We measured red cell volume (RCV) with the nonradioactive marker sodium fluorescein (SoF) in 30 patients undergoing gynecological operations. Sixteen patients underwent preoperative isovolemic hemodilution (PIHD). RCV measurements were performed before and after PIHD and at the end of the operation. All RCVs were related to corresponding hematocrit (hct) levels. We report a simplified method for its clinical application by reducing the number of blood samples required. To validate our method, we compared RCV within the PIHD bags (bag RCV) with the difference of the patients' RCV before and after PIHD. Bag RCV obtained during PIHD (mean 399+/-81 mL) was measured with a precision of 4.2% by using SoF. There was a significant difference (mean 286+/-401 mL; P < 0.05) between intraoperatively estimated and measured blood loss. The blood loss tended to be underestimated and, in some cases, was underestimated or overestimated substantially. Preoperative and postoperative hct values only offered an imprecise estimation of the patients' RCV. We conclude that RCV measurement using SoF is a precise method for monitoring changes in RCV during PIHD and surgical operation.
Implications: We measured red cell volume changes of 30 patients with the nonradioactive marker sodium fluorescein before and after hemodilution and postoperatively with a high precision. We frequently found large differences between intraoperatively estimated and measured blood loss. Preoperative hematocrit values offered an imprecise estimation of the patients' red cell volume.