Serum sodium shift in hyponatremic patients undergoing liver transplantation: a retrospective cohort study

Abstract

Introduction: We aimed to describe the pre-operative incidence of hyponatremia in patients undergoing liver transplantation (LTx), as well as the rate and consequences of rapid peri-operative sodium rises in these patients. Methods: This was a retrospective before and after observational study performed at a University-affiliated LTx center between January 2007 and June 2013. The primary exposure was pre-operative hyponatremia, defined as a serum sodium (SNa) <133 mmol/L. The primary outcome was occurrence of a rapid SNa shift, defined as ≥10 mmol/L in the first 24 h following LTx. The rates of rapid peri-operative SNa shift were compared before and after a focused quality assurance (QA) initiative performed in July 2009. Results: Of 366 LTx, 69 (18.9%) had pre-operative hyponatremia, 6 (8.7%) of whom had a rapid rise in serum sodium (SNa). Rapid rise was associated with a greater intra-operative positive fluid balance (p < 0.001) and use of intra-operative continuous renal replacement therapy (CRRT) (p = 0.017). A rapid rise in SNa was associated with more neurological investigations in the post-transplant period (brain computed tomography, electroencephalogram, swallow studies), increased neurological deficits (p = 0.006), more abnormal swallowing assessments (p = 0.003), a tendency for more neurology consultations (p = 0.058), increased discharge to a rehabilitation or long-term care facility (p < 0.001), and increased 6-month mortality (p < 0.001). Following a QA initiative, rapid peri-operative rises in SNa among hyponatremic patients was significantly reduced (20% vs. 0%, p < 0.003). Conclusion: Pre-operative hyponatremia and rapid peri-operative SNa shifts are associated with a more complicated post-operative course and worse outcomes following LTx. Increased education and awareness, along with process changes, such as standardizing CRRT prescription, can reduce iatrogenic rapid peri-operative shifts in SNa.