Combined measurement of tissue fluid, blood volume and hemodynamics in hemodialysis

During recent decades hemodialysis (HD) therapy has gained momentum.. However, one of the main problems induced by maintenance HD is the occurrence of hypotension. Approximately 25 to 30% of patients display symptomatic hypotension during a regular session (1). In the course of a HD session uremic patients are exposed to rapid variations in body fluid composition (2). The effect of these variations on the hemodynamic status of the HD patient is thought to be multifactorial. Due to the withdrawal of fluid by ultrafiltration (UF) directly from the intravascular compartment blood volume (BV) will decrease. Compensatory mechanisms to minimize this decrease are the process of interstitial refill and alterations in the cardiovascular system. However, former studies have shown that compensatory mechanisms will often fail in chronic renal failure patients (3, 4). In this review the possible causes of intradialytic hypotension are reviewed. The factors which play a role in the shortcomings of the cardiovascular response and the interstitial refill during conventional HD will be discussed consecutively. Newly developed non-invasive methods for the continuous surveillance of body fluid balance and hemodynamics during HD are described. Two clinical studies in which these non-invasive techniques were used will be discussed. The aim of this review is to make clear that all the variables of importance to monitor and prevent hypovolemia and hypotension are currently available on a non-invasive basis.