Critical care nephrology · KIMS Secunderabad
Hyperkalemia — High Potassium and Why It Is a Medical Emergency
Potassium is the most abundant intracellular cation — 98% of the body's potassium is inside cells, maintaining the electrical gradient across cell membranes that is essential for nerve conduction and muscle contraction, including the cardiac muscle. Serum (extracellular) potassium is tightly regulated within the narrow range of 3.5 to 5.0 mEq/L by the kidneys, which excrete essentially all of the daily dietary potassium load (approximately 70 to 100 mEq/day). When the kidneys fail — in CKD or AKI — potassium accumulates in the blood, causing hyperkalemia (serum potassium above 5.5 mEq/L). As potassium rises, the resting membrane potential of cardiac cells is progressively destabilised — producing the ECG changes of hyperkalemia and ultimately fatal ventricular fibrillation.
Hyperkalemia is therefore a medical emergency when it is significant — above 6.5 mEq/L with ECG changes, or above 7.0 mEq/L regardless of ECG findings. It is one of the most common indications for emergency dialysis at KIMS. But it is also a condition that is frequently preventable in CKD patients with appropriate dietary counselling and medication management.
Causes
Reduced renal excretion
CKD (most common cause of chronic hyperkalemia) · AKI · Type 4 RTA (hyporeninaemic hypoaldosteronism — common in diabetic nephropathy) · Adrenal insufficiency.
Medications
ACE inhibitors and ARBs (reduce aldosterone-mediated potassium excretion — the most common drug cause in CKD patients) · Potassium-sparing diuretics (spironolactone, amiloride) · NSAIDs (reduce renal potassium excretion) · Trimethoprim (blocks tubular potassium secretion) · Beta-blockers (reduce potassium cellular uptake) · Heparin (suppresses aldosterone).
Transcellular shift (K+ out of cells)
Metabolic acidosis (every 0.1 pH unit fall raises serum K+ by 0.5 mEq/L) · Insulin deficiency (diabetes with poor control) · Rhabdomyolysis · Tumour lysis · Massive haemolysis · Succinylcholine (depolarising muscle relaxant) · Digoxin toxicity.
Excess potassium intake
High dietary potassium in the setting of CKD or AKI (coconut water, bananas, potatoes, tomatoes, orange juice — all very high in potassium) · Potassium supplements prescribed without monitoring · Salt substitutes (contain KCl instead of NaCl — patients with CKD who use these develop severe hyperkalemia).
ECG changes — the clinical urgency guide
The ECG is the most important bedside tool for assessing the clinical urgency of hyperkalemia — the degree of ECG change correlates better with cardiac risk than the absolute potassium level.
Normal ECG + K+ 5.5–6.0 mEq/L — dietary restriction, medication review, close monitoring.
Peaked T waves (tall, symmetrical, narrow-based T waves) — K+ typically 6.0–6.5 mEq/L. Earliest ECG sign. Urgent treatment required.
Prolonged PR interval, widened QRS (above 120ms) — K+ typically 6.5–7.0 mEq/L. Serious — immediate treatment.
Sine wave pattern (P waves absent, QRS and T waves merging into broad sinusoidal complexes) — K+ above 7.0–8.0 mEq/L. Pre-terminal. Emergency — dialysis immediately.
Ventricular fibrillation or asystole — K+ above 8–9 mEq/L. Cardiac arrest.
Hyperkalemia above 6.5 mEq/L with any ECG changes, or above 7.0 mEq/L regardless of ECG, is a medical emergency requiring immediate IV calcium gluconate and emergency dialysis preparation. Call KIMS emergency: 040-4488-5000.
Emergency treatment at KIMS — the five-step approach
1. Cardiac membrane stabilisation — immediate
IV calcium gluconate 10ml of 10% solution over 2 to 3 minutes — does not lower potassium but temporarily stabilises the cardiac membrane by raising the threshold potential, buying 30 to 60 minutes while other treatments work. Repeat every 5 minutes if ECG does not improve. Only treats the cardiac danger — does not reduce potassium.
2. Shift potassium into cells — within 15–30 minutes
IV insulin 10 units + 50ml of 50% dextrose (to prevent hypoglycaemia) — shifts potassium into cells, lowering serum potassium by 0.5 to 1.0 mEq/L within 15 to 30 minutes, lasting 2 to 6 hours. IV sodium bicarbonate (150 mEq in 1 litre of 5% dextrose over 2 to 4 hours) — corrects metabolic acidosis, shifting potassium into cells (most effective when metabolic acidosis is present). Nebulised salbutamol (10 to 20mg via nebuliser) — beta-2 stimulation drives potassium into cells, lowering potassium by 0.5 to 1.5 mEq/L. All three can be used simultaneously.
