Electrolyte Abnormalities, Life Threatening


Indications for Testing

  • Clinical scenario where electrolyte abnormality is suspected (eg, unconscious or confused patient, patient on diuretic therapy)

Laboratory Testing

  •  Evaluate whether elevation or decrease is real
    • Hyperkalemia – hemolysis present?
    • Hyponatremia – hyperglycemia or hyperlipidemia present?
  • Initial screen – panel should include sodium, potassium chloride, bicarbonate, BUN, creatinine, glucose, and calcium
  • If calcium abnormality suspected – order concurrent serum albumin
    • If hypocalcemia suspected – also order magnesium
  • Other high-risk situations (eg, diabetes mellitus, alcoholism, diuretic therapy) – order magnesium

Differential Diagnosis

  • Refer to individual topics in Clinical Background under causes

Clinical Background

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).

  • Calcium
    • 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 ICU or in any clinical setting where albumin concentration is significantly altered
      • Corrected serum Ca (for albumin) – CCa= (4 g/dL-plasma albumin) x 0.8 + serum Ca
    • Normal ranges
      • Serum – 8.4-10.2 mg/dL
      • Ionized – 1.11-1.30 mmol/L
        • Needs correction for pH outside of normal range
    • Calcium-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 (EKG) – prolonged QT internal, Torsades de Pointes
        • Etiologies
          • Removal or destruction of parathyroid glands (hypoparathyroidism)
          • Hyperphosphatemia secondary to rhabdomyolysis or renal failure
          • Pancreatitis
          • Hypovitaminosis D (liver, kidney disease)
          • Parathyroid hormone (PTH) resistance secondary to hypomagnesemia (Mg <1.0 mg/dL)
      • Hypercalcemia – defined as ≥10.3 mg/dL (serum), >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 – EKG shows QT interval shortening, prolongation of PR
          • >15 mg/dL – heart block, cardiac arrest
        • Etiologies
    • Three controlling mechanisms
      • Intake
      • Distribution – intracellular and extracellular fluid
        • Cellular distribution affected by insulin and beta-adrenergic receptors, renal excretion
      • Excretion
    • Normal range – 3.3-5.0 mmol/L
      • Rapid changes have life-threatening consequences – may affect serum pH (inverse relationship)
    • Potassium-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
          • EKG – prolonged QT, Torsade de Pointes
        • Etiologies
          • Drugs (diuretics, beta agonists)
          • Diarrhea (laxative abuse)
          • Diabetes (uncontrolled)
          • Inadequate intake
      • 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
          • EKG – peaked waves, widening of QRS
        • Etiologies
          • Sample collection error – usually hemolysis of specimen
          • Drugs – angiotensin-converting enzyme (ACE) inhibitors, potassium sparing diuretics (particularly in patients with chronic kidney disease)
          • Rhabdomyolysis
          • Metabolic acidosis
          • Renal failure, renal tubular acidosis type IV
          • Hypoaldosteronism
          • Hypoglycemia
          • Tumor lysis syndrome
          • Addison disease
    • Consistent serum osmolality maintained through a balance of sodium and water intake and excretion
      • Normal serum range – 136-144 mmol/L
      • Serum osmolality reference interval – 280-303 mOsm/kg
        • Calculated serum osmolality = (2xNa) + (glucose/18) + (BUN/2.8)
    • Sodium-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
        • Symptoms
          • 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, GI losses
          • Euvolemic – syndrome of inappropriate antidiuretic hormone (SIADH), hypothyroidism, HIV, certain cancers, glucocorticoid deficiency
          • Hypervolemic – psychogenic polydipsia, congestive heart failure, cirrhosis, and renal failure 
      • Hypernatremia – defined as serum Na >145 mmol/L
        • Symptoms – mimics symptoms of hyponatremia
        • Etiologies
          • Hypovolemic – body fluid losses, diuretic use, GI losses, heat injury, osmotic diuresis
          • Euvolemic – central diabetes insipidus, fever, mediating tumors
          • Hypervolemic – Cushing syndrome, hemodialysis, hyperaldosteronism, latrogenic (eg, saline enemas)
    • Aids in cellular transport of Ca, Na, K – balance maintained by kidneys
      • Normal serum range – 1.6-2.6 mg/dL
    • Magnesium-related disorders
      • Hypomagnesemia (common) – defined as serum Mg <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
          • EKG – widening QRS or QT and peaked T waves, premature ventricular contractions
        • Etiologies
          • Gastrointestinal losses – diarrhea, small bowel surgery, malabsorption, pancreatitis
          • Renal losses – diuretics, nephrotic drugs, tubular necrosis
          • Diabetes (uncontrolled)
      • Hypermagnesemia – defined as serum Mg >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

