Pulmonary Hypertension

Question 1

What is hypoxia?

Answer 1

a relative deficiency of oxygen in arterial blood

Question 2

What is the clinical significance of OI?

Answer 2

to determine the severity of hypoxemia

Question 3

What is the OI calculation?

Answer 3

OI= (FiO2 x MAP)/ PaO2

Question 4

What are the mechanisms by which decreased delivery of oxygen to the tissues can occur?

Answer 4

1) decreased amount of O2 in the blood
2) anemia
3) decreased perfusion

Question 5

What is the expected OI of an infant with HMD?

Answer 5

8-10

Question 6

What sustained OI is an indication for ECMO?

Answer 6

> 40

Question 7

What is one of the most common reasons to require ECMO?

Answer 7

pphn

Question 8

What are the causes of pulmonary hypertension as categorized by primary disease process?

Answer 8

1) lung dysfunction (MAS, RDS, PNA, CDH, pulmonary hypoplasia)
2) pulmonary vascular (idiopathic- pulmonary arteries can constrict all by themselves w/o comorbid lug dz- rare)
3) cardiac dysfunction

Question 9

How can cardiac dysfunction cause pulmonary hypertension?

Answer 9

poor contractility (or development) of LV, causes blood to back up creating LA hypertension and back up into the pulmonary vasculature

Question 10

What is the definition of PPHN?

Answer 10

a clinical, pathologic syndrome a/w various lung dz or idiopathic; previously referred to as persistent fetal circulation

Question 11

What is the incidence of pulmonary hypertension?

Answer 11

2 per 1,000 live births

Question 12

What is the associated mortality with pulmonary hypertension?

Answer 12

11%-48%; mortality is bad if you don’t have access to iNO or ECMO

Question 13

What is the clinical presentation of pulmonary hypertension?

Answer 13

1) marked pulmonary hypertension and vasoliability
2) labile hypoxemia (caused by extrapulmonary R>L shunting at PFO or PDA)- independent of FiO2
3) tachypnea
4) respiratory distress- rtx. nasal flaring
5) progressive cyanosis
* clinically at the bedside what you will see is marked sat lability with an inability to oxygenate

Question 14

Why did PPHN used to be called persistent fetal circulation?

Answer 14

in utero, pulmonary HTN is an expected developmental mechanism; pHTN after birth is apathological process as a failure to transition to extrauterine life; clinical symptoms reflect underlying pulmonary dz

Question 15

Regardless of etiology, what are the common threads underlying PPHN?

Answer 15

1) elevated pulmonary resistance
2) pulmonary vasoconstriction
3) altered pulmonary reactivity

Question 16

What is the end result of altered vascular reactivity?

Answer 16

• results in high pulmonary pressure, which may lead to:
• R>L shunting across FO
• R>L shunting across DA
• tricuspid regurg

Question 17

What is the key finding with PPHN?

Answer 17

increased pulmonary vascular resistance; blood is not having trouble at the alveolar level, but difficulty accessing the alveoli

Question 18

What is the effect of PPHN on the right side of the heart?

Answer 18

b/c blood can’t get out of the heart to the lungs, there will be a back up of blood and will follow the path of least resistance. increased RV pressure and subsequently RA, perpetuating R>L intracardiac shunt (PFO) into LA.

Question 19

What is the clinical presentation in the cardiac exam of PPHN?

Answer 19

because the RV is working so hard, you frequently have a murmur as blood regurgs across the tricuspid valve. persistent condition may lead to RV dilation.

Question 20

How is CO affected by intrauterine stress?

Answer 20

only 7% of combined CO goes to the lungs and when stressed, can be reduced to 1%

Question 21

How does the mechanism of intrauterine stress manifest?

Answer 21

the more stressed a fetus is, the better they are at “clamping down” and preventing blood from flowing into the pulm vasculature- this is a protective, evolutionary mechanism
*PPHN babes usually have a h/o stress prior to birth

Question 22

What type of intrauterine stressors contribute to PPHN post delivery?

Answer 22

1) the sicker the MOB
2) the worse intrauterine environment
3) the lower available O2
4) high altitude
5) meconium stress
6) post dates
all contribute to the infant’s ability to R>L shunt; the longer the baby has been stressed, the more hypertrophied the vessels

Question 23

What is an extrapulmonary shunt?

Answer 23

R>L shunting across fetal channels: FO or DA

if an infant has a h/o stress and has concomitant lung dz, infant will try and persist in fetal circulation

Question 24

Why is prophylactic PDA closure not helpful in the PPHN course?

Answer 24

ligation of the ductus doesn’t change pressure in the lungs and therefore doesn’t force blood into the right side. the end result was right side dilation and right sided heart failure, which can lead to death

Question 25

What should be the aim of PPHN interventions?

Answer 25

opening the pulm veins and arteries to limit R>L shunting. the problem is not the ductus, the problem is the elevated pressures in the pulmonary beds.

Question 26

How is PPHN diagnosed?

Answer 26

• hyperoxia test
• ECHO
• Differential PaO2 or SaO2
• cardiac cath
• hyperventilation

Question 27

What is an infant with PPHN’s response to the hyperoxia test?

Answer 27

not responsive; they have a large V/Q mismatch- make sure the lungs are inflated and its not the lungs fault that the baby is not responding to O2; differential is PPHN v CHD

Question 28

What are the interventions that can improve intrapulmonary shunting?

Answer 28

surf, good CXR, good expansion, gentle mechanical ventilation, increased PEEP

Question 29

What ECHO findings are c/w PPHN?

Answer 29

1) elevated PA pressure reliably estimated, compared with simultaneous systemic pressure
2) R>L or bidirectional PDA shunting
3) R>L or bidirectional PFO shunting

Question 30

What is intrauterine PA pressure?

Answer 30

65-50mmHg

Question 31

What is an intrapulmonary shunt?

Answer 31

pulmonary arterial blood that reaches the pulmonary venous side without passing through ventilated areas of the lung

Question 32

What is the standard approach to therapy for PPHN?

Answer 32

1) lung recruitment and supplemental O2
2) avoid overinflation and underinflation
3) assess and optimize cardiac fx
4) avoid acidosis
5) minimize risks a/w mechanical ventilation
6) achieve pulmonary vasodilation (iNO)