1. Hypernatremia and Fluid Resuscitation
Staci Smith, DO

2. Hypernatremia serum sodium level >145 mEq/L
hypertonic by definition
usually due to loss of hypotonic fluid
occasionally infusion of hypertonic fluid
due to too little water, too much salt, or a combination
typically due to water deficit plus restricted access to free water
approximately 1-4% of hospitalized patients
tends to be at the extremes of age

3. Mortality Eye Opener
mortality rate across all age groups is approximately 45%.
mortality rate in the geriatric age group is as high as 79%

4. Hypernatremia sodium levels are tightly controlled
by regulation of urine concentration
production and regulation of the thirst response
normally water intake and losses are matched
to maintain salt homeostasis, the kidneys adjust urine concentration to match salt intake and loss
kidneys' normal response
is excretion of a minimal amount of maximally concentrated urine

5. Hypernatremia normal plasma osmolality (Posm ) 275 to 290 mosmol/kg
Na is the primary determinant of serum osmolarity
number of solute particles in the solution
mechanisms to return the Posm to normal
sensed by receptor cells in the hypothalamus
affect water intake via thirst
water excretion via ADH
increases water reabsorption in the collecting tubules

6. ADH

7. ADH Mechanism of Action

8. Protection Mechanism
major protection against the development of hypernatremia
is increased water intake
initial rise in the plasma sodium concentration stimulates thirst
via the hypothalamic osmoreceptors

9. Hypernatremia usually occurs in infants or adults
particularly the elderly
impaired mental status
may have an intact thirst mechanism but are unable to ask for water
increasing age is also associated with diminished osmotic stimulation of thirst
unknown mechanism

10. Hypernatremia cells become dehydrated
sodium acts to extract water from the cells
primarily an extracellular ion
is actively pumped out of most cells
dehydrated cells shrink from water extraction
effects seen principally in the CNS

11. Protective Mechanism cells respond to combat this shrinkage
by transporting electrolytes across the cell membrane
altering rest potentials of electrically active membranes
intracellular organic solutes
generated in an effort to restore cell volume and avoid structural damage

12. Risk factors for hypernatremia
Age older than 65 years
Mental or physical disability
Hospitalization (intubation, impaired cognitive function)
Residence in nursing home
Inadequate nursing care
Urine concentrating defect (diabetes insipidus)
Solute diuresis (diabetes mellitus)
Diuretic therapy

13. Assessment Two important questions:
What is the patient's volume status?
Is the problem acute or chronic?
Does the patient complain of polyuria or polydipsia ?
Central vs Nephrogenic DI
often crave ice-cold water

14. Clinical Manifestations
lethargy
general weakness
irritability
weight loss
diarrhea
twitching
seizures
coma
orthostatic hypotension
tachycardia
oliguria
prerenal :High BUN-to-creatinine ratio
dry axillae/ dry MMM
hyperthermia
poor skin turgor
nystagmus
myoclonic jerks

15. Work-up : Sodium levels
more than 170 mEq/L usually indicates long-term salt ingestion
mEq/L usually indicates dehydration
chronicity typically has fewer neurologic symptoms

16. Lab Work-up : Sodium levels
order urine osmolality and sodium levels
glucose level to ensure that osmotic diuresis has not occurred
CT or MRI head
water deprivation test
ADH stimulation

17. Hypernatremia Work -Up
Head CT scan or MRI is suggested in all patients
Traction on dural bridging veins and sinuses
Leads to intracranial hemorrhage
most often in the subdural space

18. Intracranial Hemorrhage

19. Intracranial Hemorrhage

20. Treatment Replace free water deficit
IVF
TPN / tube feeds
Rapid correction of extracellular hypertonicity
passive movement of water molecules into the relatively hypertonic intracellular space
causes cellular swelling, damage and ultimate death

21. Treatment First, estimate TBW (Total Body Water)
TBW= .60 x IBW x 0.85 if female & 0.85 if elderly
IBW for women= 100 lbs for the first 5 feet and 5lbs for each additional inch
IBW men= 110 lbs for the first 5 feet and 5 lbs for each additional inch
Our pt IBW= 120 (5 ft , 4’’)
TBW= 52.0
= .60 x 120 x

