Acidosis and alkalosis Flashcards
Steps to working out ACID BASE
1- pH - acid or alkali
2 - PaCO2 - contributing or compensating (cause or not)
3 - Base - BE + HCO3 (acute or chronic)
4 - PaO2 - Type I or II resp failure
What are the normal parameters for pH
7.35-7.45
What does a low pH with a high PaCO2 signal?
Respiratory acidosis
What does an acidic pH and a low PaCO2 signal?
Metabolic acidosis
What does a raised pH and normal or increased PaCO2 signal>
Metabolic alkalosis
What does a raised pH and decreased PaCO2 =
Respiratory alkalosis
When is a pH problem acute?
When the base picture (metabolic) hasnt responded - takes hours to days to change, resp is much more sensitive
What type of respiratory failure has both hypoxia and hypercapnia?
2
What is the sign of type I respiratory failure?
Hypoxia alone
What is the level of hypoxia?
Less thna 8 kpa PaO2
What level is hypercapnia?
Over 6kpa PaCO2
What causes the repiratory drive?
Level of carbon dioxide - very sensitive, RR changes in minutes to hours in response
Why is type II resp failure also hypercapnia?
Drive becomes hypoxia, unable to blow off enough CO2 to keep levels normal
What pH disorder will vomitting in Excess cause
Loss of H+ -> metabolic alkalosis ->
Why is decreased ventilation seen in metabolic alkalosis?
To retain CO2 and raise acidity
What can a high otuput ileostomy cause?
Metabolic acidosis - loss of HCO3- as high conc in GI tract
What happens to ventialtion in metabolic acidosis
Increased RR -> Tachypnoea
If metabolic compensation is seen for hypercpania (eg raised HCO3-), is the acidosis acute or chronic?
CHronic
Parameters for PaCO2
4.6-6.4
Parameters for HC03-
21-28
Base excess parameters
-2 to +3 (any value away from 0 is not good)
When is metabolic ocmpensation seen?
In a chronic problem
When is a pH disorder fully compensated?
When the pH value is still in range
What is the picture in COPD CO2 retainers?
Increased CO2
Increased HCO3- - metabolic compensation
pH in normal range
Chronic respiratory acidosis with full compensation
