Electrolyte Abnormalities, Life Threatening

Electrolyte Abnormalities, Life Threatening

 

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 ≥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