[Electrolyte balance in major abdominal surgery. III. On insensible water losses from the peritoneal cavity (author's transl)].

Two groups of 16 patients each were studied during abdomino-surgical procedures. Patients of one group received an isotonic glucose solution to cover insensible water losses from the peritoneal cavity whilst patients of the other group were not treated with glucose. In these we found a significant increase in plasma osmolality and in mean corpuscular hemoglobin concentration of the red cells during anaesthesia and operation. The balance of osmotic free water was calculated from changes of plasma osmolality during the observation period. Calculating output as difference between known input and balance we found losses of osmotic free water amounting to approximately 4.5 ml per kilogram bodyweight per hour of operation in both groups. These losses are, in our opinion, identical with the insensible water loss from the peritoneum. Plasma sodium concentration in both groups showed decreasing tendency compared with plasma osmolality. This was partly due to dilution with increased extracellular glucose concentration and partly to an extra-intracellular shift of sodium (without net-water-flux). Plasma potassium concentration decreased in patients receiving glucose but increased in patients without glucose. Red cell potassium concentration decreased in both groups. Urin-to-plasma ratio of osmolality was equal in both groups in spite of a different water balance. Patients receiving glucose had higher urine outputs and therefore (with equal osmolar U/P ratio) a higher osmolar clearance and a higher free-water-reabsorption. It is demonstrated that under conditions as described the amount of free-water reabsorption and concomitantly a favourable effect on water balance during mild dehydration is mainly depending on osmolar clearance.