Hemorrhage and operation cause a contraction of the extracellular space needing replacement - evidence and implications? A systematic review

Background. Hemorrhagic hypotension or operative trauma is believed to cause a contraction of the extracellular fluid volume (ECV) beyond the measured fluid losses. The aim of this review was to explore the evidence and implications of ECV loss. Methods. We performed a systematic review of original trials measuring ECV changes during hemorrhage or operation. PubMed, relevant periodicals, and reference lists were searched until no further original articles appeared. The quality of both the scientific and the technical methods of the trials were evaluated. Results. A total of 61 original articles were found. The pattern appeared that all investigators reporting shock or operation to cause a disparate reduction of the ECV had measured the ECV with the same method. The ECV was calculated from very few blood samples that were withdrawn after 20 to 30 minutes of equilibration of a tracer (the (SO4)-S-35-tracer). Trials calculating ECV from multiple blood samples, after longer equilibration times, or using other tracers did not find a contraction of the ECV On the contrary, trials using a bromide tracer found the ECV to be expanded after operation. Conclusions. The evidence supporting the idea that hemorrhage or operation cause a contraction of the LCV is weak, and probably a result of flowed methodology.