Hyperkalemia

Potassium Homeostasis - Background

Epidemiology

Causes

1. Pseudohyperkalemia (Factitious)

• Traumatic hemolysis during blood drawing (most common cause of a "high" reported lab value)
• Fist clenching / tourniquet use causing local K⁺ efflux
• Thrombocytosis, leukocytosis, or erythrocytosis - cellular K⁺ released during clot formation in the sample tube
• Acute anxiety-induced respiratory alkalosis with redistribution

2. Increased Potassium Load

• Large exogenous IV K⁺ bolus (iatrogenic - wrong IV fluid)
• High dietary intake (especially with impaired renal excretion)
• Massive cell breakdown: intravascular hemolysis (mismatched transfusion), crush injuries, burns, rhabdomyolysis, tumor lysis syndrome, GI bleeding with intestinal reabsorption
• Chemotherapy-induced cell death

3. Transcellular Redistribution (K⁺ shifts out of cells)

• Metabolic acidosis (non-organic - inorganic acidosis causes larger shift than organic)
• Insulin deficiency (insulin is required for cellular K⁺ uptake)
• β-adrenergic blockade (inhibits Na-K-ATPase and cellular uptake)
• Digitalis toxicity (inhibits Na-K-ATPase pump)
• Succinylcholine - depolarizes muscle, releasing K⁺; the risk is greatly amplified in denervated muscle (burns, crush injuries, prolonged immobility)
• Hypertonicity (e.g., mannitol, hyperglycemia) - water draws out K⁺ by solvent drag
• Hyperkalemic periodic paralysis
• Drugs opening KATP channels (cyclosporine, nicorandil)

4. Impaired Renal Excretion (most common cause of sustained hyperkalemia)

• Advanced renal failure (any cause - GFR <20 mL/min)
• Hypoaldosteronism - primary adrenal insufficiency, isolated aldosterone deficiency, hyporeninemic hypoaldosteronism (diabetic nephropathy, NSAIDs, ACE inhibitors, heparin)
• Medications blocking the RAA axis: ACE inhibitors, ARBs, spironolactone, eplerenone, amiloride, triamterene, NSAIDs, trimethoprim, pentamidine, calcineurin inhibitors
• Decreased distal Na⁺ delivery (limits K⁺ secretion)
• Tubulointerstitial diseases, urinary obstruction, sickle cell disease, SLE
• Medical Physiology, p. 1196 | Brenner & Rector's The Kidney | Current Surgical Therapy 14e

Clinical Manifestations

Cardiac (most important)

Note: ECG changes correlate only roughly with K⁺ level. A normal ECG does not exclude dangerous hyperkalemia - get a serum level. Hypocalcemia, hyponatremia, and acidosis all worsen cardiac effects.

Neuromuscular

• Skeletal muscle weakness generally not seen until K⁺ >8 mEq/L
• Can progress to flaccid paralysis (ascending)

Contractility

Diagnosis & Workup

1. Rule out pseudohyperkalemia - repeat K⁺ in non-hemolyzed sample
2. 12-lead ECG immediately - do not wait for labs if suspected
3. Serum electrolytes, creatinine, BUN, osmolality, CBC, glucose, Mg²⁺, Ca²⁺
4. Urine electrolytes (Na⁺, K⁺, osmolality, creatinine) for TTKG (transtubular K⁺ gradient) or urine K⁺/creatinine ratio
5. Plasma renin activity and aldosterone if cause unclear
6. History: medications (ACE-I, ARBs, NSAIDs, K⁺-sparing diuretics), diet, salt substitutes, urine output changes

Clinical approach to hyperkalemia - Brenner & Rector's The Kidney

Treatment

Step 1 - Cardiac Membrane Stabilization (Fastest, does NOT lower K⁺)

Caution with digoxin: Hypercalcemia potentiates digoxin toxicity. If the patient is on digoxin, dilute calcium gluconate in 100 mL D5W and infuse over 20-30 min.

Step 2 - Redistribution into Cells (Temporary, buys time)

β-agonists and insulin/glucose effects are additive. Bicarbonate is a distant third choice.

Step 3 - Removal of K⁺ from the Body (Definitive)

Severity-Based Decision Framework

Special Situations

• CKD patients: Even modest K⁺ loads (dietary, from drugs like β-blockers or ACE-I) can precipitate severe hyperkalemia. A K⁺ of 6 mEq/L is potentially dangerous even without ECG changes. Succinylcholine should be used with caution (though true ESKD without denervation is lower risk than previously thought).
• Cardiac arrest with CKD: Assume hyperkalemia and treat empirically during resuscitation.
• Succinylcholine + denervated muscle (burns, crush, immobility): AVOID - causes massive, exaggerated K⁺ efflux.
• Combination RAAS blockade: ACE-I + ARB + mineralocorticoid antagonist together greatly increases hyperkalemia risk, especially in CKD stage IV-V (eGFR <30). Maximum spironolactone dose with ACE-I/ARB is 25 mg/day.
• Novel K⁺ binders (patiromer, ZS-9): A 2025 systematic review and network meta-analysis confirms their efficacy for chronic hyperkalemia management in CKD and heart failure, particularly enabling continued RAAS inhibitor therapy.

