Lung surfactants and antenatal corticosteroids: Nursing pharmacology

Lung surfactants are lipoproteins produced and secreted by type II pneumocytes lining the lung alveoli to keep them from collapsing when air is exhaled.

The production of surfactants typically begins at around week 26 of gestation, and reaches sufficient levels by week 35.

So, preterm babies born before that don't produce enough lung surfactants. As a consequence, their alveoli collapse, leading to neonatal respiratory distress syndrome.

To prevent this, preterm babies are administered exogenous lung surfactants.Commonly used exogenous lung surfactants include beractant, which is a bovine lung derivative; calfactant, which is a calf lung derivative; and poractant alfa, which is a porcine lung derivative.

Exogenous surfactants are usually administered directly into the newborn’s airways through an endotracheal, or ET tube, or via less invasive surfactant administration or LISA for short, such as nebulized surfactant preparations, laryngeal masks, and intratracheal instillation.Once administered, lung surfactants form a film that coats the inner walls of the alveoli.

This film decreases the surface tension, which helps maintain the alveolar shape by preventing the inner walls from sticking to each other and collapsing during expiration.

Now, before birth, corticosteroids like betamethasone and dexamethasone can be administered to promote fetal lung maturation.

This is also known as antenatal corticosteroid therapy, and it is usually administered intramuscularly to pregnant clients at 24 to 33 weeks and 6 days of gestation who are expected to go into preterm labor.

Administration of antenatal corticosteroids reduces the risk of respiratory distress syndrome in premature babies. Also, it has been shown to have other benefits too, including a reduced risk of neonatal mortality; sepsis; intraventricular hemorrhage, or bleeding in the brain; and necrotizing enterocolitis, a serious intestinal condition affecting premature babies.

Once administered, antenatal corticosteroids travel from the client’s bloodstream to the fetus. Here, they stimulate the development of both type I and type II pneumocytes in the fetal alveoli, leading to alveolar development as well as an increased production of endogenous lung surfactant.

This allows the alveoli to stay open, which improves gas exchange; moreover, the lungs become more compliant, meaning they are less stiff and easier to ventilate.Now, both lung surfactants and antenatal corticosteroids are rarely associated with side effects.

However, during administration of lung surfactants, transient bradycardia and oxygen desaturation may be observed. In very low birth weight premature infants, surfactant administration may cause pulmonary hemorrhage.

Lung surfactants are relatively contraindicated in infants with an existing pulmonary hemorrhage or with a congenital diaphragmatic hernia.

Finally, lung surfactants should not be administered in neonates with respiratory distress that’s not caused by lung immaturity.On the other hand, fetal side effects of antenatal corticosteroids can include short-lived effects such as reduced fetal movements and fetal heart rate variability; while maternal side effects include increased risk of infections, a transient rise in serum glucose levels, and rarely, an increased risk of pulmonary edema.

Finally, antenatal corticosteroid therapy should not be administered to clients where immediate delivery is needed, as in cord prolapse, placental abruption, or chorioamnionitis.Now, when caring for a pregnant client who is at risk for preterm labor, you will likely be administering antenatal corticosteroids as part of your client care.

Before administering the medication, confirm the estimated gestational age of the fetus and the results of prenatal gestational diabetes screening.

Then teach the client about the purpose of the steroid injection, potential side effects, and the monitoring you will be doing after administration such as glucose monitoring and respiratory assessments.

Administer the injection intramuscularly into a large muscle. The ventrogluteal injection site is common for this medication.

Do not massage the injection site as this may damage the underlying muscle. As you continue to monitor your client for preterm labor, monitor for side effects by assessing vital signs, auscultating lung sounds, and checking glucose levels.

Okay, as a nurse caring for an infant receiving surfactant, you have a key role in assisting before, during and after the medication is administered.

First off, educating and reassuring the baby’s parents is an important responsibility, as the situation can be very scary for parents.

Take time to clearly explain the procedure, how the medication works, and its potential side effects. Answer any questions and reinforce that you and the team are there to keep their baby safe throughout the procedure.Next, you’ll need to ensure the infant’s weight is accurately measured and documented before administration so the correct dosage can be calculated per kilogram.

Double check that the prescribed dose is correct, based on the current weight. Other pre-administration assessments include ensuring that correct placement of the tube has been confirmed and documented, applying continuous cardiorespiratory monitoring as well as either transcutaneous or pulse oximetry.

You’ll need to suction the infant for several minutes before the surfactant is administered in order to clear secretions that could interfere with the instillation of the medication.

Also, ensure that the surfactant is brought to room temperature 20 minutes before it’s administered. Just before the medication is drawn up, gently swirl the medication without shaking it to allow the suspension to mix thoroughly.Now, ongoing assessment and monitoring is essential during surfactant administration.

Because instillation of the surfactant could cause transient impairment of ventilation, you’ll need to be alert for signs such as bradycardia, oxygen desaturation, or cyanosis.

If any of these occur, dosing should be slowed or temporarily stopped; provide ventilatory support until the infant stabilizes.

Also keep in mind that with some types of surfactant the total surfactant dose is divided into smaller doses that are administered one after the other.

For example, beractant requires that the total dose is separated into 4 smaller doses called aliquots; and each aliquot is administered with the infant in a different position to ensure the surfactant reaches all areas of the lungs.

So, the first dose is administered with the head and body inclined down and turned to the right; then the head and body are inclined down and turned to the left for the second dose; next, the head and body are inclined up and turned to the right for the third dose; and finally, the head and body are inclined up and turned to the left for the fourth dose.

You will be needed to assist with infant positioning and to provide ventilation to ensure the infant is stable between doses.

After administration, your role is to continue close assessment and monitoring. Assess skin color, heart rate, and oxygen saturation, and try to avoid suctioning the endotracheal tube for 1-2 hours in order to avoid suctioning out the medication.

If the infant is on a ventilator, be ready to adjust the ventilator settings fairly rapidly as the surfactant begins to improve lung compliance.

Alright, as a quick recap…lung surfactants are naturally occurring compounds that reduce the surface tension in the alveoli and keep them from collapsing during exhalation.

Babies who are born before 34 weeks of gestation do not have enough lung surfactant and therefore are at risk for neonatal respiratory distress syndrome.

Exogenous lung surfactants are administered to decrease the surface tension in the lungs and prevent collapse of the alveoli.

Side effects that may occur during administration include transient bradycardia, oxygen desaturation, and cyanosis. Antenatal corticosteroids are administered to clients at risk for preterm labor, usually between 24 weeks to 33 weeks and 6 days of gestation.

Corticosteroids stimulate the development of both type I and type II pneumocytes in the fetal alveoli, leading to alveolar development as well as an increased production