Life-Threatening Electrolyte Abnormalities

Electrolyte abnormalities are common in both outpatient and inpatient settings. Uncorrected electrolyte abnormalities may have life-threatening consequences. Important electrolytes include calcium (Ca), potassium (K), sodium (Na), and magnesium (Mg).

Diagnosis

Indications for Testing

Suspected electrolyte abnormality (eg, patient with loss of consciousness, or patient receiving diuretic therapy)

Laboratory Testing

  • Evaluate whether elevation or decrease is real
    • Hyperkalemia – evaluate for hemolysis in sample
    • Hyponatremia – evaluate for presence of hyperglycemia or hyperlipidemia
  • Initial screen – panel should include Na, potassium chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, glucose, and Ca
  • Mg
  • Albumin
    • Order serum test concurrently if calcium abnormality suspected
    • If hypocalcemia suspected – also order Mg
  • For further evaluation, refer to hypocalcemia

Differential Diagnosis

Refer to individual topics in Background.

Background

Electrolytes

  • Ca
    • Normal ranges
      • Serum Ca – 8.4-10.2 mg/dL
      • Ionized Ca – 1.11-1.30 mmol/L
        • Needs correction for pH outside of normal range
    • Serum Ca measurement is directly related to serum albumin unless measured as ionized (total Ca directly proportional to albumin concentration)
      • Recommend following ionized Ca level in patients in intensive care unit (ICU) or in any clinical setting in which albumin concentration is significantly altered
      • Corrected serum Ca (for albumin) – CCa = (4 g/dL-plasma albumin) x 0.8 + serum Ca
    • Ca-related disorders
      • Hypocalcemia – defined as <8.4 mg/dL (serum) or <1.11 mmol/L (ionized)
        • Symptoms
          • Tetany – latent tetany may result in Trousseau and Chvostek signs
            • Trousseau sign – inflating blood pressure cuff on arm for 3 minutes to systolic blood pressure will cause spasm of hand
            • Chvostek sign – tapping on facial nerve near temporal mandibular joint will cause grimace and spasm of facial muscles
          • Seizures
          • Circumoral numbness
          • Paresthesias
          • Carpopedal spasm
          • Electrocardiogram (ECG) – prolonged QT interval, Torsades de Pointes
        • Etiologies
          • Removal or destruction of parathyroid glands (hypoparathyroidism)
          • Hyperphosphatemia secondary to rhabdomyolysis or renal failure
          • Pancreatitis
          • Hypovitaminosis D (liverkidney disease)
          • Parathyroid hormone (PTH) resistance secondary to hypomagnesemia (Mg <1.0 mg/dL)
      • Hypercalcemia – defined as ≥10.3 mg/dL (serum) or >1.30 mmol/L (ionized)
        • Symptoms
          • 10.3-12 mg/dL – stones, bones, psychic moans, and abdominal groans
          • >12 mg/dL – stupor and coma
          • >13 mg/dL – ECG shows QT interval shortening, prolongation of PR
          • >15 mg/dL – heart block, cardiac arrest
        • Etiologies
  • K
    • Normal range – 3.3-5.0 mmol/L
      • Rapid changes have life-threatening consequences – may affect serum pH (inverse relationship)
    • Three controlling mechanisms
      • Intake
      • Distribution
        • Intracellular and extracellular fluid
        • Cellular distribution affected by insulin beta-adrenergic receptors and renal excretion
      • Excretion
    • K-related disorders
      • Hypokalemia
        • Definition
          • Mild – 3-3.2 mmol/L
          • Moderate – 2.5-2.9 mmol/L
          • Severe – <2.5 mmol/L
        • Symptoms – may vary from asymptomatic to fulminant respiratory failure
          • Most common – weakness, fatigue
          • Electrocardiogram (ECG) – prolonged PR interval, Torsade de Pointes
        • Etiologies
          • Drugs (eg, diuretics, beta agonists)
          • Gastrointestinal losses
          • Renal losses (eg, osmotic diuresis, mineralocorticoid excess)
          • Hypomagnesemia
          • Dialysis/plasmapheresis
          • Inadequate intake (eg, anorexia, dementia)
          • Transcellular shifts (eg, alkalosis, hypothermia)
      • Hyperkalemia
        • Definition
          • Mild – >5.1-6.0 mmol/L
          • Moderate – 6.1-7 mmol/L
          • Severe – >7 mmol/L
        • Symptoms – usually occurs only >7 mmol/L
          • Muscle weakness, cardiac arrhythmias
          • ECG – peaked T waves, widening of QRS, ventricular tachycardia
        • Etiologies
          • Sample collection error – usually hemolysis of specimen
          • Drugs (eg, angiotensin-converting ​​enzyme [ACE] inhibitors, potassium-sparing diuretics)
          • Rhabdomyolysis
          • Metabolic acidosis
          • Renal failure, renal tubular acidosis type IV
          • Hypoaldosteronism
          • Hypoglycemia
          • Tumor lysis syndrome
          • Addison disease
  • Na
    • Normal range – 136-144 mmol/L
      • Consistent serum osmolality maintained through a balance of Na and water intake and excretion
      • Serum osmolality reference interval – 280-303 mOsm/kg
        • Calculated serum osmolality = (2 x Na) + (glucose/18) + (BUN/2.8)
    • Na-related disorders
      • Hyponatremia – defined as <135 mmol/L
        • Most often a chronic condition but may worsen in acutely ill patients
        • Symptoms – most often found in patients with abrupt changes in sodium level
          • Nausea/emesis
          • Headache
          • Lethargy
          • Severe hyponatremia – seizures, coma, death
        • Etiologies
          • Pseudohyponatremia
            • Hyperglycemia – for every 100 mg/dL increase of glucose, serum Na is lowered by 1.7 mmol/L
            • Hyperlipidemia
            • Hyperproteinemia (eg, multiple myeloma)
          • Hypovolemic – thiazide diuretics, osmotic diuresis, adrenal insufficiency, ketonuria, gastrointestinal (GI) losses
          • Euvolemic – syndrome of inappropriate antidiuretic hormone (SIADH), hypothyroidismHIV, certain cancers, glucocorticoid deficiency
          • Hypervolemic – psychogenic polydipsia, congestive heart failurecirrhosis, and renal failure
      • Hypernatremia – defined as >145 mmol/L
        • Symptoms – mimics symptoms of hyponatremia
        • Etiologies
  • Mg
    • Normal range – 1.6-2.6 mg/dL
      • Aids in cellular transport of Ca, Na, K
      • Balance maintained by kidneys 
    • Mg-related disorders
      • Hypomagnesemia (common) – defined as <1.6 mg/dL
        • Symptoms – not usually evident until Mg <1.0 mg/dL
          • Neurologic manifestations similar to hypocalcemia
          • Tetany, muscle weakness, Chvostek, and Trousseau signs
          • Electrocardiogram (ECG) – widening QRS or QT and peaked T waves, premature ventricular contractions
        • Etiologies
      • Hypermagnesemia – defined as >2.6 mg/dL
        • Rare disorder – usually mild elevation with no symptoms
        • Kidneys able to rapidly respond if functioning normally
        • Symptoms – occur when Mg ≥4 mg/dL
          • 4-6 mg/dL – nausea, lethargy, flushing
          • 6-10 mg/dL – somnolence, hypocalcemia, hypotension, bradycardia
          • >10 mg/dL – respiratory paralysis, complete heart block, cardiac arrest
        • Etiologies
          • Impaired renal function
          • Large load of Mg or Mg-containing drugs
          • Parenteral Mg therapy for preeclampsia
          • Elderly patient with gastrointestinal disease receiving cathartics

