ABG Flashcards
How long should color take to return to hand after conducting the modified Allen’s test?
10-15 seconds
What is the most common site for an ABG
The radial aftery
How long do you apply pressure to artery after drawing an ABG
5 minutes
What should you always ask patient before conducting ABG
If they are on anticoagulants. Such as heparin, Coumadin, warfarin, lovenox, or aspirin.
For every 1 mmHg of PaO2 this is how much dissolve O2?
0.003 ml
What is the oxygen carrying capacity for Hb
1.34 ml of oxygen
Gas exchange and transport varies directly with
VA
PA02 equation
Pb - PH20 - PaCO2/0.8
Alveolar air equation
PAO2 = (PB - Ph2O) FiO2 - PaCO2/0.8
Normal PAO2
Normal < 10 mmHg (less than 60 y.o )
What does PvO2 reflect
Tissue oxygenation
Hypoxemia states
Normal = 80-100 mmHg
Mild hypoxemia = 60-79 mmHg
Moderate hypoxemia = 40-59 mmHg
Severe hypoxemia = below 40 mmHg
Hyperoxyemia = over 100 mmHg
What effect does a shift to the left on the HbO2 dissociation curve have
Increases the affinity of Hb for O2
Less easily unloaded to the tissues
What effect does a shift to the right on the HbO2 dissociation curve have
Decreases the affinity of Hg for O2
More easily unloaded to the tissues. (Unloading of O2 to the tissues is assisted.)
Causes of a shift to the left
Increased pH (Bohr effect) Decreased PaCO2 Decreased temperature Decreased 2,3 DPG Increased levels of HbCO MetHb HbF (fetal hemoglobin)
Causes for shift to the right
Decreased pH
Increased PaCO2
Increased temperature
Increased 2,3 DPG
Normal ABG Values
- pH 7.34-7.45
- PaCO2 35-45 mmHg
- PaO2 80-100 mmHg
- HCO3 22-26 mEq/L
- BE
- +/- 2
- SaO2 greater than or equal to 95%
What is the Bohr effect
As the RBC travels to the tissue it releases the O2. This release of O2 is due to the fact that elevated CO2 levels at the tissues, decreases Hb’s affinity for 02
What is the Haldane effect
As O2 combines with the Hb the release of CO2 is enhanced
What is a CO2 of greater than 45 mmHg
Hypercapnia
Respiratory acidosis
Alveolar hypoventilation
Metabolic function is impaired with acidosis, what is the treatment
Increase alveolar ventilation by increasing the rate or increasing the Vt or minute volume
CO2 less than 35
Hypocapnia
Respiratory alkalosis
Alveolar hypoventilation
Treatment for hypocapnia
Decrease alveolar ventilation
Decrease rate
Decrease Vt or minute volume
Henderson-hasselbalch equation
-pH = 6.1 (pk) + log [HCO3]/ [PCO2 x 0,03]
HCO3 < 22 mEq/L or BE < - 2 metabolic acidosis — hypobasemia
What is the treatment
Administer NaHCO3
Metabolic acidosis with a normal AG is generally caused by
Excessive Cl in the plasma
Metabolic acidosis with an increased AG is generally caused by
An increased amount of fixed acids (renal failure, increased keto or lactic acid)
HCO3 greater than 26 or a BE greater than +2 metabolic alkalosis — hyperbasemia
Treatment
Correct electrolyte imbalance or underlying cause
For every 10 torr decrease in pco2 there is a
.10 increase in pH
For every 20 torr increase in pco2 there is
.10 decrease in pH
-pH electrode —
Sanz electrode
O2 electrode
Clark electrode
CO2 electrode
Severinghaus electrode
Calibration and quality control equation
(PB - PH2O) x % gas used = calibration point
What is a trend
A pattern of six or more results that show an increasing or decreasing pattern. Trends may be caused by worn electronic components, protein contamination on electrodes, or deterioration of electrodes
What is a shift error code
Six or more results falling on the same side of the mean. These may be caused by use of a new batch of quality controls, electronic component deterioration, use of new reagents or an incorrect calibration
What is a random error
Causes out of range points to occur. This can be cause by operator mishandling of the sample, sample contamination or just the statistical probability of an occasional out of point range.
How long does an abg last with air bubbles in the sample or with ice
> 30 minutes
What happens if an abg is left at room temperature
Pao2 decreases, PaCO2 increases, HCO3 decreases, pH decreases
