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
Authors: Nwosu Amara Callistus , Stanley Sarah , Mayland Catriona R , Mason Stephen , McDougall Alexandra , Ellershaw John E 
Published: August 2023

AbstractBackgroundOral 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.AimTo evaluate hydration status and its associations with clinical outcomes in advanced cancer patients, and those in the last week of life.Materials and methodsAn 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.Results125 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).ConclusionsIn 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 a core outcome set to evaluate how hydration affects symptoms and quality of life in cancer.Key messageWe used bioelectrical impedance analysis (a non-invasive body composition assessment tool) to evaluate associations between hydration status and clinical outcomes in people with cancer. Hydration status was significantly associated with biological sex, physical signs, symptoms and psychological outcomes. In the dying phase, hydration status did not significantly change compared to baseline, and hydration status was not significantly associated with survival. The development of a standardised core outcome set for cancer hydration studies, to evaluate how hydration affects symptoms, quality of life and outcomes in cancer patients, will help to establish a meaningful evidence base for clinical practice.