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Persistent Pulmonary Hypertension of the Newborn John Salyer RRT-NPS, MBA, FAARC Director Respiratory Therapy Seattle Children’s Hospital and Research Institute. Sense and Sensibility??!?.

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Persistent Pulmonary Hypertension of the NewbornJohn Salyer RRT-NPS, MBA, FAARCDirector Respiratory TherapySeattle Children’s Hospital and Research Institute

sense and sensibility
Sense and Sensibility??!?
  • Of the deaths in England in 1859, no less than 184,264 -- two in every five of the deaths of the year -- were of children under five years of age
  • Above half of these -- 105,629 -- had scarcely seen the light, and never saw one return of their birthday.”
  • 43 to 45 infant deaths take place in every 100 births -- 45 per cent! Almost half of the children who are born, die -- perish miserably!
  • And this is far from representing the whole mass of pain and suffering, which it is the calamity of children to endure.”

M.A. Barnes 1862: Excessive Infant Mortality: How Can It Be Stayed?

British Social Science Association

it s the best time to be alive so far
It’s the Best Time to Be Alive(So Far)

Respiratory Care Service-CHRMC

pphn pathophysiology
PPHN Pathophysiology
  • Pulmonary hypertension is a normal and necessary state for the fetus
  • In utero, only 5 -10% of the combined ventricular output is directed to the pulmonary vascular bed.
  • 80% of drop in pulmonary artery pressure occurs in 1st 24 h, by local vasodilatation
  • Neonatal vessels greater vasoconstrictive response
  • Oxygen vasodilates vessels
  • Hypoxemia may release vasoconstrictive mediators, perpetuating vasospasm
pphn pathophysiology1
PPHN Pathophysiology
  • At Birth
    • Rapid  PVR and  in pulmonary artery pressure
    • 10-fold rise in pulmonary blood flow.
    • Signals for these transitional changes
      • mechanical distension of the lung,
      •  PaCO2,
      •  PaO2
epidemiology
Epidemiology
  • Severe PPHN has been estimated to occur in 2 out of 1000 live-born term infants, and
  • Some degree of pulmonary hypertension complicates the course of more than 10% of all neonates with respiratory failure.
  • Respiratory failure and hypoxemia in the term newborn results from a heterogeneous group of disorders, and the therapeutic approach and response often depend on the underlying disease.
  • Idiopathic pulmonary hypertension is responsible for 10-20% of all infants with PPHN.

Respiratory Care Service-CHRMC

slide11

PPHN: Pathophysiology

Clin Perinatol 11: 525, 1984.

slide14

Pulmonary Vascular Resistance

  • Pulmonary venous return
  • LA pressure

Ventilation

Foramen Ovale closes

L -> R ductusarteriosus shunt

  • PO2
  • RA pressure
  • IVC Return

DuctusVenosus Closes

Remove Placenta

  • Umbilical venous return
  • Systemic Vascular Resistance
slide15

Effects of lung volume on PVR

A

Extra alveolar vessels have high resistance at low and high lung volumes

B

Alveolar vessels compress with lung inflation

transition

Decreased PVR

Vasodilation

Hypoxia/low pH

Pulmonary problems

Endothelin-1 (hypoxia induced)

ThromboxaneA2 (hypoxia induced)

Leukotrienes C4 and D4

Platelet-activating factor

Low production of vasodilators (PGI2 and NO)

Overinflation/Underinflation

Excessive muscularization

Altered mechanical properties

of smooth muscle

Fetal vasculature opposing vasodilation

Hypothermia (pulmonary venous constriction)

Polycythemia

NO

PgI2

PDE5

Adenosine

ATP

Magnesium

Bradykinin

Atrialnatriuretic

factor

Oxygen

Lung inflation

Structural changes

in endothelial cells

Changes in interstitial

fluid and pressure

Shear stress

Transition

Increased

PVR

Vasoconstriction

1 pphn mechanisms lung disease
1) PPHN mechanisms: Lung disease

Abnormally constricted pulmonary vasculature

  • MAS
  • Pneumonia
  • RDS

MAS

GBS pneumonia

RDS

postulated pathogenic mechanisms
Postulated Pathogenic Mechanisms
  • Repeated intrauterine closure of ductus
    • May occur in Mothers taking high dose Aspirin near term
  • Abnormal responsiveness of pulmonary vasculature to hypoxia with inability to relax after stimulus is removed – birth asphyxia
  • Repeat intrauterine hypoxia = hypertrophy of medial muscles surrounding pulmonary arterioles
  • Pulmonary hypoplasia
  • Alterations in vasoactive mediator levels
    • Mediators participate in transition from fetal to neonatal circulation
    • Nitric Oxide is one mediator
  • Microthrombus formation in pulmonary vascular bed
    • Most often associated with perinatal asphyxia, hypoglycemia, hypocalemia and sepsis

