Changes in red blood cell volume during transition of heart failure status: a reflection of cellular hydration status?

This study examined how changes in heart failure (HF) status induce changes in the index of erythrocyte hydration based on mean red blood cell volume (MCV). Data from 47 HF patients (32% men; 78.2 ± 9.7 years) that experienced worsening and recovery of HF were analysed. Blood tests included measurements of MCV, albumin, serum solutes and b-type natriuretic peptide (BNP). Among a total of 47 worsening HF events, changes in MCV were positively correlated with changes in body weight (r = 0.31, p = .034), serum sodium (r = 0.417, p = .0036), and chloride (r = 0.457, p = .0012), and negatively correlated with changes in blood urea nitrogen (r= -0.389, p = .0069) and creatinine (r= -0.494, p = .0004). At recovery from worsening of HF by conventional diuretic therapy, change in MCV was positively correlated with the change in body weight (r = 0.457, p = .0012), serum sodium (r = 0.466, p = .001) and chloride (r = 0.484, p = .0006). Multivariate regression analysis demonstrated an independent association between the increase in serum chloride and MCV from stability to worsening of HF (odds ratio [OR] 6.02, 95% confidence interval [CI] 1.09-33.2, p = .039) and the increase or absence of change in serum chloride concentration and preserved MCV after decongestion (OR 11.5, 95% CI 1.53-85.9, p = .017). In conclusion, this study demonstrates that the changes in MCV under transition in HF status do not reflect a change that occurs in parallel with changes in HF-related markers, such as body weight and serum BNP level, but is independently associated with a change in the serum chloride concentration. Whether changes in MCV actually reflect the bodily cellular hydration status warrants further research.