[Relevance of erythrocyte parameters on fluid management in critical care]

To manage fluid therapy in severely ill patients through investigating the relationship between erythrocyte parameters and central venous pressure (CVP) and its denoted blood volume.

The research project was divided into two parts. Part I: CVP and concurrent erythrocyte parameters [red blood count (RBC), hemoglobin (Hb), haematocrit (HCT)] were serially recorded in a severely ill patient every morning for 38 days. The obtained values of CVP were divided into three groups (<8 cm H2O group, 8-10 cm H2O group, >10 cm H2O group), then erythrocyte parameters of each period were compared to obtain the relationship among them. At the same time, "the best" CVP (blood volume was in suitable state) and "the best" erythrocyte parameters (accordingly the blood was not be diluted or concentrated) were obtained. Part II: "the best" CVP and corresponding "the best" erythrocyte parameters were determined in another patient. When the patient's blood volume was in doubt, detected her erythrocyte parameters right away. If the variance between the "practical" and "the best" values was notable, blood volume replenishment or diureses were performed. Then the resulting CVP of fluid expansion or diuresis before and after the treatment were compared, or else other influencing factors should be seeked.

Part I: the values of RBC, Hb and HCT in group CVP>10 cm H2O were lower than those of group CVP<8 cm H2O and CVP 8-10 cm H2O (RBC: 3.05±0.32×10(9)/L vs. 3.59±0.25×10(9)/L, 3.42±0.24×10(9)/L; Hb: 85.3±6.8 g/L vs. 104.2±3.6 g/L, 97.5±4.9 g/L; HCT: 0.271±0.023 vs. 0.321±0.015, 0.309±0.019, all P<0.01), and Hb in group CVP 8-10 cm H2O was lower than group CVP<8 cm H2O (97.5±4.9 g/L vs. 104.2±3.6 g/L, P<0.01). CVP was negatively correlated with RBC, Hb and HCT, and coefficients of correlation (r value) were -0.735, -0.903 and -0.822, respectively (all P<0.01), and positive correlations were found among RBC, Hb and HCT, with r value 0.804, 0.931 and 0.863, respectively (all P<0.01). The patient's vital signs were stable when CVP was 8 to 10 cm H2O, therefore it was assigned as "the best" CVP, and the corresponding "the best" erythrocyte parameters were determined (RBC was 3.43×10(9)/L, Hb was 97.4 g/L, HCT was 0.310). Part II: "the best" CVP of the this patient was 8 to 10 cm H2O too, accordingly "the best" erythrocyte parameter in term of Hb was 105 g/L. The CVP was obviously elevated in the group in which Hb was higher than "the best" Hb subsequent to fluid expansion (8.29±1.80 cm H2O vs. 5.86±1.57 cm H2O, P<0.05), and the CVP was obvious lowered in the group which Hb was lower than "the best" Hb through diuresis (8.80±2.39 cm H2O vs. 12.20±1.92 cm H2O, P<0.05).

CVP was negatively correlated with erythrocyte parameters, "the best" erythrocyte parameters accompanying "the best" CVP would probably guide fluid therapy best in severely ill patients.