Fluid & Electrolyte Pearls Key points for your Board Review
Maintenance fluids calculation: 4/2/1 rule (4mL/kg for first 10kg, 2mL/kg for second 10kg, 1mL/kg for remaining weight to max 120mL/hr)
Volume overload due to: excessive fluid/salt intake, congestive heart failure, cirrhosis, nephrotic syndrome, steroids
Dehydration due to: vomiting/diarrhea, diuretics, sweating, pancreatitis, crush injury
Hyponatremia categorized as: hypervolemic (treat with water restriction), euvolemic (treat with water restriction), hypovolemic (treat with normal saline)
Asymptomatic hyponatremia (Na 120-140mEq/L) = no emergent treatment
Symptomatic hyponatremia goal correction = 0.5mEq/hr; rapid correction can cause central pontine myelinolysis
Hypertonic saline reserved for Na <120mEq/L + Altered mental status/Coma/Seizure
Hypernatremia: calculate free water deficit, goal correction = 1-2mEq/hr; rapid correction can cause cerebral edema
Most common cause of hyperkalemia = lab error or lab-draw error
Hyperkalemia: widened QRS = calcium chloride
Hypokalemia: replete potassium with magnesium
Hypercalcemia: “Bones/Moans/Groans/Thrones/Psychic Overtones”; treat with IV fluids (calcitonin, bisphosphonates, glucocorticoids per consultation)
Trousseau’s sign and Chvostek’s sign: think hypocalcemia
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