Arterial blood gas

Question 1

causes of respiratory acidosis

Answer 1

Hypoventilation in:
Lung disease (COPD, severe asthma attack, pulm oedema)
Respiratory depression (e.g. opiates)
Mechanical lung dysfunction -
Guillain-Barre, obesity Myasthenia gravis
Iatrogenic (incorrect mechanical ventilation settings)

Question 2

Causes of respiratory alkalosis

Answer 2

Hyperventilation in
Anxiety
Pain – increases resp rate
Hypoxia
Acute pulmonary insult (PE, pneumonia, asthma attack, pulm oedema, ptx)
Iatrogenic (excessive mechanical ventilation)

Question 3

what is the anion gap

Answer 3

used to calculate if metabolic acidosis is caused by increased acid production or ingestion vs decreased acid excretion r loss of HCO3-

Question 4

causes of increased anion gap

Answer 4

DKA, lactate acidosis, Aspirin overdose (ingestion of acid)

Question 5

causes of decreased anion gap

Answer 5

GI loss of HCO3— diarrhoea, ileostomy, proximal colostomy
Renal tubular acidosis (retaining H+)
Addison’s disease (retaining H+)

Question 6

Causes of metabolic alkalosis

Answer 6

Gastrointestinal loss of H+ ions – vomiting/diarrhoea
Renal loss of H+ ions – loop and thiazide diuretics / heart failure / nephrotic syndrome / cirrhosis / Conn’s syndrome
Iatrogenic – addition of alkali (e.g. milk-alkali syndrome)