The effect of sodium and ultrafiltration modelling on plasma volume changes and haemodynamic stability in intensive care patients receiving haemodialysis for acute renal failure: a prospective, stratified, randomized, cross-over study.

Background. Haemodynamic stability in intensive care unit (ICU) patient with acute renal failure (ARF) during intermittent dialytic support has been the focus for several variations to dialysis delivery. Indeed this has been noted by many as a possible cause for prolonged renal dysfunction created by repeated hypotensive renal insult, as well as a reason for the lower delivered dialysis dose afforded. End-stage renal failure patients supported by intermittent dialysis have benefitted from variable sodium dialysate and variable ultrafiltration rate protocols. The current study has focused upon the response to these dialysis variations in the ICU ARF patient. Methods. Successive ICU patients with defined characteristics of ARF requiring dialytic support were entered into a prospective, stratified (by Cleveland Clinic Foundation ARF Acuity Score), randomized, cross-over designed study to evaluate haemodynamic effects and need for interaction during dialysis therapy delivering a fixed dialysis dose based upon urea kinetic analysis. Subjects were supported either by a fixed dialysate sodium (140 meq/dl) and fixed ultrafiltration rate (Protocol A), or a variable sodium dialysate (160-140 meq/dl) and variable ultrafiltration (50% UF during the first third of treatment time, 50% UF over the last two thirds treatment time) (Protocol B). After three sessions, the patients were crossed to the other protocol, and if continued, after three sessions returned to the original protocol. Mean arterial pressures, Cardiac output, serum electrolytes, serum albumin, and relative blood volume changes were measured. Frequency of nursing intervention, quantity and type of volume replacements as well as pressor agent use was standardized, documented and compared. Results. Ten ARF patients (age: 64.2±13.7 years), CCF acuity score (13.3±3.9), APACHE II score (28.7±4.7). MAP (V NA : 82.8±16.9; F NA : 86.2±18.9 mmHg), CO, cardiac index, pressor support interventions required (V NA : 16%; F NA : 48.4%, P<0.001), blood volume changes (Critline) (V NA : -6.6±5.2; F NA : -7.59 ± 6.7, P<0.05), S. albumin (V NA : 2.4 ± 0.6; F NA : 2.81 ± 0.9 g/dl, ns) pre/post S.Na ( V NA : 138.7 ± 5.1/141.7±2.3; F NA : 136.6±5.96/139.1±3.71 mmol/dl), osmolality, Urea (V NA : 69.5 ± 0.6; F NA : 70.5 ± 0.6%, ns) and Creatinine (V NA : 56.6 ± 0.5; F NA : 59.6 ± 0.5%, ns) Reduction ratio, dialysis time (V NA : 4.8±0.5; F NA : 4.6±0.45h) and achieved UF (V NA : 2.0± 1.2; F NA : 1.56±1.3 L, P < 0.05) were measured. Conclusion. Haemodynamic stability was greater during Protocol B than during Protocol A in all patients. Significantly less intervention was noted during Protocol B, despite the same dialysis delivery during both Protocols. Relative Blood volume ch.anges were less during Protocol B, despite a greater total ultrafiltration. Variable sodium dialysate coupled with a variable ultrafiltration rate seems to be the preferred dialysis prescription for ICU ARF patients undergoing intermittent haemodialysis.