Hello Mr. Roof: BTIM simplified
A volume extender replaces fluid volume presumably lost through bleeding, and is expected to help maintain blood pressure; thereby, circulation and perfusion.
A blood substitute is primarily expected to transport oxygen to the tissues (and carbon dioxide from the tissues). Other blood-like properties would be desirable but have not been addressed as much as respiration has for blood substitute candidate materials.
Blood is not given for efforts to maintain pressure. Blood is transfused for its living tissue qualities for which there is no substitute; oxygenation, clotting, white blood cells, etc. A volume extender replaces water lost through hydraulic loss (bleeding) or shock (fluid going from the vascular system into the intra- and extracellular volumes [outside the vascular system, but within the non-vascular tissues]).
The last I heard on blood substitutes some years ago was that although they looked promising in laboratory testing, they seemed to kill patients in unexpected ways and that impasse has remained the last decade. In vitro and critter testing did not smoothly extend into the clinical setting.
Blood is a vital tissue, and as stated by the Creator in Deuteronomy, 'the life of every creature is in its blood'. In contrast, a volume extender is a compatible solvent for blood, but is not alive as is the blood tissue.
Regards,
m |
