Hyponatremia in Cirrhosis

Kinsley Ojukwu

Background

  • Hyponatremia in cirrhosis is often defined as serum Na < 135 mmol/L
  • Very common problem; prevalence: ~50% of individuals have serum < 135 mmol/L, ~22% < 130 mmol/L
  • Degree of hyponatremia is associated with progression of cirrhosis; patients with hypona have greater incidence of HE, SBP, and HRS, increased complications & mortality pre/post-tx.
  • Patients most commonly have hypervolemic (dilutional) hypona.
  • Pathophysiology
    • Hypovolemic hyponatremia: 2/2 excessive diuretic use
    • Hypervolemic hyponatremia: Advanced cirrhosis -> chronic inflammation and fibrosis in liver -> increased resistance to portal flow -> portal hypertension -> release of vasoactive compounds (primarily nitric oxide) -> splanchnic arterial vasodilation -> reduced effective arterial blood volume (splanchnic veins contain 20% to 50% of the total blood volume) -> reduced effective intravascular volume leads to activation of RAAS + ADH + sympathetic nervous system ->RAAS encourages Na retention and ADH causes insertion of aquaporins in distal tubule and collecting duct to increase water reabsorption -> dilutional (hypervolemic) hyponatremia

Evaluation

  • Uosm, Sosm, UNa to rule out competing processes (e.g. beer potomania)

Management

  • Do not correct Na faster than 6-8mEq/L in 24 hours
  • Discontinue anti-hypertensives (including beta blockers) in patients with ascites and hypona. Hold diuretics when Na <125
  • Fluid restriction is recommended only in patients with Na <125. Restriction is generally effective at 1-1.5L and must be less than daily UOP to increase free water excretion
  • Replete K to 4.0
  • 25% albumin infusion (1g/kg split into BID dosing), has been shown to increase serum Na and have higher rates of hypona resolution at 30 days
  • Treatment considerations include vasopressors, urea tabs
  • Vaptans are generally not used in clinical practice given recent RCTs showing harm with use
  • Salt tabs should not be used to raise serum Na due to worsening hypervolemia
  • Nephrology should be consulted if not improved after 48 hours
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