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Snapshot
  • A 56-year-old man is brought to the emergency department by his son due to mild confusion and shortness of breath. Prior to symptom develop he needed to sleep on a recliner due to feeling short of breath while supine. Medical history is significant for chronic obstructive pulmonary disease and a prior myocardial infarction requiring coronary artery bypass grafting. On physical exam, the patient is altered but able to follow commands. There is jugular venous distension, an S3 heart sound, and 2+ lower extremity pitting edema. Laboratory testing is significant for a brain natriuretic peptide 950 pg/mL and serum sodium of 130 mmol/L. (Hyponatremia secondary to congestive heart failure)
Potassium
 
Electrolyte Disturbances
Hyponatremia Hypernatremia
  • Definition
    • serum sodium of < 135 mmol/L
  • Etiology
    • pseudohyponatremia
      • hyperglycemia
      • hyperlipidemia
    • hypervolemic hyponatremia
      • congestive heart failure
      • nephrotic syndrome
      • cirrhosis
      • renal insufficiency
    • hypovolemic hyponatremia
      • vomiting and diarrhea
      • burns
      • sweating
      • cystic fibrosis
      • diuretic use (e.g., thiazides)
      • angiotensin converting enzyme (ACE) inhibitor
      • adrenal insufficiency
    • euvolemic hyponatremia
      • psychogenic polydipsia
      • hypothyroidism
      • syndrome of inappropriate anti-diuretic hormone (SIADH)
      • diuretic use
      • ACE inhibitors
  • Presentation
    • stupor
    • coma
    • seizures
    • nausea
    • malaise
  • Studies
    • assess volume status
    • serum electrolyte and urine studies
  • Treatment
    • address underlying cause
    • asymptomatic
      • free water restriction
    • moderate hyponatremia
      • IV normal saline
        • loop diuretics may be added
    • severe hyponatremia
      • hypertonic (3%) saline
  • Complications
    • rapid correction of hyponatremia can lead to osmotic demyelination syndrome
  • Definition
    • serum sodium of > 145 mmol/L
  • Etiology
    • insensible losses (e.g., sweating)
    • osmotic diarrhea
    • osmotic diuresis
      • e.g., diabetic ketoacidosis
    • poor fluid intake
    • diuretic use
    • osmotic diuresis
    • vomiting and diarrhea
    • central and nephrogenic diabetes insipidus
    • hypertonic sodium gain
  • Presentation
    • stupor
    • coma
    • seizure
  • Studies
    • assess volume status
    • serum electrolyte and urine studies
  • Treatment
    • address underlying cause
    • intravenous (IV) 5% dextrose in water (D5W)
  • Complications
    • rapid corrrection of hypernatremia can lead to cerebral edema and herniation
Hypokalemia Hyperkalemia
  • Defintion
    • serum potassium of < 3.5 mEq/L
  • Etiology
    • ↑ insulin
    • hyperglycemia
      • this stimulates endogenous insulin secretion from the pancreas in normal conditions
    • β2-adrenergic agonists
    • alkalosis
    • hyposmolality
    • diarrhea
  • Presentation
    • muscle and cardiac dysfunction
      • muscular symptoms
        • abdominal cramping
        • muscle weakness and cramping
      • cardiac symptoms
        • palpitations
    • parasthesias
    • nausea and vomiting
  • Studies
    • electrocardiogram (ECG) findings
      • U waves
      • T wave flattening
  • Treatment
    • address underlying cause
    • potassium repletion
      • remember to not use dextrose-containing fluids as this will stimulate insulin release and shift potassium within the cell
        • this worsens the hypokalemia
    • replace magnesium in magnesium deficiency
  • Definition
    • serum potassium of > 5-5.5 mEq/L
  • Etiology
    • insulin deficiency
    • β2-adrenergic antagonists
    • acidosis
      • cells attempt to buffer excess hydrogen ions to shift these ions into the cells
        • in exchange for this intracellular uptake of hydrogen, potassium is transferred out the cell
          • this attempts to achieve electroneutrality
    • digitalis
      • secondary to dose-dependent Na+/K+ -ATPase pump inhibition
    • cell lysis (e.g., rhabdomyolysis)
    • exercise
    • hyperosmolarity
    • succinylcholine
    • TMP-SMX
    • ACE inhibitors
  • Presentation
    • muscle and cardiac dysfunction
      • muscular symptoms
        • myalgias
        • muscle paralysis
        • chest pain
      • cardiac symptoms
        • arrhythmias and palpitations
    • nausea and vomiting
    • parasthesias
  • Studies
    • ECG findings
      • peaked T waves and wide QRS
  • Treatment 
    • address underlying cause
    • IV calcium gluconate
      • has no effect on potassium levels but stabilizes the myocardium
    • shifting potassium within cells
      • insulin plus glucose
      • β2-adrenergic agonists
    • lowering body potassium
      • sodium polystyrene sulfonate
        • this is a cation exchange resin
    • dialysis
