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Abstract: SA-PO733

Modified Formula to Predict a Change in Serum Sodium in Patient with Hyponatremia Requiring RRT

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Shettigar, Shruti, Cleveland Clinic Florida, Weston, Florida, United States
  • Cohen, Scott D., Cleveland Clinic Florida, Weston, Florida, United States
  • Bobart, Shane A., Cleveland Clinic Florida, Weston, Florida, United States
  • Gebreselassie, Surafel K., Cleveland Clinic Florida, Weston, Florida, United States
Introduction


Hyponatremia is a common and feared electrolyte imbalance encountered, but rapid correction of sodium is what most physicians dread. In patients with hyponatremia requiring RRT, controlling the rate of sodium correction can be challenging & often requires the use of a hypotonic solution to dilute the dialysate. Here we present a case of a patient with hyponatremia pending liver transplant, who was started on CVVHD & rather than using a hypotonic solution we used a slower dialysate flow rate to prevent rapid correction of sodium.

Case Description



39 year old male with decompensated cirrhosis presented with acute, asymptomatic hypervolemic hyponatremia. Initial labs showed S.Na 120, S.Osm 273, U.Osm 328, U. Na 49, BUN 74, Creatinine 2.36, CO2 17, normal TSH & cortisol. Despite fluid restriction, hypertonic saline, furosemide & tolvaptan, his sodium did not improve and fluctuated between 120-124. He also developed worsening renal failure needing initiation of CVVHD. To avoid overcorrection of sodium, the following modified formula was used to predict the rate of correction:
[{Dialysate Na (140) - Patient's Na (120)} /TBW {0.6 X patient’s weight(141)}] X Dialysate flow Rate(1L/hr) = Rate of sodium correction (~0.23mEq/L/hr)
In our patient we used Qd (Dialysate flow Rate) as 1.5L/hr to get 0.35mEqL/hr as the rate of sodium correction
His sodium corrected to 127 on day 1,131 on day 2 and plateaued at 134 on day 3.

Discussion


Rapid correction of hyponatremia in cirrhosis runs a higher risk of patients developing osmotic demyelination syndrome. On CVVHD there is a risk for rapid correction if adjustments like diluting the dialysate with a hypotonic solution to reduce the dialysate sodium, are not made. The above formula helps us adjust the dialysate flow rate so that we can predict the rate of sodium correction to be <8mEq/24hrs, thus preventing an overcorrection of hyponatremia. Various factors can affect the serum sodium in patients on CVVHD like IV infusions, insensible losses, etc. which explains why there wasn't an exact correction of sodium as predicted in this patient. However by setting an upper limit of sodium correction using a slower dialysate flow on CVVHD we could prevent overcorrection of hyponatremia. If predicted change in hourly serum sodium is higher, consider adding hypotonic solution to avoid overcorrection.