Disorders of Water Balance Hypo/Hypernatremia

1. Disorders of Water BalanceHypo/Hypernatremia

2. Water-drinking contestants say they weren't told of health risks From Associated Press7:18 PM PST, January 15, 2007 SACRAMENTO (AP) -- Two people who competed in a radio station's water drinking contest with a 28-year-old mother of three who later died said they were never warned they were putting their health at risk, a newspaper reported Monday.Gina Sherrod said that family members listening in on KDND-FM's "Hold Your Wee for a Wii" contest told her that a nurse called into the program to warn that drinking too much water was dangerous, but that she did not worry until she learned of Jennifer Lea Strange's death.

3. Outline • Hyponatremia: Physiology, differential, treatment. Case. • Hypernatremia. Physiology, differential, treatment. • Case

4. Question • How is water balance achieved in the face of increased water intake? • By the excretion of dilute urine.

5. Changes in Urinary Volume and Osmolality along the Nephron

6. Defense against hyponatremia

8. Control of Serum Na

9. Retain 1L Water

10. Serum Na Falls by 5meq/l

11. Decreases Vasopression Release

12. Approach to the hyponatremic patient

13. Hyponatremia with high or Nml Osmolality • TRANSLOCATION • GLUCOSE • MANNITOL • GLYCINE • MALTOSE • PSEUDOHYPONATRE • PROTEIN • LIPIDS

14. Pseudohyponatremia • Normally serum is 93%water and 7% lipids. • If non aqueous portion of serum rose to 20% • Serum measured Na would be: • 150x0.8=120 as opposed to 150x0.93

15. Pseudohyponatremia

16. Approach to the hyponatremic patient with Low plasma osm

17. Low Solute intake Urine flow= urinary solute excretion urinary osmolality

18. Sources of urinary solutes

20. Psychogenic Polydipsia • Usually acute • Common in institutionalized schizophrenics • Abnormal weight gains (as much as 10%) • Episodic symptoms that resolve with water restriction

22. Beer Potomania • Large intake of fluid with beer as sole source of nutrition • Beer sodium content <2meq/L • Beer Potassium content 10-12meq/L

23. Beer Potomania • Assume Beer consumption of 5L • Na intake 10mM • K intake 50mM • Obligatory urea excre 80mM • V=Soluteexcretion 5=200 • Uosm 40

24. Approach to the hyponatremic patient with low plasma osm

27. Diuretic Induced Hyponatremia • Thiazides block diluting segment • May appear euvolemic • Most common in small elderly women • Associated with increased water intake and low protein intake

30. Hyponatremia in Edematous disorders • Reflects advanced disease and poor prognosis • Decreased delivery to diluting sites • Increased vasopressin levels • Increased AQP2 expression

32. Cerebral Salt wasting • Most common in subarachnoid hemorrhage • Increased ANP and BNP • Loss of sodium, volume depletion which then leads to increased ADH. • Different from SIADH as volume depleted. • Treat with saline

36. Hyponatremia and SSRIs • Four fold higher incidence than non users • First 2 weeks • More common in elderly • Not related to drug levels

40. Features of SIADH • Clinically euvolemic • Uosm>100mosm • Una=Na intake usually >20meq/L • Low bun and Uric acid

41. Malignancies and SIADH • Most common with small cell lung ca (10-15%) • mRNA for AVP in tumor • Head and neck tumors • Other isolated cases

43. Treatment of Hyponatremia

44. Treatment of Hyponatremia • Three key Questions • How long has the hyponatremia been present? • Does the patient have symptoms? • Does the patient have risk factors for the development of neurologic complications?

45. Duration of Hyponatremia acute • <48hrs • Severe brain edema • Rapid correction is well tolerated • BUT WHEN IN DOUBT…Treat as chronic

47. SXS of Hyponatremia • Seizures • Herniation • Coma • Respiratory depression • death

48. Patients at increased risk for neurologic complications • Post op menstruant females • Elderly women on HCTZ • Children • Hypoxemic patients • Psychogenic polydipsia

49. Duration of Hyponatremia Chronic • 48hrs or unknown duration • Mild cerebral edema <10% • Sensitive to correction