Electrolyte Abnormalities, Life Threatening

Clinical Background

Electrolyte abnormalities are common in 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 (Ca)

Calcium measurement is directly related to serum albumin unless it is measured as ionized calcium (total calcium is directly proportional to albumin concentration)
- Recommend following ionized calcium in the intensive care unit (ICU) or in any clinical setting where albumin concentration is significantly altered
- Corrected serum calcium (for albumin) CCa= (4 g/dL-plasma albumin) X 0.8 + serum calcium
Normal ranges
- Serum - 8.4-10.2 mg/dL
- Ionized - 1.11-1.30 mmol
Calcium-related disorders
- Hypocalcemia
  - Defined as <8.4 mg/dL (serum) or <1.11/mmolL (ionized)
  - Symptoms
    - Tetany, seizures
    - Circumoral numbness
    - Paresthesias
    - Carpopedal spasm
    - Latent tetany may result in Trousseau and Chvostek signs
    - Electrocardiogram (EKG) - prolonged QT internal, Torsades de Pointes
- Causes
  - 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)
- Treatment
  - Measure phosphate, magnesium, potassium, creatinine, PTH
  - Administer calcium gluconate IV in acute symptomatic disease
Measure calcium (ionized) every 4-6 hours
- Hypercalcemia
  - Defined as >10.2 mg/dL (serum), >1.30 mmol/L (ionized)
  - Symptoms
    - 10.3-12 mg/dL - stones, bones, psychic moans and abdominal groans
    - >12 mg/dL - coma and stupor
    - >13 mg/dL - EKG; QT interval shortening, prolongation of PR
    - >15 mg/dL - heart block, cardiac arrest
  - Causes
    - Cancer with bone metastasis (in particular prostate and breast)
    - Hyperparathyroidism
  - Treatment
    - >14 mg/dL or symptomatic >12 mg/dL needs immediate intervention
    - Administer IV fluids rate of 200 cc/hour normal saline in moderate hypercalcemia; increase rate for severe hypercalcemia
    - Measure phosphate, magnesium and potassium concentrations

Potassium (K)

Cellular distribution affected by insulin and beta-adrenergic receptors, renal excretion
3 mechanisms control potassium
- Intake
- Distribution between intracellular and extracellular fluid
- Renal excretion
Rapid changes have life-threatening consequences
- May affect serum pH (inverse relationship)
Normal range - 3.3-5.0 mmol/L
Potassium-related disorders
- Hypokalemia
  - Defined as:
    - 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 commonly manifests as weakness, fatigue
    - EKG - prolonged QT, Torsade de Pointes
  - Causes
    - Drugs (diuretics, beta agonists)
    - Diarrhea (laxative abuse)
    - Diabetes (uncontrolled)
    - Inadequate intake
  - Treatment
    - Potassium replacement
      - Mild: oral replacement
      - Moderate: oral, IV if cardiac arrhythmias
      - Severe: IV required in most cases
- Hyperkalemia
  - Defined as:
    - Mild: >5.1-6.0 mmol/L
    - Moderate: 6.1-7 mmol/L
    - Severe: >7 mmol/L
  - Symptoms
    - Usually only occurs above 7 mmol/L
    - Muscle weakness, cardiac arrhythmias
    - EKG - peaked waves, widening of QRS
  - Causes
    - Sample collection error - hemolysis of specimen (most common cause)
    - Drugs - ACE inhibitors, potassium sparing diuretics
    - Rhabdomyolysis
    - Metabolic acidosis
    - Renal failure
    - Hypoaldosteronism
    - Hypoglycemia
    - Tumor lysis syndrome
  - Treatment
    - Remove exogenous sources
    - 5.5-7 mmol/L - administer sodium polystyrene sulfonate
    - >7.0 mmol/L - administer insulin and IV glucose, calcium, chloride, sodium bicarbonate, loop diuretics and perform dialysis

Sodium (Na)

