Factors influencing the ionization of calcium during major surgical procedures.

The existence of a clinically feasible calcium electrode makes it possible to obtain rapid, accurate levels of ionized calcium. It is now possible to study the actual ionization of calcium under normal and abnormal physiologic conditions. The present investigation was directed at changes in ionized calcium during major surgical procedures.

Colloid oncotic pressure and levels of albumin and total protein during major surgical procedures.

From the results of this study, it appears that whole blood alone or red blood cells reconstituted with saline solution do not adequately replace the loss of albumin and concomitant decrease in colloid oncotic pressure that occur during extensive intraabdominal and intrathoracic operations. Since colloid oncotic pressure is a major factor in the restitution of intravascular volume from stores of interstitial fluid and since it may also play a role in the development of postoperative pulmonary problems, it is important to maintain a relatively normal colloid oncotic pressure during the operation and in the immediate postoperative period. Although dextran can be used for this purpose, its short half-life of four to six hours and associated coagulation problems militate against its use in large quantities.