Phys · renal
Potassium Disorders — Hyperkalaemia and Hypokalaemia
Also known as hyperkalaemia · hyperkalemia · hypokalaemia · hypokalemia · potassium · peaked T waves · sine wave · calcium gluconate · insulin-dextrose · insulin glucose · patiromer · sodium zirconium cyclosilicate · SZC · sodium polystyrene sulfonate · resonium · Bartter syndrome · Gitelman syndrome · primary aldosteronism · Conn syndrome · pseudohyperkalaemia · tumour lysis syndrome · rhabdomyolysis
Consultant-physician-depth guide to potassium homeostasis and its two emergencies. Covers hyperkalaemia (K+ above 5.5): the renal and pharmacological causes (AKI, CKD, RAAS inhibitors, K-sparing diuretics, Addison's, rhabdomyolysis, tumour lysis, acidosis), the ECG progression from peaked T waves through PR prolongation and QRS widening to sine wave and cardiac arrest, and emergency management with calcium gluconate for membrane stabilisation, insulin-dextrose and salbutamol to shift K+ intracellularly, bicarbonate in acidosis, the potassium binders (patiromer, sodium zirconium cyclosilicate, resonium) and dialysis. Covers hypokalaemia (K+ below 3.5): the GI and renal causes, diuretics, Bartter and Gitelman syndromes, Cushing and Conn syndromes, alkalosis, insulin, and refractory hypomagnesaemia; the clinical features of weakness, cramps, and U waves with QT prolongation; oral versus IV replacement with the maximum 10 to 20 mmol/h central-line rate; and the 24h urine potassium, renin/aldosterone and acid-base workup. Structured for FRACP DWE and DCE preparation.
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Red flags
- Hyperkalaemia with ECG changes (peaked T waves, PR prolongation, QRS widening, sine wave) — give calcium gluconate 10 mL of 10% IV immediately for membrane stabilisation; do not wait for the potassium to fall
- Sine wave on the ECG or broad-complex bradycardia in hyperkalaemia — imminent VF or asystole; calcium then insulin-dextrose then urgent dialysis
- K+ above 7.0 mmol/L — severe hyperkalaemia; treat as an emergency regardless of ECG, because the ECG may be normal even at lethal levels
- Hypokalaemia below 2.5 mmol/L or with arrhythmia, marked weakness, or ascending paralysis — admit for IV replacement under cardiac monitoring
- Refractory hypokalaemia that will not correct despite high-dose replacement — the commonest cause is unrecognised hypomagnesaemia; check and replete magnesium first
- Periodic paralysis (thyrotoxic or familial) — sudden K+ shift into cells produces profound weakness with a low serum K+; treat cautiously, the K+ rebounds
- Addisonian crisis with hyperkalaemia, hyponatraemia, hypotension — give parenteral hydrocortisone immediately; the hyperkalaemia is mineralocorticoid-deficiency driven and steroids correct it
- Tumour lysis syndrome — hyperkalaemia, hyperphosphataemia, hypocalcaemia, AKI within 12 to 72 hours of starting cytotoxic therapy; give rasburicase and IV fluids preemptively in high-risk haematological malignancies
Potassium Disorders — Hyperkalaemia and Hypokalaemia
The answer first
Potassium is an intracellular ion. Only 2 percent of total body potassium is in the extracellular fluid, yet that small fraction is what the serum potassium measures and what determines membrane excitability — in the heart most acutely. The serum potassium is therefore a poor index of total body potassium; it reflects the balance between intake, excretion, and the distribution of potassium across the cell membrane. A clinician faced with an abnormal potassium must answer three questions in parallel: is this real, what is the threat to the heart, and what is driving the disturbance [1][2].
The two emergencies are mirror images. Hyperkalaemia (K+ above 5.5 mmol/L) threatens the heart by depolarising the resting membrane potential: the myocyte cannot repolarise, conduction slows, and the rhythm degenerates from peaked T waves through QRS widening to a sine wave and ventricular fibrillation or asystole. Hypokalaemia (K+ below 3.5 mmol/L) hyperpolarises the membrane, prolongs repolarisation, and produces arrhythmias — classically QT prolongation with torsades, atrial ectopy, and re-entrant ventricular arrhythmias — as well as skeletal and smooth muscle weakness. [1]
In both, the ECG determines urgency more than the absolute number, but the ECG is imperfect: severe hyperkalaemia can have a near-normal ECG, and the first manifestation of an arrhythmia may be the arrest itself. Treat the patient and the trend, not the single value [13].
References13ShowHide
- [1]Kovesdy CP Management of hyperkalaemia in chronic kidney disease Nat Rev Nephrol, 2014.PMID 25223988
- [2]Gennari FJ Hypokalemia N Engl J Med, 1998.PMID 9700180
- [3]Weir MR, Bakris GL, Bushinsky DA, et al. Patiromer in patients with kidney disease and hyperkalemia receiving RAAS inhibitors N Engl J Med, 2015.PMID 25415805
- [4]Kosiborod M, Rasmussen HS, Lavin P, et al. Effect of sodium zirconium cyclosilicate on potassium lowering for 28 days among outpatients with hyperkalemia: the HARMONIZE randomized clinical trial JAMA, 2014.PMID 25402495
- [5]Moussavi K, Garcia J, Tellez-Corrales E, et al. Reduced alternative insulin dosing in hyperkalemia: A meta-analysis of effects on hypoglycemia and potassium reduction Pharmacotherapy, 2021.PMID 33993515
- [6]Lemoine L, Le Bastard Q, Batard E, et al. An Evidence-Based Narrative Review of the Emergency Department Management of Acute Hyperkalemia J Emerg Med, 2021.PMID 33423833
- [7]Long B, Warix JR, Koyfman A Controversies in Management of Hyperkalemia J Emerg Med, 2018.PMID 29731287
- [8]Rafique Z, Weir MR, Onuigbo M, et al. Expert Panel Recommendations for the Identification and Management of Hyperkalemia and Role of Patiromer in Patients with Chronic Kidney Disease and Heart Failure J Manag Care Spec Pharm, 2017.PMID 28485203
- [9]Maxwell AP, Linden K, O'Donnell S, et al. Management of hyperkalaemia J R Coll Physicians Edinb, 2013.PMID 24087806
- [10]Mahoney BA, Smith WAD, Lo DS, Tsoi K, Tonelli M, Clase CM Emergency interventions for hyperkalaemia Cochrane Database Syst Rev, 2005.PMID 15846652
- [11]Fulchiero R, Seo-Mayer P Bartter Syndrome and Gitelman Syndrome Pediatr Clin North Am, 2019.PMID 30454738
- [12]Viera AJ, Wouk N Potassium Disorders: Hypokalemia and Hyperkalemia Am Fam Physician, 2015.PMID 26371733
- [13]Lindner G, Burdmann EA, Clase CM, et al. Acute hyperkalemia in the emergency department: a summary from a Kidney Disease: Improving Global Outcomes conference Eur J Emerg Med, 2020.PMID 32852924