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