Volume Contraction and Hypernatremia

Question 1

Adaption to ECF depletion

Answer 1

Vasoconstriction - high catecholamines and vasopressin (ADH)

Na and water retention (low UNa and high U osm)

Increase symp activity
Increased RASS
INcreased arginine vasopressin release
Decreased natriuretic peptides

Question 2

Sx of ECF depletion

Answer 2

Delay in cap refill
Tachycardic 
Post hypotension
low JVP 
Oliguria 

Cyanosis, poor turgor, supine hypotension signs of severe

Question 3

ECF volume depletion from renal causes

Answer 3

Diuretics use/abuse, renal tubular defects, or lack of aldosterone all impair Na reabsorption…urinary Na would be high DESPITE hypovolemia

Question 4

Major nonrenal and renal causes of ECF depletion

Answer 4

Non-renal (usually U Na <20)

GI losses, hemorrhage, sweat/burn, third space sequestration

Renal - usually U Na over 20

Diuretics
Renal Tubular disordrs
Hormonal disturbances - mineralcorticoid def, diabetes

Question 5

Lab of ECV depletion

Answer 5

Hemoconcentration (high hemoglobin and high albumin)

Decreased GFR (prerenal azotemia)

High BUN/Cr ratio (enhanced urea reasborption due to slow urine flow)

Concentratrated urine (specific gravity over 1,015, osm over 450) with hyaline casts

Hypernatremia…hypo if volume loss replaced by hypotonic solution

Avid renal reabsorption…U Na and Cl <10 meq
FEna under 1%

Question 6

Hyaline cast means

Answer 6

Concentrated urine and high urinary protein

Question 7

High BUN/creatinine ratio

Answer 7

Prerenal azotemia (low flow)
Protein loading
GI bleed
Catabolic steroids
Tetracycline

Question 8

Tx of ECF volume depletion in this patient

Answer 8

Increase ECF volume
INcrease IC fluid lilely to be present as well
Reduce plasma osmolarity

Physiologic (isotonic) 0.9% saline will restore volume without further increasing osmolarity…once stable, switch to hyhpotonic saline

Question 9

General principles of ECV depletion

Answer 9

Correct hypovolemia with volume expanders…gentler in elderly or cardiac hx

Replace deficits
Replace H2O def
Replace on going fluid losses with solution of similar composition (usually 0.45% saline)…replace other electrolytes

Question 10

Causes of prerenal azotemia

Answer 10

Intravascular volume depletion

Decreased cardiac output (CHF)

Decreased SVR (drugs, sepsis, anaphylaxis, liver)

Renal vasoconstriction (drugs, sepsis, liver failure, hypercalcemia)

Abnormal renal autoregulation (ACEI/ARB/NSIAD) with dec perfusion

Question 11

How to calculate H2O def

Answer 11

Solute free water is equally distributed in all body compartments

EC Na concentration reflects total body water content

TBW = BW*.6

% increadse in plasma Na = (current Na/normal Na)

Total H2O def = TBW*%increase in plasma Na

Question 12

Danger of giving patient fluid

Answer 12

Can cause cerebral edema

Gave pt a hypotonic solution so water rushed into the cell

Swelling of the cells

Look for papilledema

Question 13

Diff of hypernatremia

Answer 13

Water or hypotnic fluid loss (w/out replacemet)
Insensible and sweat losses, GI loss, diabetes insipidus, osmotic diuresis, abnorma thirst mech

Sodium overload - hypertonic saline

Question 14

Tx of hypernatremia

Answer 14

FIRST correct hypoveolmia with 0.9% saline

Then slowly replace water deficit…avoid Na reduction by more than 12 meq.day