ASSESSMENT OF REFILL AND HYPOVOLEMIA BY CONTINUOUS SURVEILLANCE OF BLOOD-VOLUME AND EXTRACELLULAR FLUID VOLUME

During renal replacement therapy hypovolaemia due to ultrafiltration ( UF) may, when not sufficiently counteracted by refill from the interst itium, result in hypotension. Combining two recently developed methods the haemodynamic process of refill was studied in order to find chara cteristics featuring hypotension. Relative blood volume (BV) and extra cellular fluid volume (EFV) were measured continuously in 40 stable ha emodialysis patients by means of an optical and a conductivity techniq ue respectively. Regarding their postdialytic (PD) EFV the patients we re divided into three groups: normohydrated (N, n = 20), dehydrated (D , n = 11) and overhydrated (O, n = 9). Significant differences between the groups were assessed in BV decrease (after 2 h until the end of t reatment P < 0.05 and after 3 h P < 0.01), EFV decrease (after 3 h P < 0.05) and occurrence of hypotensive episodes (N,5; D,7; O,none; P < 0 .01). During the entire session the speed of BV decrease was significa ntly higher in hypotensive patients (H) than in non-hypotensive patien ts (non-H). At the moment of hypotension (after 141 +/- 49 min) residu al BV was less (P < 0.0005) in H (87.7 +/- 5.2%) than at the correspon ding moment in non-H patients (96.5 +/- 4.0%). PD BV and PD EFV, both expressed as a percentage of the starting value, correlated significan tly (r = 0.63, p < 0.005) and UF-volume (differences between the group s were not significant) correlated to EFV decrease (r = 0.45, P < 0.00 5). In conclusion, the combination of both non-invasive methods elucid ates the pathophysiology of UF-induced hypotension and provides a mean s of reducing dialysis morbidity. The influence of tissue hydration st ate on these variables has been shown.