Severe hyperkalaemia with ECG changes
PLAB 2 & PRES 3 · emergency medicine / nephrology · hard · 8 minutes
Candidate brief
You are an FY2 doctor/SHO in the Emergency Department. Mr Peter Collins, 68, presents with worsening weakness, nausea and palpitations. Observations: Airway patent. Respiratory rate 20 breaths/min. SpO₂ 97% on air. Heart rate 48 beats/min. Blood pressure 104/68 mmHg. Temperature 36.5°C. GCS 15. Capillary glucose 6.2 mmol/L. Results: Potassium 7.2 mmol/L. Sodium 134 mmol/L. Bicarbonate 17 mmol/L. Urea 24 mmol/L. Creatinine 365 micromol/L. Previous creatinine 210 micromol/L. eGFR 14 mL/min/1.73 m². Magnesium 0.82 mmol/L. Calcium 2.25 mmol/L. ECG shows sinus bradycardia, tall peaked T waves, reduced P-wave amplitude and QRS widening. Assess the patient, interpret the findings and initiate appropriate emergency management. Verbalise any examinations, investigations and treatments you would undertake.
What examiners look for
Severe hyperkalaemia is generally defined as a serum potassium above 6.5 mmol/L. ECG changes may include tall peaked T waves, PR prolongation, reduced or absent P waves, QRS widening, bradycardia, sine-wave patterns and ventricular arrhythmias. A normal ECG does not reliably exclude dangerous hyperkalaemia. Do not delay emergency treatment while waiting for a repeat result when severe hyperkalaemia and ECG changes are convincing. Intravenous calcium stabilises the cardiac membrane but does not reduce the serum potassium. Insulin with glucose shifts potassium into cells temporarily. Nebulised salbutamol is an adjunct and should not be used as the only treatment. Patients can develop delayed hypoglycaemia following insulin-glucose treatment and require repeated glucose monitoring. Potassium must also be removed from the body using potassium binders, urinary excretion where appropriate or dialysis. Look for AKI, chronic kidney disease, acidosis, tissue breakdown, urinary obstruction and contributing medicines. ACE inhibitors, ARBs, spironolactone, NSAIDs and trimethoprim can contribute to hyperkalaemia. Rebound hyperkalaemia can occur after the temporary intracellular-shifting treatments wear off.
Guideline references
- https://www.resus.org.uk/professional-library/2025-resuscitation-guidelines/special-circumstances-guidelines
- https://www.ukkidney.org/health-professionals/guidelines/treatment-acute-hyperkalaemia-adults-0
- https://guidelines.ukkidney.org/hyperkalaemia/
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