AKI with refractory hyperkalaemia — FFICM MCQ

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EasyRenal and MetabolicAKI with refractory hyperkalaemiaFFICM

A 72-year-old man with septic shock has oliguric AKI. Potassium is 6.9 mmol/L with broad QRS complexes on ECG, pH is 7.18 and creatinine is 386 micromol/L. He has received intravenous calcium, insulin-glucose and nebulised salbutamol but potassium remains 6.7 mmol/L after 40 minutes. What is the most important immediate action?

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Correct answer: A — Start urgent renal replacement therapy

The correct answer is A, start urgent renal replacement therapy. This patient has severe, ECG-positive hyperkalaemia (potassium 6.9 falling only to 6.7 mmol/L, broad QRS complexes) with oliguric AKI and metabolic acidosis (pH 7.18), and it remains refractory after calcium, insulin-glucose and salbutamol have been given. These temporising measures shift potassium intracellularly or stabilise the myocardium but do not remove potassium from the body, so when they fail to correct a life-threatening picture within a reasonable timeframe, definitive potassium removal by RRT is required. Current UK Kidney Association guidance states that in patients with life-threatening hyperkalaemia resistant to initial medical therapy, the decision to start RRT should be taken urgently by a nephrologist or critical care specialist, reflecting exactly this scenario of established AKI unable to excrete potassium. Why the other options are wrong: C. Repeat calcium every 6 hours: calcium gluconate only stabilises the cardiac membrane transiently (30 to 60 minutes) and does nothing to lower total body potassium, so repeated dosing without addressing the underlying failure of excretion leaves the patient at ongoing risk of arrhythmia. B. Give oral sodium bicarbonate and observe: oral bicarbonate acts too slowly for an emergency with ECG changes, and simple observation is inappropriate when potassium remains dangerously high with acidosis and oliguric AKI. D. Restrict dietary potassium and review tomorrow: dietary restriction is a chronic, non-urgent measure with no immediate effect on serum potassium and is wholly inadequate for a patient with ECG changes and refractory hyperkalaemia. E. Wait for renal ultrasound before escalation: imaging to characterise the AKI is not urgent when the patient is at immediate risk of cardiac arrest; escalation to RRT must not be delayed for investigations that will not change the immediate need for potassium removal. Key point: when temporising treatments fail to control life-threatening hyperkalaemia in the setting of established oliguric AKI, urgent renal replacement therapy is the definitive next step because only RRT actually removes potassium from the body.

Reference: UK Kidney Association, Renal Association Clinical Practice Guideline: Treatment of Acute Hyperkalaemia in Adults, Guideline 19.6 (RRT in treatment of hyperkalaemia in acutely unwell patients), 2023 update, https://guidelines.ukkidney.org/hyperkalaemia/