Anesthesiology APPLIED Exam › Critical care, resuscitation and trauma

Hyperkalemia

Critical care, resuscitation and trauma·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 64-year-old man, 92 kg, with end-stage renal disease on hemodialysis, needs an urgent below-knee amputation for wet gangrene of the foot. He missed his last dialysis session. He takes lisinopril. Potassium is 6.8 mmol/L, and the ECG shows peaked T waves with a normal QRS. Blood pressure is 158/90 and he is alert.

Question

How will you manage his potassium, and does the operation go ahead?

Ideal answer

Headline6.8 with ECG changes is severe hyperkalemia:¹ calcium chloride 1 g IV now, then shift and remove. The urgent amputation proceeds, without succinylcholine.

Calcium chloride 1 g IV first, through a good line, to stabilize the membrane; I treat the ECG, not the number alone.
Shift: insulin 10 units with 25 g dextrose, albuterol 10–20 mg nebulized, hyperventilation once intubated; bicarbonate only for metabolic acidosis, not routinely.¹
Remove: dialysis and a binder, because shifting removes nothing and he has no urine to speak of. I stop the sources: potassium in fluids, succinylcholine, old blood, ACE inhibitor.
Proceed with an arterial line, because it is urgent; dialysis first if surgeons and infection allow a few hours.
Potassium at 1, 2, 4, 6 and 24 hours, glucose hourly: the shift wears off, potassium rebounds.¹

Watch for: a widening QRS on the continuous ECG.

Breaking down the answer

Proceed or postpone — Elective: postpone above 5.5 mmol/L and treat; an emergency proceeds with treatment started. Dialysis: last run? Baseline? The ECG decides: a chronic 5.8 with a normal ECG differs from an acute 5.8 with peaked T waves.
Calcium — antagonizes the depolarizing effect on the myocyte membrane in 1–3 minutes. Chloride 1 g holds triple gluconate's elemental calcium; it lasts only 30–60 minutes, so I repeat it if ECG changes persist,¹ even on digoxin when the alternative is arrest.
Insulin and dextrose — potassium falls within 15 minutes, 0.65–1.0 mmol/L at the 30–60 minute peak, rebounding after about 2 hours;¹ hypoglycemia comes late, around hour two. I omit dextrose only if glucose exceeds 250 mg/dL.
Hyperventilation and bicarbonate — a 0.1 rise in pH lowers potassium roughly 0.5 mmol/L, so hyperventilation is my fastest tool under anesthesia. Bicarbonate works only with acidosis to correct, and its sodium load matters in renal failure.
Removal options — furosemide 40–80 mg if there is urine. Sodium zirconium cyclosilicate works within about an hour and is now recommended for severe hyperkalemia; the old resin is no longer routine.¹
Succinylcholine — contraindicated after the acute phase of major burns, multiple trauma, extensive denervation and upper motor neuron injury (extrajunctional receptors), peaking at 7–10 days.² After those injuries I treat it as safe only in the first 24 hours; here, rocuronium with sugammadex available.

Follow-up question

Twenty minutes into the case, the ECG goes from peaked T waves to a sine wave and the arterial pressure trace disappears. What do you do?

Follow-up answer

HeadlineHyperkalemic arrest; I announce it and run ACLS with the specific treatment attached.

Chest compressions and epinephrine as standard; calcium chloride 1 g repeated every 5 minutes, insulin 10 units with dextrose, bicarbonate 50–100 mEq and hyperventilation. AHA 2025 grades these as of uncertain benefit in arrest and advises against inhaled beta-agonists.³ The arrest will not resolve until the potassium falls, so I tell the team we compress longer than for another cause, and I call for emergent dialysis. I hunt the source: succinylcholine, old packed cells through a rapid infuser, rhabdomyolysis from a tourniquet or crush, or malignant hyperthermia if end-tidal CO2 has been climbing. Potassium after each round.

Pitfalls that cost points

"I would cancel" for a dialysis patient at 5.6 whose baseline is 5.5 and whose ECG is normal.
Avoiding lactated Ringer's because it "contains potassium," then giving large volumes of saline, whose acidosis raises potassium more.

Rapid-fire

Q: Why does calcium work when it does not change the potassium? A: It restores the gap between resting membrane potential and threshold, so the myocyte depolarizes normally; potassium is unchanged, the membrane is stabilized.

Q: Why is the ECG more important than the level? A: The rate of rise determines the effect; chronic renal patients tolerate 6.0 with a normal ECG, while an acute rise to 6.0 widens the QRS.

Q: Why does succinylcholine release so much potassium after a burn? A: Receptors spread from the junction across the whole muscle membrane, so depolarization opens channels along the entire fiber, and the efflux can arrest the heart.

Q: Why does old blood raise the potassium? A: Stored red cells leak potassium about 1 mEq/L per day toward a plateau near 60 mEq/L, faster after irradiation;⁴ a rapid infuser delivers it to the heart before it dilutes.

Numbers to know

Item	Value
Severe hyperkalemia	≥ 6.5 mmol/L; treat any level with ECG change¹
Calcium chloride	10 mL of 10% (1 g) over 5 min; repeat if ECG changes persist¹
Insulin / dextrose	10 units with 25 g dextrose; peak 30–60 min, wanes by about 2 h¹
Albuterol nebulized	10–20 mg, never as monotherapy¹
Bicarbonate	Not routine; only if acidotic
pH effect	0.1 pH rise lowers K by ~0.5 mmol/L
Succinylcholine rise	0.5–1 mmol/L in a normal patient

Sources

1.Clinical Practice Guidelines: Treatment of Acute Hyperkalaemia in Adults · UK Kidney Association, 2023 · renal.org
2.QUELICIN (succinylcholine chloride) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
3.Part 10: Adult and Pediatric Special Circumstances of Resuscitation (2025 AHA Guidelines) · AHA, 2025 · cpr.heart.org
4.Transfusion-Associated Hyperkalemic Cardiac Arrest in Neonatal, Infant, and Pediatric Patients · Frontiers in Pediatrics (PubMed Central), 2021 · ncbi.nlm.nih.gov

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.