RESUMO
BACKGROUND: A correct estimation of volume status and dry weight in dialysis patients remains a difficult clinical problem. Clinical status and chest X-ray are not sensitive enough, while invasively measured central venous pressures are not routinely available. Recently, the ultrasonographic determination of the diameter and collapse index of the inferior vena cava has been proposed as a noninvasive method for estimating intravascular volume. We tried to evaluate the clinical relevance of this method in dialysis patients by comparing it with alphahuman-atrial natriuretic peptide (alpha-h-ANP) and cyclic guanosine 3:5-monophosphate (cGMP) levels. METHODS: Using echocardiography, the diameter of the inferior vena cava (VCD) and its decrease on deep inspiration (collapse index : CI) were evaluated in 27 hemodialysis patients. Echocardiography of the inferior vena cava (IVC) was performed in the supine position after 10 minutes rest. The transducer was placed in the subxiphoid region and long and short axis views of the IVC were obtained just below the diaphragm in the hepatic segment. VCD was measured before the P-wave on the electrocardiogram to avoid interference with A-wave and V-wave on the venous pressure curve, and corrected for body surface area. Preand post-hemodialysis levels of the plasma alpha-h-ANP and cGMP were measured by radioimmunoassay. The relationship between VCD, CI determined by echocardiography, and alpha-h-ANP and cGMP concentrations were studied. RESULTS: The levels of alpha-h-ANP and cGMP were markedly elevated before hemodialysis and significantly lower values were found after hemodialysis (alpha-hANP : 162.7 102.6 pg/ml vs 90.6 61.0 pg/ml , cGMP : 35.3 8.8 pmol/ml vs 21.3 6.2 pmol/ml). A significant correlation was found between VCD and alpha-h-ANP before (r=0.81, p 0.05) and also no relation was observed between the decrease of cGMP during hemodialysis and VCD before hemodialysis (r=0.12, p > 0.05). A significant correlation between the percent change in body weight and the percent change in VCD during hemodialysis (r=0.91, p<0.05) and also significant relation was observed between the pecent change in body weight and the percent change in alpha-h-ANP levels (r=0.40, p , 0.05). CONCLUSION: Echocardiography of the inferior vena cava allow an estimation of changes of intravascular volume in ESRDpatients without cardiac filling impairment as shown by the correlation to other indices of intravascular volume, such as alpha-h-ANP. In this study, CI and cGMP levels were less informative. Inferior vena cava echocardiography is noninvasive and easily available and serial measurements of VCD and alphah-ANP levels allow an estimation of chages of intravascular volume in ESRD patients on maintenance hemodialysis.