Hyperkalaemia — SAQ

Stem

A 68-year-old man with CKD stage 4, on ramipril and spironolactone, is sent in from the community with a potassium of 7.1 mmol/L. He feels weak climbing stairs. The monitor shows tall peaked T waves and a widening QRS. Use sourced definitions, bands, and doses — not mixed regional numbers without naming the source. ^[2]

Questions

a) Define hyperkalaemia and give the UKKA/ERC severity bands. Why do 5.5 and 6.5 change management? (3 marks)

• Definition: serum potassium at or above 5.5 mmol/L (Lehnhardt: exceeds 5.5 mmol/L; UKKA uses the ERC threshold of at least 5.5 mmol/L). Do not quote Kim/Ben Salem's 5.0 mmol/L laboratory cutoff as the UKKA band. ^[1][2]
• UKKA bands: mild 5.5 to 5.9, moderate 6.0 to 6.4, severe at or above 6.5 mmol/L.
• Why it changes management: 5.5 means the disease is real — stop K-retaining drugs, prove the sample, treat the cause. 6.5 or any ECG change is the emergency ladder. UKKA gives calcium when the ECG is abnormal and insulin-glucose for confirmed severe hyperkalaemia even if the trace is still quiet. ^[2]

b) This man might have a false number. Name the artefact, its three clusters, and when you still treat before the repeat. (3 marks)

• Pseudohyperkalaemia: haemolysis and excessive potassium leakage during or after collection; also haematological disorders with leucocytosis and thrombocytosis. Reverse pseudohyperkalaemia: plasma higher than serum from heparin-induced membrane damage in leukaemia. ^[5]
• Fix: repeat without a tourniquet, no fist-clenching, prompt analysis — or an ABG potassium; compare serum with plasma if the counts are high.
• Do not wait if the ECG is already diagnostic (peaked T, wide QRS here). Treat the membrane first. ^[2][3]

c) Give Step 1 calcium: what it does not do, the US 10 mL teaching, and the UKKA 6.8 mmol equivalent. (3 marks) ^[2][3]

• Calcium reverses electrocardiographic changes and reduces arrhythmia risk but does not lower serum potassium. ^[3]
• Long (US EM): calcium gluconate 10% 10 mL IV; 10 mL calcium chloride if in cardiac arrest. That 10 mL of gluconate is 2.26 mmol Ca2+, not 10 mmol.
• UKKA: equivalent dose 6.8 mmol when there is ECG evidence of hyperkalaemia. 10 mL 10% calcium chloride = 6.8 mmol; 10 mL 10% gluconate = 2.26 mmol, so three gluconate ampoules match. Effective within 3 minutes; repeat if no effect in 5-10 minutes; duration 30-60 minutes. ^[2]

d) Give Step 2 insulin-glucose and salbutamol with sourced numbers, plus the hypoglycaemia trap. (3 marks)

• UKKA: 10 units soluble insulin in 25 g glucose for K+ at or above 6.5 mmol/L (1B); extra 10% glucose 50 mL/h for 5 hours if pretreatment glucose under 7.0 mmol/L; glucose checks up to 12 hours. ^[2]
• Harel: 10-unit bolus lowered K+ 0.78 mmol/L at 60 minutes vs 0.79 mmol/L with 20 units over 60 minutes; a 10-unit infusion fell only 0.39 mmol/L. Recommend 50 g glucose with 10 units because almost one fifth became hypoglycaemic. Monitor hourly at least 4-6 hours (Moussavi). ^[4]
• Salbutamol 10 to 20 mg nebulised as adjuvant, not monotherapy (UKKA 1A against monotherapy in severe disease). ^[2]

e) Name Step 3 removal, the binder that is retired, and the Addisonian parallel if this man also had hyponatraemia and shock. (3 marks)

• Removal is the only durable step: loop diuretic if urine output allows, SZC or patiromer, or haemodialysis (most efficient; drugs are the bridge). SPS / calcium resonium is not for emergency severe hyperkalaemia (Geldermann: no longer recommended; UKKA: not for emergency severe). ^[2][3][7]
• Addisonian crisis: parenteral hydrocortisone, rehydration, and electrolyte management — do not wait for the cortisol result. Infection is the major precipitant. Do not invent a 100 mg / 200 mg-per-24-h pair unless you are quoting a sourced emergency card. ^[6]

Marking tips

Full marks require the UKKA bands, the 6.8 mmol vs 10 mL gluconate distinction, 10 units in 25 g (UKKA) vs 50 g (Harel), and not treating a well normal-ECG patient until the sample is proven while still treating this man's wide QRS immediately. ^[2]

References7ShowHide

1. [1]Lehnhardt A, Kemper MJ. Pathogenesis, diagnosis and management of hyperkalemia Pediatr Nephrol, 2011.PMID 21181208
2. [2]Alfonzo A, Harrison A, Baines R, Chu A, Mann S, MacRury M. Clinical Practice Guidelines: Treatment of Acute Hyperkalaemia in Adults UK Kidney Association (Renal Association), 2020.Source
3. [3]Long B, Warix JR, Koyfman A. Controversies in Management of Hyperkalemia J Emerg Med, 2018.PMID 29731287
4. [4]Harel Z, Kamel KS. Optimal Dose and Method of Administration of Intravenous Insulin in the Management of Emergency Hyperkalemia: A Systematic Review PLoS One, 2016.PMID 27148740
5. [5]Meng QH, Wagar EA. Pseudohyperkalemia: A new twist on an old phenomenon Crit Rev Clin Lab Sci, 2015.PMID 25319088
6. [6]Dineen R, Thompson CJ, Sherlock M. Adrenal crisis: prevention and management in adult patients Ther Adv Endocrinol Metab, 2019.PMID 31223468
7. [7]Geldermann N, Dzimiera J, Fischer H, et al. Acute hyperkalaemia in emergency care: evidence-based approaches Emerg Med J, 2026.PMID 41506858