Hypokalaemia

Question 1

What are the causes of Hypokalaemia?

Answer 1

Hypertensive – Cushing’s, Conns,
Normotensive – GI loss (Diarrhoea, vomiting, fistula), Diuretics, Metabolic Alkalosis, Salbutamol Toxicity, Renal Tubular Acidosis, Liquorice toxicity

Question 2

What will you find on a history taking of Hypokalaemia?

Answer 2

Symptoms:
Cardiac arrhythmias - Palpitations, syncope, SOB
Weakness
Hypotonia
Hyporeflexia
Cramps
Tetany
Constipation 

Risk Factors:
Alcoholism
History of vomiting, diarrhoea, NG suction, or an eating disorder
History of steroid use – May predispose to Cushing’s
Underlying GI condition – E.g. Pyloric stenosis (for example as a result of a peptic ulcer) that may cause recurrent vomiting

Question 3

What will you find on examination of Hypokalaemia?

Answer 3

End of the bed:
Look for volume depletion as may indicate recent vomiting and diarrhoea
Hands:
Blood pressure – Differentiate causes based if hypertensive or normotensive
Tachycardia (Bradycardia in severe hypokalaemia)
Chest:
Tachypnoea – Respiratory muscle weakness

Question 4

What investigations will you order in Hypokalaemia?

Answer 4

Bedside:
ECG – Small/Flat T waves, U wave (after T wave), Prolonged PR interval, ST depression, QT elongation, ST depression
Full set of Observations - Looking at BP (If raised could indicate Cushing’s or Conns)
Urinalysis and urine pH - Looking for renal tubular acidosis, urine pH will be raised

Bloods:
ABG - Looking at acid/base status, metabolic alkalosis if lots of Vomiting, metabolic acidosis if lots of diarrhoea, DKA or RTA
U&E - Will show the hypokalaemia, or other electrolyte disturbances if alcoholism etc
Late-night salivary cortisol then Dexamethasone suppression test for Cushing’s

Imaging:
CT scan of the adrenal glands - If Cushing’s, conns suspected

Special Tests:
Urinary Potassium

Question 5

What is the treatment of Hypokalaemia?

Answer 5

Medical:
Asymptomatic - Monitor ECG and give Oral K+ supplements (Reassess after 3 days)
Symptomatic or K<2.5 - IV K+ given cautiously (No more than 20 mmol/h or 40mmol/L) Never give K+ as a bolus
Treat the underlying cause

Question 6

What is Hypokalaemia?

Answer 6

Normal Potassium levels are between 3.5 and 5. Any value below 3.5 is hypokalaemic.