arterial blood gas Flashcards
What is an acid?
Molecule with loosely bound proton it can donate (proton donor)
What is a base?
Negatively charged ion capable of reversibly binding protons to reduce amount that is free
Why must acidity of blood be tightly regulated?
Changes 3D structure of proteins
What produces rapid compensatory response to change in PH?
Changes in ventilation to change CO2 elimination (hyperventilation to eliminate more CO2)
What produces slow compensatory response to change in PH?
Changes in bicarbonate and proton retention and secretion by the kidneys
what is base excess?
- concentration of bases (predominantly bicarbonate) compared with the ‘expected concentration’.
- An exact match is 0, an excess of base is positive and a base deficit is negative
what is formula for pH?
pH=-log10[H+]
What is formula for concentration of protons?
[H+] = 10^-pH
How do you interpret an ABG?
- look at pH (acidosis/alkalosis)
- cause (respiratory or metabolic - look at Co2 & bicarbonate)
- compensation (look at BE and CO2 to see if compensation).
- oxygenation (hypoxaemia/hyperxaemia)
Case of low pH, high CO2.
if BE normal what is it?
If BE high what is it?
If BE low what is it?
BE normal: uncompensated respiratory acidosis
BE high: partially compensated respiratory acidosis
BE low: mixed acidosis
Case of high pH, low CO2.
if BE normal what is it?
If BE high what is it?
If BE low what is it?
BE normal: uncompensated respiratory alkalosis
BE high: mixed respiratory alkalosis
BE low: partially compensated respiratory alkalosis
Case of low pH, low bicarbonate.
If CO2 normal?
If CO2 high?
If CO2 low?
CO2 normal: uncompensated metabolic acidosis
CO2 high: mixed acidosis
CO2 low: partially compensated metabolic acidosis
Case of high pH, high bicarbonate.
If CO2 normal?
If CO2 high?
If CO2 low?
CO2 normal: uncompensated metabolic alkalosis
CO2 high: partially compensated metabolic alkalosis
CO2 low: mixed alkalosis
