Renal Physiology (VII) - Volume Regulation

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by dr Mohammed Abel Gawad (drgawad@gmail.com): Nephrology Specialist at Kidney & Urology Center - Alexandria - Egypt. website: www.nephrotube.blogspot.com

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Renal Physiology (VII) - Volume Regulation

  1. 1. 1RENAL PHYSIOLOGY (VII) mVOLUME REGULATION Mohammed Abdel Gawad
  2. 2. OBJECTIVES2  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  3. 3. OBJECTIVES3  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  4. 4. TBW is affected by: Gender and Age4
  5. 5. Total body water Compartments5
  6. 6. Intravascular Compartment6
  7. 7. Intravascular Compartment7
  8. 8. Electrolytes and Non-Electrolytes dissolved in the TBW8
  9. 9. Total body water Compartments
  10. 10. Osmolality is the number of particles (mmol) contained in one liter of water, so measured in mmol/L. i.e. it is the concentration by number
  11. 11. Water, Electrolytes & Non-Electrolytes Distribution (1)11
  12. 12. Water, Electrolytes & Non-Electrolytes Distribution (2)12
  13. 13. Osmolality of all three compartments13  Osmolality of all three compartments is the same, because water is able to move freely among all three compartments
  14. 14. OBJECTIVES14  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  15. 15. Movement of water – Starling’s Forces15 The amount of water in each body compartment is dependent on:  1- osmotic pressure  2- hydrostatic pressure (filtration)  + 3- Membrane characteristics
  16. 16. Osmolality is the number of particles (mmol) contained in one liter of water, so measured in mmol/L. i.e. it is the concentration by number
  17. 17. Starling’s Forces – Osmotic pressure17
  18. 18. Starling’s Forces – Osmotic pressure18
  19. 19. Starling’s Forces – Hydrostatic pressure19
  20. 20. Membrane Factors20  Membrane permeability (s) is clinically relevant in disorders which disrupt membrane integrity (e.g., sepsis).
  21. 21. Body Fluid Exchange21  1- Osmosis  2- Filtration  3- Diffusion (the most important)
  22. 22. OBJECTIVES22  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  23. 23. Effective Circulating Volume23
  24. 24. Effective Circulating Volume: Plasma Volume24
  25. 25. Effective Circulating Volume: Plasma Volume25
  26. 26. Effective Circulating Volume: Blood Pressure26
  27. 27. OBJECTIVES27  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  28. 28. Volume Regulation General Concept28 1 → 2 → 3
  29. 29. Volume Regulation General Concept29 1 → 2 → 3
  30. 30. Volume Regulation General Concept: 1- Monitoring30
  31. 31. Volume Regulation General Concept31 1 → 2 → 3
  32. 32. Volume Regulation General Concept: 2- Signaling32 • Renin-angiotensin II-aldosterone and sympathetic activity are the primary signals of volume regulation; these signals are activated together. • ADH is only employed when volume is extremely low i.e. secondary line. • If ADH is active, then renin-angiotensin II-aldosterone and sympathetic activation are already engaged.
  33. 33. Volume Regulation General Concept: 2- Signaling - RAAS33
  34. 34. Volume Regulation General Concept34 1 → 2 → 3
  35. 35. Volume Regulation General Concept: 3- Action at Targets35
  36. 36. Volume Regulation General Concept: 3- Action at Targets – Angiotensin II36 Angiotensin II is the most potent vasoconstrictor in the body
  37. 37. Volume Regulation General Concept: 3- Action at Targets – Aldosterone37 The effect of aldosterone on sodium reabsorption is so powerful that it can reduce the urine sodium concentration to as low as 1 mEq/L
  38. 38. Volume Regulation General Concept: 3- Action at Targets – Aldosterone38
  39. 39. Volume Regulation General Concept: 3- Action at Targets – Aldosterone39 Aldosterone Overview•An increase in the plasma potassium concentration of 0.1 mEq/L is enough to stimulatethe release of aldosterone.• Although aldosterone release is not affected by acid-base disorders, aldosterone playsan important role in the generation and maintenance of many acid-base disorders.•Increased aldosterone activity results in metabolic alkalosis and decreased activityresults in metabolic acidosis (type 4 RTA).
  40. 40. Volume RegulationGeneral Concept: 3- Action at Targets – Sympathetic Activity40
  41. 41. Volume Regulation General Concept: 3- Action at Targets – ADH41•ADH is only released when a substantial (10-15 mmHg) fall in blood pressure occurs.•Although it is an emergency defense, ADH is not a very effective defense againsthypovolemia. Because water distributes among all three body water compartments,water resorption at the collecting tubules causes only a minimal rise in plasma volume.•The primary function of ADH is the regulation of plasma osmolality.
  42. 42. Volume Regulation General Concept: Atrial natriuretic peptide42 Atrial natriuretic peptide is the only volume regulatory hormone that decreases effective volume •The physiologic significance of ANP is uncertain. •Although congestive heart failure is associated with volume overload and elevated levels of ANP, the kidney still excretes minimal amounts of sodium. This contradiction is explained by the theory that ANP activity requires a normal blood pressure. •Since CHF is typically associated with a lower than normal blood pressure, the effect of ANP is blocked.
  43. 43. OBJECTIVES43  Body water compartments  Electrolytes & Non-Electrolytes distribution  Starling’s forces & Membrane permeability  Effective circulatory volume  Volume regulation (General Concept)  Volume regulation (Clinical Correlation)
  44. 44. Volume Regulation Clinical Correlation44
  45. 45. Volume Regulation Clinical Correlation45 + lymphatic obstruction
  46. 46. Volume Regulation Clinical Correlation46
  47. 47. 47 Follow On www.nephrotube.blogspot.com & Facebook Group NephroTube
  48. 48. 48 Gawad

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