Some DHA questions test what you know. The better ones test whether you know what to do first. Hyperkalaemia is a classic example. Let’s work through the case, identify the correct management sequence, and see where candidates commonly get caught out.
Clinical Case
A 68-year-old man with stage 5 chronic kidney disease misses a dialysis session and presents with weakness. Serum potassium is 7.1 mmol/L. The ECG shows tall tented T waves and early QRS broadening. What should you do?
A. Intravenous calcium gluconate 10%
B. Intravenous insulin with dextrose
C. Nebulised salbutamol
D. Oral calcium resonium
E. Urgent haemodialysis
Correct Answer A. Intravenous calcium gluconate 10%
In any hyperkalaemia with ECG changes, intravenous calcium is given first. It does not lower the potassium, but it rapidly antagonises the effect of potassium on the myocardial membrane and stabilises cardiac conduction within minutes, buying time while potassium-lowering measures take effect.
Why the other options are wrong
B. Insulin with dextrose lowers potassium by shifting it into cells, but onset is 15–30 minutes and it does not protect the myocardium in the critical first minutes — it is the second step, not the first.
C. Nebulised salbutamol also shifts potassium intracellularly and is a useful adjunct, but as a sole agent the effect is modest and unreliable.
D. Oral calcium resonium removes potassium over hours and has weak evidence; it has no role in the acute ECG-positive emergency.
E. Haemodialysis is definitive in a dialysis-dependent patient but takes time to arrange — give calcium while organising it.
Exam Trap
Choosing insulin–dextrose first because it 'lowers the number' — it leaves the heart unprotected. Membrane stabilisation with calcium comes first whenever the ECG is abnormal.
Reference UK Renal Association / Resuscitation Council UK — Treatment of Acute Hyperkalaemia in Adults.
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