Acidosis and Alkalosis
The Henderson-Hasselbach Equation…..
The lungs control the volume of CO2
The kidneys control the volume of BCO3
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Acidosis or Alkalosis….
What is the normal pH range?
CO2 and HCO3-
What is the normal range of pCO2? What is the normal range of HCO3
-?
What’s going on here?
pH 7.2pCO2 9.3 kPaHCO3
- 28mmol/LpO2 7.9kPa
Normal RangespH 7.35 – 7.45pCO2 4.5 – 6.1HCO3
- 22-28
1) Look at the pH, is this acidosis or alkalosis?2) Look at the pCO2 , is it high or low?3) Look at the HCO3
- is it high or low?Respiratory acidosis
Asthma Attack
Metabolic or respiratory?
Acidosis or alkalosis?
Compensation mechanism?
Respiratory
Acidosis – constriction of airways
None – asthma attack is acute so compensation mechanisms are too slow
DKA
Metabolic or respiratory?
Acidosis or alkalosis?
Compensation mechanism?
Metabolic
Acidosis - ketones
Hyperventilation to lower CO2 (respiratory alkalosis)
Vomiting
Metabolic or respiratory?
Acidosis or alkalosis?
Compensation mechanism?
Metabolic
Alkalosis – loss of electrolytes
Slower breathing to retain CO2 (respiratory acidosis)
Panic Attack
Metabolic or respiratory?
Acidosis or alkalosis?
Compensation mechanism?
Respiratory
Alkalosis – due to low CO2
None – panic attack is acute so compensation mechanisms are too slow
Sepsis
Metabolic or respiratory?
Acidosis or alkalosis?
Compensation mechanism?
Metabolic
Acidosis – lactic acid
Hyperventilation to lower CO2 (respiratory alkalosis)
Case Example
A 60 year old man presented to A&E after suffering from SOB, pyrexia and a productive cough over the last 2 days. He has a history of COPD. An ABC was performed and the following values were obtained:pH: 7.2, pCO2: 9.3kPa, HCO3
-: 27mmol/L, pO2: 7.9kPapH = 7.35 – 7.35 pCO2 = 4.5-6.1 HCO3
- = 22-28
Respiratory acidosis
Case Example
An 80 year old man presents with a 2 day history of persistent vomiting. He is lethargic and has myalgia. He has gastroenteritis and is dehydrated.An ABC was performed and the following values were obtained:pH: 7.5, pCO2: 6.0kPa, HCO3
-: 37mmol/L, pO2: 11.3kPapH = 7.35 – 7.35 pCO2 = 4.5-6.1 HCO3
- = 22-28
Metabolic alkalosis
Acidosis and Alkalosis