What potassium level counts as severe hyperkalaemia?

A serum potassium of 6.5 mmol/L or above. The UK Kidney Association's 2023 guideline grades hyperkalaemia as mild at 5.5 to 5.9 mmol/L, moderate at 6.0 to 6.4 mmol/L and severe at 6.5 mmol/L or above.

How much calcium gluconate do you give in hyperkalaemia?

For severe hyperkalaemia with ECG changes, guideline 16.2a recommends an equivalent 6.8 mmol dose of intravenous calcium: 30 mL of 10% calcium gluconate over 10 minutes, or 10 mL of 10% calcium chloride over 5 minutes.

Does calcium lower the potassium?

No. Calcium stabilises the myocardium against arrhythmia and does not change the serum potassium at all. That is why it is step two of five, and why insulin-glucose and salbutamol follow it to shift potassium into cells.

What is the insulin-glucose dose for hyperkalaemia?

Guideline 16.3.1 recommends 10 units of soluble insulin in 25 g of glucose by intravenous infusion for severe hyperkalaemia. If the pre-treatment blood glucose is below 7.0 mmol/L, guideline 16.3.3 adds 10% glucose at 50 mL per hour for 5 hours.

When does a hyperkalaemic patient need an ECG?

Guideline 14.1 recommends an urgent 12-lead ECG for all hospitalised patients with a potassium of 6.0 mmol/L or above. Guideline 14.2 recommends continuous three-lead monitoring at 6.5 mmol/L or above, or with ECG features of hyperkalaemia.

When should you call the renal team about hyperkalaemia?

Guideline 19.1 recommends referring patients with severe hyperkalaemia, at 6.5 mmol/L or above, to the local renal or critical care team. Where renal services are not on site, guideline 19.2 sends the referral to critical care first.

Which drugs cause hyperkalaemia?

The ones that appear in interview scenarios are ACE inhibitors and angiotensin receptor blockers, potassium-sparing diuretics such as spironolactone, trimethoprim, NSAIDs and potassium supplements. Stopping the culprit is step five, preventing recurrence.

Hyperkalaemia — IMT Interview Clinical Station Answer

Hyperkalaemia is the clinical-station scenario where precise numbers are available and expected. The UK Kidney Association's October 2023 guideline gives three severity bands, a five-step sequence and exact doses, so vagueness is audible.

Key takeaways

The UK Kidney Association defines hyperkalaemia as a serum potassium of 5.5 mmol/L or above, taking the European Resuscitation Council definition, and grades it mild at 5.5 to 5.9, moderate at 6.0 to 6.4 and severe at 6.5 mmol/L or above.
Guideline 14.1 recommends an urgent 12-lead ECG for every hospitalised patient with a serum potassium of 6.0 mmol/L or above.
Guideline 14.2 recommends continuous three-lead ECG monitoring for any patient at 6.5 mmol/L or above, anyone with ECG features of hyperkalaemia, and patients at 6.0 to 6.4 mmol/L who are clinically unwell or rising quickly.
For severe hyperkalaemia with ECG changes, guideline 16.2a recommends an equivalent dose of 6.8 mmol of intravenous calcium: 30 mL of 10% calcium gluconate over 10 minutes, or 10 mL of 10% calcium chloride over 5 minutes.
Guideline 16.3.1 recommends insulin-glucose, being 10 units of soluble insulin in 25 g of glucose by intravenous infusion, to treat severe hyperkalaemia.
Guideline 19.1 recommends that patients with severe hyperkalaemia are referred to the local renal or critical care team.

How do you recognise hyperkalaemia and how sick is the patient?

You recognise hyperkalaemia on the blood result and you grade the danger on the ECG, not on the potassium alone. The UK Kidney Association's first step is to assess the risk of arrhythmias.

The guideline describes progressive ECG changes with increasing severity of hyperkalaemia: peaked T waves, diminished P waves, widened QRS complexes, bradycardia, and a sine wave pattern in severe cases.

Mild hyperkalaemia is a potassium of 5.5 to 5.9 mmol/L.
Moderate hyperkalaemia is 6.0 to 6.4 mmol/L.
Severe hyperkalaemia is 6.5 mmol/L or above.
An urgent 12-lead ECG is recommended for every hospitalised patient at 6.0 mmol/L or above, under guideline 14.1.

Say the two things the panel is waiting for. Exclude pseudohyperkalaemia from a haemolysed or badly taken sample by repeating it, and do not delay treating a patient with ECG changes while you wait for the repeat.

What do you do in the first hour of severe hyperkalaemia?

In the first hour of severe hyperkalaemia you protect the heart, then shift potassium into cells. The UK Kidney Association sets this out as a five-step approach in guideline 16.1.

Step one, assess the risk of arrhythmias.
Step two, protect the heart with intravenous calcium.
Step three, shift potassium into cells with insulin-glucose and salbutamol.
Step four, remove potassium from the body with potassium binders or dialysis.
Step five, identify the cause and prevent recurrence.

Calcium is for severe hyperkalaemia with ECG changes, and the guideline gives two equivalent options at 6.8 mmol of calcium: 30 mL of 10% calcium gluconate over 10 minutes, or 10 mL of 10% calcium chloride over 5 minutes.

Guideline 16.2b says calcium chloride is the preferred salt in resuscitation, and calcium gluconate should be used for all other patients. Saying which salt, and why, is the sentence that separates candidates.

