Acidosis and Alkalosis

The Henderson-Hasselbach Equation…..

The lungs control the volume of CO2

The kidneys control the volume of BCO3

-

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