A haemoglobin dilution method (HDM) for estimation of blood volume variations during transurethral prostatic surgery

A method for estimation of blood volume changes during transurethral prostatic surgery is presented (haemoglobin dilution method (HDM]. It is based on a calculation of the patient's preoperative total haemoglobin content, from which losses are subtracted. The haemoglobin concentration of the blood is used as an indicator of dilution. The HDM was compared to the 131I-RISA technique in 10 patients undergoing transurethral resection of the prostate (TUR). The difference between the HDM and RISA in estimating the total operative procedure blood volume change was 0.03 +/- 0.12 l (ns) with a linearity of 0.90. The blood volume changes were also predicted by a fluid balance formula. With RISA as reference, the formula had a lower precision (0.24 l) and a poorer linearity (0.65) than the HDM. The HDM did not lose in accuracy if repeated several times during the TURs or if a theoretical formula for estimation of the preoperative blood volume was used.