2. LEARNING OBJECTIVES
Understand key difference between fetal & neonatal circulations and
physiological transition at birth
Definition -PPHN
Etiology & Pathophysiology
Diagnosis & Treatment
take home message
3. FETAL CIRCULATION
Lungs filled with fluid, no gas exchange
the placenta is the organ of gas exchange
pulmonary vasoconstriction > HIGH PVR due to low O2
right-to-left >foramen ovale and ductus arteriosus,
4.
5. TRANSITION AT BIRTH
PVR decreased
lung fluid is replaced with air to establish gas exchange
increase O2 which is potent vasodilator
Rapid increase in pulmonary blood flow(8 to 10 fold)
SVR increased
the umbilical cord is clamped> SVR
closing FO & DA.
6. TRANSITION OF CIRCULATION AT BIRTH
progressive fall in pulmonary vascular resistance (PVR)
immediate rise in systemic vascular resistance (SVR)
FAILURE OF TRANSITION
PVR > SVR
SHUNTING RT > LT ( FORAMEN OVAL & DA)
POOR XYGENATION
7.
8. DEFINITION
Persistent pulmonary hypertension of the newborn (PPHN) is defined as the
failure of the normal circulatory transition at birth.
It is a syndrome characterized by marked pulmonary hypertension that causes
labile hypoxemia due to decreased pulmonary flow and right-to-left of blood.
PPHN previously described as PERSISTENT FETAL CIRCULATION
9.
10. EPIDEMIOLOGY
The prevalence of PPHN -1.9 per 1000 live births
High risk factors for PPHN:
GA 34 to <37 weeks (late preterm), Term, post-term
Male infants
LSCS
Maternal diabetes
11. ETIOLOGY & PATHOGENESIS
PPHN
Three types of abnormalities of the pulmonary vasculature
maladaptation ( secondary PPHN, most common type)
underdevelopment
maldevelopment
12. MALADAPTATION
PPHN secondary to lung parenchymal disease
the pulmonary vascular bed is normally developed. However, adverse perinatal
conditions cause vasoconstriction and interfere with the normal postnatal fall in
PVR.
MAS, RDS,TTN,Pneumonia,Sepsis,Perinatal asphyxia
13.
14. UNDERDEVELOPMENT
pulmonary hypoplasia
congenital diaphragmatic hernia (CDH),
cystic adenomatoid malformation,
Potter sequelae,obstructive uropathy,(severe oligihydromnias)
uncommon but mortality risk is high.
15. MALDEVELOPMENT
Idiopathic pulmonary hypertension accounts for approximately 10% of the
cases of PPHN.
Normal lung parenchyma & no parenchymal lung disease.
remodeling of their pulmonary vasculature, with vascular wall thickening
hyperlucent lung fields on radiography(black lung PPHN).
16.
17.
18. CLINICAL MANIFESTATIONS
PPHN present within the first few hours of life(<8hrs)
Hall mark- labile hypoxemia & RD
Differential cyanosis
Pre – post ductal Spo2 difference >10% or Pao2 10-20mm Hg
Heart Signs-
Loud single 2ndsound & harsh systolic murmur(TR)
20. ECHOCARDIOGRAPHY IN PPHN
Direction of blood flow in DA & FO( Rt-to-Lt shunting)
Flattened or Bowing of IVS
Tricuspid regurgitation (TR) jet
right ventricular dilatation,
Exclude Cyanotic CHD
21.
22. OXYGENATION INDEX(OI)
Severity of PPHN
OI = [MAP x FiO2 ÷ PaO2] x 100
OI < 15-20(mild)general supportive care
OI ≥20-25(moderate)usually need HFOV & INO.
OI >40 (severe)ECMO
25. SUPPORTIVE MANAGEMENT
Maintaining a normal body temperature
Correction of acidosis
Minimal stimulation/handling
Sedation(fentanyl, morphine, midazolam)
Paralysis should be avoided if possible due to increased mortality
Maintain BP > GA
26. MECHANICAL VENTILATION
Almost always necessary for the newborn with PPHN.
The goal of mechanical ventilation
Optimal lung recruitment
Adequate lung expansion(8-9 ribs expansion on CXR)
Gentle ventilator strategies
optimal PEEP, relatively low PIP/MAP or Tidal volume
28. TARGET OXYGEN & BLOOD GAS
Maintaining preductal Spo2 90-97%
Post ductal O2 saturation in 70s and 80s may be acceptable
Ph >7.25,peferably 7.30-7.40
Pao2:55-80)
Pco2 40-50
Serum lactate < 3 mM/Lt,
UOP is adequate(>1ml/kg/hr)
29. SURFACTANT
Recommended in infants with secondary PPHN
Early administration associated with better outcome
Reduces need for ECMO & Mortality
Unclear whether surfactant is beneficial in CDH but recommended
39. SILDENAFIL
If blood pressure is relatively stable but hypoxemia persists
PDE 5 inhibitor > increase cGMP > vasodilatation
Dose oral 1-2mg/kg/dose 6hrly(preferred),
Reduced rebound pulmonary HT during INO weaning
Hypotension,Careful monitoring of BP during therapy
40.
41. MILRINONE
If BP is normal but evidence of ventricular dysfunction
PDE3 Inhibitor >increase cAMP>relaxes pulmonary arteries
Loading dose IV 50mcg/kg over 30-50min maintainance dose 0.3-1mcg/kg/min
BP should be closely monitored due to systemic hypotension
42. OTHER VASODILATORS
Bosentan
Prostacyclins
MgSo4
Recombinant human superoxide dismutase(SOD)
Apocynin - NADPH Oxidase inhibitor
43. OUTCOME & FOLLOW UP
Mortality related to PPHN has been declining <20-25%
Those who survive have long-term consequences like
neurodevelopmental and cognitive impairment (25%)
hearing difficulties(23%)
Essential to provide long term multidisciplinary follow up
44. Premature infants
Increasingly diagnosed in extremely PT infants
Some with RDS presents with PPHN in first few days
Some with BPD diagnosed PHN later distinct from PPHN with more protracted
course and it challenging with significant mortality
CDH
Important cause of pulmonary hypoplasia resulting in PPHN
Mortality and need for ECMO remain high
Alveolar capillary dysplasia.
Malalignment of pulmonary vasculature
Present with RF and unremitting PPHN carries 100% mortality
Neonates who fail to respond consider lung biopsy to rule out
45. TAKE HOME MESSAGE
PPHN is serious problem associated with with significant mortality & morbidity
PPHN often secondary to parenchymal lung disease
Diagnosis based on clinical and confirmed by ECHO
Management has significantly improved in last 2decades
Emphasis on gentle ventilator strategies for optimum lung recruitement
INO and HFV improved outcome and reduce the need for ECMO