Hyperkalemia

Always consider possible pseudohyperkalemia

Due to hemolysis (caused by a difficult blood draw or too long a time interval between the blood draw and the determination of the potassium in the laboratory).
In the event of an unexpected or unexplained high potassium level during a blood test, this should always be considered. In case of doubt, the blood draw is best done on site in the laboratory (externally or in the hospital) for a faster and more reliable measurement of the potassium.

1. Exclude progressive, severe renal impairment.

2. Reduce or discontinue medication that increases potassium.

RAAS blockers
- Especially MRA: Spironolactone, eplerenone
- ACE inhibitors, ARB, ARNI, renin inhibitors
Other potassium-sparing diuretics (amiloride, triamterene)
NSAIDs
Trimethoprim (in Bactrim or Eusaprim, together with sulfamethoxazole).
Antifungals (ketoconazole, fluconazole, itraconazole)
Ciclosporine, Tacrolimus.

3. Potassium-restricted diet, only if there is also severe renal impairment (GFR < 30 ml/min).

Potassium-rich food
- Raw vegetables (juices) and soup, legumes
- Whole wheat bread
- Fruit (juices) (highest concentration in bananas and melon)
- Potatoes (unless cooked twice) and fries
- Chocolate (cocoa)
- Nuts
- Coffee
Potassium-poor food
- Rice, pasta, white bread
- Well-cooked vegetables, canned fruit
- Lemonades
- Tea

4. If there are signs of fluid retention::

Associate a thiazide diuretic, which increases urinary potassium excretion.
Associate or increase a loop diuretic.

5. Chronic renal impairment and metabolic acidosis (bicarbonate < 20 mmol/l) ?

Consult with treating cardiologist/nephrologist for starting peroral NaHCO3 supplements (magistral preparation, 1 gram tablets, dosage: 1 or 2 tablets 1 to 3 times daily, to be taken 2 hours after meals). By correcting the acidosis (increase in blood pH) a shift of potassium occurs to the intracellular compartment, resulting in a decrease in the potassium level in the blood.

6. HFrEF (or HFmrEF) and therapy with ACE inhibitor / ARB / ARNI / MRA ?

This therapy should preferably not be reduced or stopped as long as there is no symptomatic hypotension and as long as renal function remains acceptable (with a GFR ≥ 30 ml/min). If real hyperkalemia is confirmed with two different blood tests, it is best to consult with the treating cardiologist/nephrologist to associate an oral potassium binder. These drugs bind the potassium from food in the intestine, so that it is no longer absorbed into the body, but is excreted with the stool. There are currently 3 oral potassium binders available, two of which are reimbursed in Belgium specifically for heart failure, namely sodium zirconium cyclosilicate and patiromer.

Symptoms.

Not always present.
General muscle weakness and fatigue, dyspnea.
Paresthesia.
Nausea.
Drowsiness.
Bradycardia to asystole with syncopes and/or sudden death.
Hypotensions.

Possible ECG abnormalities

As hyperkalemia becomes more severe > 6.0 mmol/l, changes in the ECG may occur:

Potassium > 6-7 mmol/l : pointed T-waves (' tented T-wave').
Potassium > 7-8 mmol/l : bradycardia, flattening to disappearance of P waves, prolonged PR interval, even higher pointed T waves.
Potassium > 8-9 mmol/l : widening of the QRS complex and even higher T-waves.
Potassium > 9 mmol/l : evolution towards sinus wave pattern, ventricular fibrillation, AV block, asystole or PEA ( pulseless electrical activity).

Hyperkalemia should be suspected as the cause of any unexplained bradycardia, AV block or cardiac arrest.

BWGHF

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