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Surfactant Flashcards

1
Q

What is surfactant?

A

Surfactant alters the surface tension of the alveoli and the resulting pressures needed for alveolar inflation. It is a surface-active agent that reduces surface tension.

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2
Q

What else is surfactant known as

A

Detergent

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3
Q

Without surfactant reducing surface tension what will happen in the lungs

A

Every breath would take a considerable amount of pressure to expand the lung, comparable to the 80 to 90 cm H2O of pressure required for a newborn’s first breath

The lung would rapidly collapse during exhalation

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4
Q

What are surfactant agents?

A

They regulate the surface tension at gas-liquid interfaces.

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5
Q

What is Laplace’s Law?

A

Physical principle describing and quantifying the relationship between the internal pressure of a drop or bubble, the amount of surface tension and the radius of the drop or bubble.

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6
Q

Laplace’s Law is defined as?

A

The higher the surface tension, the more likely the alveolus will collapse.

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7
Q

What is LaPlace’s law relating to an alveolus?

A

Pressure = (2 x Surface tension)/Radius.

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8
Q

What are exogenous surfactants?

A

They are administered to replace missing pulmonary surfactant in RDS of the newborn. Artificial Surfactant/not native to the patient.

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9
Q

What type of surfactant is clinically indicated for the treatment or prevention of RDS in the premature newborn?

A

Exogenous surfactants.

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10
Q

What does the term Exogenous describe in regards to surfactant?

A

Surfactant that is produced outside of the patients’ body.

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11
Q

What is the typical method for administering exogenous surfactant to infants?

A

By direct instillation to the airway.

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12
Q

Exogenous Surfactants are indicated for the treatment/prevention of?

A

Respiratory Distress Syndrome in newborns.

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13
Q

What type of patients need Exogenous Surfactant to be given as a rescue treatment?

A

Rescue treatment for infants who have developed RDS.

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14
Q

What are the indications for the use of Exogenous Surfactant?

A

In premature infants at risk for RDS and as a rescue agent for infants with RDS.

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15
Q

What type of patients can exogenous surfactant as a prophylactic preventative be given?

A

immature lungs and infants at risk of developing RDS.

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16
Q

How is exogenous surfactant given to newborns?

A

Placed as a liquid down the ET tube (Intratracheal).

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17
Q

How many doses of Exogenous Surfactant are usually needed before improvement is seen?

A

1-2.

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18
Q

When and where will surfactant be produced

A

Type 2 alveolar cell will begin to produce surfactant around 24 weeks gestation and will be stored in the lamellar bodies in they cytoplasm of the alveolar type 2 cells

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19
Q

Surfactant Composition

A

The surfactant produced is composed of phospholipids, lipids, and proteins
Main lipid is dipalmitoylphosphatidylcholine (DPPC)

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20
Q

Surfactant Reabsorption

A

Surfactant will be reabsorbed into the alveolar type 2 cells

Up to 90% of DPPC will be recycled

This is the basis of success for surfactant replacement therapy as the surfactant given will be reprocessed and re-secreted

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21
Q

Function of Surfactant

A

Promotes the homogeneous gas distribution during inhalation and allows a residual volume of gas to be evenly distributed throughout the lung during exhalation and maintain FRC

Lessens the WOB (oxygen consumption)

Optimizes surface area for gas exchange and ventilation perfusion matching

Optimizes lung compliance

Protects the lung epithelium and facilitates clearance of foreign material

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22
Q

In the absence of surfactant what happens to ventilation

A

In the absence of surfactant, distribution of ventilation becomes uneven, the lungs become stiff, and atelectasis ensues during exhalation

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23
Q

Surface Tension

A

Surface tension is a force which is the result of the attraction between like molecules that occurs at a gas-liquid interface

Surface tension forces are present in the alveolus and must be overcome in order to inflate the alveolus

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24
Q

Surfactant and Surface Tension

A

Pulmonary surfactant lowers the surface tension at all lung volumes and a critical function as alveolar surface area decreases during expiration

As surface tension will decrease with a decreased lung volume, alveoli will require different distension pressures when at different sizes
 Small alveoli would empty into large ones and there would be an overall tendency for the lung to coalesce into a smaller number of large alveoli as lung volume diminished.
 This would significantly decrease the surface area for gas exchange as well.
• Surfactant not only decreases surface tension but also reduces it to a greater degree at low lung volume, counter- acting the effects of decreasing alveolar size.

