RESUMO
PURPOSES: To apply the criteria for classifying the normo- or hypovolaemic state to the blood volume of patients previously diagnosed of relative polycythaemia (RP). PATIENTS AND METHODS: The blood volume of 30 patients previously diagnosed of RP was chosen at random for analysis. Directly measured cell volume (CV) was used to calculate both the total blood volume (WBV) and the plasma volume (PV) of each case expressed as mL and mL/Kg, respectively. WBV was estimated according to Nadler's predictive formula, CV and PV being deductive values expressed in mL. Corrected venous haematocrit (CVH) CV and PV measured as mL/Kg were compared with respective reference intervals of the laboratory (RIL). Weinreb's criteria, modified in accordance to RIL, were used to classify blood volume as normo- or hipovolaemic. RESULTS: Of the 30 patients, 27 were men and 3 women. Mean CVH was 0.51 L/L (range 0.45-0.58 [L/L]). In mL/Kg, 80% of the patients had normal CV with reduced PV, 10% showed normal CV and PV, and the remainders had increased CV with normal PV in 3.3% and decreased PV in 6.7%. Hypovolaemic state was found in 100% of the patients. CONCLUSIONS: Male sex was confirmed as predominant with regard to RP patients. Mean CVH was lower than that of absolute polycythaemia patients, and its wide range stresses the importance of blood volume in the diagnosis of this type of patients, even though reduced PV with normal CV, according to RIL in mL/Kg, are not present. The previous diagnosis was corroborated, hypovolaemic stated being confirmed in all cases at the moment of the study, so more accurate diagnosis and adequate therapeutic indications could be granted, in accordance to the patient's status.