Computational analysis of blood volume curves and risk of intradialytic morbid events in hemodialysis

Computational analysis of blood volume curves and risk of (HD) has not been achieved comprehensively thus far intradialytic morbid events in hemodialysis. (1), presumably due to the inconsistent relationship be- Background. Blood volume (BV) curves have been used to tween time-dependent BV reduction and the occurrence prevent intradialytic morbid events (IMEs) caused by hypoten- of IMEs. Moreover, standardized parameters to describe sive episodes in hemodialysis treatment. However, no stan- BV reduction do not exist at present. dardized parameter is available to describe BV dynamics and to enable online interference with ultrafiltration rates in unse- Hypotensive episodes, the main cause of IMEs, result lected patients. Moreover, only time-dependent BV reduction from an excess of ultrafiltration (UF) in relationship and absolute hematocrit threshold, but not BV variability, have to vascular refilling. Since the UF refilling balance is been suggested as markers of pending hypotension. The pres- influenced by several oscillating factors such as neuro- ent study therefore deals with a computer-aided analysis of hormonal status, cardiac output, and venous preload (2), indices characterizing both BV reduction per time and BV variability in treatments of nonselected maintenance hemodial- it is suggested that a manual change of the UF rates by ysis patients. the dialysis staff can be too slow to compensate for pend- Methods. The methodology uses indices obtained by mathe- ing hypotension and IMEs (3). Moreover, manual inter- matical analysis of BV curves and was designed to potentially ference in UF cannot be standardized in daily clinical enable automatic interference with ultrafiltration. Results. In 46 out of 380 treatments (12.1%), IMEs occurred. practice. For these reasons, standardized recommenda- In these treatments, the indices for long- and short-term vari- tions for UF manipulation following BV data are not ability and slope of the curves were significantly lower than in available. The need for further research in this field has treatments without IMEs. Moreover, the last 10 minutes before been emphasized by the DOQI expert committee (4). an IME were characterized by additionally decreased variabil- To resolve the therapeutic challenge, one solution ity and slope. In a risk analysis of long-term variability and IMEs, we established an index below 16 to be associated with might be to manage the UF rates automatically by using the highest risk of IMEs. the individual's BV data. Before automatic BV-UF feed- Conclusions. Using these kind of index thresholds and on- back can be established, clusters of BV dynamics associ- line analysis of BV curves, automatic management of ultrafil- ated with IMEs need to be analyzed. Whereas the influ- tration by BV dynamics could be a promising concept to avoid ence of absolute and relative BV reduction on the intradialytic morbidity. occurrence of hypotension has already been investigated (3), no data are available concerning the impact of BV variability. Moreover, no standardized and reproducible It has been suggested that the frequency of intradia- mathematical tool is available to describe BV reduction lytic morbid events (IMEs), such as hypotension, vom- iting, lightheadedness, and muscular cramps, can be re- and variability in a manner that potentially enables on- duced by continuous monitoring of blood volume (BV) line UF manipulation. The group of Steuer et al, who changes by means of online optical measurement of he- developed a noninvasive, optical BV measurement (Crit- matocrit values. This goal of a smoother hemodialysis linee instrument), employed a manual approach using both an individual "crash-crit" and a threshold of 8% BV reduction per hour to interfere with UF rates in