Hyperkalaemia

Introduction

Hyperkalaemia = Serum potassium above 5.5mmol/l.

Dangerous hyperkalaemia can cause sudden death with no warning.  The absolute level of potassium is important but the rate of rise of the potassium level is also important as some patients live with chronically elevated potassium levels (chronic renal failure) with no adverse effects.

Usual intake of [K+] is approximately 1mmol/kg/day, but homeostasis can be maintained at intakes of 20-500 mmol in those with normal renal function.

Acute causes

• • Excess intake/supplementation/generation
    • Potassium rich food / K supplements
    • Tumour lysis/haemolysis/cell damage
    • Blood transfusion
    • Steroids
  • Shifting from intracellular K to extra cellular space:
    • hyperglycaemia
    • acidosis
    • drugs:
      • cardiac glycosides
      • heparin
      • beta blockers
    • inherited disorders
  • Impaired excretion
    • Decreased mineralocorticoid levels
    • Adrenocortical insufficiency
    • Drugs
      • Spironolactone
      • ACE-inhibitors
      • AT2-antagonists
      • K-sparing diuretics
    • Hypoaldosteronism
  • Spurious blood sample
    • Delayed analysis in laboratory / haemolysis blood sample

Presentation

• • Can be asymptomatic.
  • Paraesthesia and perioral tingling.
  • Muscle weakness
  • Malaise

Investigations

U&Es: AKI or chronic renal disease?

Glucose: is the patient hyperglycaemic?

ABG: is the patient acidotic?


ECG: look for..

• • P-wave widening + low amplitude due to slowing of conduction
  • QRS widening
  • Fusion of QRS-T
  • Loss of the ST segment
  • Tall tented T waves

Treatment

• • ABCDE
  • Oxygen
  • IV access

Flow chart for hyperkalaemia in non dialysis-dependent patients, _{[StaffNet Source]}

Hyperkalaemia in Dialysis Dependent Patients, _{[StaffNet Source]}

Following drugs can be used to manage hyperkalaemia:

• • Intravenous calcium gluconate (10% in 10mL over 10 minutes): if there are ECG changes.

This does not change K-concentration, but reduces the excitability of the (cardiac) membranes

• • Intravenous dextrose + Insulin

Lowers the K by 0.7-1.6mmol/l

• • Salbutamol

Similar to dextrose in efficacy

NB. the above treatments do not remove, they only redistribute [K+].

• • Dialysis

A standard haemodialysis removes 40-60mmol [K+]
Removal of [K+] by haemofiltration or peritoneal dialysis is much slower

• • Calcium resonium (orally)

Not useful in acute setting but may be short/medium term option if dialysis not desirable or possible. Causes constipation.

• • Diet

May explain acute hyperkalaemia; important for prevention.

Banana Bomb