Hyponatremia and Sodium Handling By Brent Lee Lechner
Hyponatremia and Sodium Handling By Brent Lee Lechner, DO MAJ, MC, USA
Basic Concepts in Urine Evaluation • U Na+ reflects renal perfusion independent of S Na+: – Low U Na+ (<10 to 20 m. Eq/L) • Renal Perfusion is decreased • Possible Tubular defect – High U Na+ (>20 m. Eq/L) • Renal Perfusion is increased or normal • Defect in tubule reabsorption – So: If U Na+ elevated in clinical circumstance when renal blood flow is expected : Identify renal reabsorption defective.
Basic Concepts in Urine Evaluation • U OSM reflects H 20 removal from tubule fluid: – Normal U OSM (200 -1200 m. Osm/L) – SG in urine 1. 010 = U OSM 300 m. Om/L – U OSM > 1. 5 X S OSM: ADH must be acting on collecting duct – irrespective of S OSM – Physiologic stimuli for ADH release • Increase S OSM/ S Na+ • Decrease intravascular volume – If U OSM/S OSM > 1. 5 without increased S OSM or decreased intravascular volume – ADH secretion is non-physiologic – irrespective of urine volume.
Clinical Utilization of U Na and U OSM Increased Weight U Na U OSM Decreased Weight Hypoalbuminema Nephrosis/Cirrhosis AGN <10 >500 Dehydration/Volume Depletion Acute Volume expansion <10 <300 Diabetes Insipidus >50 <= 300 Adrenal Insufficiency Cystic Fibrosis Water Intoxication Excess IV Fluid Acute Renal Failure Sepsis, Shock, Nephrotoxin Salt-losing Nephropathy Interstitial Npehritis/Cystic Dz/ Urinary Tract Obstruction Non-Physiologic ADH >500 DKA Osmotic Diuretics
Case Series Change in Weight Na Decreased 125 Increased 125 Decreased 125 K 4. 5 7. 5 5. 0 6. 2 4. 5 6. 1 Serum Osm Glucose BUN/Cr 255 90 40/0. 5 255 40 40/1. 2 250 90 40/1. 0 285 450 40/1. 0 250 90 5/0. 5 285 90 90/4. 5 Urine Na Osm <10 750 60 550 <10 400 50 450 60 800 60 260
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