Pulmonary surfactant Flashcards
When was surfactant initially identified
In 1920 but was not understood until the 1950’s
What is surfactant:
surface active lipoprotein complex ford by the type II alveolar cells, lines the alveoli and smallest bronchioles
When and where does surfactant production start
in the type II cells during terminal sac stage (17-26 weeks)
When do lamellar bodies appear?
20 weeks gestation
How is alveolar surfactant broken down?
by macrophages and/or reabsorbed into lamellar structures of type II cells. Up to 90% of surfactant is recycled from alveolar space in the newborn
3 conditions that negatively effect surfactant quality and production:
hyperinsulinism, acidosis, meconium aspiration (chemical pneumonitis)
Alveolar storage pool of term infants
100 mg/kg of surfactant
Alveolar storage pool of preterm infants
4-5 mg/kg of surfactant
Surfactant and compliance:
Increases the ability of the lungs and thorax to expand
Surfactant and surface tension:
Lungs are 25 d/cm and at end of expiration compressed surfactant phospholipid molecules decrease the surface tension to near 0. BY REDUCING SURFACE TENSION, FLUID FROM CAPILLARIES IS NOT DRAWN IN THE ALVEOLAR SPACES
Other functions of surfactant
facilitates recruitment of collapsed airways, protection of the pulmonary epithelium, prevents atelectasis at the end of expiration ( INCREASES FRC). Decrease in V/Q mismatch
Alveolar size contributes to what
As they increase the surfactant becomes distributed and expand at the same time
Primary phospholipid in surfactant
DPPC dipalmitoylphosphatidycholine STRONGEST
Composition of surfactant
40% DPPC
40% other phospholipids
5% proteins (SP-A,B,C,D) B and C in exogenous surfactants
Cholesterol
Diseases related to surf deficiency
RDS, Congenital surfactant deficiency, pulmonary alveolar proteinosis
MAS and surfactant
meconium inhibits surfactant function leading to alveolar collapse
Pulmonary hemorrhage/pneumonia and surfactant
routine use not recommended, efficacy uncertain
Types of surfactant
Synthetic: Exosurf (with or without protein)
Curosurf: porcine lung
Survanta: bovine lung
Infasurf: calf lung lavage fluid
Evidence for re-administration of surfactant
for persistent or worsening RDS, low threshold for repeat dosing should be used for RDS who have perinatal depression or infection
Pneumothorax risk with surfactant
decreased risk with multiple dose therapy
How to monitor for surfactant therapy
ET patency and position, oxygen sats, EKG, BP, blocked airway
Adverse effects/precautions
reflux up ETT, oxygen desats, pulmonary hemorrhage (2-4% of smallest pts with untreated PDA)
Post dose: hyperoxia, hypocarbia, overventilation
