6Acceptable ABGs: Sick Baby pH: 7.25 – 7.35PaCO2: 35-55Depends on pHPaO2: 50-70HCO3: 18-21B.E.: +/- 2%sat: 90% or >
7Capillary gases use the same values EXCEPT for PO2 Capillary PO2: 35-50Capillary %sat: 75-85%
8Why 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 PaO2Presence of HBFDecreased 2,3-DPGNeonate not considered hypoxemic until PaO2 is less than 50!
9Cyanosis Classic definition: 5 grams% of unsaturated hemoglobin Infant may not show signs of cyanosis until PaO2 < 40 (%sat between 75-85%)
10Effects of Hypoxia Decreased tissue oxygenation Lactic acidosis HypoglycemiaIncreased PVR and PAPMay allow shunting across ductus arteriosus or foramen ovaleDecreased surfactantWorsening of hypoxemiaDecreased thermogenesisCold stress/hypothermiaBrain & CNS damage
11Hyperoxia may damage the neonate’s eyes and/or lungs Hyperoxia: PaO2 > 100Hyperoxia may damage the neonate’s eyes and/or lungs
12Retinopathy of Prematurity (ROP) Hyperoxia causes vasospasm and ischemia in retinal arteriolesIschemia and compensatory vasodilation and proliferation causes retinal edema which may lead to detachment and blindnessROP incidence increases with these three factors:Prematurity, hyperoxia (it’s the PaO2, not the FIO2), and the duration of O2Vitamin A and/or E may help prevent it
13O2 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 surfactantInflammatory exudate and hyaline membrane formationSloughing of alveolar epitheliumFibrosis
14Management 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 mmhgAvoid Flip-Flop phenomenonChanging FIO2 by more than 5-10% at one time may cause sudden deteriorationThe longer the infant is on O2, the more prone he is to Flip-FlopIt is not unusual to limit changes in FIO2 to 1-2%!
16Nasal Cannula Should be used with a blender One or both prongs may be removedSpecial flowmeters allow flows of less than 1 LPM to be usedVapotherm– high humidity and flow through cannula, e.g. 5-6 LPM
17Hoods Best to use a blender to flood the hood with a precise FIO2 Flow needs to be 5-7 LPM to flush out CO2Noise inside hood may be damaging to infants hearingNote: A heated, humidified flow of LPM may be used in isolette