Hypokalaemia

E87.6

DESCRIPTION

A serum potassium level <3.5 mmol/L.

Mild to moderate symptoms: muscle weakness (respiratory, as well as, GIT muscles) and cramps.

Severe symptoms: rhabdomyolysis, paralysis, dysrhythmias, diaphragmatic weakness.

Signs of hypokalaemia: cardiac arrhythmias as well as ECG abnormalities (ST –segment changes).

It is usually due to gastro-intestinal losses (vomiting, diarrhoea) or renal losses (diuretic therapy, hyperaldosteronism).

MEDICINE TREATMENT

For chronic asymptomatic hypokalaemia, look for and manage the cause:

  • Potassium chloride, oral, 600 mg, 1–2 tablets 8 hourly.
    • Each 600 mg potassium chloride tablet contains 8 mmol of potassium chloride.
    • Titrate according to response to therapy.
    • Maximum daily dose: 6 g (i.e.10 tablets per day in divided doses).
    • Review potassium levels after 4 weeks.

LoEIII [9]

Note: Routine supplementation with potassium chloride in patients who are on diuretics is usually inappropriate. Co-administration of ACE-inhibitors and/or spironolactone counteracts the hypokalaemia from furosemide or thiazides.

For mild to moderate hypokalaemia in a non-vomiting patient (potassium level usually 3–3.4 mmol/L):

  • Each 600 mg potassium chloride tablet contains 8 mmol of potassium chloride.
    • Titrate according to response to therapy.
    • Maximum daily dose: 6 g.
    • Continue treatment until the serum potassium concentration is persistently above 3.5 mmol/L and symptoms or signs have resolved.

LoEIII [10]

For severe symptomatic hypokalaemia :

  • Potassium chloride, IV by peripheral line, 40 mmol in 1 L of 0.9% or 0.45% sodium chloride, mixed thoroughly.
    • Administer at a maximum rate of 20 mmol per hour over 3 hours. Beware of volume overload (See POTASSIUM CHLORIDE, IV for individual dosing and monitoring for response and toxicity).
    • Repeat as required, monitoring potassium serum levels after each replacement dose.
    • Potassium chloride 15% 10 mL ampoule contains 20 mmol potassium.
    • Maximum allowed daily dose of K+ is 3 mmol/kg/day (or 400 mmol/day).

LoEIII [11]

CAUTION

Potassium chloride ampoules must always be diluted before infusion.

Reduce the rate of intravenous potassium repletion or change to oral therapy once the hypokalaemia is no longer severe. Continue treatment until the serum potassium concentration is persistently above 3.5 mmol/L and symptoms or signs have resolved.

Online calculator for calculating potassium deficit: http://www.medicinehack.com/2011/07/hypokalemia-potassium-replacement.html

If not responding to therapy, check for hypomagnesaemia as low serum magnesium may potentiate potassium loss.