Electrolyte Free Water Clearance

  • Published on
    07-May-2015

  • View
    17.347

  • Download
    2

Embed Size (px)

DESCRIPTION

this is an 18 slide subset of the way too long lecture on sodium called Hyponatremia Dreadnaught

Transcript

<ul><li>1.True hyponatremia <ul><li>Hyponatremia occurs when water intake exceeds water excretion. </li></ul></li></ul> <p>2. True hyponatremia </p> <ul><li>Hyponatremia does not occur when sodium excretion exceeds sodium intake. </li></ul> <p>Negative salt balancecauses hypovolemia 3. </p> <ul><li>If a person drinks more water than the kidney is capable of clearing the excess water will dilute the plasma. </li></ul> <p>Causes of hyponatremia: Increased intake </p> <ul><li>To exceed the maximal renal clearance of water an adult needs to drink about 18 liters a day. </li></ul> <p>clearing 4. Water clearance </p> <ul><li>Clearance as a general concept: </li></ul> <ul><li><ul><li>The clearance of any substance is the volume of blood cleared of that substance in a set unit of time. </li></ul></li></ul> <ul><li>Water clearance </li></ul> <ul><li><ul><li>Total water clearance is equal to urine output. Not a useful concept. </li></ul></li></ul> <p>5. Free water clearance and soup </p> <ul><li>Imagine urine divided into two components </li></ul> <ul><li><ul><li>A solute component containing all of the solute at the same osmolality as plasma. </li></ul></li></ul> <ul><li><ul><li><ul><li>Loss of this component does not change plasma osmolality </li></ul></li></ul></li></ul> <ul><li><ul><li><ul><li>Ladle of soup </li></ul></li></ul></li></ul> <ul><li><ul><li>A free water component providing the balance of the volume. </li></ul></li></ul> <ul><li><ul><li><ul><li>Loss of thissolute freewater will change serum osmolality. </li></ul></li></ul></li></ul> <ul><li><ul><li><ul><li>Boiling off water from soup </li></ul></li></ul></li></ul> <p>In regards to sodium all that matters is the free water component 6. Free water clearance 0.5 liter free water Solute component(plasma osmolality 284 mOsm/kg) Use clearance to calculate the osmolar clearance 1 liter 142 mOsm/Kg 0.5 liter 284 mOsm/Kg 7. Free water clearance Solute component(Solute Clearance) ? 0.5 liter Zero mOsm/Kg Free water component(Free water Clearance) The free water component equals urine volume minus the solute component 1 liter 142 mOsm/Kg 0.5 liter 284 mOsm/Kg 8. Free water clearance 0.5 liter 568 mOsm/Kg 1 liter 284 mOsm/Kg -0.5 liter 568 mOsm/Kg 9. Free water clearance Solute component(plasma osmolality 284 mOsm/kg) Use clearance to calculate the osmolar clearance 1 liter 284 mOsm/Kg 0.5 liter 568 mOsm/Kg 10. Free water clearance Solute component(Solute Clearance) ? Free water component(Free water Clearance) 0.5 liter 568 mOsm/Kg 0.5 liter Zero mOsm/Kg 1 liter 284 mOsm/Kg 11. Free water clearance: Implications Dilute urine increases serum osmolality Concentrated urine de-creases serum osmolality Dilute urine Solute free water Concentrated urine Negative free water Na + Na + 12. Free water clearance: The math 13. Free water clearance: Math Examples 14. Electrolyte free water clearance </p> <ul><li>Osmolality doesnt cause problems, rather tonicity causes changes in cell volume which cause clinical syndromes. </li></ul> <ul><li>So free water clearance must be refined to measure clinically significant changes in tonicity. </li></ul> <p>15. Electrolyte free water clearance </p> <ul><li>Osmotically active particles (those that contribute to tonicity): </li></ul> <ul><li><ul><li>Sodium </li></ul></li></ul> <ul><li><ul><li>Potassium </li></ul></li></ul> <ul><li><ul><li>Albumin, calcium and others </li></ul></li></ul> <ul><li>Sodium is the dominant osmotically active solute of serum to the point that others can be ignored. </li></ul> <ul><li>Urine has a significant potassium content so in urine sodium and potassium are equal partners in determining urinary tonicity. </li></ul> <p>16. Electrolyte free water clearance </p> <ul><li>Convert the free water clearance calculation to electrolyte free water clearance </li></ul> <ul><li><ul><li>Substitute urine osmolality with the sum urine Na + K </li></ul></li></ul> <ul><li><ul><li>Substitute serum osmolality with serum sodium </li></ul></li></ul> <p>Free water clearance Electrolyte free water clearance 17. Electrolyte free water clearance: CHF vs. SIADH </p> <ul><li>Heart Failure </li></ul> <ul><li><ul><li>Urine Osmolality: 800 </li></ul></li></ul> <ul><li><ul><li>Serum Osmolality: 270 </li></ul></li></ul> <ul><li><ul><li>Urine Volume: 800 </li></ul></li></ul> <ul><li><ul><li>Urine Na: 5 </li></ul></li></ul> <ul><li><ul><li>Urine K: 40 </li></ul></li></ul> <ul><li><ul><li>Serum Na: 125 </li></ul></li></ul> <ul><li>SIADH </li></ul> <ul><li><ul><li>Urine Osmolality: 800 </li></ul></li></ul> <ul><li><ul><li>Serum Osmolality: 270 </li></ul></li></ul> <ul><li><ul><li>Urine Volume: 800 </li></ul></li></ul> <ul><li><ul><li>Urine Na: 125 </li></ul></li></ul> <ul><li><ul><li>Urine K: 40 </li></ul></li></ul> <ul><li><ul><li>Serum Na: 125 </li></ul></li></ul> <p>18. Etiology of hyponatremia </p> <ul><li>Hyponatremia occurs when water intake exceeds water excretion. </li></ul> <ul><li>Hyponatremia occurs when water intake exceeds electrolyte free water clearance. </li></ul> <p>Ingestion &gt; EFW clearance </p>