Ask the lab: Was it haemolysed? What was the previous value and when? If the number is a surprise, send an urgent non-haemolysed repeat — and then treat and monitor now, rather than waiting for the repeat to come back and agree with you. Ask the nurse: ECG now, and put him on the monitor. Stop any potassium-containing fluid.
Tell the nurse: 12-lead ECG immediately · cardiac monitor · IV access · stop potassium infusions, and pull the chart for spironolactone, ACE inhibitor, ARB, trimethoprim, NSAIDs, potassium supplements.
The ECG raises the urgency. It cannot lower it. That distinction is the whole entry, and Edition 1 got it half wrong. A potassium of 6.1 with peaked T waves in a fresh AKI is worse than 6.8 with a clean trace in a stable dialysis patient — but 6.8 is still severe, still needs treatment, monitoring and a senior tonight, and a normal ECG has never once excluded a lethal potassium. Urgency comes from the value, the rate of rise, the trace, the renal function, the acid–base state and the patient in the bed. A quiet ECG is not a negative test. It is an ECG.
Look for: peaked T waves → flattened P waves → widened QRS → sine wave. Any ECG change = calcium now — and UKKA 2023 means 30 mL of 10% calcium gluconate over 10 minutes, or 10 mL of 10% calcium chloride over 5, the salt depending on access and circumstance. Your protocol may phrase it differently. Read it before tonight, not during.
FIRST MOVES — THE THREE JOBS, IN ORDER
- Protect the heart. IV calcium (gluconate or chloride per local protocol) if there are any ECG changes. It does not lower potassium; it buys you time. Repeat if changes persist.
- Shift it inward. Insulin with glucose is the workhorse — and the hypoglycaemia afterwards is the classic iatrogenic injury on this call, so write the glucose checks in the same breath as the insulin. UKKA 2023 schedules them at 0, 30, 60, 90, 120, 180, 240, 300 and 360 minutes. Follow your local protocol where it specifies a schedule of its own. Where it does not, use the UKKA one, or get urgent senior or pharmacy advice — but do not invent an interval at 3 a.m. Nebulised salbutamol is an adjunct, not a plan. Bicarbonate is not routine — UKKA advises against it as a standard part of acute treatment, so if you are giving it you should be able to say why, out loud, to someone senior.
- Remove it. Loop diuretic if volume-replete and the kidneys work, a binder — UKKA recommends sodium zirconium cyclosilicate at 6.5 and above and considers it from 6.0, lists patiromer as an option, and has retired calcium resonium from routine acute use, though what is actually on your shelf is a local matter. Dialysis if refractory or anuric.
Then find the cause: AKI, drugs, tissue breakdown (rhabdomyolysis, tumour lysis, large haematoma), adrenal insufficiency, or a spurious sample. And book the repeat potassiums before you leave the ward — UKKA suggests at least 1, 2, 4, 6 and 24 hours. Shifting potassium into cells is a loan, not a payment.
Critical result: potassium [X] mmol/L on a [ARTERIAL/VENOUS] sample, previous [X] on [DATE]. Haemolysed: [Y/N/UNKNOWN]. [AGE]-year-old [SEX], admitted for [REASON]. 12-lead ECG: [PEAKED T / WIDE QRS / LOST P / NORMAL / OTHER]. Creatinine [X] (baseline [X]), urea [X], bicarbonate [X], pH [X], glucose [X]. Urine output last 6h [X mL]. Known CKD/dialysis: [Y/N]. Drugs: [ACEi/ARB/SPIRONOLACTONE/TRIMETHOPRIM/NSAID/K SUPPLEMENT/OTHER]. Possible tissue breakdown: [RHABDO/TUMOUR LYSIS/HAEMATOMA/NO]. Assess urgency from all of it — the value, the rate of change, the ECG, renal function, acid-base state and how the patient actually looks — and state explicitly why a normal ECG does not make a severe potassium safe. Then the three-step plan with actual doses, the exact glucose-monitoring schedule after insulin, which of this patient's drugs I stop tonight, and my escalation threshold.