Clinical Disorders of ECF Volume

Question 1

discuss the fluid distribution across the body compartments

Answer 1

• total body water (TBW) = 60% of total boday weight
  
  • TBW = intracellular fluid (2/3) + extracellular fluid (1/3)
    
    • ECF = plasma (1/4) and intersitial fluid (3/4)

Question 2

what are the major causes of ECF volume contraction

Answer 2

• diarrhea
• burns
• sweating
• diuretics
• kidney failure

Question 3

define mild, moderate, and severe ECF volume contraction

Answer 3

• mild: ECF loss < 5%
• moderate: ECF loss 5-10%
• severe: ECF loss > 10%

Question 4

symptomatology of mild ECF loss (< 5% )

Answer 4

• thirst
• dry mucous membranes
• poor skin turgor

Question 5

symptomatology characteristics of moderate ECF loss (5-10% loss)

Answer 5

• orthostatic hypotension
• tachycardia

Question 6

symptomatology characteristic of severe ECF loss (>10%)

Answer 6

• possible shock
• hypotension
• tachycardia
• tachypnea
• poor capillary refill
• confusion

Question 7

right heart catheterization - uses, pros & cons

Answer 7

• assess pressure in the pulmonary artery via the right heart
• pros: provides a definitive diagnosis of volume status (hyper-, hypo, euvolemic)
• cons: invasive

Question 8

what defines orthostatic pressure?

Answer 8

= any of the three changes when patient goes from supine to sitting or sitting to standing:

• a 20 mmHg drop in systolic pressure
• a 10 mmHg drop in disatolic pressure
• rise of 20 beats/min in pulse

Question 9

what is the “fluid challenge” and what is it used to determine

Answer 9

• use: used to determine if fluid replacement would be effective in a patient with a contracted ECV
• test:
  
  • patient supine with upper body at 45 degrees
  • legs are lifted above head and their CO is monitored
  • if CO improves, it indicates they would be responsive to fluid replacement

Question 10

when assessing a hypervolemic patient

• what should you look for/what will you likelhy see on an exam?
• what pertinent medical history should you ask about =?

Answer 10

• exam
  
  • lung rales on exam
  • EDEMA
    
    • pulmonary edema on chest xray
    • pitting edema
• PMHx:
  
  • want to rule out disease that would decrease ECBV and lead to hypervolemia
    
    • CHF
    • chronic kidney disease
    • cirrhosis
  • want to check past echo

Question 11

common symptoms of hypervolemia

Answer 11

common symptoms of hypervolemia

• weight gain
• pitting edema
• dyspnea (difficultly breathing)
• orthopena (difficultly breathing when sitting up)

Question 12

general treatments for hypervolemia

Answer 12

• diruetics
• fluid restriction
• sodium restriction
• strict monitoring of intake/ouput

Question 13

define volume “contraction” and “expansion” in terms of fluid shifts

Answer 13

based on volume of fluid in the extracellular space

• volume contraction = decrease in ECF
• volume expansion = increase in ECF

Question 14

isosomotic fluid contraction

• describe the volume status of compartments
• causes?

Answer 14

• occurs with a loss of isosomotic fluid
  
  • osmolarity of ECF remains the same, so there is no shift in fluid in or out of the ECF
    
    • ECF volume = decreased
    • ICF volume = the same
• causes:
  
  • diarrhea
  • fluid loss at burn sites

Question 15

hyperosmotic volume contraction

• volume status of each compartment?
• causes?

Answer 15

• caused by a loss of hypotonic fluid from the ECF. remaining ECF fluid is hypertonic, and draws in water from the ICF to equilibrate osmolarity
  
  • ECF vollume = decreased
  • ICF volume = decreased
• causes
  
  • sweating
  • dehydration

Question 16

hypoosmotic contraction

• volume status of each compartment?
• causes?

Answer 16

• hypertonic fluid is lost from the ECF. the fluid remaining in the ECF is hypotonic to the ICF, so water diffuses into the ECF
  
  • ECF volume = decreased
  • ICF volume = increased
• causes:
  
  • ​aldosterone deficiency:
    
    • results in less Na+ reabsorption at the collecting duct. Na+ remains in the tubular fluid, and the hypertonic filtrate is exceteed

Question 17

treatment for isotonic, hypertonic, and hypotonic volume contraction

Answer 17

• isotonic contraction: treat with isoosomolar fluild
• hypertonic contraction: treat with IV isosmolar/hyposmolar fluid
• hypotonic contraction: give mineralcorticoids
  
  • ex: fludicortisone

Question 18

isoosmotic volume expansion

• volume status of compartments?
• causes?

Answer 18

• due to an increase of isotonic fluid in the ECF
  
  • osmolarity across compartments remains the same, so no fluid shifts
    
    • ECF volume = increased
    • ICF volume = the same
• example: excess amount of IVF (IV fulid) aministered

Question 19

hyperosmotic volume expansion?

• volume status of compartments?
• causes?

Answer 19

• an increase in osmolarity in the ECF. water is drawn from the ICF into the ECF to equilibrate osmolarity
  
  • ECF volume = inceases
  • ICF volume = deceases
• cause: consuming foods high in sodium

Question 20

hypoosmotic expansion

• volume status of compartments?
• causes?

Answer 20

• an increase in free water in the ECF decreases ECF osmolarity, and water diffuses from the ECF into the ICF until osmolarities equilibrate
  
  • ECF volume increases
  • ICF volume increases
• causes:
  
  • SIADH: excess reabsoprtion of water due to ADH
  • polydispia: excess water consumption

Question 21

treatment for hyperosmotic volume expansion?

Answer 21

• reduce salt intake
• diuresis

Question 22

treatment for hypoosmotic expansion?

Answer 22

• fluid restriction
• (vasopressin) ADH receptor blockers
  
  • tolvaptan
  • conivaptan