[Measurement and calculation of the colloid-osmotic pressure in the normal postoperative course]

In 26 patients undergoing elective surgery (general or urological) the colloid osmotic pressure (COP) of serum was followed up until the sixth postoperative day. COP was measured at an artificial membrane by a transducer as described by Weil et al. Simultaneous measurements of the concentrations of total protein and albumin were used to calculate COP by the formula of Keys. Measured COP and calculated COP were in close agreement; to eliminate the systematic (although small) difference, a correction of the Keys formula was developed. COP decreased postoperatively, but never below 20 mm Hg. While no circulatory or pulmonary dysfunction can be found, it seems superfluous to substitute COP if not below 20 mm Hg. The possible value of protein substitution is discussed.