08 Flashcards
Primary purpose of ABG
Adequacy of oxygenation and ventilation
What measurement on ABG assesses oxygenation BEST
PO2
What measurement on ABG measures ventilation BEST
PCO2
Major hazards of arterial puncture
ARTERY LACERATION
Bleeding/hemorrhage
Blood flow obstruction
Infection at site
Absolute contraindications of arterial puncture
Thrombolytic tx (clot buster)
Abnormal/negative Allen’s test
Dialysis shunt
PVD (lesion/infection)
Relative contraindications of arterial puncture
Coagulopathy Anticoagulation theraypy (warfarin, heparin, etc)
Order of preference for arterial puncture
Radial (R/L), Brachial (R/L), femoral, dorsalis pedis
Purpose of Allen’s test
Test collateral blood flow
What artery do you release on Allen’s test
Ulnar
Positive Allen’s test time for refill
3-5 seconds
Max time for pink color return of positive Allen’s test
10-15 seconds
Correct technique for redirecting needle if first puncture was not placed in artery
Bring needle up until you see bevel, not all the way out
Action for repositioning a needs when pulsation flow prematurely stops
Retract slightly
What degree and what way should the bevel be facing when pulling ABG
45 degree angle, bevel up
You pull ABG _____ flow of blood flow
Opposite
Drug in needle
Heparin
How to prep heparin for ABG
Pump needle
Technique for covering needle for needle without capping device
Scooping
How to prepare sample for lab analysis and max time allowed
Ice within 30 minutes, label, cap, discard needle in sharps
What should be on lab slip that accompanies ABG
Date, time, FiO2, pt ID/DOB, location of puncture
Why is radial puncture preferred?
Safest
Superficial
Easy to Palpate/stabilize
ART line locations
Radial, brachial, femoral,
Air in sample effect on ABG results
Lower PCO2, raise pH
Raises low PO2
Lowers high PO2
How to identify air in sample
Visible bubbles/foam
Low PCO2 inconsistent with pt status
How to prevent air in sample
Remove all bubbles
Discard foamy samples
Mix after air removed
Cap syringe quickly
Effect of venous admixture on ABG results
Raises PCO2
Lowers pH
Can greatly lower PO2
How to identify venous admixture
Failure of syringe to fill by pulsations
Pt has no sx of hypoxemia
How to prevent venous admixture
Avoid brachial/femoral sites Do not aspirate sample Short bevel needle Avoid artery overshoot Cross check w SpO2
Effect of excess anticoagulant (heparin)
Lowers PCO2
Raises pH
Raises low PO2
Lowers high PO2
How to identify excess anticoagulant
Visible liquid heparin in syringe before sampling
How to prevent excess anticoagulant
Remove visible heparin
Collect >2ml (adults)
Collect >0.6ml (infants)
Use dry heparin
Metabolic effects effect on ABG
Raises PCO2
Lowers pH
Lowers PO2
How to identify metabolic effects on ABG
Too much lag time since collection
Values inconstant w pt status
How to prevent metabolic effects in ABG
Analyze within 15 minutes
Place sample in ice bath
ABG troubleshooting
Palpate tOo firm -> inhibits blood flow
Do not reposition more than 2x
Do not stick pt more than 2x
Hold pressure post puncture for
3-5 min
Amt of time to wait before drawing ABG on COPD pt
20-30 minutes
Amt of time to wait before drawing ABG w normal lungs
5-10 minutes
Parameters directly measured by blood gas analyzer
PCO2, pH, PO2
Parameters calculated with blood gas analyzer
Hb saturation (SO2), bicarbonate, base excess
Name of electrode that measures pH
Sanz
Name of electrode that measures oxygen tension
Clark polarographic
Name of electrode that measures carbon dioxide tension
Severinghaus/Stowe-sanz
Types of hemoglobin measured by hemoximeter
Oxyhemoglobin, methemoglobin, CO
How accuracy of blood gas analyzer is determined
Comparing analyzers measurement to know values (given)
Maintenance standard for lab gas analyzers
Calibration
How frequently blood gas machines should be calibrated
1 point every 30 minutes
2 point every 8 hours
Calculation for partial pressure of gas when given concentration of certified gas tank
(PB - 47) x % O2 (or CO2) = PO2 (PCO2)
Random error in ABG analysis and how to fix
Contamination, human error, just happens
One spot on graph off
Recalibrate, rerun controls, rerun sample
Systemic error types/how to fix
System failure:
Trend- gradual loss of reliability
Shift- abrupt movement outside acceptable range
Check function/repair/replace failed components
General acceptable standards of deviation and drift in calibration
PH +/- 0.04, PCO2 and PO2 +/- 3
2 SD
In Vitro oxygen analyzation
Remove blood THEN analyze
In Vivo oxygen analyzation
Measures INSIDE artery
Advantage of point-of-care testing
Fast
When to ice ABG sample
When taken to lab
