Endgames Case Review

Hyperkalaemia on the surgical ward

BMJ 2015; 351 doi: https://doi.org/10.1136/bmj.h5531 (Published 21 October 2015) Cite this as: BMJ 2015;351:h5531
  1. David P Baird, core medical trainee1,
  2. Robert W Hunter, clinical lecturer and specialty registrar1,
  3. John J Neary, consultant1
  1. 1Department of Renal Medicine, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
  1. Correspondence to: D P Baird davidbaird86{at}hotmail.com

A 56 year old woman was admitted with an infected stump wound at the site of a below the knee amputation. Her medical history included type 2 diabetes, diabetic foot ulcer, and painful peripheral neuropathy. Her regular drugs were metformin, amitriptyline, lansoprazole, Humulin I and Novorapid SC insulin, aspirin, paracetamol, morphine sulfate, gabapentin, and carbamazepine. In hospital, she was also prescribed dalteparin 5000 units subcutaneously once daily, intravenous benzylpenicillin, and flucloxacillin.

Before admission, serum potassium was 4.6-4.8 mmol/L (reference range 3.6-5.0). During admission, she had persistent hyperkalaemia peaking at 6.2 mmol/L and received repeated doses of insulin-dextrose and salbutamol over three days. Renal function was stable throughout (creatinine 60-85 μmol/L (60-120), estimate glomerular filtration rate >60 mL/min/1.73 m2). She was mildly acidotic (bicarbonate 18-20 mmol/L (22-30)) and serum lactate was 1.9 mmol/L (0.6-2.4). A paired sample of serum and urine showed serum: potassium 5.7 mmol/L, osmolality 312 mOsm (280-296); urine: sodium 69 mmol/L, potassium 18 mmol/L, osmolality 370 mOsm.

Questions

  • 1. From the history, what are the likely causes of the hyperkalaemia?

  • 2. How do the paired serum and urine results help determine the cause of hyperkalaemia?

  • 3. What are the treatment options in this case?

Answers

1. From the history, what are the likely causes of the hyperkalaemia?

Short answer

Potassium in intravenous penicillin preparations or release of intracellular potassium from necrotic muscle in the stump. Potassium excretion may be impaired due to type IV renal tubular acidosis associated with diabetes or dalteparin.

Discussion

Hyperkalaemia is common in patients in hospital, with a reported incidence of 1.3-10%.1 2 3 It is important to recognise and treat hyperkalaemia promptly because it can cause life threatening cardiac arrhythmias without warning.

Potassium is the principal intracellular cation; 98% of total body potassium is intracellular.4 Serum potassium levels are usually efficiently maintained within the normal range (3.6-5.0 mmol/L) because of buffering against the intracellular pool and by …

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