2. 588 D.K. Vasudev and D. Field
a small number of patterns have been recognized (e.g., alveolar capillary
dysplasia), and these are now being linked to specific genetic
abnormalities.
II. Pathophysiology
The exact pathophysiology varies with the underlying mechanism.
A. Reduced lung size (e.g., secondary to thoracic dystrophy).
B. Structural immaturity (e.g., secondary to oligohydramnios).
C. Diffusion deficit (e.g., secondary to alveolar capillary dysplasia). The main
functional problem that results in all the above is pulmonary insufficiency.
The main clinical problem tends to be oxygen transfer (lack of adequate
pulmonary surface area).
III. Diagnosis
A. Antenatal. Diagnosis may be anticipated on the basis of maternal antenatal
ultrasound scan (e.g., severe oligohydramnios, small fetal chest cavity).
Magnetic resonance imaging is also being used.
B. Postnatal. Diagnosis may be apparent immediately after birth if hypoplasia
is severe (i.e., cannot be resuscitated, or severe respiratory distress from
birth), or is part of recognizable syndrome (e.g., oligohydramnios sequence).
When the infant presents later with apparently isolated mild to moderate
respiratory distress, the diagnosis may be delayed. Syndromes either pri-
marily or secondarily associated with pulmonary hypoplasia should be con-
sidered. Similarly, conditions that can mimic these signs (e.g., infection)
should be excluded. In all cases where hypoplasia is the possible diagnosis,
the following should be considered:
1. Genetics consult
2. Measurement of lung volumes
3. Measurement of pulmonary compliance
4. Examination of surfactant genotype
5. Lung biopsy
C. The choice of investigation will vary with the severity of the child’s prob-
lem. In severe respiratory failure, lung biopsy may be performed as a termi-
nal event to permit diagnosis and counselling for future pregnancies (see
below). If more minor respiratory problems (e.g., unexplained persistent
tachypnea), assessment of pulmonary mechanics is appropriate.
Table 66.1 Factors which can impair lung growth in utero
1. Compression of chest (e.g., oligohydramnios—all causes)
2. Compression of lung (e.g., effusion, diaphragmatic hernia)
3. Reduction in fetal breathing (e.g., neuromuscular disorder)
3. 58966 Pulmonary Hypoplasia/Agenesis
IV. Management
A. Antenatal. If a diagnosis of pulmonary hypoplasia is made in utero, families
should be counselled by the obstetrician, neonatologist, clinical geneticist,
and surgeon (if appropriate). Potential options will vary according to the
following:
1. Primary diagnosis and its prognosis
2. Degree of diagnostic certainty resulting from the evaluation. Essentially
parents must decide between
a. Termination of pregnancy (criteria and regulations vary markedly
among and within countries).
b. Continuing the pregnancy with postnatal intervention and
“treatment.”
c. Antenatal intervention, practiced only in relation to certain condi-
tions (e.g., bilateral pleural effusions). Results vary with both the
nature and severity of underlying problem. Evidence of benefit for
such interventions is not established.
B. At delivery, standard resuscitation should take place. Where antenatal scans
indicate, special measures (e.g., draining pleural effusions) should be per-
formed. Vigorous resuscitation of infants with small volume lungs often
results in pneumothorax. If dysmorphic features in the child indicate a
lethal syndrome, or if oxygenation proves impossible, intensive care may
be withdrawn.
C. In the NICU
1. Establish routine monitoring. Invasive blood pressure/arterial access is
essential in the severest cases; central venous pressure monitoring, if
available via the umbilical vein, is of great help in fluid management.
2. Ensure adequate systemic blood pressure (maintain tissue perfusion and
minimize right-to-left shunting). This may require both infusion of flu-
ids and inotropes. Take care not to induce fluid overload.
3. Provide adequate respiratory support. Infants with mild hypoplasia may
not require ventilation. For those requiring invasive support, local prac-
tice usually governs the first choice; both conventional and high-
frequency devices can be used with success. Aim to provide stability of
blood gases (i.e., sufficient oxygenation to prevent metabolic acidosis).
More aggressive ventilation may induce pulmonary damage and further
impair lung function. If blood gas control proves impossible despite
maximum support, the child should be considered nonviable.
4. Attempts to “treat” pulmonary hypoplasia using a combination of con-
tinuous positive airway pressure (CPAP) with inhaled nitric oxide (iNO)
over a prolonged period has shown some promise but requires fuller
evaluation.
4. 590 D.K. Vasudev and D. Field
5. Introduce pulmonary vasodilators as indicated; pulmonary hypertension
is often a complication. Echocardiography may help confirm the diag-
nosis. Inhaled nitric oxide appears to be the agent of choice.
6. Surfactant. There is no clear role for surfactant use in this situation
(other than treatment of RDS if the baby has it), but it is frequently tried
in an attempt to rescue a deteriorating baby.
7. Extracorporeal Membrane Oxygenation (ECMO) is clearly able to pro-
vide stability, but there is no evidence of benefit over other forms of care
in pulmonary hypoplasia.
8. A role for the use of partial liquid ventilation is not established.
9. Investigate to establish the diagnosis. Where there are no clear features
to support a diagnosis of pulmonary hypoplasia, routine tests should
exclude all other causes of respiratory distress.
V. Prognosis
Pulmonary hypoplasia results from a large number of different conditions. The
prognosis is governed mainly by the etiology and any associated anomalies.
A. Mild cases often become asymptomatic with growth. Abnormalities of
function can still be measured in later childhood.
B. Infants with moderate hypoplasia can survive with intensive care but often
need long-term respiratory support. The effect of growth is uncertain and
death in later childhood can occur.
C. Severely affected babies die despite full support. No current intervention is
known to help in such cases.
VI. Counselling about future pregnancies
A. Some infants will be affected by conditions that can recur in future
pregnancies.
B. A proportion of severely affected cases cannot be diagnosed without exami-
nation of lung tissue. Lung biopsy may be impossible to perform safely
while the child is alive.
C. Postmortem study should be obtained whenever possible. If permission for
postmortem examination is not obtained, an open or needle biopsy of the
lung obtained soon after death may still allow a tissue diagnosis (in many
areas, consent to do so is required).
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