Electrolyte Abnormalities

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Electrolyte abnormalities refer to imbalances in the levels of electrolytes in the body, which are crucial for maintaining various physiological functions. Electrolytes include sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphate.

Aetiology

Electrolyte imbalances can result from various causes, including:

  • Dehydration or overhydration.
  • Kidney disease or dysfunction.
  • Medications: Diuretics, laxatives, and certain antibiotics.
  • Endocrine disorders: Diabetes, Addison's disease, hyperparathyroidism.
  • Gastrointestinal losses: Vomiting, diarrhoea, and malabsorption.
  • Dietary imbalances: Excessive or insufficient intake of electrolytes.
  • Chronic diseases: Heart failure, liver disease.

Pathophysiology

Electrolyte imbalances can disrupt cellular function and physiological processes. For example:

  • Hyponatraemia (low sodium): Can cause cellular swelling, particularly in the brain, leading to neurological symptoms.
  • Hyperkalaemia (high potassium): Can disrupt cardiac electrical activity, leading to arrhythmias and potential cardiac arrest.
  • Hypocalcaemia (low calcium): Can affect neuromuscular function, causing muscle cramps, tetany, and seizures.
  • Hypermagnesaemia (high magnesium): Can depress neuromuscular function and cardiac conduction.

Risk Factors

  • Chronic kidney disease (CKD).
  • Heart failure.
  • Endocrine disorders.
  • Gastrointestinal disorders causing fluid loss.
  • Use of certain medications (e.g., diuretics).
  • Severe dehydration or overhydration.
  • Intensive physical activity or heat exposure.

Signs and Symptoms

  • Muscle cramps and weakness.
  • Fatigue and lethargy.
  • Nausea and vomiting.
  • Irregular heartbeat or palpitations.
  • Confusion and dizziness.
  • Seizures in severe cases.
  • Edema or fluid retention.
  • Tingling or numbness.

Investigations

  • Clinical history and physical examination.
  • Blood tests: Serum electrolyte levels (sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate).
  • Urinalysis: To assess kidney function and electrolyte excretion.
  • ECG: To detect cardiac abnormalities associated with electrolyte imbalances.
  • Additional tests: Depending on the suspected underlying cause (e.g., renal function tests, endocrine evaluations).

Management

Primary Care Management

  • If the patient is unwell, refer urgently to hospital and then stabilise the patient, ensuring airway, breathing, and circulation (ABCs).
  • Correction of the underlying cause (e.g., treating dehydration, adjusting medications).
  • Oral or intravenous electrolyte replacement therapy.
  • Monitoring of electrolyte levels and renal function.
  • Patient education on maintaining a balanced diet and recognising symptoms of electrolyte imbalance.
  • Referral to a specialist (nephrologist or endocrinologist) if symptoms persist and the patient has been assessed in the hospital and told to go to the GP (if they have not already been referred by hospital doctors).

Specialist Management

  • Advanced diagnostic evaluations to identify the underlying cause of the electrolyte imbalance.
  • Tailored treatment plans: Including medication adjustments, electrolyte supplements, and dietary modifications.
  • Close monitoring of electrolyte levels, renal function, and cardiac status.
  • Management of complications: Such as cardiac arrhythmias or neuromuscular symptoms.

Here are some common electrolyte abnormalities with their causes, symptoms, and management:

Electrolyte Abnormalities

Electrolyte Abnormalities

High Potassium (Hyperkalaemia)

Mild: 5.5–5.9 mmol/L

Moderate: 6.0–6.4 mmol/L

Severe: ≥6.5 mmol/L

History

Key questions to ask the patient:

  • Recent dietary changes or potassium supplements?
  • History of kidney disease or recent changes in urine output?
  • Any new medications or changes in medication dosage?
  • Symptoms of muscle weakness, fatigue, or palpitations?