What are the named doses for shifting potassium?

The named doses for shifting potassium in hyperkalaemia are 10 units of soluble insulin in 25 g of glucose by intravenous infusion, and nebulised salbutamol at 10 to 20 mg as an adjuvant.

Guideline 16.3.1 recommends insulin-glucose for severe hyperkalaemia at 6.5 mmol/L or above, and guideline 16.3.2 suggests it for moderate hyperkalaemia at 6.0 to 6.4 mmol/L.
Guideline 16.3.3 recommends starting an infusion of 10% glucose at 50 mL per hour for 5 hours, giving 25 g, in patients whose pre-treatment blood glucose is below 7.0 mmol/L.
Guideline 16.4.1 recommends nebulised salbutamol at 10 to 20 mg as adjuvant therapy for severe hyperkalaemia, not as a treatment on its own.
Guideline 16.6.1a recommends sodium zirconium cyclosilicate in the emergency management of severe hyperkalaemia.

Mention hypoglycaemia before the panel does. The reason the 2023 guideline added the follow-on glucose infusion and blood glucose monitoring is that insulin-glucose regimens cause late hypoglycaemia, and it is the avoidable harm here.

What is the definitive management of hyperkalaemia?

Definitive management of hyperkalaemia is removing potassium from the body and removing the cause, because calcium, insulin and salbutamol buy time without changing total body potassium.

Potassium binders, with sodium zirconium cyclosilicate recommended in the emergency management of severe hyperkalaemia.
Renal replacement therapy, where the potassium is life-threatening or refractory.
A full medication review, because renin-angiotensin system blockers, potassium-sparing diuretics, trimethoprim, NSAIDs and potassium supplements all appear in these scenarios.
Treatment of the precipitant, most often acute kidney injury, but also rhabdomyolysis, tumour lysis, adrenal insufficiency and metabolic acidosis.

Guideline 19.6 says decisions on the timing, suitability and modality of renal replacement therapy in life-threatening hyperkalaemia are made urgently by nephrology or critical care specialists. That is not your decision alone, and saying so is a strength.

When do you escalate a patient with hyperkalaemia, and to whom?

You escalate hyperkalaemia at 6.5 mmol/L. Guideline 19.1 recommends that patients with severe hyperkalaemia are referred to their local renal or critical care team, judged on the clinical context and the response to treatment.

Guideline 19.2 says that where renal services are not available on site, referral goes to the local critical care team in the first instance.
Guideline 19.3 says patients are referred to critical care by a senior member of the team, either from the outset or if initial treatment fails.
Guideline 19.4 says any patient with problems of airway, breathing, circulation or conscious level is referred to the local critical care team.
Guideline 19.5 says stable patients with severe hyperkalaemia are admitted to an area with facilities for continuous cardiac monitoring, such as an acute medical, renal or critical care unit.

How do you hand over a patient with hyperkalaemia in one minute?

Hand over hyperkalaemia with the potassium, the ECG and the clock. The receiving team needs to know what has already been given and when the calcium will wear off.

Use SBAR, and make the recommendation specific with a time frame. The handover is scored as its own domain at the IMT interview, weighted 0.8, so it is marked separately from your clinical reasoning.

A worked version, said aloud: this is a 68-year-old man on ramipril with a potassium of 7.1 and peaked T waves. He has had 30 mL of 10% calcium gluconate and insulin-glucose at 14:20. I need renal to see him now, and he is on continuous cardiac monitoring.

What does the panel listen for in a hyperkalaemia answer?

The panel listens for whether a hyperkalaemia answer has a sequence. Protect, shift, remove, prevent is the shape, and candidates who list drugs without that order sound like they are reciting rather than treating.

That you ask for an ECG before you ask for anything else, and know the threshold that triggers it.
That you name a calcium salt, a volume, a strength and a time.
That you say calcium protects the myocardium without lowering potassium.
That you plan for the hypoglycaemia insulin-glucose causes rather than being reminded of it.
That you stop the drug that caused it, which is the step candidates skip most often.

What are the common mistakes in a hyperkalaemia station?

The commonest mistake in a hyperkalaemia station is giving insulin-glucose first and calcium second. Protecting the heart comes before shifting potassium when there are ECG changes.

Treating the number and never mentioning the ECG.
Giving salbutamol as sole therapy, when the guideline recommends it as an adjuvant in severe hyperkalaemia.
Forgetting that calcium is temporary, so the patient needs monitoring and a repeat potassium rather than reassurance.
Quoting the archived 2022 version of the guideline. The current UK Kidney Association guideline is the October 2023 one, with a review date of October 2026.
Not saying who you would call. The escalation recommendations in section 19 are the part of this guideline a panel can test in one closed question.

How this comes up at the IMT interview

At the IMT interview, hyperkalaemia sits in station 2, a clinical scenario of up to ten minutes on investigations, diagnosis and management, followed by a one-minute handover of the same patient.

It also appears inside acute kidney injury and sepsis scenarios, because hyperkalaemia is the complication that turns a ward problem into a resuscitation-room problem within minutes.

internalmedicineinterview's bank of 361 IMT questions across 56 scenarios includes clinical-station cases with model answers and AI-marked spoken practice, so you can hear whether your sequence held under time pressure.

Hyperkalaemia: Severity, Protecting the Heart and the Five Steps