The prognostic value of the non-protein nitrogen (NPN) content in the serum and the cerebrospinal fluid.

The amounts of total protein and nonprotein nitrogen (NPN), together with the pH were determined in serum and lumbar cerebrospinal fluid (CSF) of controls and comatose patients before and after death. The serum/CSF ratio of NPN was calculated. Under normal conditions the value of this ratio is 1.65. The decrease of this value is a sign of worsening of barrier functions. If the NPN content of the serum and CSF becomes identical, i.e., when the serum/CSF ratio approaches or even equals 1.0, and at the same time the pH decreases in the CSF, then the prognosis is hopeless.