Disorders of water and sodium balance

1. Disorders of water and sodium balance Zhao Chenghai Pathophysiology

2. Outline • Introduction of water and sodium balance • Edema • Alterations in isotonic fluid volume • isotonic fluid volume deficit • isotonic fluid volume excess • Alterations in sodium concentration • hyponatremia • hypernatremia

3. Introduction of water and sodium balance

4. Water and sodium balance • Total fluid volume and distribution • Body fluid composition • Osmolality of the body fluid • Water balance • Mechanisms of regulation of body fluid and sodium balance

5. Total fluid volume and distribution • Total body fluid accounts for 60% of body mass in males. • Total body fluid is mainly distributed in intracellular and extracellular compartments • Intracellular fluid ( ICF) : 40% • Extracellular fluid (ECF): 20% • Interstitial fluid: 15% • Plasma: 5%

6. Body fluid composition • The ICF is separated from the ECF by a selective cell membrane that is only permeable to a limited number of substances such as water, oxygen and carbon dioxide, but not to most of the electrolytes in the body. • The concentration of ions in the interstitial fluid and plasma are considered to be equal except for protein.

7. Osmolality of the body fluid • The total osmolality is almost equal among plasma, the interstitial and intracellular fluids with a range from 280-310 mOsm/L, due to a free permeability of cell membrane to water. • Nearly 80% of the osmolality of plasma and the interstitial fluid is induced by sodium and chloride ions. And approximately half of the intracellular osmolality is caused by potassium.

8. Water balance • Water intake • Ingestion in the form of liquid and water in food: 2100ml/day • Metabolism in the body following the oxidation of carbohydrates: 300ml/day • Water output • Insensible evaporation from respiratory tract and through the skin: 700ml/day • Sweating: 100ml/day • Feces: small amount • Urine: 1500ml/day

9. Mechanisms of regulation of body fluid and electrolyte balance • Sensation of thirst • Antidiuretic hormone (ADH) • Renin-angiotensin-aldosterone system • Atrial natriuretic peptide (ANP)

10. ADH • Main target sites: distal tubules and collecting ducts in kidney • Function: to Promote the water reabsorption and cause increased ECF volume and decreased urinary output. • Stimulating factors: • Blood pressure↓ • Plasma osmolality↑ • Blood volume ↓

11. Renin-angiotensin-aldosterone system Arterial pressure ↓ Plasma sodium content↓ Sympathetic nerve ↑ Arterial pressure↑ ECF volume ↑ Glomerulus (juxtaglomerular cells) Renal retention of sodium Increase potassium secretion renin Angiotensin I Angiotensin II Adrenal gland aldosterone Angiotensin converting enzyme

12. ANP • ANP is a hormone produced by specific cells of cardiac atrim in response to blood volume expansion. • Function: ANP inhibits the reabsorption of sodium and water by the renal tubules, which in turn increases urinary excretion and helps to return blood volume back toward normal. • ANP exerts a negative regulation against ADH in the central nervous system.

13. Edema

14. Definition of edema • Edema can be defined as palpable swelling produced by expansion of the interstitial fluid volume. • Edema is caused by excessive fluid in the interstitial compartment.

15. Causes and pathogenesis of edema • Increased capillary filtration pressure • Decreased capillary colloidal osmotic pressure • Increased capillary permeability • Obstruction to lymph flow

16. Increased capillary filtration pressure • Increased vascular volume • heart failure • kidney disease • pregnancy • Venous obstruction • liver disease with portal vein obstruction • venous thrombosis

17. Decreased capillary colloidal osmotic pressure • Increased loss of plasma proteins • protein-losing kidney diseases • extensive burns • Decreased production of plasma proteins • liver disease • starvation • malnutrition

18. Increased capillary permeability • Inflammation • Allergic reaction • Malignancy • Tissue injury and burns

19. Obstruction to lymph flow • Malignant obstruction of lymphatic structures • Surgical removal of lymph nodes

20. Manifestations of edema • Life threatening in some locations, such as brain, larynx, lungs. • Interfering with movement and limiting joint motion. • Increasing the distance for diffusion of oxygen, nutrients and wastes at the tissue level.

21. Treatment of edema • Correcting or controlling the cause , and preventing tissue injury • Diuretic therapy • Elastic support stockings and sleeves for patients with lymphatic or venous obstruction • Administering albumin intravenously to raise the colloidal osmotic pressure when edema is caused by hypoalbuminemia.

