Hyper and hypokalaemia

Question 1

Name three factors that increase cellular potassium uptake

Answer 1

• Insulin
• Beta agonists
• Alkalosis
• Alpha antagonists
• Theophyllines

Question 2

Name three factors that increase cellular release of potassium

Answer 2

• Acidosis
• Hyperglycaemia
• Beta blockers
• Alpha agonists
• Exercise; Cell death

Question 3

Where does the majority of renal potassium reabsorption occur?

Answer 3

Over 90% reabsorbed in the proximal tubule and loop of Henle

Question 4

List five causes of hypokalaemia

Answer 4

• Increased loss
  
  • Thiazide or loop diuretics
  • DaV; laxative abuse
  • Burns; increased sweating
  • Hyperaldosteronism: Conn’s syndrome
  • Hypomagnesaemia
  • Renal tubular acidosis
• Transcellular shift
  
  • Alkalosis
  • Insulin; glucose; beta agonists; adrenaline
• Inadequate intake; anorexia nervosa
• Chronic alcoholism
• Chronic peritoneal dialysis

Question 5

Describe the clinical features of hypokalaemia

Answer 5

• Mild (3.0-4.0): Asymptomatic
• Moderate (2.5-3.5):
  
  • Arrhythmias
  • Fatigue; weakness; muscle pain
  • Constipation
• Severe (<2.5):
  
  • Severe muscle weakness; paralysis
  • Respiratory failure
  • Ileus
  • Paraesthesia; tetany

Question 6

What ECG changes are seen with hypokalaemia?

Answer 6

• ST depression
• Small T wave
• U wave
• Prolonged QT - beware digoxin toxicity
• Arrhythmias
  
  • Ectopic beats
  • AF; sinus bradycardia; AVNRT/AVRT
  • VT/VF

Question 7

How is hypokalaemia treated?

Answer 7

• Treat any underlying causes where possible
  
  • Withdrawal of thiazide and loop diuretics
  • Assess fluids with inadequate potassium replacement
  • Mg²⁺
• If mild without arrhythmia: oral potassium supplements
• Continuous ECG monitoring if arrhythmia or K⁺ <2.5
• IV 40mmol/L KCl: 10 mmol/hr max rate

Monitor potassium hourly until arrhythmias resolve and K⁺ >3.0

Question 8

Name three causes of hyperkalaemia

Answer 8

• After vigorous exercise: acute self-limiting
• Increased cell release:
  
  • Acidosis; DKA
  • Rhabdomyolysis; tumour lysis syndrome; trauma
  • Digoxin poisoning
• Decreased excretion:
  
  • AKI; CKD
  • Addison’s disease
• Drugs: Amiloride; spironolactone; ACEi; ARBs; NSAIDs; beta blockers

Question 9

Name three drugs that may cause hyperkalaemia

Answer 9

• Amiloride
• Spironolactone
• ACEi; ARBs
• NSAIDs; heparin
• Beta blockers

Question 10

Describe the clinical features of hyperkalaemia

Answer 10

• Asymptomatic
• Muscle weakness; paralysis; reduced tendon reflexes
• Dyspnoea
• Fatigue
• If metabolic acidosis: Kussmaul breathing
• Hypotension, bradycardia, asystole

Question 11

Describe the ECG changes with hyperkalaemia

Answer 11

Question 12

Outline the emergency management of severe hyperkalaemia

Answer 12

• ABC assessment; alert senior
• ECG + EWS monitoring every 15 min; IV access
• Slow IV 30ml of 10% calcium gluconate over 5 minutes
• Neb salbutamol 20mg
• IV insulin (10 units) + glucose (25g) over 15 minutes
• Hourly urine output monitoring; repeat VBG
• Correct severe acidosis: IV sodium bicarbonate
• Request ITU review; consider repeat insulin-glucose
  
  • Haemofiltration or haemodialysis
  • Resins

Question 13

What is the maximum rate can KCL infusions be given?

Answer 13

10 mmol/hr