What potassium level counts as severe hyperkalaemia?

The UK Kidney Association 2023 guideline defines severe hyperkalaemia as a serum potassium of 6.5 mmol/L or more, moderate as 6.0 to 6.4 and mild as 5.5 to 5.9. Severe hyperkalaemia requires urgent hospital assessment.

What is the calcium dose for hyperkalaemia with ECG changes?

According to the UKKA 2023 guideline, 30 ml of 10% calcium gluconate over 10 minutes, or 10 ml of 10% calcium chloride over 5 minutes, which are equivalent doses of 6.8 mmol. Calcium chloride is preferred in cardiac arrest or peri-arrest; calcium gluconate for all other patients.

How do I give insulin-glucose safely?

The UKKA guideline recommends 10 units of soluble insulin in 25 g of glucose by intravenous infusion, followed by 10% glucose at 50 ml/hour for 5 hours if the pre-treatment glucose was under 7.0 mmol/L, with blood glucose checked at 0, 30, 60, 90, 120, 180, 240, 300 and 360 minutes.

Is calcium resonium still used for acute hyperkalaemia?

No. The UKKA 2023 guideline recommends that calcium resonium should no longer be routinely used in acute hyperkalaemia. Sodium zirconium cyclosilicate is recommended for severe and suggested for moderate hyperkalaemia, and patiromer is an option at 6.0 mmol/L or more.

When should hyperkalaemia be referred to renal or critical care?

The UKKA guideline suggests referral of severe hyperkalaemia (6.5 mmol/L or more) to the local renal or critical care team for an urgent opinion, and recommends critical care first for any patient with a problem with airway, breathing, circulation or conscious level. Decisions on renal replacement therapy are made urgently by a nephrologist or critical care specialist.

How often should I recheck the potassium after treatment?

The UKKA guideline suggests checking serum potassium at least at 1, 2, 4, 6 and 24 hours after identification and treatment of moderate or severe hyperkalaemia, to confirm the response and catch rebound.

Hyperkalaemia — CST Interview Clinical Station Answer

Hyperkalaemia is a serum potassium above 5.5 mmol/L, and the UK Kidney Association guideline of October 2023 grades it as mild at 5.5 to 5.9, moderate at 6.0 to 6.4 and severe at 6.5 mmol/L or more. On a surgical ward it arrives with acute kidney injury, rhabdomyolysis, tissue ischaemia, blood transfusion and the drug chart. The CST clinical station wants the five-step treatment said in order with the doses, the ECG rule, the monitoring times and a named renal or critical care call.

Key takeaways

UKKA 2023: mild 5.5 to 5.9, moderate 6.0 to 6.4, severe 6.5 mmol/L or more; severe hyperkalaemia needs urgent hospital assessment
Every hospital patient with a potassium of 6.0 or more gets an urgent 12-lead ECG; continuous 3-lead monitoring for 6.5 or more, for ECG changes, or for 6.0 to 6.4 with acute illness
Step 1, protect the heart: 30 ml of 10% calcium gluconate over 10 minutes if there are ECG changes, or 10 ml of 10% calcium chloride over 5 minutes in arrest or peri-arrest
Step 2, shift potassium: 10 units of soluble insulin in 25 g of glucose by intravenous infusion, then 10% glucose at 50 ml/hour for 5 hours if the pre-treatment glucose was under 7.0 mmol/L; nebulised salbutamol 10 to 20 mg as an adjunct, never alone
Step 3, remove potassium: sodium zirconium cyclosilicate for severe hyperkalaemia and considered for moderate; calcium resonium is no longer used routinely; dialysis decisions belong to a nephrologist or intensivist
Step 4, monitor: potassium at 1, 2, 4, 6 and 24 hours, and blood glucose at 0, 30, 60, 90, 120, 180, 240, 300 and 360 minutes after insulin-glucose

How does hyperkalaemia present on a surgical ward?

Hyperkalaemia presents as a laboratory result, usually before it presents as a symptom, and the surgical causes are acute kidney injury from hypovolaemia or sepsis, rhabdomyolysis after a long lie or compartment syndrome, acute limb ischaemia and reperfusion, large transfusions, and drugs such as ACE inhibitors, potassium-sparing diuretics and trimethoprim.

The UKKA guideline puts in-hospital mortality for severe hyperkalaemia above 30% in cited series, which is why a potassium of 6.5 is treated as an emergency even in a patient who feels well. Weakness, paraesthesia and palpitations are late. The ECG is the clinical sign: peaked T waves, a flattened P wave, a widening QRS and, eventually, a sine wave.

What is the immediate management of hyperkalaemia, A to E?

Immediate management of hyperkalaemia is an ABCDE assessment with the ECG and cardiac monitor as part of circulation, and the potassium repeated on a blood gas while you act.

Airway and breathing

Confirm the airway and give oxygen if saturations are low. Respiratory muscle weakness is rare but real in severe hyperkalaemia; note the respiratory rate.

Circulation

Pulse, blood pressure and a 12-lead ECG at once, which the UKKA guideline recommends for every hospitalised patient with a potassium of 6.0 mmol/L or more. Put the patient on continuous 3-lead monitoring if the potassium is 6.5 or more, if the ECG shows hyperkalaemic changes, or if it is 6.0 to 6.4 and the patient is unwell. Intravenous access and a venous or arterial gas: the guideline recommends measuring potassium on a point-of-care gas analyser in emergencies while the laboratory result is awaited.

Disability and exposure

Conscious level, capillary glucose because insulin is coming, and a look for the cause: the fluid balance, the urine output, the drug chart, a tense compartment, an ischaemic limb, a transfusion running.

What investigations does hyperkalaemia need?

