What can electrolyte imbalances cause?

What Electrolyte Imbalances Can Cause

Electrolyte imbalances can cause life-threatening cardiac arrhythmias, cardiac arrest, neurological emergencies including seizures and altered consciousness, severe muscle weakness or paralysis, and respiratory failure. 1

Cardiac Manifestations

Hyperkalemia (Most Lethal)

• Hyperkalemia is one of the few potentially lethal electrolyte disturbances that can directly cause sudden cardiac arrest, particularly when serum potassium exceeds 6.5 mmol/L 1
• Progressive ECG changes occur predictably: peaked T waves at 5.5-6.5 mmol/L, flattened/absent P waves with prolonged PR interval at 6.5-7.5 mmol/L, widened QRS complex at 7.0-8.0 mmol/L, and sine-wave pattern leading to asystolic cardiac arrest at higher levels 1, 2
• Clinical manifestations include flaccid paralysis, paresthesias, depressed deep tendon reflexes, and shortness of breath 1
• Most commonly caused by renal failure or cellular potassium release 1

Critical pitfall: ECG changes in hyperkalemia are unpredictable and variable among individuals—a normal ECG does not exclude significant hyperkalemia 2, 3

Hypokalemia

• Causes premature ventricular contractions, ventricular tachycardia, torsades de pointes, ventricular fibrillation, cardiac arrest, AV blocks, and atrial fibrillation 2
• ECG findings include broadening of T waves, ST-segment depression, prominent U waves (>1 mm in V2-V3), and QT prolongation 2, 3
• Occurs in up to 20% of hospitalized patients and 40% of patients taking diuretics 4
• Heart failure patients must maintain potassium ≥4 mEq/L to prevent arrhythmias 2, 3

Critical pitfall: Always check magnesium when treating hypokalemia—concurrent hypomagnesemia prevents effective potassium repletion 2

Magnesium Abnormalities

Hypomagnesemia:

• Contributes to QT prolongation and increases risk of torsades de pointes, even when magnesium levels appear normal 2, 3
• Causes both atrial and ventricular arrhythmias 1
• Commonly occurs with gastrointestinal illness or malnutrition 1

Hypermagnesemia:

• Causes prolonged PR, QRS, and QT intervals 2, 3
• Severe cases result in AV nodal conduction block, bradycardia, hypotension, and cardiac arrest 1, 2
• Most likely in obstetric patients receiving IV magnesium for preeclampsia/eclampsia 1

Neurological Manifestations

• Acute electrolyte disturbances cause epileptic encephalopathies (hypomagnesemia, dysnatremias, hypocalcemia) 5
• Altered consciousness and seizures occur with severe hypermagnesemia and hypocalcemia 5
• Central pontine myelinolysis can result from inappropriately rapid correction of hyponatremia 5
• Visual loss from intracranial hypertension in respiratory or metabolic acidosis 5

Neuromuscular Manifestations

• Arreflexic weakness occurs with hypermagnesemia, hyperkalemia, and hypophosphatemia 5
• Quadriplegia with respiratory insufficiency in severe hypermagnesemia 5
• Severe muscle weakness or pain with both hypokalemia and hyperkalemia 4
• Mixed encephalopathy and weakness/paresthesias with hypocalcemia and alkalosis 5

Other Critical Manifestations

• Lethargy, vomiting, and nausea are common presenting symptoms 6, 7
• Cardiovascular collapse and hemodynamic instability 1
• Respiratory difficulties with severe hyperkalemia 1
• Fluid overload, dilutional states, and pulmonary edema from inappropriate IV electrolyte administration 8

Monitoring Requirements

Continuous ECG monitoring is mandatory for: 2, 3

• Moderate to severe potassium or magnesium imbalances
• Any electrolyte abnormality with ECG changes
• Patients with cardiac comorbidities and electrolyte disturbances
• During treatment of severe electrolyte abnormalities
• Patients receiving highly concentrated potassium solutions (300-400 mEq/L) via central route 8

Treatment Considerations for Cardiac Arrest

For hyperkalemia with cardiac arrest: IV calcium should be administered in addition to standard ACLS (Class 1, LOE C-LD) 1

For severe hypomagnesemia with cardiotoxicity/arrest: IV magnesium is recommended in addition to standard ACLS (Class 1, LOE C-LD) 1

For torsades de pointes: Magnesium bolus or infusion is recommended regardless of baseline magnesium level 2, 3

Critical contraindication: IV bolus administration of potassium for cardiac arrest in suspected hypokalemia is not recommended (Class 3: Harm, LOE C-LD) 1