22. Alterations in isotonic fluid volume

23. Alterations in isotonic fluid volume • Isotonic fluid volume disorders represent an expansion or contraction of the ECF brought about by proportionate changes in both sodium and water. • Two types: • Isotonic fluid volume deficit • Isotonic fluid volume excess

24. Isotonic fluid volume deficit • Definition: Isotonic fluid volume deficit results when water and sodium are lost in isotonic proportions • Causes: • Inadequate fluid intake • Excessive fluid losses

25. Inadequate fluid intake • Oral trauma or inability to swallow • Inability to obtain fluids • Impaired thirst sensation • Therapeutic withholding of fluids • Unconsciousness or inability to express thirst

26. Excessive fluid losses • Excessive gastrointestinal fluid losses vomiting, diarrhea, gastrointestinal suction • Excessive renal losses diuretic therapy, osmotic diuresis, adrenal insufficiency • Excessive skin losses fever, exposure to hot environment, burns and wounds that remove skin • Third-space losses intestinal obstruction, edema, ascites

27. Manifestations of isotonic fluid volume deficit • Acute weight loss • Compensatory increase in ADH • Decreased extracellular fluid volume Shock

28. Treatment of isotonic fluid volume deficit • Treating the underlying causes • Using isotonic electrolyte solutions for replacement.

29. Isotonic fluid volume excess • Definition: It represents an isotonic expansion of the extracellular fluid compartment. Water and sodium are increased in isotonic proportions. • Causes: • Inadequate sodium and water elimination • Excessive sodium and water intake

30. Inadequate sodium and water elimination • Congestive heart failure • Renal failure • Hyperaldosteronism • Liver failure

31. Excessive sodium and water intake • Excessive sodium intake Food, sodium containing medications or fluid • Excessive fluid intake • ingestion of fluid in excess of output • administration of fluids or blood at an excessive rate

32. Manifestations of isotonic fluid volume excess • Acute weight gain • Increased interstitial fluid volume • Dependent and generalized edema • Increased vascular volume

33. Treatment of isotonic fluid volume excess • Sodium-restricted diet • Diuretic therapy is commonly used to increase sodium elimination.

34. Alterations of sodium concentration

35. Alterations of sodium concentration • Hyponatremia • Hypernatremia

36. Hyponatremia • Definition Hyponatremia represents a decrease in plasma sodium concentration below 135 mmol/L.

37. Causes of hyponatremia • Excessive sodium losses and replacement with sodium-free water • Excessive water intake in relation to output

38. Excessive sodium losses and replacement with sodium-free water • Exercise- or heat-induced sweating • Gastrointestinal losses • Renal losses (some chronic renal diseases)

39. Excessive Water Intake in Relation to Output • Excessive administration of sodium-free solutions • Repeated irrigation of body cavities with sodium-free solutions • Irrigation of gastrointestinal tube with distilled water • Kidney disorders that impair water elimination • Increased ADH level

40. Manifestations of hyponatremia • Signs Related to Hypo-osmolality of Extracellular Fluids and Movement of Water Into Brain Cells and Neuromuscular Tissue Muscle cramps, Weakness, Headache, Depression, Personality changes, Lethargy and coma • Gastrointestinal Manifestations Anorexia, nausea, vomiting, Abdominal cramps, diarrhea

41. Treatment of hyponatremia • water intoxication • Limit water intake • Administer diuretics • sodium deficiency • Administer saline solution orally or intravenously

42. Hypernatremia • Definition Hypernatremia implies a plasma sodium level above 145 mmol/L.

43. Causes of hypernatremia • Excessive Water Losses • Decreased Water Intake • Excessive Sodium Intake

44. Excessive water losses • Watery diarrhea • Excessive sweating • Hyperventilation • Decrease level of ADH

45. Decreased Water Intake • Unavailability of water • Oral trauma or inability to swallow • Impaired thirst sensation • Withholding water for therapeutic reasons • Unconsciousness or inability to express thirst

46. Excessive Sodium Intake • Rapid or excessive administration of sodium-containing solutions

47. Manifestations of hypernatremia • Thirst and signs of increased ADH levels Oliguria or anuria • Intracellular dehydration • Dry skin and mucous membranes • tongue rough and fissured • decreased salivation • Signs related to hyperosmolality of ECF and movement of water out of brain cells • Headache, agitation and restlessness, seizure and coma

48. Treatment of hypernatremia • Treating the underlying causes of the disorder • Fluid replacement therapy to treat the accompanying dehydration.

49. Today you learned: • How to regulate the normal water and sodium balance? • Definition, causes, manifestations and treatment of the following pathological conditions • Edema • Isotonic fluid volume deficit • Isotonic fluid volume excess • Hyponatremia • hypernatremia