Examination Findings

Common examination findings may include:

  • Muscle weakness or paralysis
  • Cardiac arrhythmias (e.g., bradycardia, tachycardia)

Common Medications

Medications that may cause hyperkalaemia include:

  • Potassium-sparing diuretics (e.g., spironolactone)
  • ACE inhibitors (e.g., enalapril)
  • Angiotensin II receptor blockers (ARBs) (e.g., losartan)
  • NSAIDs (e.g., ibuprofen)

Management

Initial management steps:

  • Discontinue or adjust medications that may elevate potassium levels
  • Review and adjust dietary potassium intake
  • Consider medications to lower potassium (follow local guidelines)

Investigations

The following investigations can be used for the evaluation of suspected hyperkalaemia:

  • Repeat serum measurement of potassium to identify pseudohyperkalemia (1-2 weeks repeat)
  • Other laboratory studies include:
    • Urine electrolytes and creatinine
    • Arterial blood gas analysis (Hospital)
  • Further investigations may be necessary to examine co-existing illnesses:
    • Measurement of serum glucose/Hba1c - to evaluate for hyperglycaemia
  • Consider urgent ECG in patients with:
    • A serum potassium >6.0 mmol/L (severe hyperkalaemia can still be present in patients without obvious ECG changes)
    • Symptoms of hyperkalaemia
    • Suspicion of rapid-onset hyperkalaemia
    • Underlying kidney disease, heart disease, or cirrhosis who have a new case of hyperkalaemia

Monitoring

  • Mild Hyperkalaemia (5.5–5.9 mmol/L): If eGFR has not increased >10% or no acute increase in K, can repeat in 1-2 weeks. Review medications & diet for causes.
  • Moderate Hyperkalaemia (6.0–6.4 mmol/L): Recheck ASAP. If ECG changes, admit. Stop medications that may elevate K.
  • Severe Hyperkalaemia (≥6.5 mmol/L or if ECG changes present): Urgent repeat: Admit.

Low Potassium (Hypokalaemia)

Mild: 3.0–3.4 mmol/L

Moderate: 2.5–2.9 mmol/L

Severe: <2.5 mmol/L

History

Key questions to ask the patient:

  • Recent gastrointestinal losses (e.g., vomiting, diarrhoea)?
  • Use of diuretics or laxatives?
  • Dietary intake of potassium-rich foods?
  • Symptoms of muscle weakness, cramps, or palpitations?

Examination Findings

Common examination findings may include:

  • Muscle weakness or cramps
  • Hyporeflexia
  • Cardiac arrhythmias (e.g., U waves on ECG)

Common Medications

Medications that may cause hypokalaemia include:

  • Loop diuretics (e.g., furosemide)
  • Thiazide diuretics (e.g., hydrochlorothiazide)
  • Insulin (in high doses)
  • Beta-agonists (e.g., salbutamol)

Management

Initial management steps:

  • Discontinue or adjust medications that may lower potassium levels
  • Encourage dietary intake of potassium-rich foods (e.g., bananas, oranges)
  • Consider oral or intravenous potassium supplementation

Investigations

The following investigations can be used for the evaluation of suspected hypokalaemia:

  • Repeat serum measurement of potassium to confirm low levels
  • Further investigations may be necessary to examine co-existing illnesses:
    • Measurement of serum magnesium - to check for concurrent hypomagnesaemia
    • Measurement of serum renin and aldosterone - to evaluate for hyperaldosteronism
  • Consider ECG in patients with:
    • Symptoms of hypokalaemia
    • Suspicion of rapid-onset hypokalaemia
    • Underlying heart disease

Monitoring

  • Mild Hypokalaemia (3.0–3.4 mmol/L): Repeat potassium measurement in 1-2 weeks. Review medications & diet for causes.
  • Moderate Hypokalaemia (2.5–2.9 mmol/L): Recheck ASAP. Consider potassium supplementation. If ECG changes, admit.
  • Severe Hypokalaemia (<2.5 mmol/L or if ECG changes present): Urgent repeat: Admit.

High Sodium (Hypernatraemia)

Mild: 145–149 mmol/L

Moderate: 150–159 mmol/L

Severe: ≥160 mmol/L

History

Key questions to ask the patient:

  • Recent fluid loss (e.g., diarrhoea, vomiting, sweating)?
  • Inadequate fluid intake?
  • Use of diuretics?
  • Symptoms of thirst, weakness, or confusion?

