Electrolyte Disorders - Hypernatremia

Question 1

Def. of HyperN, who it’s usually seen in, and RFs

Answer 1

• Serum Na>145 mEq/L
• Seen in extreme ages (infants and elderly)
• RFs: trauma, burns, ICU, dementia, uncontrolled diabetes

Question 2

2 processes resulting in hyperN?

Answer 2

1. MCC: Unreplaced water loss (dehydration)

2. Na overload

Question 3

Examples of unreplaced water loss?

Answer 3

• GI: V/D
• Renal: diabetes, diuretics, osmotic diuresis (hyperglycemia)
• Insensible: sweating, burns, respiratory loss
• Impaired thirst (elderly)

Question 4

Examples of Na overload?

Answer 4

• Hypertonic saline infusion
• Salt tabs
• Sodium bicarb infusion
• Hemodialysis settings

Question 5

What happens to cells in hyperN

Answer 5

They shrink b/c there’s an osmotic gradient causing H2O to move out of cells and into the extracellular fluid

Question 6

Sx of hyperN?

Answer 6

• Irritability
• AMS
• Lethargy
• Ataxia
• Seizures
• Hyperreflexia
• Brain hemorrhages due to rapid cell shrinkage (MC in peds and neonates)

Question 7

Timing of acute v. chronic hyperN

Answer 7

Acute: <48 h
Chronic: >48 h or unknown duration

Question 8

Tx of acute hyperN

Answer 8

Can rapidly correct w/ little risk of cerebral edema

Question 9

Tx of chronic hyperN

Answer 9

Lower by 10-12 mEq/day

Question 10

What are the 2 steps in tx hyperN?

Answer 10

1. Replace water deficit (must know FWD) w/ D5W or other HYPOTONIC solutions (1/2 NS)
2. Correct underlying cause (think back to pathogenesis of hyperN)

Question 11

How would you determine how much fluid to give a pt who is hypernatremic?

Answer 11

• Determine FWD (med calc or actual calculation): what’s their measured Na and what’s their desired Na?
• If their FWD is 2.8 L –> 2800mL/24 h = mL/hr that you would order so you don’t replace their water too fast (too fast could lead to rapid onset of acute hyponatremia and lead to cerebral edema and uncal herniation)

Question 12

Steps in developing cerebral edema?

Answer 12

1. Rapid onset of hypoN or a rapid overcorrection of hyperN…both lead to a rapid decrease in serum sodium.
2. A decrease in serum Na causes water to flow INTO cells
3. Cerebral edema!

Question 13

Generalized steps in developing ODS?

Answer 13

1. Rapid onset of hyperN or a rapid overcorrection of hypoN…both lead to a rapid INCREASE in serum sodium
2. Increase in serum Na causes water to flow OUT of cells
3. Cell shrinkage etc…ODS!