Hyperkalaemia

Question 1

what is hyperkalaemia?

Answer 1

Plasma K+ >5.5 mmol/L

• mild: 5.5-5.9
• moderate: 6-6.4
• severe: >6.5

Question 2

name the main causes of hyperkalaemia

Answer 2

1. Renal causes
   - AKI
   - CKD
   - hypoaldosteronism and hyperkalaemic renal tubular acidosis
   - drugs inhibiting K+ secretion: spironolactone,amiloride
   - drugs interfering with RAAS: ACEi, ARBs, NSAIDs, heparin
2. Increased circulation of K+
   - exogenous: K+ supplementation
   - endogenous: tumour lysis syndrome, rhabdomyolysis, trauma, burns, drowning
3. Intracellular to extracellular space shift
   - acidosis, e.g. DKA
   - drugs: digoxin toxicity, beta-blockers, theophylline
   - hyperkalaemic periodic paralysis
4. Pseudohyperkalaemia, e.g. prolonged tourniquet time, difficult sample, etc.

Question 3

describe the possible presentation of hyperkalaemia

Answer 3

Often asymptomatic but may have:

• weakness and fatigue
• palpitations and chest pain
• muscular paralysis
• SOB

Often no signs but may have:

• bradycardia (due to heart block)
• tachypnoea (resp. muscle weakness)
• muscle weakness and flaccid paralysis
• hypo- or arreflexia

Question 4

which tests would you perform on someone with ?hyperkalaemia?

Answer 4

1. Bloods
   - UandEs: K+ >5.5 mmol/L
   - ABG: confirm high K+ and ?metabolic acidosis
   - glucose: ?DKA
2. ECG: look for classical changes although may be normal in some cases.

Question 5

describe the typical ECG changes in hyperkalaemia

Answer 5

1. Tall tented T waves
2. P wave changes: progressive flattening, elongation of PR interval, eventual disappearance of P waves. Bradycardia is common and AV blocks may occur.
3. Broad QRS complexes (>0.12 s)
4. Dev. of sine wave pattern (combination of tall T waves and wide QRS).
5. Ventricular fibrillation

Question 6

describe the emergency management of a pt with severe hyperkalaemia

Answer 6

1. 10% calcium gluconate 10 mL slow IV (to protect cardiac membrane, will improve ECG within 1-3 min). If no improvement, 10 mL every 10 min until ECG normalises.
2. Insulin-glucose IV infusion - 10 units insulin added to 25 g glucose (to shift K+ into cells).
3. Nebulised salbutamol 10-20 mg (to shift K+ into cells)

In resistant hyperkalaemia:

• give further IV glucose-insulin or IV calcium
• input from renal physician: can use sodium bicarbonate or haemodialysis

Question 7

how can hyperkalaemia be treated in a non-acute situation?

Answer 7

Remove K+ from body using 15 g calcium resonium 3-4x/day with regular lactulose over several days