Respiratory Care Service-CHRMC

pphn diagnosis
PPHN: Diagnosis
  • Suggested by hypoxemia out of proportion to severity of lung disease
    • Swings of oxygenation without ventilator change
    • Inability to maintain PaO2 > 60 in 100% O2
  • Gradient in preductal (right radial) and postductal PaO2 (>20 mm Hg) or O2 saturations (> 6%)
  • Oxygenation Index (OI) > 15-20
  • Echocardiogram: document shunting, PA pressure
diagnosis of pphn
Diagnosis of PPHN
  • Term or near term
  • Cyanosis
  • Respiratory distress
  • Normal X-ray
    • Unless aspiration, Hyaline membrane disease, CDH

Respiratory Care Service-CHRMC

three classifications of pphn
Three Classifications of PPHN
  • Primary PPHN
    • Radiographically normal lungs, no evidence of parenchymal disease
  • Secondary PPHN
      • Hyaline Membrane Disease
      • Meconium Aspiration
      • Aspiration Pneumonia
      • Transient Tachypnea of the Newborn
      • Sepsis-Group B Strep
  • Associated with Hypoplasia of the Lungs
    • Most often Congenital Diaphragmatic Hernia

Respiratory Care Service-CHRMC

pphn treatment 1
PPHN: Treatment #1
  • Confirm diagnosis of PPHN (R/O Heart Disease
  • Correct underlying abnormalities:
    • metabolic (hypocalcemia, hypoglycemia)
    • acidosis
    • hypothermia
    • polycythemia,
    • sepsis
    • surfactant Txfor IRDS
    • evacuate pneumothoraces
pphn treatment 2
Maintain pH 7.35-7.50

Try high frequency ventilation

Consider sedation, paralysis

Induce metabolic alkalosis

Elevate systemic pressure

Maximize cardiac output (preload, and Dobutamine)

PPHN: Treatment #2

Ventilation strategies

Other Strategies

  • Consider NO if OI > 20
  • Consider ECMO if OI >40
treatment of pphn
Treatment of PPHN
  • Early diagnosis
  • Improve alveolar oxygenation
  • Minimize pulmonary vasoconstriction
    • Hyperventilation – CO2 above 25 mmHG
    • Work to reduce pulmonary trauma
    • Consider different forms of ventilation
  • Sedation and paralytics
  • Consider induction of alkalotic state – sodium Bicarbonate
    • Vasoconstriction appears related to intracellular pH rather than CO2 levels
    • End product of sodium bicarbonate is increased CO2

Respiratory Care Service-CHRMC

treatment of pphn continued
Treatment of PPHN Continued
  • Maintain systemic blood pressure and perfusion
    • In theory increasing systemic arterial pressure may result in decreased right to left shunt – improving oxygenation
    • Dopamine and Dobutamine are frequently used
  • Nitric Oxide
    • Free radical gas
    • Increases cyclic GMP in smooth muscles = vascular relaxation
    • Must get to pulmonary capillary bed

Respiratory Care Service-CHRMC

treatment of pphn continued1
Treatment of PPHN Continued
  • Vasodialators
    • Tolazoline (Priscoline)
      • Appears to be a alpha-sympathetic blocker = vasodialator
      • Can cause large drops in systemic vascular blood pressure
      • Can be administered through endotracheal tube
  • Prostaglandin 12
    • Major endogenous vasodialator in lung
    • Normally produced when pulmonary vessels are constriced
    • May be helped if Tolazoline has failed
  • ECMO

Respiratory Care Service-CHRMC

contraindications for ino use
Contraindications for iNO use
  • Congenital heart disease that is dependent on right-to-left shunting across ductusarteriosus
      • Critical Aortic Stenosis
      • Interrupted Aortic Arch
      • Hypoplastic Left Heart Syndrome
  • May worsen pulmonary edema in patients with TAPVR due to the fixed venous obstruction
prostacyclin pgi 2 analogues
Prostacyclin (PGI2) Analogues
  • Stimulates membrane bound adenylatecyclase, increases cAMP
  • Acutely relaxes vascular smooth muscle
  • Inhibits pulmonary artery smooth muscle cell proliferation in vitro; inhibits platelet aggregation; ameliorates endothelial injury
  • Reverses vascular remodeling
  • Reduces synthesis and clears ET-1
  • Exerts positive inotropic effects
prostacyclin pgi 2 analogues1
Prostacyclin (PGI2) Analogues
  • Continuous i.v. infusion of epoprostenol (Flolan™)
  • Costly, ½ life 3-5 minutes
  • Escalation of dosing is frequently required
  • Acute withdrawal can lead to fatal PH
  • May lower systemic vascular resistance, worsening ductal or atrial level R -> L shunt
  • May worsen intrapulmonary shunts by vasodilating non-ventilated areas of the lung
outcomes
Outcomes
  • Before ECMO death rates were above 50%, with ECMO death rates are about 15%
  • Status post ECMO neonates have reported 45% morbidity rates
  • Moderate to severe lung disease
  • With high alkaline states, can have some degree of deafness
  • Right ventricular hypertrophy
  • With CDH, can have many residual complications

Respiratory Care Service-CHRMC