Electrolyte Abnormalities, Life Threatening

Diagnosis
Background
Lab Tests
References
Related Topics

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 – evaluate for hemolysis in sample
- Hyponatremia – evaluate for presence of hyperglycemia or hyperlipidemia
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
  - For further evaluation, refer to hypocalcemia
Other high-risk situations (eg, diabetes mellitus, alcoholism, diuretic therapy) – order concurrent magnesium concentration

Differential Diagnosis

Refer to individual topics in Clinical Background under causes

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

Potassium

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 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
    - EKG – 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

Sodium

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)

Magnesium

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

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.

Comprehensive Metabolic Panel 0020408
Method: Quantitative Ion-Selective Electrode/Quantitative Enzymatic/Quantitative Spectrophotometry

Recommended Use

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

Recommended Use

Evaluates Mg concentrations in blood

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

Recommended Use

Follow up abnormal serum calcium result

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

Recommended Use

Follow up abnormal serum calcium result

Osmolality, Serum or Plasma 0020046
Method: Freezing Point

Recommended Use

Use for classification of Na disorders and evaluation of unmeasured ions

Guidelines

Verbalis JG, Goldsmith SR, Greenberg A, Korzelius C, Schrier RW, Sterns RH, Thompson CJ. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013; 126(10 Suppl 1): S1-42. PubMed

General References

Assadi F. Hypomagnesemia: an evidence-based approach to clinical cases. Iran J Kidney Dis. 2010; 4(1): 13-9. PubMed

Bosworth M, Mouw D, Skolnik DC, Hoekzema G. Clinical inquiries: what is the best workup for hypocalcemia? J Fam Pract. 2008; 57(10): 677-9. PubMed

Braun MM, Barstow CH, Pyzocha NJ. Diagnosis and management of sodium disorders: hyponatremia and hypernatremia. Am Fam Physician. 2015; 91(5): 299-307. PubMed

Cohen DM, Ellison DH. Evaluating hyponatremia. JAMA. 2015; 313(12): 1260-1. PubMed

Cooper MS, Gittoes NJ. Diagnosis and management of hypocalcaemia. BMJ. 2008; 336(7656): 1298-302. PubMed

Goff DA, Higinio V. Hypernatremia. Pediatr Rev. 2009; 30(10): 412-3; discussion 413. PubMed

Henry DA. In The Clinic: Hyponatremia. Ann Intern Med. 2015; 163(3): ITC1-19. PubMed

Musso CG. Magnesium metabolism in health and disease. Int Urol Nephrol. 2009; 41(2): 357-62. PubMed

Nyirenda MJ, Tang JI, Padfield PL, Seckl JR. Hyperkalaemia. BMJ. 2009; 339: b4114. PubMed

Palmer BF, Clegg DJ. Electrolyte and Acid-Base Disturbances in Patients with Diabetes Mellitus. N Engl J Med. 2015; 373(6): 548-59. PubMed

Ranadive SA, Rosenthal SM. Pediatric disorders of water balance. Endocrinol Metab Clin North Am. 2009; 38(4): 663-72. PubMed

Sterns RH. Disorders of plasma sodium--causes, consequences, and correction. N Engl J Med. 2015; 372(1): 55-65. PubMed

Viera AJ, Wouk N. Potassium Disorders: Hypokalemia and Hyperkalemia Am Fam Physician. 2015; 92(6): 487-95. PubMed

Medical Reviewers

Genzen, Jonathan R., MD, PhD, Co-Medical Director, Automated Core Laboratory at ARUP Laboratories; Assistant Professor of Clinical Pathology, University of Utah

Adrenal Insufficiency

Adrenal Insufficiency Testing Algorithm

Aldosteronism

Hyperaldosteronism Testing Algorithm

Diabetes Mellitus

Hypercalcemia

Hypercalcemia Testing Algorithm

Hypocalcemia

Hypocalcemia Testing Algorithm

Hypopituitarism

Metabolic Acidosis

Last Update: August 2016

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Electrolyte Abnormalities, Life Threatening

Indications for Testing

Laboratory Testing

Differential Diagnosis

Guidelines

General References

Medical Reviewers

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