Non-invasive technology to assess hydration status in advanced cancer to explore relationships between fluid status and symptoms: an observational study using bioelectrical impedance analysis

Background Oral fluid intake decreases in people with advanced cancer, especially when they approach the dying phase of their illness. There is inadequate evidence to support hydration assessment and decision making in the dying phase of illness. Bioelectrical impedance analysis (BIA) and vector analysis (BIVA) are validated methods of hydration assessment, with research demonstrating that hydration status is associated with specific symptoms, and survival in advanced cancer. However, further research is needed to better understand the relationships between hydration status and clinical outcomes in advanced cancer, particularly at the end-of-life. Aim To evaluate hydration status and its associations with clinical outcomes in advanced cancer patients, and those in the last week of life. Materials and methods An observational study of people with advanced cancer in three centres. Advance consent methodology was used to conduct hydration assessments in the dying. Total body water was estimated using the BIA Impedance index (Height, H (m)2 /Resistance, R (Ohms)). We used backward regression to identify factors (signs, symptoms, quality of life) that predict H2/R. Participants in the last 7 days of life were further assessed with BIA to assess hydration changes, and its relationship with clinical outcomes. Results 125 people participated (males n=74 (59.2%), females, n=51 (40.8%). BIVA demonstrated that baseline hydration status was normal in 58 (46.4%), more-hydrated in 52 (41.6%) and less hydrated in 13 (10.4%). Regression analysis demonstrated that less hydration (lower H2/R) was associated with female sex (Beta = -0.371, p<0.001), increased anxiety (Beta = -0.135, <0.001), increased severity of physical signs (dry mouth, dry axilla, sunken eyes - Beta = -0.204, p<0.001), and increased breathlessness (Beta = -0.180, p<0.014). More hydration (higher H2/R) was associated with oedema (Beta= 0.514, p<0.001) and increased pain (Beta = 0.156, p=0.039). Eighteen participants (14.4%) were in the last week of life. For dying participants, hydration status (H2/R) was not significantly different compared to baseline (n= 18, M= 49.55, SD= 16.00 vs. M= 50.96, SD= 12.13; t(17)= 0.636, p = 0.53) and was not significantly associated with agitation (rs = -0.847, p = 0.740), pain (rs = 0.306, p = 0.232) or respiratory tract secretions (rs = -0.338, p = 0.185). Conclusions In advanced cancer, hydration status was associated with specific physical signs and symptoms. No significant associations between survival and hydration status were recorded. In the dying phase, hydration status did not significantly change compared to baseline, and was not associated with symptoms. Further work can use BIA/BIVA to standardise the process to identify clinically relevant outcomes for hydration studies, to establish aa core outcome set to evaluate how hydration affects symptoms and quality of life in cancer. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was funded by, the Academy of Medical Sciences (24,250), UKH Foundation (5,000), Anne Duchess of Westminster Charity (5,000) and the Liverpool Clinical Commissioning Group (CCG) Research Capability Funding (RCF) streams (22029), Non recurrent contingency funding, National Institute for Health Research (NIHR) North West Coast Clinical Research Network, (19,086.57). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee, North West - Haydock Ethics Research Ethics Committee, gave ethical approval for this work (REC: 17/NW/0050; IRAS ID: 196540). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript