Intraoperative endogenous erythropoietin levels and changes in intravascular blood volume in healthy humans

There is accumulating evidence of a relationship between changes in intrava scular blood volume and endogenous erythropoietin (EPO) levels. In this stu dy, eight healthy adult American Society of Anesthesiologists class-I patie nts due for prolonged elective surgery were randomised either to preoperati ve hypervolaemic haemodilution using hydroxyethyl starch, followed by intra operative crystalloid infusion, or to standard intraoperative normovolaemic fluid balance management using crystalloids (control group). Electrolytes, creatinine, urea, osmolality, urine output and blood gases were monitored pre- and intraoperatively for 6 h, Comparable cardiopulmonary and renal hom eostasis were maintained in both groups. We found that central venous press ure increased and EPO levels decreased, both significantly, in the hypervol aemic haemodilution group relative to controls. There were no significant i ntergroup changes in any other parameters. By controlling for other known d eterminants of EPO levels, our data indicate a relationship between EPO lev els and changes in intravascular blood volume in humans, supporting the not ion of EPO as a volume-regulated, and possibly volume-regulating, hormone.