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 Management address underlying cause diagnostic studies urine electrolytes serum osmolality 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) isotonic fluids when hypovolemic Complications rapid corrrection of hypernatremia can lead to cerebral edema and herniation (from organic osmolytes causing osmotic shifting of fluid into the brain) 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 consider contraction alkalosis when low volume state, high pH, and hypokalemia (treat with fluids) hyposmolality diarrhea dehydration secondary to activation of the RAA system causing K and H wasting 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 decreased albumin can cause a decreased total calcium but a normal free calcium (thus the patient is asymptomatic) 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 Oral calcium replacement appropriate if minor symptoms 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 higher calcium with more symptomatic patients (typically > 12.0 mg/dL) 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 serum calcium = free calcium + bound (to albumin) calcium 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 long term calcium control 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