Intraoperative blood salvage: fluid replacement calculations.

Intraoperative blood salvage (IBS) devices are used as adjuncts to blood conservation in spinal surgical procedures of increasing duration, complexity, and total blood loss. We applied existing information about the performance and efficiency of IBS devices together with existing information regarding the distribution of crystalloids and colloids to provide clinicians with guidelines for the prediction of the total blood loss implications of a given volume of IBS return. We also developed guidelines for estimation of the appropriate replacement volumes for the acellular component of blood loss when replacement is undertaken with either isotonic-iso-oncotic colloid or isotonic crystalloid solutions. When average hematocrit during blood loss is between 25% and 30%, total blood loss will be 3.4-4.0 times the volume of the IBS recovery. When replacement is undertaken with colloids or crystalloids, the appropriate replacement volume will be approximately 2.5 and 8.0 (respectively) times the volume of the IBS recovery. These volumes may be larger than have been appreciated by some clinicians.