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 (ScO(2)) 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. ScO(2), TA, finger blood pressure (BP), and relative change in blood volume (DeltaBV) were measured and sampled continuously. The relative TA decrease and DeltaBV were both largest in the HP group (p<0.05 for both), whereas ScO(2) decreased only in HP patients (p<0.001). Baseline TA was lower in the HP group (p<0.01). Changes in ScO(2) and TA correlated much closer than did changes in ScO(2) and DeltaBV (r=0.43 and 0.18, respectively). Our results suggest that an intradialytic decrease in cardiac output, as reflected by a fall in ScO(2), is a common feature to HD patients prone to IDH. In patients using a central vascular access, ScO(2) and TA measurements may be more specific to the pathophysiologic events preceding IDH than DeltaBV-the current standard monitoring method.

Hemodialysis: A model for extreme physiology in a vulnerable patient population

“…Notably, mean ScvO 2 levels were already as low as 52.2% and 49.7% at the start of treatment in the respective groups. 26 An observational study with a follow-up of 36 months found a significantly higher mortality in patients with lower ScvO 2 , so that in an adjusted Cox analysis a 1 percent point decrease in mean ScvO 2 was associated with a 4% increase in mortality (hazard ratio 1.04 [95% confidence interval 1.01-1.08], P = .044). 27 Future studies should investigate whether changes in ScvO 2 during HD are also related to perfusion in vital organs, and whether this tool could potentially be used as an additional tool to guide KOOMAN ET AL.…”

“…In a study in 11 hypotension‐prone and 9 stable HD patients, ScvO 2 dropped by 7.7 ± 1.7% in hypotension‐prone patients, in contrast to a rise of 1.0 ± 1.3% in the latter group. Notably, mean ScvO 2 levels were already as low as 52.2% and 49.7% at the start of treatment in the respective groups . An observational study with a follow‐up of 36 months found a significantly higher mortality in patients with lower ScvO 2 , so that in an adjusted Cox analysis a 1 percent point decrease in mean ScvO 2 was associated with a 4% increase in mortality (hazard ratio 1.04 [95% confidence interval 1.01‐1.08], P = .044) …”

Central Venous Oxygen Saturation: A Potential New Marker for Circulatory Stress in Haemodialysis Patients?

“…In the only other study to examine ScvO 2 during HD, Cordtz et al [13] attempted to assess whether ScvO 2 could be used as a surrogate for cardiac output (as measured by thoracic impedance). More interestingly, the authors reported a much greater fall in ScvO 2 in hypotension-prone patients, without a close correlation with blood volume.…”

Evaluation of intradialytic hypotension using impedance cardiography

“…Correlations have been found between CBV and intradialytic hypotension. Cordtz et al have assessed CBV using thoracic admittance and cardiac function using central venous saturation [38]. They found that reduced baseline thoracic admittance was associated with intradialytic hypotension, and that the central venous saturation was reduced in these patients, suggesting a decrease in cardiac output.…”