AbstractThree principal factors must be considered in initial fluid therapy in the treatment of shock: (a) blood volume deficit; (b) oxygen transport capacity; and (c) metabolic requirement of water and electrolytes. For the calculation of the initial volume to be used in compensatory blood volume loss, patients may be categorized thusly: group A—impending or slight loss [assumed loss of 20% of total blood volume (TBV)]; group B—moderate shock (20–35% of TBV); and group C—severe shock (>35% of TBV). These groups are treated initially with 20%, 30%, and 50% of TBV replacement, respectively. Treatment is individualized by continuous observation and changes are made as required. The relative merits and indications for use of crystalloid and colloid solutions are outlined. Oxygen delivery to the tissues must be guaranteed. The flow properties of the blood improve and the oxygen carrying capacity decreases with reducing hematocrit levels; a hematocrit reading of about 30 or slightly above is adequate. In determining the metabolic requirements, 3 factors must be considered: the physiologic daily requirement of water and electrolytes; the increased extrarenal fluid losses; and the reduction of the extracellular volume in trauma.