Blood Gas Analysis Flashcards
You want to determine the blood gas analysis at the tissue level, which sample is appropriate to assess?
Venous
Which system of the body can arterial blood gas analysis sample assess?
The pulmonary function and how well the patient is ventilating
What does the PaO2 and the PaCO2 on an arterial blood gas sample tell us?
The PaO2 tells you how well the blood is oxygenated and the PaCo2 tell you how well the patient is ventilating
Which substance in the blood is the most important buffer of acid?
Hemoglobin
How do you calculate the anion gap?
(Na+K) -(CL+ HCO3)
What does the anion gap help us determine?
If there is a mixed acid base disturbance and differentiates causes of metabolic acidemia
What is a blood buffer?
It is a base or a weak acid like extracellular HCO3 or intracellular phosphate, protein, Hb and bone
What does the BE do?
It estimates how much base needs to be added or subtracted to achieve a pH of 7.4
The PaCO2 AND the HCO2 are abnormal in the opposite direction, what is going on?
There is a mixed acid base disturbance within the patients blood
What does the PvO2 value describe?
The level of TISSUE oxygen consumption
What is the 5 x FiO2 rule?
FiO2 measures the inspired O2 level and if value of FiO2 is 5 x greater, there is poor lung function or hypoventilation in the patient
What is the A-a gradient?
It is the arteriolar-alveolar gradient..how much oxygen is being perfused relative to the amount in the artery and the alveoli. The equation is A-a=150-1.1(PaCo2)-PaO2. This only works at sea level.
What is the normal range for a healthy A-a gradient and what do the parameter need to be to be unhealthy? What condition may this deviation from normal indicate?
5-15 mmHg is normal with 15-25 mmHg abnormal and indicating venous admixture of blood due to a diffusion impairment, intrapulmonary shunt or cardiac shunt
What is the 120 rule?
An abridged A-a equation of PaCo2+PaO2, with normal values being at 140 +-10. Less than 120 indicates venous admixture
What does the PaO2/FiO2 ratio describe and what is the normal value?
It is a clinical indicator of hypoxemia and should be 500. If the value is less than 200, this indicates acute respiratory distress syndrome (ARDS) and less than 200 is Acute Limb Ischemia (ALI).
