Hyperkalaemia

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LogoWarningBox4.pngA [K+] over 6.5 mmol/l is a medical emergency and should be investigated and treated rapidly. Consult local guidelines on precise emergency management. Be aware that its the plasma potassium that determines toxicity not the usual surrougate of serum potassium

Contents

Introduction

LogoKeyPointsBox.pngIf no local guidelines available suggest urgent confirmation at [K+] > 6.0 mmol/l, with ECG, independent sample(in case of haemolysis), and venous blood gas sample (to exclude pseudohyperkalaemia on a serum specimen) and start treating pending confirmation. Below this level decide if problem chronic, subacute or acute, and react in an appropriate timescale.

Potassium is the major intracellular cation.

  • Hyperkalaemia is regarded as a plasma [K+] > 5.0 mmol/l
  • Severe hyperkalaemia is regarded as a plasma [K+] > 6.5 mmol/l and is considered to be a medical emergency as it can lead to cardiac arrest.

Clinical

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Symptoms

Investigations

Plasma [K+]

  • Ensure it is not haemolysed and is a fresh sample
  • Also look for biochemical evidence of ARF

ECG will show changes

Causes

LogoKeyPointsBox.pngHyperkalaemia is always an indication for careful review of recent drug and fluid therapy. Common is ACE or angiotension II inhibitors combined with diuretic (especially potassium retaining ones) and/or NSAIDs.

Treatment

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  • Calcium resonium is powerful and patients have had a hypokalaemic cardiac arrest from 72 hours treatment when the acute cause of the hyperkalaemia was removed on presentation
  • Remember to monitor the blood glucose every 30 minutes for 6 hours after giving soluble insulin and glucose
  1. Remove underlying cause.
  2. Calcium (either as gluconate or chloride) gives cardioprotection (but does not lower K+)
  3. Insulin + glucose to shift K+ back into cells
    • Most evidence based on 10 international units insulin and 25g of 50% glucose[3]
    • Provides too little insulin to achieve maximal hypokalaemic effect possible with the hormone and too little glucose to avoid hypoglycaemia
    • Lowers blood glucose by about 1.5 mmol/L at 1 hour
    • This is not appropriate in diabetic ketoacidosis
    • It will tend to induce hypos, especially in advanced renal failure
    • So monitor blood glucose
      • Weight based regimes are safer (eg 0.1 units/kg up to 95kg
    • In non-diabetics a glucose load alone will cause almost a good drop in the potassium
  4. Salbutamol nebuliser (or infusion if you are where its available) will also shift K+ back into cells
  5. Binding resins such as calcium resonium
  6. Haemofiltration and dialysis
    • The definitive treatment

Cochrane has published a systematic review on emergency interventions for hyperkalaemia [1]. They conclude that inhaled or nebulised, or IV insulin-and-glucose are the first-line therapies for the management of emergency hyperkalaemia that are best supported by the evidence. In combination they may be more effective than either alone, and should be considered when hyperkalaemia is severe. In the presence of arrhythmias anecdotal evidence suggests that IV calcium is effecting in treating arrhythmia. Bicarbonate has a very limited role, but interestingly may have some efficacy in the hyperkalaemic cardiac arrest situation[5]


External links

Guidelines for the treatment of hyperkalaemia in adults.

References