Physiology : Fluid Balance

Question 1

Formula for Osmolality (corrected for hyperglycemia and high BUN)

Answer 1

OSM = 2(Na) + (BUN/2.8) + (Glucose/18)
N = 300 mosm (285-295)
Greatly Na dependent

Question 2

Forces involved in Filtration

Answer 2

Hydrostatic pressure in the capillaries (push out)

Oncotic pressure in the interstitial (pull out)

Question 3

Forces of Resorption

Answer 3

Hydrostatic pressure in interstitial fluid (push in)

Oncotic pressure in the capillaries (pull in)

Question 4

What maintains hydrostatic pressure

Answer 4

Constriction and dilatation of the afferent and efferent arterioles (om na ma hydrostatic pressure)

Question 5

Force of flow (Qf) =

Answer 5

Forces of filtration - Forces of Resorption

Question 6

How does mannitol affect osmolality?

Answer 6

It has initial osmotic draw into the intravascular space but then it will diffuse into the cells slowly – hence expand volume of both ecf and icf.

Question 7

Most of the water is in what cellular space?

Answer 7

Intracellular

2/3

Question 8

What conditions will cause pitting edema?

Answer 8

Cirrhosis, nephrotic syndrome, CHF

Question 9

Poor renal perfusion would cause an increase in

Answer 9

Angiotensin, renin and aldosterone

Question 10

Main mechanism of pulmonary edema

Answer 10

Increased hydrostatic pressure in the pulmonary capillaries