Examination Findings

Common examination findings may include:

  • Dry mucous membranes
  • Decreased skin turgor
  • Tachycardia
  • Confusion or altered mental status

Common Medications

Medications that may cause hypernatraemia include:

  • Loop diuretics (e.g., furosemide)
  • Osmotic diuretics (e.g., mannitol)
  • Hypertonic saline solutions

Management

Initial management steps:

  • Identify and treat underlying causes (e.g., rehydrate with hypotonic fluids)
  • Discontinue or adjust medications that may increase sodium levels

Investigations

The following investigations can be used for the evaluation of suspected hypernatraemia:

  • Repeat serum measurement of sodium to confirm high levels
  • Other laboratory studies include:
    • Blood biochemistry for kidney function
    • Urine electrolytes and osmolality
  • Consider further investigations for underlying causes:
    • Measurement of urine osmolality
    • Measurement of serum glucose/Hba1c - to check for hyperglycaemia

Monitoring

  • Mild Hypernatraemia (145–149 mmol/L): Repeat sodium measurement in 1-2 weeks. Review medications & fluid intake for causes.
  • Moderate Hypernatraemia (150–159 mmol/L): Recheck ASAP. Adjust fluid intake. If symptomatic, consider admission.
  • Severe Hypernatraemia (≥160 mmol/L or if symptoms present): Urgent repeat: Admit.

Low Sodium (Hyponatraemia)

Mild: 130–134 mmol/L

Moderate: 125–129 mmol/L

Severe: <125 mmol/L

History

Key questions to ask the patient:

  • Recent fluid loss (e.g., vomiting, diarrhoea)?
  • Fluid intake patterns?
  • Use of diuretics, SSRIs, or antipsychotics?
  • Symptoms of headache, nausea, confusion, or seizures?

Examination Findings

Common examination findings may include:

  • Confusion or altered mental status
  • Decreased skin turgor
  • Orthostatic hypotension
  • Seizures (in severe cases)

Common Medications

Medications that may cause hyponatraemia include:

  • Thiazide diuretics (e.g., hydrochlorothiazide)
  • Selective serotonin reuptake inhibitors (SSRIs) (e.g., fluoxetine)
  • Antipsychotics (e.g., risperidone)
  • Antiepileptics (e.g., carbamazepine)

Management

Initial management steps:

  • Discontinue or adjust medications that may lower sodium levels
  • Fluid restriction if appropriate
  • Consider hypertonic saline in severe cases with symptomatic hyponatraemia

Investigations

The following investigations can be used for the evaluation of suspected hyponatraemia:

  • Repeat serum measurement of sodium to confirm low levels
  • Other laboratory studies include:
    • Blood biochemistry for kidney function
    • Urine osmolality
  • Consider further investigations for underlying causes:
    • Assessment of fluid balance and intake/output
    • Measurement of serum glucose/Hba1c - to check for hyperglycaemia
    • Measurement of thyroid and adrenal function - serum TSH, serum cortisol

Monitoring

  • Mild Hyponatraemia (130–134 mmol/L): Repeat sodium measurement in 1-2 weeks. Review medications & fluid intake for causes.
  • Moderate Hyponatraemia (125–129 mmol/L): Recheck ASAP. Adjust fluid intake. If symptomatic, consider admission.
  • Severe Hyponatraemia (<125 mmol/L or if symptoms present): Urgent repeat: Admit.

High Calcium (Hypercalcaemia)

Mild: 2.6–2.9 mmol/L

Moderate: 3.0–3.4 mmol/L

Severe: ≥3.5 mmol/L

History

Key questions to ask the patient:

  • Symptoms of fatigue, muscle weakness, or bone pain?
  • History of kidney stones?
  • Use of calcium or vitamin D supplements?
  • Family history of hypercalcaemia or related conditions?

