Hyperkalaemia Summary

Severity Levels

  • Mild: 5.5-5.9 mmol/L
  • Moderate: 6.0-6.4 mmol/L
  • Severe: ≥6.5 mmol/L (Emergency)

ECG Changes

  • Peaked T waves
  • Widening QRS
  • Loss of P waves
  • Sine wave → Arrest

Emergency Treatment

  • 1. Calcium chloride: Cardiac protection
  • 2. Insulin + glucose: Shift K+ intracellular
  • 3. Salbutamol nebulised: Shift K+
  • 4. K+ binders/dialysis: Remove K+

Common Causes

  • Renal failure
  • ACEi/ARBs + K+ sparing diuretics
  • Rhabdomyolysis
  • Metabolic acidosis

Key Investigations

  • ABG (true K+ level)
  • ECG immediately
  • U&E, creatinine
  • Exclude pseudohyperkalaemia

Monitoring

  • Continuous ECG
  • Repeat K+ 1-2 hourly
  • Glucose monitoring with insulin
  • Consider dialysis referral

Hyperkalaemia

Comprehensive clinical guide for diagnosis and management

Definition & Classification

The most common electrolyte disorder associated with cardiac arrest (occurs in up to 10% of hospitalized patients)

Severity Potassium Level Clinical Significance
Mild 5.5 - 5.9 mmol/L Often asymptomatic
Moderate 6.0 - 6.4 mmol/L May have symptoms
Severe ≥ 6.5 mmol/L Medical emergency

Causes

Excessive Potassium Load

  • Exogenous: Supplements, diet
  • Endogenous:
    • Haemolysis
    • Rhabdomyolysis
    • Burns
    • Tumour lysis syndrome
    • Trauma (crush injuries)

Redistribution

  • Metabolic acidosis
  • Insulin deficiency (e.g., DKA)
  • Drugs:
    • Beta-blockers
    • Digoxin
    • Succinylcholine

Decreased Excretion

  • Renal failure
  • Addison's disease
  • Drugs:
    • NSAIDs
    • ACE inhibitors
    • K+-sparing diuretics

Pseudohyperkalaemia

  • Haemolysis in test tube
  • Poor venepuncture technique
  • Prolonged storage

Clinical Features

Neuromuscular

  • Muscle weakness/paralysis
  • Paraesthesia
  • Hypotonia
  • Hyporeflexia

CNS

  • Lethargy
  • Confusion

Cardiac

  • Arrhythmias
  • Cardiac arrest

ECG Changes (Progressive)

  1. Peaked T waves
  2. Widening/flattening of P waves
  3. Prolonged PR interval (1° heart block)
  4. Widening QRS complex
  5. Loss of P waves
  6. Sine wave pattern (S-T merging)
  7. Cardiac arrest (PEA, VF/pVT, asystole)

Management

General Approach

  • Stop all K+-containing fluids/medications
  • Monitor ECG continuously
  • Check ABG for true K+ level
Severity Management
Mild (5.5-5.9) Address cause, K+ binders if needed
Moderate (6.0-6.4) Glucose/insulin, K+ binders
Severe (≥6.5) Expert help, glucose/insulin/salbutamol, consider dialysis
ECG changes Calcium chloride first, then shift K+, then remove K+

5 Key Steps for Severe Hyperkalaemia

  1. Cardiac protection:

    Calcium chloride 10mL 10% IV over 2-5 min (onset 1-3 min)

  2. Shift K+ intracellularly:
    • Salbutamol 10-20mg nebulised
    • Insulin 10U + glucose 25g IV over 15-30 min
    • NaHCO3 if severe acidosis/renal failure
  3. Remove K+ from body:
    • K+ binders (calcium resonium 15-30g)
    • Sodium zirconium cyclosilicate
    • Haemodialysis if refractory
  4. Monitor K+ levels
  5. Prevent recurrence

Hyperkalaemic Cardiac Arrest

Modified CPR Protocol
  1. Confirm with ABG
  2. Calcium chloride 10mL 10% IV bolus
  3. Insulin 10U + glucose 25g IV bolus
  4. NaHCO3 50mmol IV if acidosis/renal failure
  5. Consider early dialysis

Dialysis Patients in Cardiac Arrest

Investigations

Essential Tests

  • ABG: True K+ level (exclude pseudohyperkalaemia)
  • U&E: Renal function
  • ECG: For changes
  • Glucose: Before insulin therapy

Additional Tests Based on Suspected Cause

Suspected Cause Tests
Renal failure U&E, urine output
Rhabdomyolysis CK, urine myoglobin
Addison's disease Cortisol, ACTH
Tumour lysis Urate, phosphate, LDH
Drug toxicity Digoxin level

Pseudohyperkalaemia

Consider if:

  • Normal renal function
  • Normal ECG
  • Haematological disorder

Diagnosis: [Serum K+] - [Plasma K+] > 0.4 mmol/L