Prematurity and Respiratory Distress Syndrome (RDS)

00:01 The care of premature newborns constitutes a huge percentage of the role of a neonatologist.

00:08 We’re going to go through, in this lecture, the major issues that show up as a result of prematurity.

00:14 Remember, a premature infant is any infant born under 37 weeks of age.

00:19 This is about 10% of U.S. infants and we break them down into subcategories.

00:24 For instance, a child who is born between 34 and 37 weeks, we might define as late preterm because these infants often don’t have any problems.

00:34 In infants who are less than 32 weeks, we won’t just call them preterm, we will call them very preterm.

00:41 And in infants who are born less than 28 weeks, we might say extremely premature.

00:45 Okay.

00:47 So what are the major problems that happened to these infants? Well, prematurity affects multiple different organ and I’m going to go through them and we’re going to describe some of the main problems that happen.

00:58 In the pulmonary system, patients may develop respiratory distress syndrome.

01:03 They also might just have apnea where they stop breathing because the brain is not pretty mature to regular their breathing.

01:10 They may also long-term develop chronic lung disease, perhaps as a result of some of the therapy we provided for their respiratory distress syndrome.

01:21 Premature infants are more likely to have heart disease, for example, a patent ductus arteriosus.

01:27 Premature infants are more likely to have renal disease, especially they can have acid-base disturbances or electrolyte disturbances.

01:35 Or they may progress to renal failure.

01:38 Eye problems are a classic problem in a premature infant who has been exposed to too much oxygen, specifically they may get retinopathy of prematurity.

01:47 The GI tract can be a real problem in extremely premature infants.

01:51 They are at increased risk for necrotizing enterocolitis and they may develop cholestasis.

01:57 And lastly, the brain can certainly be affected.

02:00 Associated with premature birth is an increased risk for hemorrhage inside the brain in the peripartum period.

02:07 Patients may also get a mild sort of damage called periventricular leukomalacia or they may just develop seizures.

02:14 So, all of these are potential problems in a premature infant.

02:18 Let’s start with respiratory distress syndrome.

02:20 This is probably the single entity that takes up the most time on any one patient in the neonatal intensive care unit.

02:29 So RDS or respiratory distress syndrome is caused by a low level of surfactant in the lung in a premature baby or at the time of birth.

02:40 This affects 90% of premature babies.

02:45 Its severity is related to how premature the infant is.

02:49 So, younger infants who are born earlier are going to have more severe disease.

02:55 Let’s have a timeout and talk about surfactant.

02:58 Surfactant is produced by the type 2 pneumocyte.

03:02 It’s like a lubrication for the lung.

03:05 And what this allows for is efficient inflation in atelectatic lung.

03:11 Let’s say you’re blowing up a balloon.

03:14 You can remember doing this.

03:16 When you started blowing up the balloon, it was very hard to blow up the balloon getting it started.

03:23 As a child, you remember blowing really hard to get it started and then once that it had gotten better, like this child, it could just keep expanding.

03:33 What’s going on is LaPlace’s law.

03:35 This is a basic law of physics.

03:38 The tension on that balloon is higher when it is smaller.

03:45 So now imagine you are an infant and your lungs are really millions and millions of very small balloons and you’re taking your first breath.

03:56 You’re trying to inhale and inflate all these tiny balloons.

04:00 If we don’t have this lubricant present, this infant is going to have a horrible time inflating their lungs.

04:08 This is respiratory distress syndrome.

04:10 They can’t inflate their lungs and when they’re breathing, the lungs might collapse down and be very hard to inflate again.

04:17 That natural lubricant that lets this happen is the surfactant and it’s missing.

04:24 As a result, we need to diagnose these infants who are having respiratory distress early in childhood.

04:31 These infants will have a very classic chest x-ray, which you can see a picture of here.

04:36 We call this a ground-glass appearance.

04:39 It’s a diffuse, sort of haziness throughout all the lung fields.

04:43 All those millions of atelectatic alveoli are in that X-ray clouding things up, so this is the ground-glass appearance you will see in respiratory distress syndrome.

04:54 We see this on x-ray, we know it’s a premature infant, we’re pretty sure we know what’s going on.

05:00 These patients will usually develop respiratory distress within four hours of birth.

05:07 If we know infants are going to be born early and we have some time, we could hold off on that delivery.

05:13 We can give the mother steroids.

05:16 By giving the mother steroids, it actually reduces the morbidity and mortality of the infant after they're born.

05:23 This is because the steroid enhances lung maturation and improves surfactant expression in the baby after birth.

05:33 We also may give this infant some surfactant.

05:36 So what you can do is you could intubate and you can spray artificial surfactant down into the lungs to help lube things up.

05:45 As we’re caring for these infants and we’re managing their breathing generally on the ventilator, we want to reduce the amount of pressure we’re providing.

05:55 That’s because long-term exposure to pressure is causing damage to those lungs which can result in a chronic lung disease of infancy.

06:04 But also we don’t want to give too much oxygen.

06:07 This is a tricky balance.

06:10 We avoid excessive oxygen because oxygen causes damage to the eyes in infants because of free radical activity.

06:17 So these infants can develop a retinopathy of prematurity that can result in blindness.

06:23 We want to avoid extra pressures because of that concern of chronic lung disease.

06:29 So with these two things together, we have to be very careful about our management of these children’s ventilators.

06:36 Sometimes, we put them on oscillators where the respiratory rate is very, very high and it’s just oscillating the air in there.

06:43 Other times, we will usually allow for a high CO2 level.

06:48 We call it permissive hypercarbia.

06:50 It’s okay if this child has a little bit of a respiratory acidosis, I’d rather that than lung disease or blindness.