Examination Findings

Common examination findings may include:

  • Muscle weakness
  • Bone tenderness
  • Polyuria or polydipsia
  • Confusion or altered mental status

Common Medications

Medications that may cause hypercalcaemia include:

  • Calcium supplements
  • Vitamin D supplements
  • Thiazide diuretics (e.g., hydrochlorothiazide)
  • Lithium

Management

Initial management steps:

  • Discontinue or adjust medications that may increase calcium levels
  • Encourage oral hydration to dilute serum calcium
  • Consider intravenous fluids and bisphosphonates in severe cases

Investigations

The following investigations can be used for the evaluation of suspected hypercalcaemia:

  • Repeat serum measurement of calcium to confirm high levels
  • Other laboratory studies include:
    • Blood biochemistry for kidney function
    • Serum phosphate and PTH levels
    • Vitamin D levels
  • Consider further investigations for underlying causes:
    • Measurement of serum and urine calcium
    • Assessment for malignancy (e.g., PTHrP levels, imaging studies)

Monitoring

  • Mild Hypercalcaemia (2.6–2.9 mmol/L): Repeat calcium measurement in 1-2 weeks. Review medications & diet for causes.
  • Moderate Hypercalcaemia (3.0–3.4 mmol/L): Recheck ASAP. Adjust calcium intake. If symptomatic, consider admission.
  • Severe Hypercalcaemia (≥3.5 mmol/L or if symptoms present): Urgent repeat: Admit.

Low Calcium (Hypocalcaemia)

Mild: 2.0–2.1 mmol/L

Moderate: 1.9–1.99 mmol/L

Severe: <1.9 mmol/L

History

Key questions to ask the patient:

  • Symptoms of tingling, muscle cramps, or tetany?
  • History of thyroid or parathyroid surgery?
  • Dietary intake of calcium and vitamin D?
  • Family history of hypocalcaemia or related conditions?

Examination Findings

Common examination findings may include:

  • Chvostek's sign (facial muscle twitching upon tapping)
  • Trousseau's sign (carpopedal spasm with blood pressure cuff inflation)
  • Hyperreflexia
  • Seizures (in severe cases)

Common Medications

Medications that may cause hypocalcaemia include:

  • Bisphosphonates
  • Loop diuretics (e.g., furosemide)
  • Phenytoin
  • Corticosteroids

Management

Initial management steps:

  • Discontinue or adjust medications that may lower calcium levels
  • Encourage dietary intake of calcium-rich foods (e.g., dairy products, green leafy vegetables)
  • Consider oral or intravenous calcium supplementation
  • Vitamin D supplementation if deficiency is suspected

Investigations

The following investigations can be used for the evaluation of suspected hypocalcaemia:

  • Repeat serum measurement of calcium to confirm low levels
  • Other laboratory studies include:
    • Blood biochemistry for kidney function
    • Serum magnesium and phosphate levels
    • PTH levels
  • Consider further investigations for underlying causes:
    • Measurement of serum albumin (to correct total calcium)
    • Vitamin D levels

Monitoring

  • Mild Hypocalcaemia (2.0–2.1 mmol/L): Repeat calcium measurement in 1-2 weeks. Review medications & diet for causes.
  • Moderate Hypocalcaemia (1.9–1.99 mmol/L): Recheck ASAP. Consider calcium supplementation. If symptomatic, consider admission.
  • Severe Hypocalcaemia (<1.9 mmol/L or if symptoms present): Urgent repeat: Admit.

References

  1. NICE. (2024). Acute Kidney Injury: Prevention, Detection and Management. Retrieved from NICE
  2. NHS. (2023). Electrolyte Imbalance. Retrieved from NHS
  3. National Kidney Foundation. (2021). Electrolyte Imbalances and Kidney Disease. Retrieved from National Kidney Foundation
  4. Mount, D. B., & Zandi-Nejad, K. (2012). Disorders of Potassium Balance. In T. W. Post (Ed.), UpToDate.
  5. Felsenfeld, A. J., & Levine, B. S. (2012). Hypocalcemia: Pathogenesis, Differential Diagnosis, and Management. In T. W. Post (Ed.), UpToDate.

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