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25
Surfactant Mechanism of Action
1. Lack of endogenous surfactant leads to high surface tension and alveolar collapse during expiration 2. Exogenous surfactant can be distilled down the ETT 3. Surfactant spreads across the inner layer of the alveoli reducing surface tension 4. The established surfactant monolayer will facilitate oxygen diffusion
26
Corticosteroids for pregnant women
• A single course of corticosteroids is currently recommended for pregnant women between 24 weeks and 34 weeks of gestation who are at risk of preterm delivery within 7 days. o This may consist of betamethasone (2 doses, 24 hours apart) or dexamethasone (4 doses, 12 hours apart). o A single rescue course may be considered if the first course was given more than 2 weeks prior in women less than 32 6/7 weeks of gestation who are likely to deliver within the next week. • The full effect on surfactant production is present by 48 hours after the first dose.
27
Bovine Lipid Extract Surfactant (BLES®)
Most common surfactant used in Calgary Kept frozen or refrigerated and then rewarmed to room temperature and no greater than 37o C BLES has lower viscosity and high protein concentration which allows for a rapid distribution
28
BLES Indications
• Rescue treatment for RDS that is confirmed by CXR, require mechanical ventilation with PaO2/PAO2 of < 0.22 o BLES is to be given ASAP once oxygenation criteria met • Prophylaxis for infants < 27 weeks of age • Moderate or severe meconium aspiration syndrome • Contraindicated in patients with active pulmonary hemorrhage • Not studied in infants < 380 grams or > 4460 grams
29
BLES dosing
The recommended dose is 5 ml/kg given via direct instillation Can repeat dose up to 3 times within the first 5 days of life when needed
30
Hazards and Complications of Surfactant Therapy can be the result of
o Dosing procedure  Large volumes of the drug will be instilled which can result in blocked gas exchange o Therapeutic effect of the drug itself
31
Hazards and Complications of Surfactant Therapy
• Obstruction during instillation (airway (with debris) and physically with the fluid) leading to desaturations and bradycardia • Increased lung compliance and FRC resulting in high PaO2 o FiO2 must be lowered if PaO2 increase to prevent over oxygenation • Over-ventilation and hypocarbia o As compliance improves peak pressure, baseline pressure and ventilatory rate must be adjusted to avoid overventilation leading to hypocapnia and pneumothorax • Apnea • Pulmonary Hemorrhage – in  700 g at birth 10% incidence o Pulmonary hemorrhage is the only consistent pulmonary complication seen with surfactant delivery o Not seen in infants > 700 grams. o PH more frequent in younger, smaller, males, PDA’s
32
What are exogenous surfactants?
They are administered to replace missing pulmonary surfactant in RDS of the newborn. Artificial Surfactant/not native to the patient.
33
What is surface tension?
It is the force caused by the attraction between like molecules that occurs at liquid-gas interfaces and holds the liquid surface intact.
34
How does surface tension affect the lungs?
The higher the surface tension of the liquid the greater is the compressing force inside the alveolus which can cause collapse or difficulty in opening the alveolus.
35
Would you give surfactant to a 36 week old gestational aged newborn that shows no signs of respiratory distress and has stable vitals?
No, because the proper gestational term for surfactant is 24-29 weeks.
36
What are surface-active agents that lower surface tension?
Surfactant agents.
37
What is another name for surface active agents?
Detergent.
38
What is the force caused by attraction between like molecules that occurs at liquid-gas interfaces and holds liquid surface intact?
Surface tension.
39
What typically results in a lack of surfactant in respiratory distress syndrome of the newborn?
High surface tension.
40
What is surfactant primarily composed of?
Phospholipids.
41
What is endogenous surfactant produced by?
Alveolar type II cells.
42
Where is surfactant produced by type II alveolar cells stored?
Lamellar bodies.
43
What is the major stimulus for secretion of surfactant into the alveolus?
Inflation of the lung via a chemically coupled stretch response.
44
What is the key feature of surfactant production?
The recycling activity.
