#1762 Reduction in intradialytic glycemia and increased oxygen consumption as potential indicators of intradialytic parenchymal stress
Authors: Caporotondi Benedetta , Rotondi Silverio , Tartaglione Lida , Pasquali Marzia , Lai Silvia , Perrotta Adolfo Marco , Tinti Francesca , Mazzaferro Sandro 
Published: May 2024

Abstract

Background and Aims
Patients undergoing chronic hemodialysis (HD) face heightened all-cause and cardiovascular mortality due to various risk factors, with intradialytic stress playing a fundamental role. Recently, the assessment of intradialytic oxygen trends has emerged as a potential parameter for evaluating parenchymal stress. Specifically, an intradialytic increase in the oxygen extraction ratio (OER), derived from the ratio of peripherical oxygen saturation to central venous oxygen saturation, identifies patients at a greater risk of intradialytic events and increased clinical risk. In addition to OER, intradialytic consumption of glucose indicates higher tissue metabolic demand, likely indicative of parenchymal stress. We hypothesize that OER and intradialytic glucose consumption may be phenomena related to increased intradialytic parenchymal stress and, therefore, may be correlated.
This study aimed to assess the potential correlation between intradialytic glycemia trends and oxygen extraction (OER).

Method
Patients in chronic HD treatment with a central venous catheter (CVC) for HD were enrolled from January 2019 to January 2020. The exclusion criteria were: ongoing acute pathology, diabetes mellitus, and undergoing hemodialysis for less than six months. OER and glycemia were measured during three consecutive HD sessions at baseline, 15, 30, 60, and 120 minutes into treatment, and post-HD. For statistical analysis, average values for each patient across the three dialysis sessions were considered.

Results
Twenty patients with a permanent CVC (10 males, 10 females; age 74 ± 13 years; HD vintage 46 ± 34 months) were enrolled. The pre-HD mean OER in the initial three HD sessions was 34 ± 7, increasing to 46 ± 9 post-HD, with a mean percentage delta OER of 39 ± 20%. Evaluating OER trends in the entire population revealed an increase in OER (∆OER) from the first 15 minutes of treatment (∆OER% 15’: 14 ± 7; ∆OER% 30’: 18 ± 22, p &lt; 0.01). Patients' baseline glycemia was 120 ± 31 mg/dl at the start of the HD session and 111 ± 21 at the end, with a delta of −11 ± 21 mg/dl and a glucose delta percentage of 4%. Patients with higher oxygen consumption after 15 and 30 minutes of treatment experienced a greater decrease in glycemia.
Specifically, ∆OER at 15’ negatively correlated with glycemia values at 15’ (r: −0.494, p &lt; 0.05), 30’ (r: −0.521, p &lt; 0.05), 60’ (r: −0.644, p &lt; 0.01, Fig. 1), and 120’ (r: −0.714, p &lt; 0.01), and post-HD (r: −0.634, p &lt; 0.05). Patients were then divided based on the magnitude of mean O2 consumption measured post-HD into two groups: ΔOER ≤ mean and ΔOER &gt; mean (threshold 40%). Patients with a higher ∆OER showed a more significant decrease in glycemia from the first 15 minutes of HD, confirmed at the end of HD (ΔOER ≤ 40%: Δglucose post-HD −2 ± 40; ΔOER &gt; 40%: −22 ± 28, p &lt; 0.05, Fig. 2).

Conclusion
The data confirm that oxygen extraction during hemodialysis progressively increases from the first 30 minutes of treatment. Changes in OER are associated with a reduction in glycemia, particularly patients with higher ΔOER have a more pronounced decrease in glycemia. This association between OER and glycemia supports the hypothesis that these two parameters are linked to the same pathophysiological phenomenon, such as increased intradialytic cellular metabolic activity. Studies with larger populations will help confirm this association and propose glycemia delta as an indicator of intradialytic parenchymal stress.