Utilization of Osmometry in Critically III Surgical Patients-Reply

To the Editor.  —Dr. Børresen's communication has been reviewed, and although some of his statements are correct, the application of these generalizations to the critically ill, shock patient is not valid.The addition of solutes to a solution causes a change in the colligative properties of the solution. In pure solutions, this change is predictable and quantitative. Depending on the solute, the effects are summative, but not necessarily truly arithmetically additive. In impure solutions (eg, biological fluids), the same principle generally holds.¹ However, with rapid extreme change such as is observed in the serum of a shock patient, these changes are sometimes erratic. Our clinical observations are documented, and have suggested by fairly good correlations (r = 0.793) with lactic acid levels that some of the elevation observed in these patients resulted from lactate (measured in the same serum sample). Many other solutes have been found to be increased