[Inadequate doses of hemodialysis. Predisposing factors, causes and prevention].

Patients receiving sub-optimal dose of hemodialysis have increased morbidity and mortality. The objectives of this study were to identify predisposing factors and causes of inadequate dialysis, and to design a practical algorithm for the management of these patients. A cross-sectional study was conducted. Ninety patients in chronic hemodialysis at Hospital Privado Universitario de Córdoba were included, during September 2015. Twenty two received sub-optimal dose of hemodialysis. Those with urea distribution volume (V) greater than 40 l (72 kg body weight approximately) are 11 times more likely (OR = 11.6; CI 95% = 3.2 to 51.7, p < 0.0001) to receive an inadequate dose of hemodialysis, than those with a smaller V. This situation is more frequent in men (OR = 3.5; 95% CI 1.01-15.8; p = 0.0292). V greater than 40 l was the only independent predictor of sub-dialysis in the multivariate analysis (OR = 10.3; 95% CI 2.8-37; p < 0.0004). The main cause of suboptimal dialysis was receiving a lower blood flow (Qb) than the prescribed (336.4 ± 45.8 ml/min vs. 402.3 ± 28.8 ml/min respectively, p < 0.0001) (n = 18). Other causes were identified: shorter duration of the session (n = 2), vascular access recirculation (n = 1), and error in the samples (n = 1). In conclusion, the only independent predisposing factor found in this study for sub-optimal dialysis is V greater than 40 l. The main cause was receiving a slower Qb than prescribed. From these findings, an algorithm for the management of these patients was developed.