Subsection c6

1. HYPONATREMIA Subsection c6

2. 51 y/o, F • CC: vomiting

3. HISTORY OF PRESENT ILLNESS

4. PAST MEDICAL/SOCIAL HISTORY • Known hypertensive--- 10 years • Have had bipedal edema amlodipine was discontinued • Telmisartan 40 mg daily for the past month • HCTZ 12.5 daily for the past month

5. PHYSICAL EXAMINATION • Weak-looking, wheelchair-borne • Wt: 50 kg (usual: 53 kg) • Poor skin turgor, dry mouth, tongue and axillae • BP: supne-120/80, sitting: 90/60 (usual 130/80) • CR: supine-90 bpm; sitting-105 bpm • JVP: <5 cm H2O at 45 degrees.

6. REVIEW OF SYSTEMS • UNREMARKABLE

7. LABORATORY TESTS • Hgb=132 mg/dL • WBC=12.5 • Plasma Na=123 mEq/L • Plasma K=3.7 mEq/L • Chloride=71/mEq/L • Urine Na=100mmol/L mEq/L • Uosm=540 mosm/L • hematocrit= 0.35 • Neutrophils= 0.88 • Lymphocyte= 0.12 • BUN= 22mg/dL • Serum Crea= 0.9 mg/dL • Glucose= 98 mg/dL

8. Urinalysis: • Yellow, slightly turbid, pH 6.0, Sp.Gr. 1.020 • (-) Albumin and Sugar • Hyaline cast 5/hpf • Pus cells 10-15/hpf • RBC: 2-5/hpf (not dysmorphic • ABG • Ph =7.3 • CO2 = 35 • HCO3 = 18

9. GUIDE QUESTIONS

10. 1. What is the diagnosis? Basis?

11. APPROACH TO HYPONATREMIA

12. Diagnosis HypovolemichyponatremiaSecondary to VOMITING AND THIAZIDE USE with Urinary tract infection

13. -vomiting

14. HYPOVOLEMIA • 2-day history of vomiting (3 episodes, 50cc/episode) • Has been taking HCTZ daily for 1 month • Orthostatic hypotension • Poor skin turgor, dry mouth, yongue and axillae patient is dehydrated • Low JVP

15. Urinary tract infection • fever, dysuria and urgency • Hyaline cast 5/hpf • Pus cells 10-15/hpf • RBC: 2-5/hpf (not dysmorphic

16. 2. What factors contributed to the development of hyponatremia in the patient?

17. Factors that contributed to hyponatremia • Vomiting and dehydration • HCTZ (Hydrochlorothiazide)

18. 3. Compute for the plasma osmolality and effective plasma osmolality. What is the importance for computing such?

19. OSMOLALITY • Count of the total number of osmotically active particles in a solution • Equal to the sum of the molalities of all the solutes present in that solution • affected by changes in water content

20. EFFECTIVE PLASMA OSMOLALITY • Tonicity • Shift of water through biomembranes produced by osmotically active particles • Effective osmolality determined by restricted solutes • Na= reflection of ECF volume • K= reflection of ICF volume • In the ECF: • Na+ : 145 mEq/L  Major cation • Cl-:105 mEq/L HCO3-:25 mEq/L  Major anions • Ineffective osmoles • Don’t contribute to water shifts • Urea

21. Plasma Osmolality • Serum Na+ = 123 mEq/L • Glucose = 98 mg/dL • BUN = 22 mg/dL • Serum Osmolality • = {Serum Na (mEq/L) x 2} + {Glucose (mg/dL)/18} + {Urea (mg/dL)/2.8} • = {123 mEq/L x 2} + {98 mg/dL ÷ 18} + {22 mg/dL ÷ 2.8} • = 259.30 mOsm/Kg H2O

22. Effective Plasma Osmolality • Effective Plasma Osmolality • = {Serum Na (mEq/L) x 2} • = {123 mEq/L x 2} • = 246 mOsm/Kg H2O  LOW • Normal Plasma Osmolality • 285 – 295 mOsm/Kg H2O

23. Importance • Serum Osmolality • Useful when dealing with patients with an elevated plasma [Glucose] secondary to DM and in patients with CRF whose plasma [Urea] is increased • Investigation of Hyponatremia • Identification of Osmolar gap

24. Hyponatremia • Hypotonic Hyponatremia: < 280 • ECF volume status may be: Low, Normal or High • Isotonic Hyponatremia: 280 – 295 • Very high blood levels of lipid or protein • Pseudohyponatremia • Hypertonic Hyponatremia: > 295 • associated with shifts of fluid due to osmotic pressure • Diabetes Mellitus

25. Osmolar Gap • Measured Osmolality – Calculated Osmolality • If > 10 mmol/L • presence of unmeasured osmotically active substances in the plasma (ethanol, methanol, ethylene glycol, acetone, or isopropyl alcohol)

26. 4. What are the significance of urine osmolality (Uosm) and urine sodium (UNa)?