A balance exists between sodium and water intake and excretion to maintain constant serum osmolality
- Serum osmolality reference interval: 280-303 mOsm/Kg
Normal range: 136-144 mmol/L
Sodium-related disorders
- Hyponatremia
  - Defined as <136 mmol/L
  - Symptoms
    - Nausea
    - Headache
    - Lethargy
    - Emesis
    - Severe hyponatremia can cause seizures, coma, death
  - Causes
    - Hypertonic hyponatremia
      - Hyperglycemia - for every 100 mg/dL increase of glucose, serum sodium is lowered by 1.7 mmol/L
    - Isotonic hyponatremia (pseudohyponatremia)
      - Excess lipids or proteins in serum
      - May or may not be an issue; dependent on sodium method used in laboratory
    - Hypotonic hyponatremia - 3 categories
      - Hypovolemic - thiazide diuretics, osmotic diuresis, adrenal insufficiency, ketonuria
      - Isovolemic - syndrome of inappropriate antidiuretic hormone (SIADH), hypothyroidism, HIV, certain forms of cancer
      - Hypervolemic - psychogenic polydipsia, multiple tap water enemas, congestive heart failure
  - Treatment
    - Hypovolemic - saline replacement
    - Isovolemic, hypervolemic - fluid restriction
    - To calculate deficit
      - Na deficit = (desired Na-measured serum Na) X .06 (males) or 0.5 (females) X body weight (in kg)
    - For severe symptoms - use 3% saline solution (513 mmol/L)
    - For less severe - use normal saline solution
- Hypernatremia
  - Defined as serum sodium >144 mmol/L
  - Symptoms
    - Mimics symptoms of hyponatremia
  - Causes
    - Insensible losses (eg, fever)
    - Diabetes insipidus (central, nephrogenic)
    - Cushing disease
    - Hyperaldosteronism
  - Treatment
    - To calculate free water deficit
      - Free water deficit = [(measured plasma Na-140)/140] X body weight (in kg) X 0.6 (males) or 0.5 (females)
    - Mild - oral fluids
    - Severe - IV fluids; replace deficit with 5% dextrose in water (DSW)

Magnesium (Mg)

Physiologically - magnesium aids in cellular transport of Ca, Na, K
- Balance maintained by kidneys
Normal range in serum - 1.6-2.6 mg/dL
Magnesium-related disorders
- Hypomagnesemia is a common disorder
  - Defined as serum Mg <1.6 mg/dL
  - Symptoms
    - Neurologic manifestations similar to hypocalcemia
    - Tetany, muscle weakness, Chvostek and Trousseau signs
    - EKG - widening QRS or QT and peaked T waves, premature ventricular contractions (PVCs)
  - Causes
    - Gastrointestinal losses - diarrhea, small bowel surgery, malabsorption, pancreatitis
    - Renal losses - diuretics, nephrotic drugs, tubular necrosis
    - Uncontrolled diabetes mellitus
  - Treatment
    - Oral replacement in nonemergent situations
    - IV replacement for EKG changes or in critically ill patients
- Hypermagnesemia
  - Defined as serum Mg >2.6 mg/dL
  - Symptoms
    - Usually mild elevation and therefore no symptoms
    - Symptoms when Mg greater than or equal to 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
  - Causes
    - Patient has impaired renal function
    - Patient receiving large load of magnesium or magnesium-containing drugs
    - Patient receiving parenteral magnesium therapy for preeclampsia
    - Elderly patient with gastrointestinal disease receiving cathartics
  - Treatment
    - Remove sources of magnesium
    - IV replacement for calcium
    - Dialysis for severe disease

See Also

Adrenal Insufficiency

Diabetes Mellitus Diagnosis

Tests

Tests generally appear in the order most useful for common clinical situations

Test name: Electrolyte Panel

ARUP #: 0020410

Methodology: Ion-Selective Electrode/Enzymatic

Use:

Determine electrolyte imbalances in blood

Limitations:

Follow-up:

Test name: Calcium, Serum or Plasma

ARUP #: 0020027

Methodology: Spectrophotometry

Use:

Determine calcium concentrations in blood

Test name: Potassium, Plasma or Serum

ARUP #: 0020002

Methodology: Ion-Selective Electrode

Use:

Determine potassium concentrations in blood

Test name: Magnesium, Plasma or Serum

ARUP #: 0020039

Methodology: Spectrophotometry

Use:

Determine magnesium concentrations in blood

Test name: Sodium, Plasma or Serum

ARUP #: 0020001

Methodology: Ion-Selective Electrode

Use:

Determine sodium concentrations in blood

Test name: Calcium, Ionized, Whole Blood

ARUP #: 0020140

Methodology: Ion-Selective Electrode/pH-Electrode

Use:

Determine ionized calcium concentrations in blood

Test name: Sodium, Urine

ARUP #: 0020851

Methodology: Ion-Selective Electrode

Use:

Determine sodium concentrations in urine

Test name: Calcium, Ionized, Serum

ARUP #: 0020135

Methodology: Ion-Selective Electrode/pH-Electrode

Use:

Determine ionized calcium concentrations in serum

Additional Tests Available

Test name: Comprehensive Metabolic Panel

ARUP #: 0020408

Methodology: Refer to individual components

Comments:

Test name: Electrolytes, Urine

ARUP #: 0020498

Methodology: Ion-Selective Electrode

Comments:

