Hyperkalaemia

James talks to Associate Professor Darren Roberts about hyperkalaemia on the wards.

Summary Writer:  Elizabeth Campbell

Editor:  James Edwards

Interviewee:  Darren Roberts

About Darren Roberts

Darren Roberts is a physician working in both clinical pharmacology/toxicology and nephrology in Sydney and Canberra and an Associate Professor at the Australian National University. He is the current Chair of the clinical pharmacology Special Interest Group and a member of various national and international government, professional and clinical committees. Darren’s research interests include pharmacokinetics and drug dosing in impaired renal function, influence of dialysis on xenobiotic clearance and evidence-based clinical toxicology. He works part-time at Royal Prince Alfred Hospital as a clinical pharmacologist and toxicologist, and undertook a portion of his renal training in Royal Prince Alfred Hospital and Concord Hospitals.

Hyperkalaemia

With Associate Professor Darren Roberts, Physician in Clinical Pharmacology, Toxicology, and Nephrology, at Canberra Hospital

Introduction

The definition of hyperkalaemia may vary, depending on where you work. A serum potassium concentration greater than 5.5 is abnormal, and levels greater than 6-6.5 are very concerning. It is important to consider the reason for the hyperkalaemia and whether the potassium level is likely to continue to increase. If you have doubts about a result (e.g. suspecting a haemolysed blood sample), repeat the test. Blood gas testing is an accurate and quick way to confirm the serum potassium concentration.

When considering the causes of hyperkalaemia, it is helpful to think of either too much potassium getting into the blood (e.g. tissue damage), or difficulty getting the potassium out of the body (e.g. acute kidney injury). There may be a combination of factors leading to hyperkalaemia, for example, drug side effects (ACE inhibitors, spironolactone) with an associated acute kidney injury.

Case

A 70-year-old man with end-stage renal failure presents to ED, unwell after missing dialysis for several days. He has a serum potassium concentration of 9 mmol/L.

  • Life-threatening emergency – involve senior staff immediately
  • Assume the worst-case scenario with this potassium measurement – do not spend time repeating the blood test
  • Focus on risk stratification and immediate treatment in this patient. You may get some history and examination, but this will likely be concurrent with your treatment.
  • ECG is the first-line investigation. Textbook progression of ECG features: peaked T waves, loss of P waves, increased PR interval, bradycardia, prolonged QRSduration, eventually leading to a sine wave appearance.
  • ECG features may be difficult to interpret in patients with cardiac comorbidities.
  • Calcium
    • Does not affect the potassium concentration. Calcium stabilises the membrane of the myocardium. It has a short-lived effect (~10 minutes).
    • Calcium gluconate: 10ml of 10% calcium gluconate, given over 10 minutes (Rule of 10s).
  • Insulin
    • Pushes potassium to the intracellular compartment. Takes 30 minutes to work, and has a short-lived effect.
    • Give 10 units of soluble short-activing insulin (Novorapid or Actrapid), with 50ml of 50% glucose.
  • Salbutamol
    • Nebulised
    • Some controversy regarding risk of transmitting viral respiratory infections with nebulisers – staff can wear protective facial masks.
    • Works in 40-50% of people.
  • Resonium
    • Doesn’t have much role in management of acute hyperkalaemia.
    • Relatively low in potency, and delayed effect.
    • Risks: bowel ischaemia
  • Sodium bicarbonate
    • Alkalaemia causes hypokalaemia
    • Risks: use is associated with hypocalcaemia, hypernatraemia, vasoconstriction and fluid overload.
  • Diuretics
    • Frusemide: causes with hypokalaemia. Wouldn’t have a role in this example (ESRF).
  • Dialysis
    • This is the definitive treatment for this patient, and must be started as soon as possible.
    • In acute kidney injury, the clearest indications for dialysis are: refractory acidosis, refractory fluid overload, and refractory electrolyte abnormality
  • Cardiac monitoring: all patients with hyperkalaemia should be on cardiac monitoring until a definitive cause is identified, and there are signs of correction.
  • Close monitoring of the serum potassium is crucial. If the initial potassium level was greater than 7, consider repeating the measurement within one hour.
  • Hyperkalaemia kills people. It is difficult to overtreat hyperkalaemia.
  • Close monitoring is crucial. It will take at least 6-12 hours to determine whether the patient is improving, deteriorating, or remaining unchanged.
  • You must involve senior staff early in the management of these patients.
  • Always consider the cause of the hyperkalaemia
    • Medications: digoxin, antibiotics (e.g. trimethoprim), antihypertensives,
    • Consider occult trauma and rhabdomyolysis
    • Check the other blood tests. For example, could there be intra-abdominal bleeding?
  • Clearly handover pending blood results at the end of your shift. Junior doctors are very busy on the wards, but it is crucial not to miss these results.

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Tags: #ACE inhibitors,#Alkalaemia,#blood gas,#calcium,#dialysis,#Hyperkalaemia,#insulin,#kidney injury,#potassium,#refractory acidosis,#refractory electrolyte abnormality,#refractory fluid overload,#serum potassium,#spironolactone

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