Inhaled Nitric Oxide use in Newborns

Question 1

Where is NO generated naturally in humans

Answer 1

lung endothelium

Question 2

What does NO do to the bodys physiology

Answer 2

it diffuses into vascular smooth muscle cells

→ activates guanylate cyclase which leads to increased cyclic guanosine monophosphate

→ pulmonary vasodilatation and improve VQ matching

Question 3

How do you calculate the oxygenation index

Answer 3

OI = (FiO2 x MAP x 100)/PaO2

Question 4

Who should be treated with iNO

Answer 4

35 wks GA and over
Hypoxic respiratory failure not responding to conventional management
OI over 20
PaO2 less than 100mmHg despite 100% FiO2

NOTE: not effective for most kids with CDH

Question 5

What should you do pre iNO

Answer 5

Echo: RO cyanotic CHD and assess pulmonary BP

OI calculation

Question 6

Are there indications for iNO in premature infants

Answer 6

Respiratory failure secondary to oligohydraminos

NOT: BPD or rescue for very sick

Question 7

What are the risks of iNO in premature infants

Answer 7

IVH
PVL
+ uncertainty regarding neurodevelopment outcomes

Question 8

What is the half life of iNO

Answer 8

2-6s

Question 9

What does do you start at and what is the maximum dose

Answer 9

in term:
20 ppm and increase to 40 ppm
above 40 ppm can get toxicity

in preterm:
10 ppm and increase to 20 ppm
They have less methemodlobin reductase so can only tolerate lower doses

Question 10

What is considered a positive response to iNO

Answer 10

response should be rapid (within 30 minutes)

increased PaO2 by at least 20 mmHg

Question 11

When would you wean iNO

Answer 11

after 4-6 hours of stability

O2 decreased to 60-80% or OI falls to less than 10

Question 12

How do you wean and why do you do it this way

Answer 12

you wean gradually: decrease by 50% Q4-6H, once you get to 5 ppm, you wean by 1 ppm Q4H
Discontinue: infant is well on 1 ppm, with PaO2 over 50 and FiO2 less than 60%
You wean slowly because you get down-regulation of endogenous NO production on iNO and abrupt cessation can cause severe hypoxia

Question 13

What is the typical duration of iNO

Answer 13

96 hours

if the kid still needs iNO at 7 days you should look for other forms of lung and cardiac pathology

Question 14

Is iNO toxic

Answer 14

it can be
Main concerns: 
1. production of NO2 - causes pulmonary injury when over 5 ppm
2. methemoglobin
3. decreased platelet aggregation
4. increased risk of bleeding
5. Sufractant dysfunction

Question 15

What is methemoglobin and why does it matter

Answer 15

when NO is absorbed into the blood, it binds with the ion of the heme protein producing nitrosyl-hemoglobin. This is oxygised to methemoglobin.
Need to keep less than 2.5%