1. Dr. Simon Prince, FACP, FASN Assistant Professor of Medicine NYU School of Medicine North Shore Nephrology Hyponatremia

2. Sodium The problems with sodium has little to do with direct effects of the ion. Disregulation of sodium causes changes in cell volume. WATER PROBLEM

3. OSMOSIS

4. Why we care about osmolality Alterations in cell size disrupt tissue function.

5. Sodium is an indicator of osmolality The clinically important variable is tonicity .

17. AD ds H ydration to the body. ADH Osmolality

18. ADH is normally used to regulate osmolality We start with an increase in the plasma osmolality This is detected by the brain The brain releases ADH ADH acts on the kidney The kidney reacts by retaining water and producing a small amount of concentrated urine. The retained water goes here not here

19. Clinical Approach

20. What Studies Are Needed?

33. The problem with compensation The starting point is after compensation has reduced the amount of intracellular solute and the ICP Now, an over-eager intern sees the low sodium and starts an infusion of 3% NaCl to raise the sodium to normal. Sodium 108 Sodium 134 The sodium draws water from the inside of the cells causing the brain to shrivel.

37. CASE REPORTS