Test name: Glucose, Plasma or Serum

ARUP #: 0020024

Methodology: Enzymatic

Comments:

Test name: Albumin, Serum or Plasma by Spectrophotometry

ARUP #: 0020030

Methodology: Spectrophotometry

Comments:

Test name: Osmolality, Serum or Plasma

ARUP #: 0020046

Methodology: Freezing Point

Comments:

Test name: Bicarbonate (HCO3), Urine

ARUP #: 0020245

Methodology: Enzymatic

Comments:

Test name: Potassium, Urine

ARUP #: 0020849

Methodology: Ion-Selective Electrode

Comments:

Test name: pH, Urine

ARUP #: 0020305

Methodology: Reflectance Photometry

Comments:

Test name: Magnesium, Urine

ARUP #: 0020477

Methodology: Spectrophotometry

Comments:

Test name: Urea Nitrogen, Urine

ARUP #: 0020480

Methodology: Spectrophotometry

Comments:

Test name: Chloride, Urine

ARUP #: 0020850

Methodology: Ion-Selective Electrode/Chloride Titration

Comments:

Test name: Magnesium, RBCs

ARUP #: 0092079

Methodology: Inductively Coupled Plasma/Mass Spectrometry

Comments:

Test name: Phosphorus, Inorganic, Plasma or Serum

ARUP #: 0020028

Methodology: Spectrophotometry

Comments:

References

General References

Baker SB, Worthley LI. The essentials of calcium, magnesium and phosphate metabolism: part I. Physiology. Crit Care Resusc. 2002;4(4):301-306.

Eledrisi MS, Alshanti MS, Shah MF, Brolosy B, Jaha N. Overview of the diagnosis and management of diabetic ketoacidosis. Am J Med Sci. 2006;331(5):243-251.

Gennari FJ. Disorders of potassium homeostasis. Hypokalemia and hyperkalemia. Crit Care Clin. 2002;18(2):273-88, vi.

Hollander-Rodriguez JC, Calvert JF Jr. Hyperkalemia. Am Fam Physician. 2006;73(2):283-290.

Kellum JA. Acid-base disorders and strong ion gap. Contrib Nephrol. 2007;156:158-166.

Liamis G, Mitrogianni Z, Liberopoulos EN, Tsimihodimos V, Elisaf M. Electrolyte disturbances in patients with hyponatremia. Intern Med. 2007;46(11):685-690.

Liamis G, Tsimihodimos V, Doumas M, Spyrou A, Bairaktari E, Elisaf M. Clinical and laboratory characteristics of hypernatraemia in an internal medicine clinic. Nephrol Dial Transplant. 2008;23(1):136-143.

Lien YH, Shapiro JI. Hyponatremia: clinical diagnosis and management. Am J Med. 2007;120(8):653-658.

Lin M, Liu SJ, Lim IT. Disorders of water imbalance. Emerg Med Clin North Am. 2005;23(3):749-70, ix.

Mouw DR, Latessa RA, Hickner J. Clinical inquiries. What are the causes of hypomagnesemia?. J Fam Pract. 2005;54(2):174-176.

Murphy E, Bassett JH, Williams GR. Disorders of calcium metabolism. Practitioner. 2006;250(1686):4-6, 8.

Offenstadt G, Das V. Hyponatremia, hypernatremia: a physiological approach. Minerva Anestesiol. 2006;72(6):353-356.

Reynolds RM, Padfield PL, Seckl JR. Disorders of sodium balance. BMJ. 2006;332(7543):702-705.

Topf JM, Murray PT. Hypomagnesemia and hypermagnesemia. Rev Endocr Metab Disord. 2003;4(2):195-206.

Verbalis JG, Goldsmith SR, Greenberg A, Schrier RW, Sterns RH. Hyponatremia treatment guidelines 2007: expert panel recommendations. Am J Med. 2007;120(11 Suppl 1):S1-21.

Worthley LI. Osmolar disorders. Crit Care Resusc. 1999;1(1):45-54.

Medical Reviewers

Hill, Harry R., M.D. Group Medical Director, Laboratory of Immunology, ARUP Laboratories, and Executive Director of the ARUP Institute for Clinical and Experimental Pathology; Professor and Division Head, Clinical Pathology, University of Utah

Lehman, Christopher M., M.D. Co-Medical Director, University Hospital Clinical Laboratory; Associate Professor, Clinical Pathology, University of Utah

Roberts, William L. , M.D., Ph.D. Medical Director, Automated Core Laboratory at ARUP Laboratories; Professor, Pathology, University of Utah

Comprehensive Review: May 2008
Last Update: September 2008