ARUP Laboratory Tests

Evaluate electrolyte abnormalities and underlying hepatic or renal dysfunction

Panel includes albumin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, bilirubin, Ca, carbon dioxide, creatinine, chloride, glucose, K, protein, Na, and urea nitrogen

Evaluate Mg concentrations in blood

Related Tests

Evaluate for kidney dysfunction in patients with known risk factors (eg, hypertension, diabetes, obesity, family history of kidney disease)

Panel includes Ca, carbon dioxide, chloride, creatinine, glucose, K, Na, and urea nitrogen

Panel includes anion gap carbon dioxide, chloride, K, and Na

Panel includes Na, K, chloride, and creatinine

Diagnose and manage diabetes mellitus and other carbohydrate metabolism disorders

Use to correct for hypoalbuminemia on serum Ca level

Determine Ca concentrations

Use for classification of Na disorders and evaluation of unmeasured ions

May be useful in assessment of tissue stores

For routine assessment of Mg deficiency, plasma or serum Mg is preferred

Medical Experts

Contributor

Genzen

Jonathan R. Genzen, MD, PhD
Associate Professor of Clinical Pathology, University of Utah
Chief Operations Officer, Medical Director of Automated Core Laboratory, ARUP Laboratories
Contributor

Lehman

Christopher M. Lehman, MD
Associate Professor of Clinical Pathology, University of Utah
Medical Director, University of Utah Health Hospital Clinical Laboratory, ARUP Laboratories

References

Additional Resources