Electrolyte Abnormalities, Life Threatening

Diagnosis

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
    • For further evaluation, refer to hypocalcemia
• 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 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, Mg, K, creatinine, PTH Administer calcium gluconate IV in acute symptomatic disease Measure ionized Ca every 4-6 hours 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 Causes Cancer with bone metastasis (in particular prostate and breast) Hyperparathyroidism, thyrotoxicosis Drug induced Granulomatous disease – sarcoidosis Treatment >14 mg/dL or symptomatic >12 mg/dL needs immediate intervention Moderate hypercalcemia – administer IV fluids at a rate of 200 cc/hour normal saline Severe hypercalcemia – increase IV rate Measure phosphate, Mg, and K concentrations

  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 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 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 Causes 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 Treatment – remove exogenous sources 5.5-7 mmol/L – administer sodium polystyrene sulfonate >7.0 mmol/L – administer insulin and IV glucose, Ca, chloride, sodium bicarbonate, loop diuretics, and perform dialysis

  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 <136 mmol/L Symptoms Nausea Headache Lethargy Emesis Severe hyponatremia – seizures, coma, death Causes Hyperosmolar hyponatremia Hyperglycemia – for every 100 mg/dL increase of glucose, serum Na is lowered by 1.7 mmol/L Iso-osmolar hyponatremia (pseudohyponatremia) Excess lipids or proteins in serum May or may not be an issue – results dependent on assay method used by laboratory Hypo-osmolar hyponatremia – 3 categories Hypovolemic – thiazide diuretics, osmotic diuresis, adrenal insufficiency, ketonuria Isovolemic – syndrome of inappropriate antidiuretic hormone, hypothyroidism, HIV, certain cancers Hypervolemic – psychogenic polydipsia, multiple tap-water enemas, congestive heart failure Treatment Na deficit = (desired Na-measured serum Na) X 0.6 (males) or 0.5 (females) X body weight (in kg) Hypovolemic – saline replacement Severe symptoms – use 3% saline solution (513 mmol/L) Less severe symptoms – use normal saline solution Isovolemic or hypervolemic – fluid restriction Hypernatremia – defined as serum Na >144 mmol/L Symptoms – mimics symptoms of hyponatremia Causes – water depletion Extrarenal losses Insensible losses (eg, fever) Gastrointestinal losses (eg, diarrhea) Renal losses Diabetes insipidus (central, nephrogenic) Hyperaldosteronism Cushing disease Salt gain – hypertonic solution or sodium bicarbonate Treatment – fluid replacement 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

  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 Causes Gastrointestinal losses – diarrhea, small bowel surgery, malabsorption, pancreatitis Renal losses – diuretics, nephrotic drugs, tubular necrosis Diabetes (uncontrolled) 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 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 Causes Impaired renal function Large load of Mg or Mg-containing drugs Parenteral Mg therapy for preeclampsia Elderly patient with gastrointestinal disease receiving cathartics Treatment Remove sources of Mg IV replacement for Ca Dialysis for severe disease

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

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Renal Function Panel 0020144 Method: Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay	Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, and urea nitrogen
Basic Metabolic Panel 0020399 Method: Immunoturbidimetry/Polymerase Chain Reaction/Fluorescence Monitoring/Isoelectric Focusing	Determine electrolyte imbalances Panel includes calcium, carbon dioxide, chloride, creatinine, glucose, potassium, sodium, and urea nitrogen
Electrolyte Panel 0020410 Method: Quantitative Ion-Selective Electrode/Enzymatic	Determine electrolyte imbalances Panel includes anion gap carbon dioxide, chloride, potassium, and sodium
Electrolytes, Urine 0020498 Method: Quantitative Ion-Selective Electrode	Determine electrolyte imbalances in the urine
Glucose, Plasma or Serum 0020024 Method: Quantitative Enzymatic	Determine glucose concentrations
Sodium, Urine 0020851 Method: Quantitative Ion-Selective Electrode	Determine Na concentrations
Sodium, Plasma or Serum 0020001 Method: Quantitative Ion-Selective Electrode	Determine 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	Determine 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	Determine Ca concentrations
Albumin, Serum or Plasma by Spectrophotometry 0020030 Method: Quantitative Spectrophotometry	Use to correct for hypoalbuminemia on serum calcium level