Surf Act Ant Replacement

SURFACTANT REPLACEMENT THERAPY

Ghazi Husein RRT

SURFACTANT

SURFACTANT REPLACEMENT THERAPY

 Pulmonary

surfactant has been recognized for several decades as a complex of phospholipids (90%) and proteins (10%) that is synthesized, stored and secreted by type II cells.

Function  The

function of pulmonary surfactant is to reduce surface tension within the alveolus at the air-liquid interface and thereby greatly decrease the force or pressure required for

In

the absence of adequate quantities of surfactant as a result of surface tension, the alveolus has a force directed to alveolar

 collapsing

alveoli needs greater pressure to produce lung expansion, this is the central feature of infant respiratory distress syndrome (RDS), or hyaline membrane disease (HMD).

 The

assumed role of surfactant deficiency in the pathogenesis of RDS is well established.  Exogenous surfactant administration is one of the cornerstones of therapy for infant respiratory distress syndrome.

Goals and Indications Surfactant replacement therapy has dramatically shortened the course of RDS and improved the prognosis for premature babies.  In fact, this therapy aimed and has proven so effective at reducing mortality in infants associated with surfactant deficiency disease.

Prophylactic administration Prophylactic administration of natural or artificial surfactant may be indicated : 1 - in infants at high risk of developing RDS because of short gestation (<32 weeks) or low birth weight (<1300g), which strongly suggests lung immaturity 

2 - Infants in whom there is laboratory evidence of surfactant deficiency such as lecithinsphingomyelin ratio less than < 2:1 , bubble stability test indicating lung immaturity, or the absence of phophatidylglycerol (PG).

 Rescue

or therapeutic administration indicated in :  (1) preterm or full-term infants who require endotracheal intubation and mechanical

a- increased work of breathing as manifested through  increased in respiratory rate,  substernal and suprasternal retractions,  grunting and

b- increasing oxygen requirements as manifested by :  pale or cyanotic skin color,  agitation and  decreases in PaO2, SaO2 or SpO2 mandating an increase in FiO2 above 0.40 .

(2) those who have clinical evidence of RDS, including chest radiograph characteristics of RDS, mean airway pressure greater than 7 cmH2O to maintain an adequate PaO2, SaO2 or SpO2.

Contraindications  Relative-contraindications-to

surfactant administration are:  1- the presence of congenital anomalies incompatible with life beyond the neonatal period.  2- Respiratory distress in infants with laboratory evidence of lung maturity.

Hazards and Complications Procedural

complications resulting from the administration of surfactant include:

 Plugging

of

ET

tube

by

surfactant  Hb desaturation / need for extra O2  Bradycardia due to hypoxia  Pharyngeal deposition of surfactant   Administration of surfactant to only one lung  Drug dosing errors

 Two

general types of surfactant are available for replacement therapy:  The modified natural surfactants are produced by adaptation of bovine and porcine surfactant.

Surfactant

is first obtained from lungs either by saline lavage of intact lungs or by rinsing minced lung tissue with saline.

 The

natural surfactant is then isolated from the saline suspension by centrifugation, extra phospholipids are added and the protein content is reduced.

Beractant

(Survanta) is a natural bovine extract, currently available.

 The

other type of surfactant that is currently available is referred to as synthetic surfactant.  Exosurf is the only artificial surfactant that is available at present in the United

 This

surfactant is a mixture

of dipalmitoylphospatidylcholi ne, hexadecanol and tyloxapol.  Both preparations are liquid suspensions that are instilled directly into the

Strategies for the Use of Surfactant

There are two fundamental approaches to the use of surfactant replacement therapy:  Rescue therapy is the use of surfactant to treat established RDS or those infants who have already

Prophylactic or at-birth therapy refers to the administration of surfactant shortly after (i.e., within minutes) the birth of an infant known to be at high risk for RDS, without any effort to ascertain whether the child actually develops RDS.  Prophylactic therapy is usually given in the delivery room. 

Monitoring The

following should be monitored as part of surfactant replacement therapy:

 Proper

placement of delivery

device  FiO2 and ventilator settings  Reflux of surfactant in to ET tube  Heart / resp rate, chest expansion, skin color .  Chest-wall movement

Variables to be monitored after surfactant administration Arterial blood gases   Chest radiograph   Ventilator PIP, PEEP, Paw, FiO2   Heart / resp rate, chest expansion, skin color, and vigor  Pulmonary mechanics and volumes  Breath sounds  Blood pressure 