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
- Order concurrently in high-risk situations (eg, diabetes mellitus, alcoholism, diuretic therapy)
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

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 (liver, kidney 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
    - Cancer with bone metastasis (in particular prostate and breast)
    - Hyperparathyroidism, thyrotoxicosis
    - Drug induced
    - Granulomatous disease – sarcoidosis

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

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), hypothyroidism, HIV, certain cancers, glucocorticoid deficiency
    - Hypervolemic – psychogenic polydipsia, congestive heart failure, cirrhosis, and renal failure
- Hypernatremia – defined as >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, iatrogenic (eg, saline enemas)

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
    - Gastrointestinal losses – diarrhea, small bowel surgery, malabsorption, pancreatitis
    - Renal losses – diuretics, nephrotic drugs, tubular necrosis
    - Diabetes (uncontrolled)
- 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 Lab Tests

Evaluate electrolyte abnormalities and underlying hepatic or renal dysfunction

0020408

Comprehensive Metabolic Panel 0020408

Method

Quantitative Ion-Selective Electrode/Quantitative Enzymatic/Quantitative Spectrophotometry

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

0020039

Magnesium, Plasma or Serum 0020039

Method

Quantitative Spectrophotometry

Related Tests

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

0020144

Renal Function Panel 0020144

Method

Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay

0020399

Basic Metabolic Panel 0020399

Method

Quantitative Ion-Selective Electrode/Quantitative Enzymatic/Quantitative Spectrophotometry

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

0020410

Electrolyte Panel 0020410

Method

Quantitative Ion-Selective Electrode/Enzymatic

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

0020498

Electrolytes, Urine 0020498

Method

Quantitative Ion-Selective Electrode

Panel includes Na, K, chloride, and creatinine

Diagnose and manage diabetes mellitus and other carbohydrate metabolism disorders

0020024

Glucose, Plasma or Serum 0020024

Method

Quantitative Enzymatic

Use to correct for hypoalbuminemia on serum Ca level

0020030

Albumin, Serum or Plasma by Spectrophotometry 0020030

Method

Quantitative Spectrophotometry

Determine Ca concentrations

0020027

Calcium, Serum or Plasma 0020027

Method

Quantitative Spectrophotometry

Asses Ca status

0020140

Calcium, Ionized, Whole Blood 0020140

Method

Ion-Selective Electrode/pH Electrode

0020135

Calcium, Ionized, Serum 0020135

Method

Ion-Selective Electrode/pH Electrode

Use for classification of Na disorders and evaluation of unmeasured ions

0020046

Osmolality, Serum or Plasma 0020046

Method

Freezing Point

May be useful in assessment of tissue stores

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

0092079

Magnesium, RBC 0092079

Method

Quantitative Inductively Coupled Plasma-Mass Spectrometry

0020849

Potassium, Urine 0020849

Method

Quantitative Ion-Selective Electrode

0020002

Potassium, Plasma or Serum 0020002

Method

Quantitative Ion-Selective Electrode

0020851

Sodium, Urine 0020851

Method

Quantitative Ion-Selective Electrode

0020001

Sodium, Plasma or Serum 0020001

Method

Quantitative Ion-Selective Electrode

0020477

Magnesium, Urine 0020477

Method

Quantitative Spectrophotometry

0020245

Bicarbonate (HCO(sub:3)), Urine 0020245

Method

Enzymatic

0020305

pH, Urine 0020305

Method

Reflectance Spectrophotometry

0020480

Urea Nitrogen, Urine 0020480

Method

Quantitative Spectrophotometry

0020850

Chloride, Urine 0020850

Method

Quantitative Ion-Selective Electrode

2011311

Chloride, Random Urine 2011311

Method

Quantitative Ion-Selective Electrode

0020028

Phosphorus, Inorganic, Plasma or Serum 0020028

Method

Quantitative Spectrophotometry

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 and Farmington Health Center Clinical 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

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Clinical inquiries: what is the best workup for hypocalcemia?

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Life-Threatening Electrolyte Abnormalities

Diagnosis

Indications for Testing

Laboratory Testing

Differential Diagnosis

Background

Electrolytes

ARUP Lab Tests

Medical Experts

Genzen

Lehman

References

20081299

18842196

25822386

25803349

18535072

19797486

26237763

19274487

19854840

26244308

19944286

25551526

24074529

26371733

Cite this page

Life-Threatening Electrolyte Abnormalities

Feedback

Diagnosis

Indications for Testing

Laboratory Testing

Differential Diagnosis

Background

Electrolytes

ARUP Lab Tests

Medical Experts

References

Related Information

Related Topics