At our trauma center, basex is used to indicate volume status of trauma pts in the acute phase: basex -2.2 or lower requires fluid resuscitation. we follow abgs as a quick way of checking how well we are keeping up on infusing fluids during a trauma resus. we like to see those basex go from -10 up to close to 0! I think the theory has to do with the production of lactic acid in tissues that are not being well perfused, which in the trauma pt is usually due to the interruption of blood flow due to blood loss. The more lactic acid is produced, (which correlates with worse perfusion i.e. more blood loss), the lower the basex. This is not a useful interpretation in other settings i.e. pts with renal failure or other metabolic acid/base disturbances.