#1384 Obstructive sleep apnea and fluid management in the hemodialysis: are clinicians putting existing scientific evidence into practice?
Authors: Cozzo Domenico , Burkhalter David Andri , Cartella Antonio , Ogna Adam , Ogna Valentina Forni 
Published: May 2024

Abstract

Background and Aims
Obstructive Sleep Apnea (OSA) prevalence was found to be higher in an intermittent hemodialysis (iHD) population of the French-speaking Switzerland than in the general population of the same geographical area. The high prevalence of OSA in iHD patients was linked to fluid overload. Interdialytic fluid management targeting a low dry weight showed to reduce OSA's severity, offering a novel therapeutic option in this population.
The aims of this study were: 1) to assess the prevalence of confirmed OSA in an end-stage renal disease (ESRD) population undergoing iHD in the Italian-speaking area of Switzerland; 2) to assess the awareness of the treating nephrologists about the OSA's diagnosis of their patients; and 3) to evaluate whether nephrologists integrate the current knowledge in their fluid management strategy of iHD patients with OSA.

Method
We performed a multicenter, cross-sectional study between July 2022 and July 2023, screening all patients attending the four iHD units of the Ente Ospedaliero Cantonale (EOC), the public hospital network of Canton Ticino (Switzerland), and including those with confirmed OSA. For these patients, we collected anthropometric parameters, iHD protocol characteristics and fluid status from electronic patient dossiers.
Fluid overload was measured by multifrequency bioelectrical impedance (Body Composition Monitor®, BCM®; Fresenius Medical Care).
Nephrologists of the four iHD units were asked to identify patients with known OSA diagnosis, without consulting the medical dossiers, and were interviewed about their specific iHD strategy in patients with OSA.
We compared the fluid management of patients identified as “OSA positive” and those with OSA diagnosis, but misclassified as “OSA negative” by the treating nephrologist.

Results
Out of 193 patients treated by iHD in the four HD units, 45 patients had a confirmed diagnosis of OSA and were included in this study. Mean age was 76.0 ± 7.5 y, 82.2% were men, mean BMI was 29.1 ± 4.5 kg/m2. They were treated 3 times per week, in mean for 3.76 ± 0.37 hours; 22 were treated by hemodialysis and 23 by hemodiafiltration.
The 23% prevalence of diagnosed OSA observed in the study population was significantly lower than the 56% prevalence found in the French Switzerland iHD cohort (p &lt; 0.001).
Out of the 45 patients with diagnosed OSA, only 27 (60.0%) were correctly identified by the treating nephrologist.
We found no difference in the dry weight target defined by the treating nephrologist between the patients correctly identified as “OSA positive” and those misclassified as “OSA negative”, both being close to the dry weight calculated with BCM® (mean difference 0.7 ± 2.3 vs 0.3 ± 1.4 kg; p = 0.564). The pre-dialysis fluid overload of the whole population was 2.4 ± 1.7 kg, being higher in the “OSA positive” group (2.9 ± 2.0 kg) than in the “OSA negative” group (1.8 ± 0.7 kg; p = 0.0172). However, we found no difference in post-dialysis achievement of dry weight between the groups (residual overweight 0.2 ± 1.0 and 0.1 ± 0.7 kg respectively; p = 0.672).
In the interviews, only half of the nephrologists (4/8) were aware of the correlation between fluid overload and OSA, and two of them reported to integrate this knowledge in their fluid management strategy, even if not systematically.

Conclusion
Nephrologists' attention to sleep apnea in iHD patients seems to be low, despite its high prevalence in this population and scientific evidence supporting that targeting fluid overload is an effective option to improve OSA severity. However, nephrologists tried to achieve the dry weight very strictly in all patients, independently of OSA.
More intensive training of nephrologists to the clinical and diagnostic peculiarities of OSA in patients with ESKD is required, in order to improve OSA diagnosis and targeted therapeutic care.