Central venous oxygen saturation and thoracic admittance during dialysis: New approaches to hemodynamic monitoring

Abstract

Intradialytic hypotension (IDH) is one of the most important short-term complications to hemodialysis (HD). Inadequate cardiac filling due to a reduction in the central blood volume is believed to be a major etiological factor. The aim of this study was to evaluate whether these pathophysiologic events are reflected in the central venous oxygen saturation (ScO2) and thoracic admittance (TA) during dialysis. Twenty ambulatory HD patients, 11 hypotension prone (HP) and 9 hypotension resistant, with central vascular access, were monitored during 3 HD sessions each. ScO2, TA, finger blood pressure (BP), and relative change in blood volume (Delta BV) were measured and sampled continuously. The relative TA decrease and Delta BV were both largest in the HP group (p < 0.05 for both), whereas ScO2 decreased only in HP patients (p < 0.001). Baseline TA was lower in the HP group (p < 0.01). Changes in ScO2 and TA correlated much closer than did changes in ScO2 and Delta BV (r=0.43 and 0.18, respectively). Our results suggest that an intradialytic decrease in cardiac output, as reflected by a fall in ScO2, is a common feature to HD patients prone to IDH. In patients using a central vascular access, ScO2 and TA measurements may be more specific to the pathophysiologic events preceding IDH than Delta BV-the current standard monitoring method