NEW TECHNIQUES TO DETERMINE FLUID STATUS IN HEMODIALYZED PATIENTS

In this paper, several newly developed techniques for the estimation o f the fluid status in hemodialysis patients were reviewed. Whereas ech ography of the inferior caval vein and the measurement of ANP and cGMP levels merely provide information about the intravascular volume, con ductivity measurements are able to detect changes in the extracellular and intracellular compartments without being able to differentiate be tween the intravascular and interstitial fluid spaces. Echography of t he inferior caval vein as a tool to assess over- and underhydration ha s been successfully validated against objective standards as right atr ial pressure, total blood volume and the change in hemodynamic paramet ers during dialysis. Conductivity measurements were significantly rela ted to vena cava measurements before and after dialysis. Whereas ANP l evels were significantly related to the vena cava diameter before dial ysis. in another group of patients. only a significant relation betwee n the vena cava diameter and cGMP was observed in patients with normal left atrial hemodynamics, whereas they were not in patients with a di lated left atrium. Furthermore. in normovolemic patients with mitral i nsufficiency, ANP levels after dialysis remained increased compared to patients without mitral insufficiency, suggesting that, in addition t o volume expansion, also altered left atrial hemodynamics influence th e release of cGMP and ANP. Conductivity measurements and ANP before an d after dialysis were not related, whereas only cGMP after dialysis wa s significantly related to conductivity measurements. ANP and cGMP wer e not related to the change in hemodynamic parameters during dialysis, questioning their reliability in the assessment of under-hydration.