old
With HLHS, the entire left side from the
mitral valve to the aortic arch is hypoplastic
The single ventricle ejects
mixed blood into the pulmonary artery
At birth with HLHS, the 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
With the Stage 1: Norwood with shunt, the connection nbetween
systemic to pulmonary circulation is created
1) atrial septectomy and creation of a common atrium
2) reconstruction of PA to aortic arch
3) ligation of the PDA
4) establish pathway for blood flow to lungs with a BTS/MBTS (right subclavian or synthetic graft to right PA)
With the Stage 1: Norwood, the anticipated arterial oxygen saturation is
75-80%**
- if SpO2 is >85% there is excessive pulmonary blood flow
- if SpO2 is <70% there is inadequate pulmonary blood flow (i.e. problems with BTT shunt or lung disease)
The Stage II: Bidirectional Glenn requires low
PVR and blood flow is passive***
- maintain adequate volume and low PVR
- expected arterial oxygen saturation is 75-85%
- IVC venous blood continues to flow into the heart and therefore systemic circulation
The stage II: bidirectional Glenn is a direct anastomosis between the
SVC and a pulmonary artery branch
“Bidirectional” indicates blood flow to both the right and left pulmonary arteries
In the Stage III: Fontan Procedure, the inferior vena cava is
connected to the pulmonary vasculature
-allows for passive blood flow from the IVC to lungs while bypassing the heart
The stage III procedure completes the
separation of the pulmonary and systemic circulations
The expected arterial oxygenation saturation of the Fontan procedure is
88-93%
Prior to stage 1, the PDA must be kept patent with
PGE1 to allow systemic perfusion
It is important to restrict excessive_____ in patients with HLHS.
pulmonary blood flow
Excessive pulmonary blood flow can be restricted via:
allowing mild hypercarbia (PCO2 45-55 mmHg)
allowing low oxygen concentrations
use of PEEP
Higher than expected oxygen saturations may imply
inadequate systemic perfusion and pulmonary overload (consider cerebral oximetry monitoring)
Additional considerations for patients with HLHS include:
patients may require inotropic support (i.e. dopamine, milrinone or epinephrine)
minimize myocardial depression
prevention and treatment of pulmonary hypertensive crisis
Chronic Fontan complications include:
dysrhythmias
protein losing enteropathy
thrombosis
Thrombosis may occur due to
dysrhythmias that cause venous stasis or sluggish flow
Protein losing enteropathy is
poorly understood development of hypoalbuminemia despite normal renal and hepatic function
Dysrhythmias may occur due to
elevated atrial pressures and atrial suture lines
Pulmonary hypertension is the result of
high blood flow and increased pressure in the pulmonary vasculature
Pulmonary hypertension is common in
unoperated CHD
A child with acute increases in pulmonary artery pressure and intracardiac communication that allows for shunting may result in:
desaturation
bradycardia
systemic hypotension
Known factors to increase pulmonary vascular tone**
hypoxemia & use of <30% FiO2 hypercarbia/acidosis hypothermia atelectasis transmitted positive pressure & PEEP Stress response/stimulation/light anesthesia
Known factors that decrease pulmonary vascular resistance****
increasing inspired oxygen to 100%
hyperventilation
potent inhalation agents reduce SVR more than PVR
nitric oxide
Vasoconstrictors such as phenylephrine increase _____ more than _____ and are acutely effective in reducing ________ shunting and increasing _____ shunting in the OR.
SVR more than PVR
right to left shunting & increasing left to right shunting
Nitric oxide is a powerful
smooth muscle vasodilator with a short half-life
-acts to decrease Calcium levels
Nitric oxide is currently used in neonates to promote
capillary and pulmonary dilation to treat pulmonary HTN
Overdose of nitric oxide results in
methemoglobin & pulmonary toxicity
The nitric oxide should be placed on the
inspiratory limb of the AGM
