Surfactant Replacement in Neonates, by Dr. Brian Walsh.
Introduction and Background.
Well welcome.
My name's Brian Walsh.
I'm a Respiratory Therapist at Boston Children's Hospital.
Today I'm going to talk to you about surfactant replacement
therapy for pre-term, term neonates
with respiratory distress syndrome.
According to the American Academy of Pediatrics,
respiratory failure secondary to surfactant deficiency
is a major cause of morbidity and mortality
in pre-term infants.
Surfactant therapy substantially reduces
mortality and respiratory morbidity for this population.
There may be an additive effect when combined
with antenatal steroids.
Surfactant deficiency can contribute to acute respiratory
morbidity in late pre-term and term neonates
with meconium aspiration syndrome, pneumonia, sepsis,
and perhaps pulmonary hemorrhage.
Surfactant replacement therapy may
be beneficial for those infants as well.
The efficacy of exogenous surfactant administration
was well established in the early 1990s in the treatment
of those premature infants.
Systematic reviews of randomized,
controlled trials confirm that surfactant administration
in pre-term infants with established
respiratory distress syndrome reduces mortality,
decreases pulmonary insult by lowering
the risk of air leak and chronic lung disease.
Subsequent trials indicate that prophylactic surfactant
or early administration of surfactant
resulted in fewer pneumothoraces, less
pulmonary interstitial emphysema,
and improved survival without bronchopulmonary dysplasia.
However, recent data recognized the benefits
of prophylactic surfactant administration
must be weighed against the risk of intubation
and positive pressure ventilation.
This change in practice is reflected
in the most recent AAP guidelines
regarding respiratory care of pre-term infants.
Switching to the treatment of term or near-term neonates,
surfactant treatment improves oxygenation
and reduces the need for ECMO without an increase
in morbidity in neonates with meconium aspiration syndrome.
Surfactant treatment in infants with congenital diaphragmatic
hernia does not appear to improve clinical outcomes.
Composition and Function of Surfactant.
So what is surfactant?
Endogenous surfactant is a biochemical compound
composed of phospholipids, neutral lipids, and proteins
that form a layer between the terminal airways, alveolar
surfaces, and alveolar gas.
Surfactant is secreted by type II pneumocytes and functions
to reduce collapse during end exhalation
by decreasing surface tension within the terminal airways
and alveoli.
This animation depicts end exhalation collapse
that occurs without surfactant.
The second animation depicts how surfactant prevents
end exhalation collapse.
Indications.
Indications for surfactant therapy
are surfactant deficiency due to prematurity or lung injury that
eliminates surfactant or hinders surfactant function,
such as meconium aspiration, pneumonia, or blood aspiration.
Complications.
Complications that exist with surfactant therapy
are transient airway obstruction.
This can be the obstruction of the endotracheal tube.
It can be hypoxia related to that transient obstruction,
bradycardia, or hyperventilation,
unilateral surfactant administration
from a malpositioned endotracheal tube, increased
compliance and FRC that leads to air leak,
hyperoxia, hyperventilation resulting in changes
in cerebral blood flow, patent ductus arteriosus,
and pulmonary hemorrhage.
Recommendations.
According to the American Academy of Pediatrics,
current recommendations are:
1.
Pre-term infants born at less than 30 weeks gestation who
need mechanical ventilation because of severe RDS
should be given surfactant after initial stabilization.
2.
Using CPAP immediately after birth
with subsequent selective surfactant administration
should be considered as an alternative
to routine intubation with prophylactic or early rescue
surfactant administration in pre-term infants.
3.
Rescue surfactant may be considered for infants
with hypoxic respiratory failure attributable
to secondary surfactant deficiency,
excluding congenital diaphragmatic hernia.
4.
Surfactant therapy should be managed by nursery or transport
personnel with the technical and clinical expertise
to administer surfactant safely and deal
with multisystem illnesses.
Case Example.
So let's use a case to describe how we would actually
deliver surfactant.
So this is baby boy AJ, who is 27 weeks gestational age
infant, weighing 880 grams, has been
intubated for severe respiratory distress syndrome.
He is on assist control volume ventilation
with a tidal volume that is set to 4.5 mLs per kilo
with a peak inspiratory pressure in the high 20s,
a respiratory rate of 30, and an oxygen requirement of 50%.
His chest x-ray is consistent with respiratory distress
syndrome and his endotracheal tube
is in the correct position.