Hyperkalaemia needs a 12-lead ECG, a repeat potassium on a lithium heparin sample or a blood gas, urea and electrolytes for the acute kidney injury that usually explains it, and a venous gas for the acid-base picture. The UKKA guideline recommends a lithium heparin sample when a rapid turnaround is needed.

If pseudo-hyperkalaemia is possible, from a haemolysed or delayed sample, the guideline recommends paired lithium heparin and clotted serum samples from a large vein taken with gentle traction and analysed promptly. However, treat first if the ECG has changed; do not wait for the repeat. Add creatine kinase if rhabdomyolysis is possible and a capillary glucose before insulin.

What is the definitive management of hyperkalaemia?

Definitive management of hyperkalaemia follows the five-step approach the UK Kidney Association recommends: protect the heart, shift potassium into cells, remove potassium from the body, monitor, and prevent recurrence.

Step 1: protect the heart

Give intravenous calcium when there are ECG changes: 30 ml of 10% calcium gluconate over 10 minutes, or 10 ml of 10% calcium chloride over 5 minutes, an equivalent dose of 6.8 mmol. The guideline prefers calcium chloride in cardiac arrest or peri-arrest and calcium gluconate for everyone else. Calcium does not lower the potassium; it buys time.

Step 2: shift potassium into cells

Insulin-glucose, 10 units of soluble insulin in 25 g of glucose by intravenous infusion, is recommended for severe hyperkalaemia and suggested for moderate. To avoid the hypoglycaemia the guideline describes as unacceptably common, patients whose pre-treatment glucose was under 7.0 mmol/L then get 10% glucose at 50 ml/hour for 5 hours. Nebulised salbutamol 10 to 20 mg is an adjunct for severe hyperkalaemia and may be used in moderate, but the guideline recommends against salbutamol as monotherapy, and suggests against routine intravenous sodium bicarbonate.

Step 3: remove potassium from the body

Sodium zirconium cyclosilicate is recommended in the emergency management of severe hyperkalaemia and suggested for moderate; patiromer is an option at 6.0 or more. Calcium resonium should no longer be used routinely. Treat the cause: fluids for the acute kidney injury, stop the offending drugs, relieve the obstruction. Renal replacement therapy for life-threatening or resistant hyperkalaemia is a decision the guideline places with a nephrologist or critical care specialist, taken urgently.

Steps 4 and 5: monitor and prevent recurrence

Potassium is checked at least at 1, 2, 4, 6 and 24 hours after treatment of moderate or severe hyperkalaemia, because rebound is expected as the shift wears off. Blood glucose is checked at 0, 30, 60, 90, 120, 180, 240, 300 and 360 minutes after insulin-glucose. Then the cause is written on the plan and the drug chart is changed so it does not happen again.

When do I escalate hyperkalaemia, and to whom?

Escalate severe hyperkalaemia to the registrar immediately and, per the UKKA guideline, refer patients with a potassium of 6.5 or more to the local renal or critical care team for an urgent opinion, guided by the clinical picture and its persistence after initial treatment. Where there is no renal service on site, the critical care team is called first.

The guideline recommends that a patient with severe hyperkalaemia and a problem with airway, breathing, circulation or conscious level goes to critical care in the first instance, that a stable patient with severe hyperkalaemia is admitted to an area with continuous cardiac monitoring, and that a senior member of the referring team makes the critical care referral if escalation is needed from the outset or the patient fails to respond. Say the ward you would move the patient to and who would make the call.

What about the other critical electrolytes?

The other critical electrolytes for a surgical SHO are sodium, calcium and magnesium, and the CST station may pivot to them once the potassium is handled. The safe answer is the same structure: confirm the result, assess the patient by ABCDE, find the surgical cause, and correct at a rate set by the relevant guideline rather than from memory.

Hypokalaemia: common after high-output stomas, vomiting and diuretics; replace with ready-mixed bags, never by adding potassium to a bag on the ward, and check magnesium
Sodium: hyponatraemia is common on maintenance fluids and after surgery; correction rates and hypertonic saline are senior and guideline-led decisions
Calcium: hypocalcaemia after thyroid or parathyroid surgery presents with perioral tingling and carpopedal spasm and needs the endocrine surgical team
Magnesium: low magnesium keeps potassium and calcium low until it is replaced

What is the interviewer listening for in a hyperkalaemia scenario?

The three severity bands and the ECG rule at 6.0, said as numbers
Calcium given for ECG changes with the dose, volume and time, and the point that it does not lower potassium
Insulin-glucose with the glucose infusion that follows it, and salbutamol as an adjunct, not alone
Sodium zirconium cyclosilicate named, and calcium resonium explicitly not used
The monitoring times, the cause found, and the renal or critical care call made by a senior

What are the common mistakes with hyperkalaemia?

The commonest mistake with hyperkalaemia at interview is quoting the old 10 ml calcium gluconate dose, which the 2023 UKKA guideline replaced with 30 ml over 10 minutes. The second is forgetting the glucose infusion and the glucose checks, so the patient is rescued from the potassium and lost to hypoglycaemia.

Waiting for the laboratory repeat when the ECG has already changed
Prescribing calcium resonium as if it were still the standard
Using salbutamol alone for a severe result
Not checking potassium again at 1, 2, 4, 6 and 24 hours, so the rebound is missed
Treating the number and not the acute kidney injury or the drug that caused it

How this comes up at the CST interview

The CST management and clinical station sets hyperkalaemia as a post-operative potassium of 6.8 with an acute kidney injury, and the panel wants the ECG ordered in the first sentence, the five steps in order with the UK Kidney Association doses, and a renal or critical care referral made by someone senior. coresurgeryinterview's 299 questions with AI-marked spoken practice include a scored version of this scenario, at /Question-Bank/Sample-Questions.

Hyperkalaemia and the Critical Electrolytes