new presentation notes for chd
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Cyanosis
What is cyanosis and how you would identify it?
Porth, (2002:1449) says that cyanosis is a bluish discolouration,
especially to the skin and mucous membranes, caused by an excess of
deoxygenated haemoglobin in the blood.
It is important for the nurse to distinguish between cardiopulmonary and
respiratory causes ensures effective management.
Hypoxemia test can be instigated
Administer 100% high-pressured oxygen for ten minutes. If the infant
responds and its colour becomes pink then cardiopulmonary causes are
discounted (McConnell & Elixson, 2002). In addition to this, arterial
blood gases should be monitored.
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Transposition of the great vessels
The great vessels of the heart include the aorta and the pulmonary artery.
In the transposition of the great vessels the aorta and pulmonary artery are
reversed (McConnell & Elixson, 2002). Hence:
The pulmonary artery is connected to the left ventricle instead of
the right ventricle.
The aorta is connected to the right ventricle instead of the left
ventricle.
This means two things:
That unoxygenatated blood returning from the body to the heart
misses out on getting oxygenated and gets pumped directly into the
system via the aorta what would happen?
Oxygenated blood returning from the lungs gets pumped back to
the lungs again what may happen with this?
In the infant with transposition of the great arteries Reddy (2002) claim
that the closure of the patent ductus arteriosus will cause a rapid onset of
cyanosis and tachypnoea. It is an emergency. Infants with the
transposition of the great vessels will not survive unless there is another
defect in the form of a patent ductus arteriosus (Muscari).
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What is a patent ductus arteriosis?
The initial breath at birth induces the circulatory switch from placental to
pulmonary oxygenation of blood. Prior to this, blood in the foetal heartbypasses the lungs and flows across the left and right ventricles to the
systemic circulation via openings called the ductus arteriosus and the
foramen ovale (Porth, 2002:522).
Within the first 24 to 72 hours of life, the switch to pulmonary
oxygenation of blood causes these openings to close, thereby separating
the ventricles into the pulmonary and systemic circulations (Porth,
2002:524).
Emergency medical care for infants with the transposition of the great
arteries is focused on maintaining the patent ductus arteriosus by
administering intravenous Prostaglandin E.
This procedure may cause apnoea. Hence the nurse must prepare for an
intubation procedure (McConnell & Elixson, 2002).
Surgical treatment is arterial switch. Preferably performed within the
first two weeks of life. If conditions do not permit this, then an atrial
switch is performed, however, this operation has a much higher long-term
morbidity rate (Porth, 2002:528).
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Tetralogy of Fallot
The tetralogy of Fallot is the most common cyanotic heart defect (Pretre
et al., 2001).
It is a complex congenital heart disorder that consists offour linked
congenital heart defects.
These include,
A ventricular septal defect,
Right ventricular hypertrophy causing right to left shunting of
unoxygenated blood. Which leads to cyanosis and hypoxemia.
Obstruction of the pulmonary outflow channel including
pulmonary stenosis. Also leads to decreasing oxygenated blood.
An aorta overriding the ventricular defect.
What happens?
The obstruction of the pulmonary outflow and pulmonary stenosis
causes the right ventricle to work harder (Porth, 2002:527).
This leads to hypertrophy of the right ventricle.
Right to left shunting through the ventricles causes mixing of
oxygenated blood and unoxygenated blood. This causes decrease inoxygenated blood to systemic circulation.
Also decrease in pulmonary blood, which causes hypoxemia and
cyanosis (Suddaby, 2001).
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Signs and Symptoms of Tetralogy of Fallot
Infants with the tetralogy of Fallot will display some cyanosis at birth.
As pulmonary obstruction and ventricular hypertrophy increase, cyanosis
will become more severe, and they will experience hypercyanotic or tet
spells
These will be evident in the infants first months of life and continue into
childhood. Pfleiger, (2005).
What are tet spells?
Activities that increase oxygen requirements such as crying, feeding,
defaecating
Increase pulmonary vascular resistance.
Right to left shunting
Decreases pulmonary blood flow.
What signs and symptoms do we see?
Child becomes acutely cyanotic.
Hyperpneic (increase to rate of breath in proportion to rate of
metabolism)
Irritable
Diaphoretic
As spell progresses child will become limp and may lose consciousness.
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What do we do?
Place child in knee to chest position increases vascular systemic
resistance and increases pulmonary blood flow.
Older children may naturally assume these positions.
Surgical Management of Tetralogy of Fallot
Palliative surgery designed to increase pulmonary blood flow and
decrease hypoxemia. A shunt to increase pulmonary blood flow called
Blalock-Taussig shunt
Corrective surgery carried out later on in childhood is cardiopulmonary bypass and
aortic cross-clamping will be necessary.