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Neonatal Intensive Care Monitoring
Overview– Neonatal Blood Gases
– Pulse Oximeters
– Neonatal Hemodynamic Equipment
– Transcutaneous Monitors
Neonatal Blood Gases - Sampling Possibilities
Arterial Gases Venous Gases Capillary
Arterial Gases
Radial, Brachial, Temporal Punctures Radial Artery Line Umbilical Artery Gases Umbilical Artery Catheter (UAC) Preductal placement vs postductal
placement
Venous Gases
Drawn from Umbilical Venous Catheter (UVC)
Not desirable but......
Capillary Gases
Drawn from heel Procedure: – heel warmed to ‘arterialize’ blood
– lancet puncture
– blood flows, trapped in capillary tube
Preferred Sites
Variability in Cap Gases
Warming time Amount of contact with air Squeezing blood As a result, not desired but .......
Comparative
pH pCO2 HCO3 PO2
Arterial 7.4 40 24 60-80(term)
Arterial 7.4 40 24 50-70(preterm)
Capillary 7.4 40 24 40-50
Venous 7.35 45 24 35-45
Pulse Oximeters
Sites of attachment
(foot and hand) Preductal placement in first twelve hours
(right hand)
Pulse Oximeters
Reads high
– Methemoglobin
– Caboxyhemoglobin
– Jaundice Reads low
– Medical dyes Other causes of inaccuracy
– Motion
– Hypothermia/vasoconstriction
– Hypotension
– Excessive ambient light on sensor probe
Hemodynamic Monitoring
Umbilical Artery Catheter (UAC) preferred
UAC Insertion Procedure
Insertional position 1/3 length heel to crown Procedure– sterile field and drape
– purse string suture around umbilicus
– cut cord and snug
– tease umbilical artery open
– insert catheter
– fix position
– follow with CXR
Monitoring UAC Post Insertion
Position of catheter tip
(aortic arch is preductal and not preferred) Normal position above diaphragm
(low position is L3-L4) Monitor leg color of
infant
(blanching indicates obstruction of flow)
Indwelling UAC Gases
Orange Medical Company PO2 electrode at tip of catheter Provides continuous reading
Cathode
Anode
Transcutaneous Gas Monitors
Useful as ‘trend’ monitor Can detect hypoxemia, hyperoxemia Can detect hypocarbia, hypercarbia Also responds to changes in blood flow
Types of Transcutaneous Monitors
Single Electrode Models PO2 most common
Types of Transcutaneous Monitors
Dual element electrodes PO2 and PCO2 Called TcPO2 and TcPCO2
Principle of Operation Tc Monitors
Heated electrode placed on skin Temperature 43 to 45 C ‘Arterializes’ sample Gas diffuses through skin
Calibration of Transcutaneous Monitors
Requires high and low calibration TcPO2– Can be done with chemical zero and room air
–Most commonly done with cylinders
Calibration value = Concentration of gas in cylinder x Pb
Calibration value = .1 x 760 = 76 mm Hg
Using a cylinder that contains 10% O2, what would be the calibration value of a TcPO2 device if the barometric pressure was 760?
Calibration of TcPCO2 Devices
Similar to TcPO2 except....... 1.6 is the factor that accounts for heating
increasing CO2 production
Calibration value = Concentration of CO2 x Pb1 .6
Calibration value = .1 x 760 = 76 = 47.51 .6 1 .6
Normal Transcutaneous Gases
TcPCO2 is 35 to 45 torr TcPO2 is 50 to 70 torr
Advantages of Transcutaneous Monitors
Decreased number of ‘sticks’– cost reduction
– lower infant risk (less invasive)
Trend tool– blood sample provides ‘view’ at one moment
– gases values wander (+ 7 torr)
– infant reaction to sample varies
Problems with Transcutaneous Monitors
Labor Intensive– Change site every 4 to 6 hours or more
– Limited choices for attachment
– (site must have perfusion)
– Air leak around electrode
Burns– called ‘hookies’ after Huch
Interpretation of Tc Results
Air leak under electrode– TcPCO2 reading near zero
– TcPO2 reading near PbO2
Decreased perfusion under electrode– TcPCO2 will increase
– TcPO2 will decrease