45
What are the three approved indications for surfactant therapy?
Prophylaxis of RDS in infants with very low birth weight (<1250g), Prophylaxis of RDS in infants with higher birth weight (>1250g), and Rescue treatment in infants with RDS
46
What are currently the two methods used for delivering surfactants into infants?
Instillation through side-port adaptor and instillation through a catheter.
47
With an infant who is currently on a pressure control ventilator, what two things must you keep a keen eye on?
Increasing tidal volumes and decreasing PaCO2 (Hypocapnia).
48
What is the main mode of action for surfactant in neonatal with RDS?
To replace and replenish missing endogenous surfactant pools.
49
What kind of patients should an artificial surfactant be administered to replace missing pulmonary surfactant?
Premature newborns with respiratory distress syndrome (RDS).
50
What does RDS in newborns come from?
A deficiency/lack of surfactant.
51
Between what weeks of gestation is a newborn considered full term?
38-40 weeks.
52
What week range can a baby be considered premature?
<34 weeks
53
Between what weeks of gestation is surfactant usually made?
24-28 week.
54
What is the role/job of surfactant?
To decrease surface tension.
55
Surface tension is a force caused by attraction between like molecules that occur at what interface?
At a liquid/gas interface and holds liquid surface intact.
56
What can high surface tension cause?
The collapse of the alveoli or difficulty in opening the alveoli.
57
What needs to be overcome to get the alveoli open?
Critical opening pressure.
58
What does lowering the surface tension do?
Make it easier to open the alveoli – easier to inflate.
59
What is endogenous surfactant?
Real and made by the body.
60
High surface tension can lead to?
Increased WOB, increased pressure, decreased volumes, and decreased compliance.
61
What can Surfactant do to the body?
Lower surface tension, increase compliance, and decrease WOB.
62
Where is Surfactant made?
In type 2 alveolar cells.
63
What is Surfactant made up of?
Lipids and proteins (almost identical to the body’s surfactant).
64
Where is Surfactant stored?
In lamellar bodies in type 2 cells.
65
What is the major stimulus for secretion of surfactant?
The inflation of the lungs.
66
How is exogenous surfactant given to newborns?
Placed as a liquid down the ET tube (Intratracheal).
67
What must be done to the infant during Surfactant administration? .
The newborn is turned side to side to make sure the surfactant gets to all parts of the lungs
68
Which Surfactant drugs work faster/better?
The ones that are natural/come from animals.
69
How are the surfactant drugs administered?
Intratracheal.
70
What is a normal birth weight for an infant?
3000 grams (6.6 lbs).
71
What should not be performed after administration of Surfactant?
Suctioning for at least 1 hour.
72
What must be done to Surfactant drugs before it is administered?
It must be warmed to room temp (except Infasurf).
73
After the administration of Surfactant, at what degree should the baby’s head be placed?
10 degree for 1-2 hours.
74
What is the mode of action for Surfactant?
Replace/replenish endogenous (body made) surfactant and to be recycled into type 2 cells and form a surfactant pool for the infant.
75
What outcome do you usually see after the administration of Surfactant?
A dramatic increase in oxygenation levels of the infant (you may also see an increased FRC and compliance).
76
What are the hazards/complications of Surfactant administration?
Airway occlusion from fast/large medication delivery – desaturation – bradycardia, high PaO2 – need to lower FiO2 after surfactant administration (Retinopathy of Prematurity), overventilation/hypocarbia (low CO2) (alveoli open suddenly), apnea and pulmonary hemorrhage (most common).
77
What is the most common hazard/complication of surfactant administration?
Pulmonary Hemorrhage
78
What does Surfactant do to the life expectancy of premature infants?
It dramatically increases it.
79
A normal PaO2 for a newborn infant is?
40-70.
80
What must be monitored during Surfactant therapy?
Pulse/Cardiac rhythm, airway occlusion, color/activity level, better chest rise and PaO2, Sat to prevent hyperoxia and hypoxia.
81
What is a normal SaO2 level for an infant?
92%.

Final Review (27 decks)

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