pulmonary surfactant

Question 1

what is surfactant?

Answer 1

a surface- active lipoprotein complex formed by the type !! alveolar cells

Question 2

where is surfactant located?

Answer 2

lines the alveoli and the smallest bronchioles

Question 3

How is surfactant produced?

Answer 3

production begins in the type 2 alveolar cells during the terminal stage of lung development (`17-26 wks); lamellar bodies appear in the cytoplasm ~20 wk GA

Question 4

How is alveolar surfactant recycled?

Answer 4

up to 90% of surf is recycled from the alveolar space; it is broken down via macrophages and/ or reabsorbed into glomerular structures of the type 2 cells

Question 5

What is the alveolar storage capacity of a preterm infant? term?

Answer 5

Preterm: estimated to have only 4-5mg/kg at birth; Term: 100mg/kg

Question 6

What are conditions that can negatively impact surfactant quality and production?

Answer 6

hyperinsulinism, acidosis and MAS (the chemical pneumonitis that occurs with MAS is thought to be the culprit)

Question 7

what is the function of surfactant in the lungs?

Answer 7

inc pulmonary compliance, dec surface tension, facilitates recruitment of collapsed airways, protection of the pulmonary epithelium and prevents atelectasis at the end of expiration

Question 8

What is pulmonary compliance?

Answer 8

the ability of the lung and thorax to expand

Question 9

Research supports the administration of exogneous surf with what correlated results?

Answer 9

a rapid improvement in oxygenation, decrease need for mech vent support, demonstrated an inc in FRC followed by a slower increase in lung compliance, a dec in VQ mismatch

Question 10

what is the normal surface tension of water v the lung?

Answer 10

water: 70 d/cm, the lung is 25d/cm

Question 11

How does surf fx play a vital role in expiration?

Answer 11

at the end of expiration compressed surf phospholipid molecules decrease the surface tension to a very low near zero level. Pulm surf greatly reduces the surface tension (resisting the pull to collapse), inc compliance therefore allowing the lungs to inflate more easily and decrease total WOB

Question 12

How does alveolar size affect surf?

Answer 12

as the alveoli increase in size, the surfactant becomes evenly distributed; this also helps all alveoli in the lungs to expand at the same rate

Question 13

How does surf keep airways ‘dry’?

Answer 13

surface tension forces also draw fluid from the capillaries to the alveolar spaces. by reducing the surface tension, the fluid from the capillaries is not drawn into the alveolar space.

Question 14

what is the composition of surf?

Answer 14

40% dipalmitoylphosphatidycholine (DPPC)
40% other phospholipids
5% surfactant associated proteins (SP- A, B, C, D) cholesterol (neutral lipid)
traces of other substances

Question 15

What is the strongest phosopholipid in the pulmonary surf mixture?

Answer 15

DPPC

Question 16

What are disease states r/t pulmonary surfactant deficiency?

Answer 16

RDS, congenital surfactant deficiencey and pulmonary alveolar proteinosis

Question 17

Can surf be utilized with MAS pts?

Answer 17

yes; the mec inhibits the surf fx leading to alveolar collapse, the chemical pneumonoitis and acidosis that also accompanies MAS also may have negative effects on surf

Question 18

Can surf be utilized in patients with pulmonary hemorrhage or pneumonia?

Answer 18

maybe; routine use of surf in these two conditions is not recommended, efficacy is uncertain but may still be utilized in clinical practice

Question 19

What are the different types of exogenous surfactant?

Answer 19

Synthetic, animal derived and human amniotic fluid derived surfactant

Question 20

what is synthetic surfactant?

Answer 20

Exosurf; may or may not have protein components

Question 21

what are animal derived surfactants?

Answer 21

Curosurf- extracted from minced pig lung; Infasurf- extracted from calf lung lavage fluid; Survanta- extracted from minced cow lung with additional DPPC, palmitic acid and tripalmitin

Question 22

What is the doseage and administration recommendations for exogenous surf?

Answer 22

doseage depends on type of surf given; admin via ETT although some discussion in the lit about via LMA (avoids complications of intubation- has yet to be studied in large randomized trials)

Question 23

What is the weight requirement for LMA use?

Answer 23

> 1500 g

Question 24

In clinical practice when is exogenous surfactant administration indicated?

Answer 24

persistent worsening respiratory dysfunction, RDS; there should be a low threshold for repeat dosing with RDS patients with perinatal depression or infix. B/c surf is rapidly metabolized and there is a functional inactivation due to soluble proteins in the small airways and alveoli subsequent doses may be req’d

Question 25

WIth exogenous surfactant administration, what monitoring should be done?

Answer 25

ETT patency and position
oxygen saturations, EKG and BP (continuously)
-monitor for postdose hyperoxia, hypocarbia and overventilation
s/s blocked airway

Question 26

What are signs that a patient is not tolerating exogenous surf admin?

Answer 26

if pt becomes dusky, agitated, bradys, O2 sats decreased by >15% or reflux of surf into the ETT

Dosing should then be slowed or stopped. May require inc FiO2 or ∆ vent settings (inc airway pressure)

Question 27

What can result from postdose over ventilation, hyperoxia and hypocarbia?

Answer 27

pneumothorax

Question 28

What percentage of patients given exogenous surfactant experience a pulmonary hemorrhage?

Answer 28

2-4%

Question 29

What type of patients given exogenous surfactant are at an increased risk for a pulmonary hemorrhage?

Answer 29

primarily in small patients with an untreated PDA; may be due to hemorrhagic pulmonary edema due to a rapid fall in pulmonary vascular resistance and results in inc pulmonary blood flow; more likely to occur in animal derived surf

Question 30

Patients who develop pulmonary hemorrhage from exogenous surfactant administration are more at risk for what?

Answer 30

death and short term morbidity