      • used in patients unresponsive to medical therapy
Hypocalcemia Hypercalemia
  • Definition
    • serum total calcium < 8.4 mg/dL
    • ionized fraction of calcium < 4.4 mg/dL
  • Etiology
    • renal failure
    • hypoparathyroidism
    • vitamin D deficiency
    • hypomagnesemia
      • inhibits PTH release
    • pancreatitis
    • alkalemia
  • Presentation
    • seizures
    • tetany
    • Chvostek sign
      • ipsilateral facial muscle contraction caused by tapping the facial nerve
    • Trousseau sign
      • carpopedal spasms by inflating the sphygmomanometer above systolic blood pressure
  • Studies
    • QTc prolongation
  • Treatment
    • address underlying cause
    • asymptomatic or patients with chronic hypocalcemia
      • oral calcium replacement therapy such as
        • calcium citrate
        • calcium carbonate
      • vitamin D supplementation
      • thiazides for patients with hypoparathyroidism
    • symptomatic patients
      • IV calcium gluconate
        • first-line
    • chronic renal failure
      • phosphate binders
      • oral calcium replacement
      • calcitriol
  • Definition
    • serum total calcium > 10.5 mg/dL
    • ionized fraction of calcium > 5.6 mg/dL
  • Etiology
    • hyperparathyroidism
    • humoral hypercalcemia of malignancy
      • secondary to parathyroid hormone-related peptide (PTHrP)
      • associated with squamous cell cancer and solid tumors involving the
        • lung
        • esophageus
        • skin
        • cervix
        • breast
        • kidney
    • vitamin D overdose
    • granulomatous diseases like
      • sarcoidosis
    • thiazide diuretics
    • lithium
    • calcium-containing antacids
    • familial hypocalciuric hypercalcemia
    • immobilization
  • Presentation
    • nephrolithiasis
    • polyuria
    • muscle weakness
    • bone pain
    • abdominal pain
      • secondary to bowel hypomotility and constipation
    • confusion
    • stupor
    • coma
    • mnemonic: stones (renal), bones (pain), groans (abdominal pain), thrones (↑ urinary frequency), and psychiatric overtones (altered mental status)
  • Studies
    • ECG
      • shortened QTc interval
  • Treatment
    • address underlying cause
    • IV isotonic normal saline
      • increases urinary calcium excretion
    • calcitonin
      • impairs bone resorption
      • increases urinary calcium excretion
    • bisphosphonates (e.g., zoledronic acid and pamidronate)
      • has a delayed onset of action
      • impairs bone resorption
    • loops diuretics
      • increases urinary calcium excretion
Hypomagnesemia Hypermagnesemia
  • Definition
    • typically serum magnesium < 1.8 mg/dL
  • Etiology
    • magnesium redistribution
      • refeeding syndrome
    • malnutrition
    • alcohol use disorder
    • anorexia nervosa
    • proton pump inhibitors
    • loop diuretics
    • digoxin
  • Presentation
    • tetany
    • torsades de pointes
    • hypokalemia
    • hypocalcemia
      • when significant (< 1.2 mg/dL)
  • Studies
    • ECG
      • U waves
      • T wave flattening
      • QT prolongation
      • widened QRS complexes
  • Treatment
    • magnesium repletion
      • asymptomatic
        • oral magnesium supplementation
      • severe or symptomatic hypomagnesemia
        • IV magnesium sulfate
  • Definition
    • typically serum magnesium > 2.6 mg/dL
  • Etiology
    • increased magnesium ingestion
      • magnesium cathartics
      • antacids
      • laxatives
      • dietary supplements
    • renal insufficiency
  • Presentation
    • ↓ deep tendon reflexes
    • bradycardia
    • cardiac arrest
    • hypocalcemia
  • Studies
    • ECG
      • PR, QRS, and QT prolongation
      • heart block
  • Treatment
    • address underlying cause
    • IV isotonic saline
    • loop diuretics can be considered
Hypophosphatemia Hyperphosphatemia
  • Definition
    • serum phosphate < 2.5 mg/dL
  • Etiology
    • refeeding syndrome
    • hungry bone syndrome
    • inadquate phosphate intake
    • hyperparathyroidism
    • phosphate binders
  • Presentation
    • weakness
    • muscle and bone pain
    • osteomalacia
    • rickets
  • Treatment
    • address underlying cause
    • mild hypophosphatemia
      • increase dietary phosphate intake
    • moderate hypophosphatemia
      • oral phosphate replacement therapy
        • IV phosphate replacement in patients who are on a ventilator
    • severe hypophosphatemia
      • IV phosphate replacement
  • Definition
    • serum phosphate > 4.5 mg/dL
  • Etiology
    • acute phosphate ingestion
    • hypoparathyroidism
    • vitamin D toxicity
    • renal failure
    • rhabdomyolysis
    • tumor lysis syndrome
  • Presentation
    • typically asymptomatic
  • Treatment
    • address underlying cause
    • dietary modifications
    • phosphate binders
      • calcium carbonate or acetate
 
 

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