Inhaled Nitric Oxide use in Newborns Flashcards
Where is NO generated naturally in humans
lung endothelium
What does NO do to the bodys physiology
it diffuses into vascular smooth muscle cells
→ activates guanylate cyclase which leads to increased cyclic guanosine monophosphate
→ pulmonary vasodilatation and improve VQ matching
How do you calculate the oxygenation index
OI = (FiO2 x MAP x 100)/PaO2
Who should be treated with iNO
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
What should you do pre iNO
Echo: RO cyanotic CHD and assess pulmonary BP
OI calculation
Are there indications for iNO in premature infants
Respiratory failure secondary to oligohydraminos
NOT: BPD or rescue for very sick
What are the risks of iNO in premature infants
IVH
PVL
+ uncertainty regarding neurodevelopment outcomes
What is the half life of iNO
2-6s
What does do you start at and what is the maximum dose
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
What is considered a positive response to iNO
response should be rapid (within 30 minutes)
increased PaO2 by at least 20 mmHg
When would you wean iNO
after 4-6 hours of stability
O2 decreased to 60-80% or OI falls to less than 10
How do you wean and why do you do it this way
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
What is the typical duration of iNO
96 hours
if the kid still needs iNO at 7 days you should look for other forms of lung and cardiac pathology
Is iNO toxic
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
What is methemoglobin and why does it matter
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%