Electrolyte Disturbances

Abstract

This electrolyte disturbances chapter is full of important pearls to the identification and treatment of hyponatremia, hypernatremia, hypokalemia, hyperkalemia, hypokalemia, and hypoglycemia. The tables are a vital tool to help identify the etiology of the patient’s electrolyte abnormality. Treatments are concise and bulleted for quick reference and action.

Hyponatremia (Na⁺ < 135 mEq/L)

Signs/Symptoms

• Altered mental status

• Lethargy

• Seizures

• Coma

• Decreased tendon reflexes

• Hypothermia

• Respiratory distress or respiratory failure, Cheyne-stokes respirations

• Anorexia

• Nausea, vomiting

• Muscle cramps

• Weakness

• Agitation

• Headaches

Type	Etiology	Notable laboratory findings	Treatment
Pseudohyponatremia	Hyperlipidemia (Na+ decreased by 0.002 × lipid mg/dL) Hyperproteinemia (Na+ decreased by 0.25 × [protein g/dL-8])	Normal serum osmolality	Treat underlying cause
Pseudohyponatremia	Hyperglycemia (Na+ decreased by 1.6 mEq/L for each 100 mg/dL rise in glucose over 100) Mannitol infusion	High serum osmolality	Treat underlying cause
Renal loss	Diuretics Adrenal insufficiency Na+-losing nephropathy Obstructive uropathy Renal tubular acidosis Cerebral salt wasting	Decreased weight ↑ Urine volume ↑ Urine Na+ ↓ Urine osmolality ↓ Urine specific gravity	Treat underlying cause Replace losses
Extrarenal loss	GI losses (diarrhea, vomiting) Skin losses Cystic fibrosis Third spacing (ascites, burns, pancreatitis, etc.)	Decreased weight ↓ Urine volume ↓ Urine Na+ ↑ Urine osmolality ↑ Urine specific gravity	Treat underlying cause Replace losses
Other	SIADH Congestive heart failure Nephrotic syndrome Acute or chronic renal failure Water intoxication Improper formula mixing Cirrhosis Hypothyroidism	Increased or normal weight ↓ Urine volume ↓ Urine Na+ ↑ Urine osmolality ↑ Urine specific gravity	Treat underlying cause Restrict fluids/free water

Emergent Management for Hyponatremia

• Treat symptomatic hyponatremia (seizures, coma, etc.) with IV hypertonic saline:

  • Give 4–6 mL/kg of 3% NaCl.

  • Each mL/kg of 3% NaCl will increase the serum Na⁺ by approximately 1 mEq/L.

  • Do not increase the serum Na⁺ to more than 130 mEq/L acutely.

• Rapid correction of hyponatremia can cause central pontine myelinolysis:

  • Avoid increasing the serum Na⁺ more than 12 mEq/L every 24 h.

• Treat asymptomatic hyponatremia with identification of underlying cause and then disease-specific treatment such as fluid and sodium replacement, water restriction, hormone replacement, or dialysis.

Hypernatremia (Na⁺ > 145 mEq/L)

Signs/Symptoms

• Altered mental status

• Lethargy

• Seizures

• Coma

• Decreased tendon reflexes

• Hyperthermia

• Respiratory distress or respiratory failure

• Nausea, vomiting

• Muscle cramps

• Weakness

• Irritability

• Headaches

Type	Etiology	Notable laboratory findings	Treatment
Renal loss	Diuretics Diabetes insipidus Nephropathy Post-obstructive diuresis Acute tubular necrosis (diuretic phase)	Decreased weight ↑ Urine volume ↑ Urine Na+ ↓ urine specific gravity	Treat underlying cause Replace free water loss
Extrarenal loss	GI losses (diarrhea, vomiting) Skin losses Respiratory loss of free water Insensible losses (premature infant, radiant warmers, phototherapy)	Decreased weight ↓ Urine volume ↓ Urine Na+ ↑ Urine specific gravity	Treat underlying cause Replace free water loss
Other	Mineralocorticoid excess Hyperaldosteronism Exogenous Na+ intake Improper formula mixing Administration of sodium containing medications or fluids (sodium bicarbonate, hypertonic saline) Seawater ingestion Inadequate oral intake (ineffective breastfeeding, child abuse/neglect, etc.)	Increased weight ↓ Urine volume ↓ Urine Na+ ↑ urine osmolality ↑ Urine specific gravity	Treat underlying cause Replace free water loss Stop exogenous intake or administration of sodium containing medications or fluids

Emergent Management for Hypernatremia

• Identify and treat underlying cause.

• Stop exogenous administration of any sodium containing fluids/medications.

• For patients with shock or severe dehydration, volume expansion with isotonic saline is recommended regardless of serum Na⁺.

• Hypernatremia should not be corrected rapidly:

  Serum Na⁺ should not be lowered more than 10–12 mEq/L per 24 h.