Key Takeaways

1. Hyperkalemia is clinically silent until life-threatening cardiac events occur - always check ECG and serum K⁺ proactively in at-risk patients (CKD, RAAS drugs, diabetes).
2. The ECG is useful but imperfect - normal ECG does not exclude dangerous hyperkalemia.
3. Calcium is always the first emergency drug - it stabilizes membranes without affecting K⁺ level.
4. Insulin/glucose and albuterol are the fastest ways to lower serum K⁺, but only temporarily.
5. Dialysis is the only reliable definitive treatment in ESKD or severe cases.
6. K⁺ ≥6.5 mEq/L or any ECG change beyond peaked T waves = medical emergency.

• Medical Physiology (Boron & Boulpaep) | Brenner & Rector's The Kidney | Morgan & Mikhail's Clinical Anesthesiology | Rosen's Emergency Medicine | Current Surgical Therapy 14e

Wilson's Disease (Hepatolenticular Degeneration)

Genetics & Epidemiology

• Gene: ATP7B on chromosome 13 - encodes a copper-transporting P-type ATPase expressed in hepatocytes
• Inheritance: Autosomal recessive; >500 known disease-specific mutations; most patients are compound heterozygotes (different mutations on each allele)
• Incidence: ~1 in 30,000-40,000 live births; carrier prevalence 1 in 90-180
• Age of onset: Usually between 6 and 40 years; can rarely present in the 5th-6th decade. Liver disease predominates in younger patients (<30 years); neuropsychiatric disease typically appears after age 20.

Pathobiology

Copper transport in normal hepatocytes vs. Wilson disease. ATP7B mutations impair both copper incorporation into ceruloplasmin (trans-Golgi) and biliary excretion (lysosomes), leading to hepatocyte copper accumulation and spillover to other tissues. - Robbins & Kumar Basic Pathology

1. Trans-Golgi network: Transfers copper into apoceruloplasmin → forms ceruloplasmin, secreted into blood
2. Lysosomes: Transports non-ceruloplasmin copper into bile canaliculi for fecal excretion (the primary excretion route; biliary copper does not undergo enterohepatic recirculation)

• Copper accumulates in hepatocyte cytoplasm and lysosomes → generates reactive oxygen species (ROS) → hepatocyte injury
• Ceruloplasmin synthesis is reduced (apoceruloplasmin is unstable without copper) → low serum ceruloplasmin (note: the low ceruloplasmin itself does not cause disease - it is a consequence, not a cause)
• As copper overloads the liver, non-ceruloplasmin-bound ("free") copper spills into circulation → hemolysis, deposits in brain, cornea, kidneys, bones, joints, parathyroid glands
• Urine copper excretion increases markedly

Clinical Manifestations

1. Hepatic (more common in younger patients)

ALF Clue: In Wilson disease ALF, the alkaline phosphatase/total bilirubin ratio is <4 and AST/ALT ratio is >2.2 - these ratios accurately distinguish it from other causes of ALF. - Sleisenger & Fordtran's GI and Liver Disease

2. Neurological (typically presents after age 20)

• Dysarthria - often the first sign
• Dystonia (including sardonic "fixed smile")
• Tremor - can be postural, action, or "wing-beating" (flapping at the shoulders)
• Rigidity
• Chorea / choreiform movements
• Ataxia, gait disturbance
• Dysphagia
• Seizures (minority)

3. Psychiatric (very common - ~50% of patients)

• Personality changes: irritability, anger, poor impulse control (most common)
• Depression (~30%)
• Anxiety
• Bipolar spectrum symptoms (~20%)
• Psychosis
• Suicidal ideation (5-15%)
• Frontosubcortical cognitive dysfunction

Wilson disease should be formally excluded in all young adults with new-onset psychiatric symptoms, especially if liver function tests are abnormal or there is a family history.