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Comprehensive Metabolic Panel 0020408
Method: Quantitative Ion-Selective Electrode/Quantitative Enzymatic/Quantitative Spectrophotometry

Evaluates electrolyte abnormalities and underlying hepatic or renal dysfunction

Panel includes albumin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, bilirubin, carbon dioxide, creatinine, chloride, glucose, potassium, protein, sodium, and urea nitrogen

Magnesium, Plasma or Serum 0020039
Method: Quantitative Spectrophotometry

Evaluates Mg concentrations in blood

Calcium, Ionized, Whole Blood 0020140
Method: Ion-Selective Electrode/pH Electrode

Follow up abnormal serum calcium result

Calcium, Ionized, Serum 0020135
Method: Ion-Selective Electrode/pH Electrode

Follow up abnormal serum calcium result

Osmolality, Serum or Plasma 0020046
Method: Freezing Point

Use for classification of Na disorders and evaluation of unmeasured ions

Additional Tests Available
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Renal Function Panel 0020144
Method: Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay

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

Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, and urea nitrogen
Basic Metabolic Panel 0020399
Method: Quantitative Ion-Selective Electrode/Quantitative Enzymatic/Quantitative Spectrophotometry

Determines electrolyte imbalances

Panel includes calcium, carbon dioxide, chloride, creatinine, glucose, potassium, sodium, and urea nitrogen

Electrolyte Panel 0020410
Method: Quantitative Ion-Selective Electrode/Enzymatic

Determines electrolyte imbalances

Panel includes anion gap carbon dioxide, chloride, potassium, and sodium

Electrolytes, Urine 0020498
Method: Quantitative Ion-Selective Electrode

Determines electrolyte imbalances in the urine

Glucose, Plasma or Serum 0020024
Method: Quantitative Enzymatic

Determines glucose concentrations

Sodium, Urine 0020851
Method: Quantitative Ion-Selective Electrode

Determines Na concentrations

Sodium, Plasma or Serum 0020001
Method: Quantitative Ion-Selective Electrode

Determines Na concentrations

Bicarbonate (HCO3), Urine 0020245
Method: Enzymatic
Potassium, Urine 0020849
Method: Quantitative Ion-Selective Electrode
Potassium, Plasma or Serum 0020002
Method: Quantitative Ion-Selective Electrode

Determines K concentrations

pH, Urine 0020305
Method: Reflectance Spectrophotometry
Magnesium, Urine 0020477
Method: Quantitative Spectrophotometry
Urea Nitrogen, Urine 0020480
Method: Quantitative Spectrophotometry
Chloride, Urine 0020850
Method: Quantitative Ion-Selective Electrode
Magnesium, RBC 0092079
Method: Quantitative Inductively Coupled Plasma-Mass Spectrometry
Phosphorus, Inorganic, Plasma or Serum 0020028
Method: Quantitative Spectrophotometry
Calcium, Serum or Plasma 0020027
Method: Quantitative Spectrophotometry

Determines Ca concentrations

Albumin, Serum or Plasma by Spectrophotometry 0020030
Method: Quantitative Spectrophotometry

Use to correct for hypoalbuminemia on serum calcium level