Postdialysis serum sodium changes and systolic blood pressure in patients undergoing online hemodiafiltration and high-flux hemodialysis

Effect of Change in Sodium after Slow Low-Efficiency Dialysis in Critically Ill Patients with Acute Kidney Injury

INTRODUCTION

The effect of sodium (Na) correction by slow low-efficiency dialysis (SLED) in dysnatremic (135 mEq/L <Na >145 mEq/L) critically ill patients is unclear.

METHODS

Prospective observational study enrolled dysnatremic critically ill adult patients with acute kidney injury undergoing the first SLED as cases and normonatremic patients as controls. Baseline and SLED-related parameters and 30-day mortality were noted.

RESULTS

100 dysnatremic and 51 normonatremic patients were included, with a median age of 31 (25-52) years and median admission SOFA scores of 10 (9-12). Patients with dysnatremia at study inclusion had a mortality of 53%, with the highest mortality in severe hypernatremia (Na >160 mEq/L) (75%), followed by those with severe hyponatremia (Na <120 mEq/L) (68.6%). SLED-associated natremia change >10 mEq/L was significantly associated with mortality, in patients with mild dysnatremia and normonatremia (Na: 130-150) (p < 0.001), and not in those with moderate to severe dysnatremia (Na <130 and Na >150) (p = 0.72). Upon multivariate logistic regression analysis, a model with pre-SLED pH, dialyzate-pre-SLED Na difference, and duration of SLED significantly predicted SLED-associated natremia change (R2 0.18, p = 0.001).

CONCLUSIONS

SLED can be safely and effectively performed in critically ill adults with dysnatremia requiring renal replacement therapy with mortality comparable to normonatremic controls.

Sodium handling in pediatric patients on maintenance dialysis

The risk of cardiovascular disease remains exceedingly high in pediatric patients with chronic kidney disease stage 5 on dialysis (CKD 5D). Sodium (Na+) overload is a major cardiovascular risk factor in this population, both through volume-dependent and volume-independent toxicity. Given that compliance with a Na+-restricted diet is generally limited and urinary Na+ excretion impaired in CKD 5D, dialytic Na+ removal is critical to reduce Na+ overload. On the other hand, an excessive or too fast intradialytic Na+ removal may lead to volume depletion, hypotension, and organ hypoperfusion. This review presents current knowledge on intradialytic Na+ handling and possible strategies to optimize dialytic Na+ removal in pediatric patients on hemodialysis (HD) and peritoneal dialysis (PD). There is increasing evidence supporting the prescription of lower dialysate Na+ in salt-overloaded children on HD, while improved Na+ removal may be achieved in children on PD with an individual adaptation of dwell time and volume and with icodextrin use during the long dwell.

Blood pressure management in children on dialysis

Hypertension is a leading cause of cardiovascular complications in children on dialysis. Volume overload and activation of the renin-angiotensin-aldosterone system play a major role in the pathophysiology of hypertension. The first step in managing blood pressure (BP) is the careful assessment of ambulatory BP monitoring. Volume control is essential and should start with the accurate identification of dry weight, based on a comprehensive assessment, including bioimpedance analysis and intradialytic blood volume monitoring (BVM). Reduction of interdialytic weight gain (IDWG) is critical, as higher IDWG is associated with a worse left ventricular mass index and poorer BP control: it can be obtained by means of salt restriction, reduced fluid intake, and optimized sodium removal in dialysis. Optimization of peritoneal dialysis and intensified hemodialysis or hemodiafiltration have been shown to improve both fluid and sodium management, leading to better BP levels. Studies comparing different antihypertensive agents in children are lacking. The pharmacokinetic properties of each drug should be considered. At present, BP control remains suboptimal in many patients and efforts are needed to improve the long-term outcomes of children on dialysis.

Haemodiafiltration at increased plasma ionic strength for improved protein-bound toxin removal

AIM

Protein-bound uraemic toxin accumulation causes uraemia-associated cardiovascular morbidity. Enhancing the plasma ionic strength releases toxins from protein binding and makes them available for removal during dialysis. This concept was implemented through high sodium concentrations ([Na⁺ ]) in the substituate of pre-dilution haemodiafiltration at increased plasma ionic strength (HDF-IPIS).

METHODS

Ex vivo HDF-IPIS with blood tested increasing [Na⁺ ] to demonstrate efficacy and haemocompatibility. Haemocompatibility was further assessed in sheep using two different HDF-IPIS set-ups and [Na⁺ ] between 350 and 600 mmol L^-1 . Safety and efficacy of para-cresyl sulphate (pCS) and indoxyl sulphate (IS) removal was further investigated in a randomized clinical pilot trial comparing HDF-IPIS to HD and HDF.

RESULTS

Compared to [Na⁺ ] of 150 mmol L^-1 , ex vivo HDF-IPIS at 500 mmol L^-1 demonstrated up to 50% higher IS removal. Haemolysis in sheep was low even at [Na⁺ ] of 600 mmol L^-1 (free Hb 0.016 ± 0.001 g dL^-1 ). In patients, compared to HD, a [Na⁺ ] of 240 mmol L^-1 in HDF-IPIS resulted in 40% greater reduction (48.7 ± 23.6 vs. 67.8 ± 7.9%; P = 0.013) in free IS. Compared to HD and HDF (23.0 ± 14.8 and 25.4 ± 10.5 mL min^-1 ), the dialytic clearance of free IS was 31.6 ± 12.8 mL min^-1 (P = 0.017) in HDF-IPIS, but [Na⁺ ] in arterial blood increased from 132 ± 2 to 136 ± 3 mmol L^-1 (0 vs. 240 min; P < 0.001).

CONCLUSION

HDF-IPIS is technically and clinically feasible. More effective HDF-IPIS requires higher temporary plasma [Na⁺ ], but dialysate [Na⁺ ] has to be appropriately adapted to avoid sodium accumulation.