Dehydration: The Daily PANCE Blueprint
A 64-year-old female presents to the ER via EMS due to severe dizziness and muscle weakness. En route, her vitals reveal hypotension (84/40 mmHg), and she is given a 400 mL NS fluid bolus. Once in the ER, the patient tells you she had a stomach ache for about of week and has been unable to keep anything down, including water. On physical exam, you note dry mucous membranes. Which of the following lab values would you most likely expect to see in this type of patient?
A. Elevated serum phosphate
B. Elevated urine sodium
C. Low serum sodium
D. Low urine sodium
E. Low urine osmolality
Answer and topic summary
The answer is D. Low urine sodium
Dehydration is defined by water loss from intracellular fluid. Causes of dehydration include GI losses (emesis, diarrhea), renal losses (osmotic diuresis, diuretics), skin losses (sweat, burns), and 3rd-space sequestration (crush injury, etc). Clinical features include dizziness, muscle cramps, weakness, decreased skin turgor, dry mucous membranes, low BP, low urine output, elevated serum creatinine, hypernatremia (sometimes hyponatremia), and elevated levels of hematocrit (i.e., reactive polycythemia). Low urine sodium concentration is VERY suggestive of reduced tissue perfusion and a hypovolemic state (this means the renin-angiotensin-aldosterone system is on). You would expect her urine osmolality to be increased since ADH is activated, increasing reabsorption of water via inserting aquaporins in the membrane of collect duct cells. She likely would be hypernatremic in the setting of lack of free water intake. Treatment is fluid resuscitation.
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Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Blueprint Renal System ⇒ ⇒
Also covered on the Pediatric Rotation topic list
