pseudohyponatremia

Introduction

• relic of days past when concentration of sodium was measured using flame photometry
  • occurred because of non-aqueous volume occupied by lipid in hypertriglyceridemia & perhaps protein in monoclonal gammopathies & polyclonal gammopathies
• ion-specific electrodes used in most modern instruments measure activity not concentration, thus making the issue of pseudohyponatremia obsolete

But like old theories, old beliefs & practices don't die, their proponents do, & reference to pseudohyponatremia still appear in Internal Medicine Board review materials in 2006.

Etiology

• hyperlipidemia
• hyperproteinemia
• hypercalcemia

Indications

• true hyponatremia (low serum osmolality)

Laboratory

• serum sodium is low
• serum triglycerides may be high
• serum protein may be high
• serum osmolality is normal

More general terms

• sign/symptom