Bromide space, total body water, and sick cell syndrome.

Displacements of the bromide space (Br-82-C, as a marker for the extracellular fluid compartment) are caused by an enhanced anatomical space and/or increased permeability of cells to bromide. The ratio Br-82-C: total body water (TBW) was evaluated to be 0.83 +/- 0.17 in critically ill patients (n = 38) compared with the normal value of 0.46 +/- 0.04 (n = 10). Because of normal TBW in critically ill patients (TBW = 505 +/- 68 ml/kg), an increased bromide penetration into cells seems to be responsible for the enlarged ratio Br-82-C: TBW. Taking into consideration measurements in patients with malabsorption (BR-82-C: TBW = 0.56 +/- 0.13; n = 13) and carcinoma of the rectum and colon (Br-82-C: TBW = 0.66 +/- 0.24; n = 18) we think that the bromide space is a good measurement of the effective extracellular water.