1. Disorders of water balance

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 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 Water output
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.
Edema is not a special disease, it’s just a symptom that occurs in some other disease.

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
Increased capillary permeability leads to the leakage of proteins from C into interstitial compartment.

19. Obstruction to lymph flow
Malignant obstruction of lymphatic structures
Surgical removal of lymph nodes
Lymphatic vessels take excessive fluid in the interstitial compartment back to blood vascular system. Obstruction of these vessels results in excessive fluid retention in the interstitial compartment.

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.
Edema affects cellular metabolism.

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
They refer to an increase or decrease in the ECF resulting from proportionate changes in both sodium and water.

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
Fluid can be lost through the following pathways

27. Manifestations of isotonic fluid volume deficit
Acute weight loss
Compensatory increase in ADH
Decreased extracellular fluid volume
Shock
Symptoms and signs of shock appear, such as increase HR, cold and pale skin, decreased BP.

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
In heart failure, water and sodium retention usually occurs as a compensatory mechanism, which is caused by increased levels of ADH and aldosterone.
In renal failure, GFR decreases.
In hypersteronism, level of aldosterone increases, which may lead to water and sodium retention.
Liver failure often leads to renal dysfunction.

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
excessive administration of sodium-containing

32. Manifestations of isotonic fluid volume excess
Acute weight gain
Increased interstitial fluid volume
Dependent and generalized edema
Increased vascular volume
Increased vascular volume will increase the preload of heart.
Within limits, increased preload results in increased cardiac output due to Frank-starling mechanism.
But long-standing or excessive preload will impair the pumping ability of the heart.

33. Treatment of isotonic fluid volume excess
Sodium-restricted diet
Diuretic therapy is commonly used to increase sodium elimination.
Restricting salt intake and using diuretics to increase sodium elimination.

34. Alterations of sodium concentration

35. Alterations of sodium concentration
Hyponatremia
Hypernatremia
The normal range of sodium concentration in plasma is between

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)
Excessive sodium losses may occur through the following pathways.

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
Laboratory Values
Serum sodium level below 135 mmol/L
Decreased serum osmolality
In hyponatremia, because of decreased osmolality in ECF, water moves into cells from EC compartment. Excessive water in brain cells and neuromuscular tissue can lead to the following symptoms and signs.

41. Treatment of hyponatremia
water intoxication
Limit water intake
Administer diuretics
sodium deficiency
Administer saline solution orally or intravenously
limiting water intake and administering diuretics to increase water elimination, when hyponatremia is caused by water intoxication.
Administering saline solution orally or intravenously, when hyponatremia is caused by sodium deficiency.

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
Increased osmolality in ECF stimulates thirst , promotes the release of ADH and results in water movement out of the cells into ECF.