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).

Tabs Content

Clinical Overview

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

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

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

Magnesium, Plasma or Serum 0020039
Method: Quantitative Spectrophotometry

Recommended Use

Evaluate Mg concentrations in blood

Medical Experts

Genzen, Jonathan R., MD, PhD, Laboratory Section Chief, Clinical Chemistry, and Medical Director, Automated Core Laboratory, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

Lehman, Christopher M., MD, Co-Medical Director, University Hospitals and Clinics Clinical Laboratory; Professor of Clinical Pathology, University of Utah

References

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

Last Update: December 2018