4. Ocular - Kayser-Fleischer (KF) Rings

Kayser-Fleischer ring: brown-gold annular copper deposition at the periphery of the cornea in Descemet's membrane. - Goldman-Cecil Medicine

• Copper deposits in Descemet's membrane at the corneal limbus
• Appear golden-brown to greenish (visible in panel C of the slit-lamp image above as a brownish ring at the iris periphery)
• First appear as a superior crescent, then inferior, then circumferential
• Present in ~95-98% of patients with neurologic disease and 50-65% of those with purely hepatic presentation
• Require slit-lamp examination to detect in early stages; may be visible to naked eye when prominent
• Also: "Sunflower" cataracts from copper deposition in the lens (anterior capsular pattern)
• KF rings fade and disappear with effective treatment

5. Other Organ Involvement

Diagnosis

• Unexplained liver disease (especially in young patients)
• ALF with hemolysis + low alkaline phosphatase
• Young adults with neurologic or psychiatric disease + abnormal LFTs
• First-degree relatives of a known patient

Laboratory Findings

Genetic Testing

• Two disease-specific ATP7B mutations (one on each allele) is diagnostic
• Over 500 mutations complicate sequencing - used mainly in family screening once a proband's mutations are known

Leipzig Scoring System

Pathology (Morphology)

• Early: Steatosis (fatty change), focal hepatocyte necrosis
• Intermediate: Chronic hepatitis pattern with inflammation, Mallory hyaline bodies, ballooned hepatocytes (resembles steatohepatitis)
• Advanced: Macronodular cirrhosis
• Special stains: Rubeanic acid or rhodanine stain shows granular copper deposits in hepatocytes (lysosomal distribution)

Treatment

1. Copper Chelation (Symptomatic Patients, Initial Therapy)

• Mechanism: Binds copper → markedly increases urinary copper excretion
• Dose: Start 250 mg twice daily, titrate to 15-20 mg/kg/day in 2-4 divided doses
• Always co-prescribe pyridoxine (vitamin B6) to prevent B6 deficiency
• Side effects: Hypersensitivity, nephrotoxicity (membranous nephropathy), hematologic abnormalities, elastosis perforans serpiginosa (skin rash at neck/axilla)
• Major concern: Paradoxical neurological worsening in 20-50% of patients with neurologic presentations - can be permanent

• Preferred over penicillamine when neurological disease is the presentation
• Fewer side effects; noninferior for maintenance therapy
• Lower risk of neurological deterioration
• Also used in penicillamine-intolerant patients

• Forms tripartite complexes with albumin and copper → biliary excretion
• Fast-acting: restores copper balance within weeks vs. months for other agents
• Especially suited for initial treatment of neurologic Wilson disease (least neurological deterioration risk)
• Still investigational in some settings

2. Zinc Therapy (Presymptomatic, Maintenance, Pregnancy)

• Mechanism: Induces intestinal metallothionein → blocks copper absorption from the gut; also promotes fecal copper excretion
• Takes 4-6 months to restore copper balance as monotherapy
• Preferred in presymptomatic patients, pregnant women (safer fetal profile than chelators), and maintenance after initial chelation
• Side effects: Dyspepsia (10-20%); slight higher rate of hepatic decompensation with long-term monotherapy vs. chelation

3. Dietary Restriction

• Avoid copper-rich foods: shellfish, liver/organ meats, mushrooms, chocolate, nuts
• Test drinking water for copper; avoid if >1.3 mg/L
• Restriction alone is insufficient - always combine with pharmacotherapy

4. Liver Transplantation

• Curative - corrects the underlying metabolic defect (functioning hepatocytes carry normal ATP7B)
• Indicated for: Acute liver failure unresponsive to medical therapy; end-stage irreversible cirrhosis
• Long-term outcomes are excellent; disease does not recur in the graft
• A 2025 systematic review and meta-analysis confirms excellent post-transplant outcomes in Wilson disease patients
• Neurological/psychiatric disease without liver failure is generally NOT an indication for transplant

5. Supportive Therapy

• Speech therapy, physical therapy, occupational therapy for neurological patients
• Treatment of tremor/dystonia
• Psychological support
• Genetic counseling and family screening of all first-degree relatives

6. Emerging Therapies

• AAV gene therapy (adeno-associated virus delivering ATP7B): Phase I/II trials ongoing; potentially curative without transplantation - Goldman-Cecil Medicine
• Deep brain stimulation (DBS): A 2025 multicenter meta-analysis shows benefit for severe refractory dystonia in Wilson disease

Summary of Drug Choices by Clinical Scenario

Prognosis

• With treatment: Generally favorable. Most neurological, psychiatric, renal, and hepatic manifestations stabilize or improve. KF rings fade with effective therapy.
• Without treatment: Progressive and fatal (liver failure, neurological deterioration)
• Non-compliance: Inevitable recurrence; long-term mortality ~3-fold higher than the general population
• Patients who develop acute liver failure have high short-term mortality without transplantation