Post-Surgery Fluid Overload and Edema: Understanding the Risks

In the first 24 hours following major surgery, patients can experience a significant positive fluid balance, sometimes as high as 6 liters. This, coupled with a positive sodium balance, for instance, 3,000 millimolar, poses a significant physiological challenge. Assuming the maximum concentrating capacity of the kidneys at this stage is approximately 500 mOsmoles per liter, excreting 6 liters of urine becomes physically impossible. This inability to excrete excess fluid leads to the development of edema.