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Water, Sodium, Potassium The Balance

Water, Sodium, Potassium The Balance. Douglas A. Stahura D.O. 8/29/2002. GOALS. Learner should be able to define: body fluid compartment components diffusion, osmosis hydrostatic pressure, oncotic pressure Learner should be able to describe: Water regulation Volume regulation. GOALS.

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Water, Sodium, Potassium The Balance

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  1. Water, Sodium, PotassiumThe Balance Douglas A. Stahura D.O. 8/29/2002

  2. GOALS • Learner should be able to define: • body fluid compartment components • diffusion, osmosis • hydrostatic pressure, oncotic pressure • Learner should be able to describe: • Water regulation • Volume regulation

  3. GOALS • Learner should be able to identify disorders and causes using history, physical, laboratory data: • Hypo/Hypernatremia

  4. Why do you Care? • Most common disorder of electrolytes in hospitalized patients = hyponatremia • Responsible for delirium/change in mental status, seizure activity • Life-threatening arrythmias • Commonly seen in DKA (diabetic ketoacidosis)

  5. Body Water • Adult is 60% water by weight • Intracellular 2/3rds (40%) • Extracellular 1/3rd (20%) • Plasma (5%) • Interstitial (15%)

  6. Electrolytes • Intravascular • Na+, Cl-, HCO3- • Interstitial • Na+, Cl- , HCO3- • Intracellular • K+ , PO43- , Proteins

  7. Transcellular Transport • Passive • diffusion • co-transport • Active • ion pumps-requires energy (ATP)

  8. Osmosis • Movement of WATER between two compartments • Osmotic pressure - particles • Osmolarity – milliosmoles of SOLUTE per Liter • Norm 275-295 mOsm/L

  9. Fluid Shifts • Hydrostatic and Oncotic pressures in balance

  10. Definitions • Na+ normal 135-145 meq/L • Osmolality normal 275-285 meq/L • Estimated serum osmolality: • 2xNa+ + Glucose/18 • Dehydration - loss of “free water”, I.e. sweat • Hypotonic - loss of water and Na+ in equal proportion

  11. Case #1 • You are hungry, and eat a bag of Salt ‘n Vinegar chips, 3 dill pickles, and two egg rolls smothered in soy sauce. You wash it down with a ham sandwich. • What are the effects on osmolality? • How does the body respond? • You feel thirsty, and in the morning, bloated

  12. Regulation of Water Balance • Osmoreceptors in Hypothalmus can sense a change of 1 mOsm/L • Brain responds with • Thirst • ADH (Anti diuretic hormone) • ADH • adds water channels to cortical collecting ducts of kidney • Release stimulated by stress, nausea, nicotine, morphine

  13. Case #2 • A 72 y/o AAM presents from XYZ Nursing Home with Hx of CVA, dementia presents with “change in mental status” He is afebrile, BP 120/70, P-110, R-18. His UA is cloudy, dark, +nitrites, +bacteria. Na+ = 169. • What is his ADH level? • What is his volume status?

  14. Regulation of Volume • Sensors: • body senses pressure/stretch • Circulation: carotid bodies, Right Atrium • Kidney: afferent arteriole • Effectors: • Circulation: Sympathetic Nervous system • Kidney: Renin-Angiotensin-Aldosterone

  15. Regulation of Volume • Sympathetic Nervous system • “Increased Sympathetic Tone” • Venous constriction • Increased Myocardial contractility/Heart Rate • Arteriolar constriction • e.g. Standing from a seated position

  16. Regulation of Volume • Adrenal hormone (aldosterone) helps regulate Volume through effects on Sodium and Potassium. (Mineralocorticoid) • Aldosterone: • Increases Na+ reabsorption, K+ excretion distal nephron • Stimulated by: • Decreased renal perfusion • Decreased Na+ delivery to distal tubules

  17. Renin-Angiotensin-Aldosterone

  18. Case #3 • An 85 y/o WF with Hx of CHF and Ejection Fraction of 20% eats the same meal you had the night before! • How will she present in the ED? • Describe the osmolal regulation. • Describe the Volume regulation.

  19. Case #4 • A 37 y/o woman seen after several days of severe diarrhea and poor oral intake. PE shows moderate to severe volume depletion. Lab data: • Na+ = 142; K+ = 3.7. • CL- = 114; HCO3- = 8. • pH = 7.22; Urine (Na+) = 4. • What is the acid-base status? • Review signs of volume depletion.

  20. Summary of Osmolality vs Volume • Osmolality is ratio of solutes to water • Volume determined by absolute amount of Na+ • Exercising on a hot day leads to loss of dilute fluid as sweat. The net effect is a risein the plasma osmolality and Na+ concentration but a fall in extracellular volume.

  21. Hypernatremia • In the presence of a normal thirst mechanism and access to water, is uncommon. • DDx: • Diabetes insipidus (Central/Nephrogenic) • Risk Factors: • age (infant/elderly) • disability(intubated/post-op/MRDD/CVA)

  22. Case #5 • 63 y/o AAM hx of Cerebral Palsy, presents with GI bleed. Intubated, bleeding stopped, Hbg = 11 and stable. At 1400 on hospital day 4 begins producing 400cc/hr of dilute urine. At 1800 BP 80/40. NS 500cc bolus given. • What will happen to his Na+? • What is the diagnosis?

  23. Diabetes Insipidus • Disease of water regulation • Central - lack of secretion of ADH • Nephrogenic - lack of response by kidney to ADH • Will result in increased sodium

  24. Hyponatremia • Hyperosmotic • Hyperglycemia • Mannitol • Isoosmotic • Hyperlidemia • Hyperproteinemia • Hypoosmotic: most frequent • Primary Na+ loss • Primary water gain • Primary Na+ gain exceeded by water gain

  25. Work-Up of Hyponatremia • Labs: • Posm • Uosm • UNA

  26. Iso-osmotic Hyponatremia

  27. Case #6 • A 40 y/o women is admitted to the hospital for elective uterine ablation for dysfunctional bleeding unresponsive to medical therapy. She is otherwise in excellent health, and takes no medications. On admission, weight = 60 kg, P-72, RR-12, BP-140/76. • The procedure is uneventful. Estimated blood loss 400ml. After 3 hours of anesthesia, she awakens with headache, nausea, vomiting. HCT has fallen from 37% to 24%. Na+ fallen from 140 to 100. • What is the most likely cause for this hyponatremia? • Severe hyperglycemia • Sorbitol administration • Severe hyperglobulinemia • Diuretic induced hyponatremia.

  28. Bladder Irrigation with Sorbitol • This patient was irrigated with 16L of Sorbitol 3%. She produced 11L of urine outflow during that time. Additionally, she was treated with aqueous vasopressin(DDAVP) for persistent bleeding.

  29. Case # 7 • 60 y/o Female, hospital day 3 • Na+=118, K+=4.5, Cl-=88, HCO3-=22 • Bun=5, Cr=0.5 • Pt has myoclonus • Sosm=244, Uosm=255, UNa=92 • TSH=3, Cortisol=0.9, Stim test: @ 30 min = 10

  30. Case #7 • Conclusion: Adrenal Insufficiency • Tx: • Hydrocortisone replacement • Hypertonic saline (3% = 512Meq/L), replace to sodium of 120-125

  31. Summary • Reviewed basic definitions and concepts • body fluids, osmolality, transport • Reviewed Hormonal water and Volume regulation • Reviewed examples of hypo/hyper natremia

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