PANCE Blueprint Genitourinary (5%)

Hypovolemia and Diabetes Insipidus

Patient will present with → neurological manifestations which include thirst, restlessness, lethargy, delirium, convulsions and coma, dry mouth, tachycardia, hypotension. Polyuria, polydipsia, and nocturia are the predominant manifestations of diabetes insipidus.

In hypernatremia the water content of the body fluid is deficient in relation to sodium content (serum sodium >145 mEq/L) and there is either too much salt or not enough water

Generally results from either inadequate fluid intake or excess water loss

  1. deficit of thirst
  2. hypotonic fluid loss
  3. urinary loss
  4. GI loss
  5. burns
  6. diuretic use
  7. osmotic diuresis (hyperglycemia)
  8. sodium excess
  9. diabetes insipidus

By definition, plasma sodium will be greater than 145 mEq/L (hypernatremia)

  • Urine - sodium may be decreased if due to extrarenal losses, urine concentrated and diluted with diabete insipidus
  • Hyperosmolar coma may be indicated by elevated serum glucose, and increased urine osmolality

Diabetes insipidus

  • Neurogenic (central) is caused by deficient secretion of vasopressin (ADH - anti-piss-hormone) from the posterior pituitary
  • Nephrogenic DI is caused by kidneys that are unresponsive to normal vasopressin levels - usually inherited X-linked or from lithium or renal disease
  • Low urine sodium and polyuria usually indicate DI
  • Urine osmolality of less than 250 despite hypernatremia, indicated Diabetes Insipidus

Patient should be treated on an ipatient basis

  • Identify the underlying cause and treat accordingly - water may be administered PO which is the preferred route
  • Hypovolemia should be treated first with isotonic saline or lactated ringers and the hypernatremia second, dialysis should be implemented if sodium is greater than 200 mEq/L
  • Use caution during treatment as rapid correction of hyponatremia can cause pulmonary or cerebral edema, especially in patients with diabetes insipidus
hypernatremia_5865_1483048136 Hypernatremia is characterized by a serum sodium level above the normal range of 145 mEq/L. Hypernatremia is a increase in osmolarity of the extracellular fluid volume (ECF). This may be attributed to an actual sodium excess in the ECF like hyperaldosteronism or a relative sodium excess which is caused by a decrease of free water in the ECF like dehydration. High serum sodium levels causes a fluid shift from the intracellular fluid volume (ICF) to the ECF. This causes cellular shrinking. Hypernatremia should be assessed along with fluid balance as it often is associated with a fluid excess or deficit.

Hypernatremia Picmonic

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Question 1
A 44-year-old man has been drinking large quantities of water, up to 12 L/day, for the last week. In addition, he has been passing large quantities of urine. Upon physical exam, there are no remarkable findings except for increased capillary refill time and tacky mucous membranes. Laboratory results show sodium 166 mmol/L, potassium 4.2 mmol/L, chloride 123 mmol/L, and bicarbonate 27 mmol/L. His fasting serum glucose is 80 mg/dL and creatinine 1.2 mg/dL. His serum osmolality is 343 mOsm/kg. Which of the following hormone deficiencies is most likely present in this patient?
growth hormone
antidiuretic hormone
Question 1 Explanation: 
This patient's symptoms and labs are consistent with diabetes insipidus. This condition results from a deficiency of antidiuretic hormone causing polyuria and polydipsia.
Question 2
A 17-year-old male high school wrestler is brought into the emergency department after he collapsed at a wrestling match. He spent time fully clothed in a hot sauna prior to the match to try to “make weight.” Labs are ordered, and results come back as follows:
  • Sodium 162 mEq/L
  • Potassium 3.8 mEq/L
  • Chloride mEq/L
  • Glucose 108 mEq/dL
  • Creatinine 2.0 mEq/dL
  • Urine sodium > 10 mEq/L
  • Urine osmolality 428 mOsm/kg
Which IV fluid regimen would most effectively treat this patient’s hypernatremia?  
Quarter normal (hypotonic) saline
See C for explanation
Half-normal saline
See C for explanation
Isotonic (normal) saline
Dextrose 5% in water
See C for explanation
Lactated Ringer’s
See C for explanation
Question 2 Explanation: 
This patient has acute hypernatremia due to volume loss from sweating and decreased oral fluid intake, also known as dehydration and hemoconcentration. In this case the most pressing issue is to correct his volume status which is best done by the administration of isotonic saline which contains 0.9% sodium. This will correct both the water deficit and serum osmolarity. The osmolarity of isotonic saline is 308 mOsm/kg and will likely be lower than that of someone who is significantly dehydrated. As the water deficit corrects the sodium will normalize. Quarter normal saline contains 0.24% sodium, half normal saline contains 0.45% sodium and the sodium content of lactated Ringer’s is similar to that of half normal saline. Dextrose 5% in water contains no electrolytes and can be used to correct the hyponatremia after the water deficit is corrected.
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