Hypokalemia (K < 3.5 mEq/L)

Signs/Symptoms

• Muscle weakness

• Muscle cramps

• Paralysis

• Ileus/constipation

• Areflexia

• Arrhythmias

• Respiratory distress

• Urinary retention

ECG changes: flattened or absent T wave, ST segment depression, presence of a U wave between T wave and P wave, ventricular fibrillation, Torsades de Pointes.

Etiologies
Decreased intake	Anorexia nervosa Poor diet (rare)
Transcellular shift	Alkalosis Insulin therapy Albuterol therapy Familiar hypokalemic periodic paralysis
Renal loss	Renal tubular acidosis Diuretics DKA Excessive mineralocorticoid effect (Bartter’s syndrome, Cushing syndrome, licorice ingestion, hyperaldosteronism) Acute tubular necrosis Fanconi syndrome Antibiotics (high urine anions, especially penicillins)
Extrarenal loss	Vomiting/excessive NG suction Pyloric stenosis Cystic fibrosis Diarrhea Laxative abuse Ureterosigmoidostomy Excessive sweating
Spurious	Leukocytosis

Emergent Management for Hypokalemia

• Obtain ECG.

• Obtain creatine kinase (CK) (hypokalemia can cause rhabdomyolysis); glucose; ABG; urinalysis; urine K⁺, Na⁺, and Cl⁻; and urine osmolality.

• If respiratory paralysis or cardiac arrhythmia is present, infuse 1 mEq/kg/h.

• If patient is not critical, calculate K⁺ deficit, and replace with potassium acetate or potassium chloride. Oral replacement is safer when feasible.

• Correct underlying causes (DKA, alkalosis, etc.).

• If IV replacement is necessary, no more than 40 mEq/L via peripheral route or 80 mEq/L via central route should be used.

Hyperkalemia (K > 5.5 mEq/L)

Signs/Symptoms

• Muscle weakness

• Paresthesias

• Paralysis

• Areflexia

• Arrhythmias

• Respiratory distress

ECG changes: ECG changes progress with increasing serum K⁺ levels. Peaked T waves, prolongation PR interval, loss of P waves with widening QRS, amplified R wave, progressive widening of QRS, bradycardia, AV block, ventricular arrhythmias, Torsades de Pointes, sinus wave pattern (wide QRS merging with T wave), cardiac arrest.

Etiologies
Increased intake	IV or PO medications Exogenous K+ intake (salt substitutes) Transfusions with aged blood
Transcellular shift	Acidosis Rhabdomyolysis Tumor lysis syndrome Large hematomas Succinylcholine Exercise Insulin deficiency Malignant hyperthermia Hyperkalemic periodic paralysis Crush injuries, trauma, burns
Decreased renal excretion	Renal failure Congenital adrenal hyperplasia K+-sparing diuretics Renal tubular diseases Urinary tract obstruction Aldosterone insensitivity Aldosterone deficiency Lupus nephritis Medications
Spurious	Hemolysis Thrombocytosis Leukocytosis Tight tourniquet during lab draw

Emergent Management for Hyperkalemia

• Obtain ECG.

• Continuous cardiac monitoring.

• Obtain repeat specimen; do not delay treatment waiting on repeat lab results!

• Stop all K⁺ infusions or medications.

• If ECG changes are present:

  • IV administration of 10–20 mg/kg (max 500 mg) calcium chloride or 100 mg/kg/dose (max dose 3 g/dose) calcium gluconate over 5 min to stabilize cardiac membrane.

  • Patient must remain on cardiac monitor and infusion stopped if HR < 60, (bradycardia can be fatal).

  • Shift K⁺ intracellularly:

    • Give IV sodium bicarbonate 1–2 mEq/kg over 5–10 min (if metabolic acidosis is present).

    • Give 5 mg nebulized albuterol.

    • Give IV insulin + glucose infusion (must give glucose with insulin therapy to prevent hypoglycemia).

• Initiate dialysis if renal failure.

• Kayexalate 1 g/kg PO or PR to bind K+ (does not work immediately).

• Give mineralocorticoids if deficiency is suspected.

• Correct any co-existing magnesium deficiency.

Hypocalcemia (Ca⁺⁺ < 7 mg/dL in Preterm Infant, <8 mg/dL in Term Infant, or < 9 mg/dL in Children)

Signs/Symptoms

• Muscular irritability

• Weakness

• Tetany

• Paresthesias

• Fatigue

• Muscle cramps

• Altered mental status

• Seizures

• Laryngospasm

• Cardiac arrhythmias

• Prolonged QT interval

• Trousseau sign (carpopedal spasm after arterial occlusion)

• Chvostek sign (perioral twitch with stimulus of the facial nerve)

Etiologies

Emergent Management for Hypocalcemia

• Obtain ECG (causes arrhythmias/prolonged QT).

