Albumin: role and discriminative use in surgery

Exogenous human serum albumin (HSA) is generally used empirically and its role in surgery is poorly defined. The function and kinetics of HSA in the body are reviewed to provide rational guidelines for its use in surgery. Starling's law of transcapillary exchange is important, especially when applied to the capillary beds of the skin and subcutaneous tissue, skeletal muscle, lungs and intestines; but it overestimates the importance of maintaining oncotic pressure in the two situations where HSA is clinically beneficial--hypovolemia and plasma volume sequestration. In hypovolemia, the harmful effects of protein dilution by massive crystalloid resuscitation are minimized initially by "edema safety factors", such as reduced oncotic pressure of interstitial fluid and increased flow of lymph, and subsequently by intravascular protein refill from extravascular sites. But in severe hypovolemia, albumin should be given early, with sufficient isotonic saline, to reduce the total volume of crystalloid required. In the first 24 hours of plasma volume sequestration, albumin infused intravenously may be lost from excessively permeable capillaries; but later, hyperoncotic HSA is useful to restore the plasma volume and to reduce interstitial edema.