What is the equation for pH that takes into account bicarb and pCO2 and what does it mean?
pH=6.1+log HCO3/pCO2 (this says that in order to keep pH at 7.4, a change in pCO2 has to be opposed by a change in HCO3 in the same direction; pCO2 goes up, HCO2 has to go up
Can a change in HCO3 ever fully compensate for a change in pCO2?
No - and if it does it is a mixed acid/base problem; not just a primary one
What happens with COPD?
They retain PCO2 - chronically. They live in the respiratory acidosis range all the time
What organ is responsible for changing bicarb levels? How long does this take?
The kidney - slow 8-24 hours
What happens in the first few hours of respiratory acidosis or alkalosis?
They have not had time to compensate yet
How does a person compensate for respiratory acidosis or alkalosis?
By changing the HCO3 level. If pCO2 goes down, bicarb will go down too. (These are the vertical lines of the graph)
What happens if the PCO2 is low?
The bicarb will be low too (to compensate for the primary respiratory alkalosis.
What happens with profuse vomiting? How fast does it occur?
Metabolic alkalosis b/c you are vomiting acid - so you slow the breathing to compensate (bring the body back to a more acidic state). This is a fast response and cant fully compensate
What does metabolic compensation for respiratiry acidosis or alkalosis look like on a graph?
It will be an arrow perpendicular to the orginal line - that moves you down one of the isobars. It never quite gets you back to normal.
What are the rules for acid base disturbances?
1. Check pH for alkalosis or acidosis
2. Is it metabolic or respiratory?
3. Is compensation appropraite? (If not then it is a mixed disorder)
4. What clinical condition is present that will explain the blood gas changes
What compensates for the primary change in respiratory status?
The kidneys - and it takes awhile. So they are stuck for awhile
What is the difference b/w acute and chronic respiratory acidosis and alkalosis in terms of pCO2 and HCO3?
Acute - for every ten points the PCO2 drops, bicarb drops by 1
Chronic - for every ten points PCO2 drops, bicarb drops by 5
What is the body's first reponse to infection?
Hyperventilation - which puts the pt into respiratory alkalosis
What does uncompensated respiratory alkalosis look like on the graph?
You just slide down the main line - and that is the bicarb and the pH
What does compensated respiratory alkalosis look like on the graph?
There is a perpendicular line down from the inital vbalue - down one of the isolines. This gives you the new pH and the new HCO3. These should increase/decrease in the same direction. The new pH is not 7.4
What is the second part of a sepsis syndrome?
respiratory alkalosis - the metabolic acidosis (due to lacate) - getting tissue hypoxia
HWat happens when a patient is in sepsis and his pH drops?
He will hyperventilate to try to push it back up to 7.4
Why is sepsis a mixed acid base problem?
respiratory alkalosis - then metabolic acidosis - which makes him hyperventilate more.
What are 6 causes of respiratory alkalosis (as a primary problem)?
4. ASA poisoning
6. cerebral hemorrhage
What is the response to aspirin posioning?
The first part is respiratory alkalosis. Later you get metabolic acidosis
What haooens if you give a "blue bloater" high levels of oxygen?
They normally have really high pCO2 levels. They breathe in response to low O2 levels, not CO2. So if you give them O2 iy knocks out their respiratory drive completely and they stop breathing. Take away the oxygen, they start breathing again
What will you normally see in a "blue boater" electrolytes? Is this a primary problem?
A very high HCO3. This is not primary - it is compensation for primary respiration alkalosis of COPD
In a chronic respiratory process, what change in HCO3 do you see with every 10 point change in PCO2?