Endocrine and metabolic · Easy
This case is fictional and exists for study. It describes no real patient.
62 years · male
A 62-year-old male with a known medical history of type 2 diabetes mellitus and stage 3 chronic kidney disease presents to the emergency department complaining of generalized muscle weakness, fatigue, and intermittent palpitations for the past 6 hours. He reports that his general practitioner recently added a new medication, spironolactone, to his regimen two weeks ago for heart failure management. On physical examination, he appears lethargic. Symmetrical lower limb weakness is noted with power measured at 4/5 bilaterally. Neurological sensation remains intact. Cardiovascular examination reveals regular bradycardia with normal heart sounds and no murmurs. An urgent 12-lead electrocardiogram is performed, showing tall, narrow, peaked T waves across the precordial leads.
Vital signs
- HR
- 52 bpm
- BP
- 112/68 mmHg
- RR
- 18/min
- Temp
- 36.6 °C
- SpO₂
- 97%
Examination findings
- Bilateral lower limb motor weakness (4/5 power)
- Bradycardia with regular rhythm
- Tall, narrow, peaked T waves on 12-lead ECG
Investigations
| Serum potassium | 7.2 mmol/L | reference: 3.5-5.0 |
| Serum sodium | 138 mmol/L | reference: 135-145 |
| Serum urea | 14.2 mmol/L | reference: 2.5-7.8 |
| Serum creatinine | 210 µmol/L | reference: 60-110 |
Question 1 of 3
What is the most appropriate immediate management step for this patient?
In severe hyperkalaemia with ECG changes, the immediate priority is cardioprotection using intravenous calcium gluconate (or calcium chloride) to stabilize the cardiac membrane and prevent fatal arrhythmias. Intravenous insulin with dextrose and nebulised salbutamol shift potassium into cells but do not directly protect the myocardium, making them second-line immediate steps after calcium administration. Sodium zirconium cyclosilicate is an oral potassium binder used to lower serum potassium over hours to days, not for emergency cardiac stabilization.
Teaching point: Intravenous calcium gluconate must be administered immediately in severe hyperkalaemia with ECG changes to stabilize the cardiac membrane.
Question 2 of 3
Which of the following ECG changes is typically the earliest manifestation of hyperkalaemia?
Tall, narrow, peaked T waves are the earliest ECG sign of hyperkalaemia, typically appearing when serum potassium exceeds 5.5 to 6.0 mmol/L. As serum potassium levels increase further, PR interval prolongation and flattening of P waves occur, followed by QRS complex widening, and ultimately a sine wave appearance prior to cardiac arrest.
Teaching point: Tall, peaked T waves represent the earliest ECG abnormality associated with hyperkalaemia.
Question 3 of 3
Which of the patient's home medications is the most likely contributing factor to this presentation?
Spironolactone is a potassium-sparing diuretic (aldosterone antagonist) that reduces renal excretion of potassium. In a patient with underlying chronic kidney disease, starting spironolactone significantly increases the risk of severe hyperkalaemia. Metformin can cause lactic acidosis but not direct hyperkalaemia. Amlodipine causes peripheral oedema, and atorvastatin can cause myopathy, but neither primary affects serum potassium handling.
Teaching point: Potassium-sparing diuretics like spironolactone carry a high risk of hyperkalaemia, especially in patients with baseline renal impairment.
Key learning points
- Severe hyperkalaemia (>6.5 mmol/L or with ECG changes) requires immediate intravenous calcium gluconate to stabilize the myocardial membrane.
- The sequence of ECG changes in hyperkalaemia starts with tall peaked T waves, followed by PR prolongation, QRS widening, and sine wave formation.
- Aldosterone antagonists (e.g., spironolactone) must be monitored closely for hyperkalaemia, particularly when coexisting with chronic kidney disease.
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