27. Urine Osmolality • An important test of renal concentrating ability • Identification of disorders of the ADH mechanism • Identification of causes of hyper-or hyponatremia • Reflects the total number of osmotically active particles in the urine, without regard to the size or weight of the particles • Evaluate electrolyte and water balance • Used in work-up for renal disease • Normal Urine Osmolality: 50-1200 mOsm/kg H2O

28. Regualtion of Osmolality • Osmoreceptors • Found in anterolateral hypothalamus • Stimulated by tonicity, effective osmolality, ECF volume • Threshold • 295 mOsm/kg H2O, thirst, suppress AVP • 280-290 mOsm/kg H2O, enhance AVP secretion • AVP/ADH • Stimulates insertion of water channels in basolateral membrane of principal cells in the collecting ducts • Passive water reabsorption

29. In the Patient • Plasma Osmolality • = {Serum Na (mEq/L) x 2} + {Glucose (mg/dL)/18} + {Urea (mg/dL)/2.8} • = {123 mEq/L x 2} + {98 mg/dL ÷ 18} + {22 mg/dL ÷ 2.8} • = 259 mOsm/Kg H2O

30. Urine Osmolality

31. Serum and Urine Osmolality levels • Hyperosmolality • Renal disease • Congestive heart failure • Addison's disease • Dehydration • Diabetes insipidus • Hypercalcemia • Diabetes mellitus/ • hyperglycemia • Hypernatremia • Alcohol ingestion • Mannitol therapy • Azotemia •  Serum and Urine Osmolality Levels • Hypoosmolality • Sodium loss due to diuretic use and a low salt diet • Hyponatremia • Adrenocortical insufficiency • SIADH • Excessive water replacement/ overhydration/water intoxication

32. Normal Value of Urine Sodium:10-40 mEq/L • Higher-than-normal Urine Sodium levels may indicate: • EXCESSIVE SALT INTAKE • Lower-than-normal Urine Sodium levels may indicate: • ALDOSTERONISM • CONGESTIVE HEART FAILURE • DIARRHEA AND DEHYDRATION STATUS • RENAL FAILURE

33. Hyponatremia • Urine sodium <10 mmol/L may indicate Extra-renal Depletion: • Dehydration (gastrointestinal or sweat loss) • Congestive heart failure • Liver disease • Nephrotic syndromes

34. Patient Urine Sodium: 100 mmol/L • Urine sodium >10 mmol/L may indicate: • diuretics, emesis, intrinsic renal diseases, Addison disease, hypothyroidism, or syndrome of inappropriate antidiuretic hormone (SIADH) • In SIADH • Urinary Sodium is usually >20 mmol/L

35. 5. cOMPute for the sodium deficit

36. Sodium Deficit • Target Sodium • = 125 – 135 mEq/L (130 mEq/L) • Sodium Deficit • = 0.6 x weight in kg X (desired Na – actual Na) • = 0.6 x 50 kg x (130 – 123) • = 210 mEq/L

37. 6. What are the the basic principles in the treatment of hyponatremia?

38. Goals of Therapy • Raise the plasma Na+ concentration by restricting water intake and promoting water loss; and • Correct the underlying disorder

39. Mild asymptomatic hyponatremia • requires no treatment • Asymptomatic hyponatremia associated with ECF volume contraction • Na repletion, generally in the form isotonic saline • restoration of euvolemia removes the hemodynamic stimulus for AVP release, allowing the excess free water to be excreted • Hyponatremiaassociated with edematous states • restriction of Na and water intake, correction of hypokalemia, and promotion of water loss in excess of Na • Hyponatremiaassociated with primary polydipsia, renal failure, and SIADH • Water restriction

40. 7. What is the complication of the rapid correction of the hyponatremia?

41. Osmotic Demyelination Syndrome • “central pontine myelinolysis” • Demyelinating lesion in the brain that occurs with overly rapid correction of hyponatremia • Characterized by acute paralysis, dysphagia, and dysarthria • Most common in those with chronic hyponatremia (usually caused by alcoholism)

42. Osmotic Demyelination Syndrome

43. Osmotic Demyelination Syndrome

44. Osmotic Demyelination Syndrome • Prevention: Correction rate=0.5-1.0meq/L/hr, with not more than 12meq/l correction in 24 hrs; should receive no more than 8-10mmol of sodium per day • Management: Supportive • Prognosis is poor

45. 8. What intravenous fluid would you use? At what rate should it be given?

46. INTRAVENOUS FLUID • 0.9% NaCl (contains 154 meq/L) • Correct at a rate in which Na concentration be raised no more than 0.5 – 1 meq/L per hour • 175 meq (sodium deficit) • 175 meq/154 meq/L = 1.14 L • 1140 mL x 15 gtt/min = 8 gtts/min • 24 hrs x 60 min/hr

47. Thank you!