3. Remove potassium from the body — within hours
Patiromer (Veltassa) or sodium zirconium cyclosilicate (Lokelma) — potassium binders that exchange potassium for calcium or sodium in the gut. More effective and better tolerated than the historical sodium polystyrene sulphonate (Kayexalate). Loop diuretics (furosemide 40 to 120mg IV) — increase urinary potassium excretion in patients with residual kidney function. Dialysis — the most effective and fastest potassium removal. Haemodialysis removes 25 to 50 mEq of potassium per session. Preferred for AKI, severe CKD, or hyperkalemia not responding to medical management.
4. Prevent recurrence
Dietary potassium restriction (below 2,000 mg/day in CKD Stage 4 and 5). Review and adjust medications (reduce ACE inhibitor/ARB dose where potassium persistently above 5.5 mEq/L). Long-term patiromer for patients on RAAS blockade who cannot tolerate potassium build-up.
Emergency Nephrology at KIMS — 24/7 for High Potassium and AKI. Call 040-4488-5000
Frequently Asked Questions — Hyperkalemia
Serum potassium above 5.5 mEq/L is hyperkalemia. Above 6.0 mEq/L is significant and requires urgent treatment. Above 6.5 mEq/L with ECG changes is a medical emergency. Above 7.0 mEq/L is immediately life-threatening regardless of ECG — the membrane potential destabilisation at this level means ventricular fibrillation can occur unpredictably. However, the ECG changes are more clinically important than the absolute number — a patient with potassium of 6.8 mEq/L and a normal ECG requires urgent but non-emergency management; the same patient with a widened QRS requires emergency treatment in the next 15 minutes.
In a patient with normal kidney function — no. The kidneys rapidly excrete excess dietary potassium, and a single banana (approximately 400 to 450mg potassium) is easily handled. In a patient with CKD Stage 4 or 5, or on dialysis — yes, dietary potassium accumulates because the kidneys cannot excrete it. A banana contains 400 to 450mg potassium. A dialysis patient restricted to 2,000mg/day can eat approximately 4 to 5 bananas — but this must be distributed across the day and other high-potassium foods must be accounted for. The most dangerous dietary sources in Indian diets for hyperkalemia are: coconut water (very high potassium), tomato juice, potato curries, orange juice, and the increasingly common practice of using potassium chloride salt substitutes (which contain potassium instead of sodium and can cause fatal hyperkalemia in CKD patients).
Yes — ACE inhibitors (ramipril, enalapril, lisinopril) and ARBs (losartan, olmesartan, telmisartan) both reduce aldosterone activity, which reduces renal potassium excretion. In patients with CKD or diabetes, this can cause clinically significant hyperkalemia. This is why potassium must be monitored every 1 to 3 months in CKD patients on ACE inhibitors or ARBs. If potassium consistently rises above 5.5 mEq/L on RAAS blockade, the options are: dose reduction, addition of patiromer or SZC to bind gut potassium, dietary restriction, or careful switching to a different antihypertensive class. The RAAS blockade should not be abandoned lightly — it provides kidney and cardiovascular protection that other antihypertensives do not.
The relationship between potassium level and cardiac risk is not linear or predictable — two patients with the same potassium level may have completely different ECG changes and risk profiles. ECG changes (peaked T waves, widened QRS, sine wave pattern) signal imminent risk more reliably than the absolute potassium level. Once a sine wave pattern is present on ECG, ventricular fibrillation or asystole may occur within minutes. At potassium levels above 7.5 to 8.0 mEq/L without ECG changes (which sometimes occurs in chronic slow-onset hyperkalemia where cardiac adaptation has occurred), the risk is still very high and emergency dialysis is required immediately.
KIMS Secunderabad — Dr. E. Ravi (Senior Consultant Nephrologist, critical care nephrology), 24/7 emergency nephrology, ECG monitoring for hyperkalemia, IV calcium gluconate + insulin-dextrose + bicarbonate protocol, patiromer and SZC for chronic management, haemodialysis and CRRT for refractory hyperkalemia. Emergency line: 040-4488-5000.