acid-base disorders

Question 1

how is metabolic acidosis classified?

Answer 1

according to anion gap
normal or raised

Question 2

what causes normal anion gap?

Answer 2

gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
renal tubular acidosis
drugs: e.g. acetazolamide
ammonium chloride injection
Addison’s disease

Question 3

what type of acidosis is in a normal anion gap?

Answer 3

hyperchloraemic metabolic acidosis

Question 4

what causes raised anion gap?

Answer 4

lactate: shock, hypoxia
ketones: diabetic ketoacidosis, alcohol
urate: renal failure
acid poisoning: salicylates, methanol

Question 5

what happens in metabolic alkalosis?

Answer 5

Metabolic alkalosis may be caused by a loss of hydrogen ions or a gain of bicarbonate. It is due mainly to problems of the kidney or gastrointestinal tract

Question 6

what causes metabolic alkalosis?

Answer 6

vomiting / aspiration (e.g. peptic ulcer leading to pyloric stenos, nasogastric suction)
diuretics
liquorice, carbenoxolone
hypokalaemia
primary hyperaldosteronism
Cushing’s syndrome
Bartter’s syndrome
congenital adrenal hyperplasia

Question 7

what causes respiratory acidosis?

Answer 7

COPD
decompensation in other respiratory conditions e.g. life-threatening asthma / pulmonary oedema
sedative drugs: benzodiazepines, opiate overdose

Question 8

what causes respiratory alkalosis?

Answer 8

anxiety leading to hyperventilation
pulmonary embolism
salicylate poisoning
CNS disorders: stroke, subarachnoid haemorrhage, encephalitis
altitude
pregnancy