BRTP08 Sampling, Analysis & Hemoximetry Flashcards
Primary purpose of taking arterial blood gases (ABG’s)
Determine adequacy of oxygenation and ventilation.
Major hazards of ABGs
Bleeding
Obstruction of vessel
Infection
Criteria for site selection
- Collateral blood flow
- Vessel accessibility
- Peripheral structures
- Hemodialysis fistula (fistula shunt)
Preferred sites for ABGs
- Radial artery
- Brachial artery
- Umbillical artery (commonly used in newborns)
- Femoral artery
What errors are shown in vitals when there is air in a sample?
Lower PaCO2
Raises pH
Raises low PaO2
Lowers high PaO2
(Will lower or raise PaO2 depending on O2 in blood)
What error is showed in vitals when venous admixture occurs?
Raises PaCO2
Lowers pH
Can greatly lower PaO2
What happens when there is excess anticoagulation?
Lowers PaCO2
Raises pH
Raises low PaO2
Lowers high PaO2
Effect of metabolic effects?
Raised PaCO2
Lowers pH
Lowers PaO2
Sample must be put on ice for 30 mins
What are the known pH values we will be using?
6.82 to 7.383
Acceptable drift limits equal to two standard deviations for pH, PaCO2, PaO2?
pH (+/-) .04
PaCO2 (+/-) 3mmHg
PaO2 (+/-) 3mmHg
How long does it take to reach steady state for normal lungs?
5-10 mins
How long does it take to reach steady state for COPD?
20-30 mins
How long should you wait to draw ABGs from a patient with COPD after making a change in oxygen percentage?
20-30 mins
ABGs reflect lung function and?
- Adequacy of oxygenation
2. Adequacy of ventilation
What is the most sensitive indicator of oxygenation directly measured?
PaO2
High PaCO2 is related to what?
Drowsiness
What is the best way to evaluate the adequacy of ventilation?
PaCO2
What are non respiratory values typically referred to as metabolic values?
HCO3 Base Excess (BE)
Contraindications to ABG sampling?
Thrombolytic therapy (clot buster)
No collateral blood flow
Surgical arteriovenous shunt (dialysis shunt) (AV)
Lesions
Infection
Evidence of PVD aka peripheral vascualr disease
Hazards of ABG Sampling
Bleeding and hemorrhage Artery laceration (most serious) Hematoma and bruising Low platelet count (thrombocytopenia) Anticoagulants Obstruction of blood flow Infection of the puncture site
Other hazards of ABG sampling
Nerve damage Pain Air or clotted blood Vasovagal response (someone strains and passes out) Self puncture
What is the preferred site for an ABG and why?
Radial artery Safest Superficial (near surface) Collateral circulation Not near any large veins
Second most common site if ABG and why?
Brachial artery
Requires additional training and riskier due to insufficient collateral circulation
Riskiest ABG site?
Femoral artery
Typically Only performed by physicians
Additional training
Alternate site or 3rd in line for ABG?
Dorsal pedis artery or pedal artery
Has collateral flow
Additional training
What indicates a positive allens test?
After squeezing ulnar and radial artery, color (flushing) returns to hand
What size needle is used for ABG in adults
22-25 gauge needle
How do you assess for a puncture site?
Allens test
Ensure no AV shunt
What is a flash?
A spurt of blood
If you see a flash but it stops prematurely what happened?
The needle went through the artery
Air bubbles effect on PaCO2?
Air bubbles will ALWAYS decrease PaCO2
What 3 things do blood gas analyzers measure?
pH
PaCO2
PaO2
Values calculated durint blood gas analyzation?
Hb saturation Plasma bicarbonate (HCO3) Base Excess (BE)
What electrode measures pH?
Sanz Electrode
What electrode measures PCO2?
Severinghaus or Stowe
What electrode measures PO2?
Clark polarographic electrode
“In vivo” meaning
Analzying INSIDE the artery
“In vitro” meaning?
Removing blood then analyzing
Outside of body
What is used for quality control?
Levey-jennings chart
How do random errors occurs in levey jennings chart and how do you correct them?
Can just happen, or caused by sample contamination or mishandling
Will be a singular error
Recalibrate, rerun controls and samples
How do systematic errors occur and how ste they corrected?
Can be caused by contaminated buffets, incorrect gas concentrations, component failure.
To correct, check function, repair or replace failed components
Will be a group of errors
What are the two types of systematic errors?
Trend- gradual loss of reliability (subtle change) will look like a slope
Shift- abrupt movement outside of acceptable range