Fluid Disorders

Question 1

What is hypovolemia?

Answer 1

Depletion of extracellular fluid (ECF)

Question 2

What causes hypovolemia?

Answer 2

1. Abnormal losses in skin, GI or renal.
2. Bleeding (hemorrhage).
3. Decreased intake
4. Movement of fluid into a non-equilibrating third space.

Question 3

What are the compensatory mechanisms in hypovolemia?

Answer 3

1. Increased sympathetic nervous system (HR and cardiac contraction).
2. Thirst.
3. Release of ADH and aldosterone.

Question 4

List 3 examples of disorders associated with third space fluid shift.

Answer 4

bowel obstruction, ascites and peritonitis

Question 5

Briefly describe the mechanism of bowel obstruction.

Answer 5

Bowel obstruction: loss of lower GI fluid caused by sequestering of GI fluid in distended bowel. Several liters may accumulate in the intestinal lumen ->lumen pressure –>damage of intestinal mucosa.

Question 6

Briefly describe the mechanism behind ascites.

Answer 6

Accumulation of fluid in the peritoneal cavity occurring in severe hepatic cirrhosis. Ascites occurs as a result of hepatic venous obstruction and retention of H20 and sodium. NB. symptomatic hypovolemia is most likely to occur after paracentesis because of rapid reaccumulation of ascitic fluid.

Question 7

List 3 conditions/factors that result in abnormal GI losses that could lead to hypovolemia.

Answer 7

1. Vomiting
2. Nasogastric (NG) suctioning
3. Diarrhea and intestinal drainage.

Question 8

What conditions could result in abnormal skin losses that could lead to hypovolemia.

Answer 8

Excessive diaphoresis (profuse sweating) from fever or exercise, burns, or cystic fibrosis.

Question 9

What conditions could result in abnormal renal losses that could lead to hypovolemia?

Answer 9

1. Diuretic therapy
2. Diabetes insupidus
3. Adrenal insufficiency
4. Osmotic diuresis (e.g. uncontrolled diabetes)

Question 10

True or False: Isotonic saline (NS) expands the ECF only

Answer 10

True, NS expands ECF only and does not enter ICF.

Question 11

True or False: Isotonic solutions are usually used as maintenance fluids, whereas hypotonic solutions are usually used as replacement fluids.

Answer 11

False: Isotonic fluids are usually used as replacement fluids because most abnormal fluid losses are isotonic, whereas hypotonic solutions are used as maintenance fluids.

Question 12

Expansion of the ECF is called?

Answer 12

Hypervolemia

Question 13

What conditions cause chronic stimulation of the kidney to conserve water and sodium?

Answer 13

1. Heart failure
2. Cirrhosis
3. Nephrotic syndrome
4. Excessive administration of glucocorticosteriods.

Question 14

What conditions can cause hypervolemia?

Answer 14

1. Abnormal renal function with reduced excretion of water and sodium. e.g. chronic and acute renal failure with oliguria (urine output < 400ml/day.
2. Excessive IV administration
3. ISF to plasma shift. e.g. excessive administration of hypertonic solutions.

Question 15

An equal rise in both BUN and creatinine reflects:

1. Volume depletion
2. Increase production of BUN and creatinine
3. A compromise in renal function
4. Dehydration

Answer 15

3. A compromise in renal function. However, a proportionately greater rise in BUN suggest volume depletion or increase production.

Question 16

What changes occur to the hematocrit during dehydration and bleeding?

Answer 16

During dehydration, hematocrit is elevated because of hemoconcentration.
During bleeding, hematocrit is decreased. It remains normal immediately after acute hemorrhage but over a period of hours there’s a shift o fluid from the ISF to the plasma resulting in hematocrit decreased.

Question 17

During hypervolemia, we may have to restrict water and sodium. List some high sodium foods.

Answer 17

Frozen, canned or package foods.
Cheeses, preserved meats, salad dressings and prepared sauces
Snack foods (chips, crackers etc), condiments (ketchup, mustard, soy sauce)

Question 18

1. If we add IVF ( 1L of dextrose in water), how would water distribution occur between ECF/ICF in the body?
2. How would 1L of normal saline (.9% NaCl) distribution occur?
3. How would 1L of 1/2 normal saline (.45% Nacl) distribution occur?
4. How would a hypertonic saline (3% NaCl) behave?

Answer 18

1. Dextrose is metabolized, and the water is distributed proportionally to all fluid compartments - i.e., 2/3 of it will distribute to the ICF and 1/3 to the ECF (which 1/4 stays in the intravascular space).
2. All of the normal saline goes to the ECF, where 1/4 stays in the intravascular space.
3. 1L of .45% NaCl - 500ml of free water go to ICF and remainder 500ml NaCl goes to ECF (1/4 to intravascular)..
4. Hypertonic saline goes to ECF, and increases it’s tonicity , establishing an osmotic gradient resulting in movement of water out of cells into the ECF until osmotic equilibrium is attained.