22. General Treatment Next, calculate the free water deficit
Free water deficit= TBW x (serum Na -140/140)
Our Pt’s FWD= 52 x ( /140)
= 52 x 0.1
= 5.2 L free water deficit

23. Avoiding Complications: Cerebral Edema
Acute hypernatremia
occurring in a period of less than 48 hours
can be corrected rapidly (1-2 mmol/L/h)
Chronic hypernatremia
rate not to exceed 0.5 mmol/L/h or a total of 10 mmol/d
Change in conc of Na per 1L of infusate = conc of Na in serum- conc of Na in infusate / TBW + 1

24. Common Na Contents 5% dextrose in water (D5W) 0 mEq Na
0.2% sodium chloride in 5% dextrose in water (D5 1/4 NS)
34 mmol/L
0.9 NS
154 mmol/L
0.45NS
77 mmol/L
Lactated Ringer’s
130 mmol/L

25. Hypervolemic Hypernatremia
Hypertonic saline
Sodium bicarbonate administration
Accidental salt ingestion
Mineralocorticoid excess (Cushing’s syndrome)
ectopic ACTH
small cell lung ca, carcinoid, pheo, MTC (MEN II)
pituitary adenoma
pituitary hyperplasia
adrenal tumor
Dx: Dexamethasone suppression test

26. Hypervolemic Hypernatremia
Treatment
D5 W plus loop diuretic such as Lasix
may require dialysis for correction

27. Hypovolemia Hypernatremia
water deficit >sodium deficit
Extrarenal losses
diarrhea, vomiting, fistulas, significant burns
Urine Na less than 20 and U Osm >600
Renal losses
urine Na >20 with U Osm
osmotic diuretics, diuretics, postobstructive diuresis, intrinsic renal disease
DM / DKA
increased solute clearance per nephron, increasing free water loss

28. Euvolemic Hypernatremia
Diabetes Insipidus
Typically mild hypernatremia with severe polyuria
Central DI = ADH deficiency
Sx, hemorrhage, infxn, ca/tumor, trauma, anorexics, hypoxia, granulomatous dz (Wegener’s, sarcoidosis, TB), Sheehan’s
U Osm less than 300
Tx is DDAVP

29. Diabetes Insipidus: Euvolemic Hypernatremia
Nephrogenic DI = ADH resistance
Congenital
Meds – Lithium, ampho B, demeclocycline,foscarnet
Obstructive uropathy
Hypercalcemia, severe hypokalemia
Chronic tubulointerstitial diseases - Analgesic abuse nephropathy, polycystic kidney disease, medullary cystic disease
Pregnancy
Sarcoidosis
Sjogren’s synd
Sickle Cell Anemia
U osm
Tx: salt restriction plus thiazide
Tx underlying cause

30. Euvolemic Hypernatremia
Seizures where osmoles are generated that cause water shifts
transient increase in Na
Increased insensible losses (hyperventilation)

31. Hypovolemia Hypernatremia
Combo of volume deficit plus hypernatremia
intravascular volume should be restored with isotonic sodium chloride (.9 NS) before free water administration

32. Summary Dehydration is NOT synonomous with hypovolemia
Hypernatremia due to water loss is called dehydration.
Hypovolemia is where both salt and water are lost.
Two important questions:
What is the patient's volume status?
Is the problem acute or chronic?
Does the patient complain of polyuria or polydipsia ?

33. Summary
Divide causes of hypernatremia into hyper, hypo, and euvolemic.
Estimate TBW (Total Body Water)
TBW= .60 x IBW x 0.85 if female & 0.85 if elderly
Free water deficit= TBW x (serum Na -140/140)
Check electrolytes frequently not to replace Na more than 0.5 mmol/L/h or a total of 10 mmol/d
Avoid cerebral edema

34. References Harrison’s Internal Medicine E-medicine