• Obtain total and ionized Ca⁺⁺ levels, phosphate level, alkaline phosphatase, magnesium level, total protein, complete metabolic profile, 25-OH vitamin D, parathyroid hormone (PTH) level, albumin, ABG (acidosis increased ionized calcium), chest X-ray to visualize the thymus, ankle and wrist X-rays to assess for rickets, and urine studies for calcium, phosphate, and creatinine.

• Correct hypomagnesemia first if present (if mg⁺⁺ < 1.5 mg/dL) before calcium infusion.

• Stop any medication or infusions that may bind calcium (blood transfusions, TPN).

• Treatment for severe tetany, seizures, or cardiac arrhythmias:

  • 10% IV calcium gluconate 100 mg/kg given slowly over 10 min.

  • Patient must remain on cardiac monitor and infusion stopped if HR < 60 (bradycardia can be fatal).

  • Never mix calcium with fluids containing phosphate or bicarbonate.

• If patient is stable, replacement therapy can be oral.

• Address and treat any underlying causes.

Hypercalcemia (Ca⁺⁺ > 11 mg/dL)

Signs/Symptoms

• Muscular irritability

• Weakness

• Lethargy

• Altered mental status/coma

• Seizures

• Abdominal cramping

• Cardiac arrhythmias

• Shortened QT interval

• Polyuria

• Polydipsia

• Pancreatitis

• Renal calculi

• Nausea, vomiting, anorexia

Emergent Management for Hypercalcemia

• Obtain ECG (causes arrhythmias/shortened QT).

• Obtain total and ionized Ca⁺⁺ levels; phosphate level; alkaline phosphatase; total protein; complete metabolic profile; 25-OH vitamin D; parathyroid hormone (PTH) level; albumin; urine studies for calcium, phosphate, and creatinine; abdominal X-ray; renal ultrasound to assess for renal calculi.

• Address and treat any underlying causes.

• Hydration to increase urine output and Ca⁺⁺ elimination, may give NS boluses for rapid hydration.

• Furosemide for diuresis.

• Severe or refractory hypercalcemia may require dialysis.

Hypoglycemia (Glucose <50 mg/dL)

Signs/Symptoms

• Diaphoresis

• Tachycardia

• Pallor

• Trembling/jitteriness

• Headache

• Confusion

• Altered mental status

• Lethargy

• Apnea

• Nausea, vomiting

• Difficulty speaking

• Weakness

• Seizures

• Ataxia

• Vision changes

• Poor feeding

Etiologies
Glucose use increased	Hyperinsulinism: Insulin-producing tumor, ingestion of oral hypoglycemic agent, insulin therapy or overdose Large tumors (e.g., Wilms’, neuroblastoma) Hyperthermia Growth hormone deficiency Polycythemia Infant of diabetic mothers
Glucose availability decreased	Decreased oral intake Fasting Malnutrition Diarrhea Vomiting Inborn errors of metabolism  Inability to mobilize glucose  Ineffective gluconeogenesis  Inadequate glycogen reserve  Ineffective glycogenolysis
Availability of alternative fuel decreased	Low/absent fat stores Enzyme deficiency in fatty acid oxidation
Others	Sepsis Shock Cardiogenic shock Burns Reye’s syndrome Medications Salicylate ingestion Alcohol ingestion Other ingestions (esp. cardiac meds) Adrenal insufficiency Hypothyroidism Panhypopituitarism Hepatitis/liver failure

Emergent Management for Hypoglycemia

• Immediate treatment of hypoglycemia: Rule of 50 (dextrose fluid × mL/kg = 50):

  • D50 = 1 mL/kg fluid bolus

  • D25 = 2 mL/kg fluid bolus

  • D10 = 5 mL/kg fluid bolus

  • D5 = 10 mL/kg fluid bolus

• Once initial hypoglycemia has been corrected, begin infusion with D10-containing fluids at 1.5–2 × MIVF rate.

• Administer stress dose of glucocorticoid (2 mg/kg of hydrocortisone).

• Laboratory studies: CBC, blood culture, complete metabolic panel, ammonia, glucagon, c-peptide, lactate, pyruvate, carnitine level, ABG, acylcarnitine profile, cortisol level, growth hormone, plasma amino acids, urine organic acids, urinalysis, urine culture.

• Do not delay therapy with dextrose in order to obtain labs: Give glucose immediately!

• Inborn errors of metabolism/genetic disorders and ingestion should be high on your differential diagnosis in infants or children presenting with hypoglycemia.

Quick Hits Electrolyte Disturbances Pearls

• 1. Rapid correction of hyponatremia can cause central pontine myelinolysis, avoid increasing the serum Na⁺ more than 12 mEq/L every 24 h.

• 2. For patients with shock or severe dehydration with hypernatremia, volume expansion with isotonic saline is recommended regardless of serum Na⁺.

• 3. For patients receiving IV calcium infusions, they must remain on cardiac monitor and infusion stopped if HR <60 (bradycardia can be fatal)!

• 4. Prompt recognition and treatment of hypoglycemia in children is critical: remember the “rule of 50” for dextrose administration!