When you look at the ventilator prior to surfactant,
you can see that the peak inspiratory
pressure is in the high 20s, in that 27 to 28 range.
When you review his blood gas, it has a pH of 7.35,
has a CO2 of 43.6, a PaO2 of 76.1--
remember this is on 50%--
and a bicarbonate of 24, giving him an oxygen index of 5.
There are largely two types of surfactant on the market,
animal-derived and synthetic-derived.
Dosing is according to manufacturer,
with most approximating 100 milligrams
per kilo of phospholipids per dose.
When it comes to delivering surfactant,
you first want to warm the surfactant to room temperature.
If you have the time, you can actually
take it out of the refrigerator and place it
in room temperature for 20 minutes,
or if you're short on time you can hold it
in your hands for approximately eight minutes.
Next you want to wash your hands and put
on personal protective equipment, including goggles.
You want to inspect the surfactant
for discoloration, a broken seal, or an expiration date.
However, you do not want to shake it.
You want to aseptically aspirate the appropriate dose
without foaming.
And I would suggest using a large bore needle to do this.
You want to assess the patient for need of suctioning prior
to surfactant administration.
Next, you want to choose the appropriate catheter size.
Here at Boston Children's Hospital,
we use an in-line system that allows
us to keep the patient on the ventilator
while delivering surfactant administration.
Alternatively, you can use a small bore feeding
tube or an umbilical catheter as long
as it's less than 6 French, as you
don't want to obstruct the majority
of the endotracheal tube.
Next, you want to determine the safe administration catheter
depth.
The goal is to go to the tip of the endotracheal tube,
but not beyond.
So for example, if you have an endotracheal tube that's
12 centimeters long and the ET tube adapter is 3 centimeters,
this means that you should not go past the 15 centimeter mark
on the catheter.
Next, you want to consider the dead space of the catheter.
Some people have used air or additional surfactant
to actually wash out this dead space.
Next, you want to perform a time out.
You suspect that AJ has surfactant deficiency
from prematurity.
He's required intubation despite CPAP.
He has a significant oxygen requirement and ventilatory
support.
His endotracheal tube is in proper position
as you saw on the chest x-ray.
We've identified the team.
We have one person to watch the monitor and to help turn.
The second person is to deliver surfactant
and you have equipment available for reintubation
and resuscitation if needed.
This video depicts the way that we do it
at Boston Children's Hospital.
First, the dose is divided into two aliquots.
We turn the patient on one side and instill
the first half of the dose.
We wait approximately 30 seconds to a minute for the surfactant
to be distributed.
Next, we reposition the neonate to the opposite side
and instill the second aliquot.
During this process, we're monitoring
for observation of chest rise and fall,
oxygen saturation, heart rate, tidal volume, FiO2
and how much oxygen is required to keep
the sats between 90 and 95.
We monitor for signs of reflux of surfactant.
When it comes to complications, we expect a slight to moderate
desaturation.
If beyond moderate or bradycardia occurs,
suspend the administration and allow the patient to recover.
Rarely does the ET tube become blocked or surfactant
have to be removed.
And you also want to carefully adjust
the ventilator as needed.
When it comes to follow-up, we want
to monitor respiratory system compliance and other indices
of oxygen and ventilation carefully for the first 15
minutes following the installation and then
another full assessment one hour following delivery.
You want to attempt to avoid suctioning for at least one
to two hours if possible.
Here's the ventilator following surfactant administration.
You will see that the peak inspiratory pressure has nicely
come down into the low 20s and high teens followed by an FiO2
now down from 50% to 30%.
It is expected that the respiratory system
compliance will improve.
If you're in pressure ventilation,
this will result in a increase in tidal volume and minute
ventilation if not manually adjusted.
You want to prevent swings in CO2.
Volume ventilation will result in a more consistent minute
ventilation.
However, it's anticipated that the peak inspiratory
pressure will decrease.
With improving compliance, pulmonary vascular resistance
may fall and oxygenation improve.
This will require vigilance to adjust and prevent
swings in oxygenation.
You also need to monitor for pulmonary edema or hemorrhage
from left to right shunting.
Repeat dosing of surfactant should not
be considered more than every 12 hours unless surfactant
is being inactivated by an infectious process, meconium,
or blood.
Thank you very much for watching.
Please help us improve the content by providing us
with some feedback.