Question

One treatment for patients suffering from widespread swelling (widespread accumulation of interstitial fluid; called "anasarca") is a two-pronged approach which involves:

1. Administration of exogenous albumin, a protein already found in high concentrations in the plasma, and

2. Administration of Lasix, a diuretic.

Based on your understanding of filtration, reabsorption, and fluid homeostasis, why would this combination help remove accumulated interstitial fluid and contribute it to urine?

Answer 1

Anasarca

Anasarca is characterized by the widespread accumulation of fluid all over the body. The abnormality in the balance ofproteins/ fluids and various other pressures contribute for leakage of fluid from circualtion and its subsequent accumulation in the tissues. It often indicates the underlying medical condition or organ damage.

The major pressure gradients that control the fluid movement across membranes are: hydrostatic/hydraulic pressure and osmotic pressure. Edema or fluid accumulation occur when there is decrease in plasma oncotic pressure or/and increased hydrostatic pressure and capillary permeability. Proteins especially albumin play important role in regulating the  oncotic pressure in the vascular system. As we seen, decreased oncotic pressure account for edema or anasarca. Therefore, administrtaion of exogenous albumin helps to increase the oncotic pressure which creates the relative water molecule deficit with water molecules pulls the fluid back into the circulatory system within the lower venous pressure end of capillaries. This increased plasma volume is regualted to the normal level by increasing the urine output by the drug called 'diuretics'.

Duretics are drugs which intentionally increases the production of urine and excretes more water and sodium from the body. The major class of diuretics prescribed for anasarca are potassium-sparing and loop diuretics. Also the presence of protein in the urine helps in increseing the urine volume by increasing its osmolarity.