1. ABGs and Oxygenation
RC 290

2. ABG Sampling Sites Umbilical artery catheter (UAC)
Clots may form on the end
Remember, it is post-ductal blood so the PaO2 may be lower than pre-ductal PaO2

3. ABG Sampling Sites: Punctures
Radial artery and temporal artery
Can be hard to hit
Brachial should not be used
NEVER use the femoral artery in an infant!

4. ABG Sampling Sites: Capillary
Easier to puncture than radial or temporal artery
PO2 may not correlate well to PaO2
Heel has to be warmed prior to puncture to “arterialize” the site

5. ABG Values: Well Baby pH: 7.30 – 7.45 PaCO2: 35-45 PaO2: 60-90
HCO3: 18-21
B.E.: +/- 2
%sat: 90% or>

6. Acceptable ABGs: Sick Baby
pH: 7.25 – 7.35
PaCO2: 35-55
Depends on pH
PaO2: 50-70
HCO3: 18-21
B.E.: +/- 2
%sat: 90% or >

7. Capillary gases use the same values EXCEPT for PO2
Capillary PO2: 35-50
Capillary %sat: 75-85%

8. Why lower PO2 values Are acceptable in the neonate
O2 dissociation curve is shifted to the left so affinity is increased – hemoglobin saturates at a lower PaO2
Presence of HBF
Decreased 2,3-DPG
Neonate not considered hypoxemic until PaO2 is less than 50!

9. Cyanosis Classic definition: 5 grams% of unsaturated hemoglobin
Infant may not show signs of cyanosis until PaO2 < 40 (%sat between 75-85%)

10. Effects of Hypoxia Decreased tissue oxygenation Lactic acidosis
Hypoglycemia
Increased PVR and PAP
May allow shunting across ductus arteriosus or foramen ovale
Decreased surfactant
Worsening of hypoxemia
Decreased thermogenesis
Cold stress/hypothermia
Brain & CNS damage

11. Hyperoxia may damage the neonate’s eyes and/or lungs
Hyperoxia: PaO2 > 100
Hyperoxia may damage the neonate’s eyes and/or lungs

12. Retinopathy of Prematurity (ROP)
Hyperoxia causes vasospasm and ischemia in retinal arterioles
Ischemia and compensatory vasodilation and proliferation causes retinal edema which may lead to detachment and blindness
ROP incidence increases with these three factors:
Prematurity, hyperoxia (it’s the PaO2, not the FIO2), and the duration of O2
Vitamin A and/or E may help prevent it

13. O2 Toxicity in the Lungs Here it is the FIO2 which causes high PAO2
This causes the following pathological changes:
Decreased alveolar volume, ie decreased FRC (why?)
Increased surface tension due to decreased surfactant
Inflammatory exudate and hyaline membrane formation
Sloughing of alveolar epithelium
Fibrosis

14. Management of O2 Therapy
Keep PaO2 between 50-70!
For hypoxemia on 21%, start FIO2 between 25-35%
Use guideline that 1% change in FIO2 will maximally change PAO2 by 7 mmhg
Avoid Flip-Flop phenomenon
Changing FIO2 by more than 5-10% at one time may cause sudden deterioration
The longer the infant is on O2, the more prone he is to Flip-Flop
It is not unusual to limit changes in FIO2 to 1-2%!

15. O2 Therapy Devices

16. Nasal Cannula Should be used with a blender
One or both prongs may be removed
Special flowmeters allow flows of less than 1 LPM to be used
Vapotherm– high humidity and flow through cannula, e.g. 5-6 LPM

17. Hoods Best to use a blender to flood the hood with a precise FIO2
Flow needs to be 5-7 LPM to flush out CO2
Noise inside hood may be damaging to infants hearing
Note: A heated, humidified flow of LPM may be used in isolette