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Water and electrolyte



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it explains the distribution of water in various compartments. how it is balanced in our body or regulated. with its disorders of water metabolism.

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Water and electrolyte

  1. 1. Fluid & Electrolyte Balance Dr . N. Sivaranjani ,MD biochem Asst prof.
  2. 2. 60% of body consists of fluid Intracellular space Extracellular space Distribution of water in different body water compartments depends on the solute content of each compartment Osmolality of the intra and extra-cellular fluid is the same, but there is marked difference in the solute content.Dr. N. Sivaranjani 3
  3. 3. Distribution of Body Water Intravascular Interstitial IntracellularICF ECF Na+ K+ Cl- Essential for normal cell function Provides medium for metabolic processes spaces between cells plasma-arteries, veins, capillaries Cerebrospinal fluid, Pleural spaces, Synovial spaces Peritoneal fluid spaces Transcellular 1 L Dr. N. Sivaranjani 4
  4. 4. Fluid composition varies with body fat, age and gender 75% water ECF=45%,ICF=30% 65% water, ECF= 25%, ICF = 40% Adult female 50% water, ECF=10-15%, ICF=40% fat cells contain little water and lean tissue is rich in water, the more obese the person, the smaller the percentage of total body water.Dr. N. Sivaranjani 5
  5. 5. Human life is suspended in a saline solution having a salt concentration of 0.9% Body fluids must remain fairly constant with regard to amount of H2O & specific electrolytes Primary component of body fluid: Water Women lower % body water than men Total body water decreases with age Dr. N. Sivaranjani 6
  6. 6. How importance is water  Water provides a medium for transporting nutrients to cells and wastes from cells and for transporting substances such as hormones, enzymes, blood platelets, and red and white blood cells  Water facilitates cellular metabolism and proper cellular chemical functioning  Water acts as a solvent for electrolytes and nonelectrolytes  Helps maintain normal body temperature  Facilitates digestion and promotes elimination  Acts as a tissue lubricant  Component in all body cavities [parietal, pleural… fluids] Water is the principal body fluid which is essential for life. Dr. N. Sivaranjani 7
  7. 7. Intake and output of water Factors that Dictate Body Water Requirement 1) Amount needed to give the proper osmotic concentration 2) Amount needed to replace water lost excretion Normal Routes of water gain and loss INTAKE OUTPUTml/day ml/day Exogenous :- Fluid intake 1,500 Food 700 Endogenous :- Metabolism 300 TOTAL 2,500 Insensible loss (skin + lung) 850 Feces 150 Urine (kidney) 1,500 TOTAL 2,500
  8. 8. Dr. N. Sivaranjani 9
  9. 9. Regulation of Body Fluid Compartments Diffusion  Molecules → from an area of ↑ concentration to an area of ↓ concentration Osmosis  is the movement of water through a semipermeable membrane to a higher concentration of solutes. Active Transport  is movement of substance across permeable membrane and gradient; requires energy and pump. Filtration  H2O & dissolved substances → from an area of high hydrostatic pressure to an area of low hydrostatic pressure Dr. N. Sivaranjani 10
  10. 10. Diffusion High Solute Concentration Low Solute Concentration Fluid Solutes Dr. N. Sivaranjani 11
  11. 11. Osmosis Fluid High Solution Concentration, Low Fluid Concentration Low Solute Concentration, High Fluid Concentration Controls body fluid movement between ICF & ECF Dr. N. Sivaranjani 12
  12. 12. Dr. N. Sivaranjani 13
  13. 13. Dr. N. Sivaranjani 14
  14. 14. Osmotic Pressure The amount of hydrostatic pressure required to stop the flow of water by osmosis Osmolality reflects the concentration of fluid that affects the movement of water between fluid compartments by osmosis Dr. N. Sivaranjani 15
  15. 15. Osmolality : Number of osmotically active particles present per kilogram of water. Osmolarity: Number of osmotically active particles present per litre of water. Electrolytes: Electrolytes are substances whose molecules dissociate into ions when placed in solution Ions : An ion is an atom or group of atoms with an electrical charge. Dr. N. Sivaranjani 16
  16. 16.  Normal plasma Osmolality = 285-292 mOsm/kg  Plasma osmolality can be measured directly using the osmometer or indirectly as the concentration of effective osmoles Osmolality =2(Na+) + 2(K+) + Urea + Glucose, mmol/L.  Plasma osmolality (mmol/kg) = 2x Plasma Na+(mmol/l)  Estimated by doubling serum Na concentration  Clinical uses :- diagnosis of disorders of water and electrolyte balance and NKHC Osmolality increases – Hyperglycemia, DKA, NKHC, Hypernatremia with water loss (DI) Decreased – Hyponatremia – water and Na gain (CCF), SIADH.Dr. N. Sivaranjani 17
  17. 17.  The difference in measured osmolality and calculated osmolality called Osmolar Gap. (normal - numerically similar)  Increase in osmotically active substances – Ethanol, Mannitol, neutral and cationic amino acids.  Fractional water content of plasma is reduced – hyperlipidemia or hyperproteinemia . Dr. N. Sivaranjani 18
  18. 18. In a healthy state, the osmotic pressure of ECF, mainly due to Na+ ions, is equal to the osmotic pressure of ICF which is predominantly due to K+ ions Dr. N. Sivaranjani 19
  19. 19. Tonicity - measure of transport of water across the biological system causing change in cell volume. 0.9% Normal SalineDr. N. Sivaranjani 20
  20. 20. 0.9% Normal Saline Dr. N. Sivaranjani 21
  21. 21. (0.45% NS) < concentration of solutes as plasma Causes H2O to move into cells & swell (hemolysis) Dr. N. Sivaranjani 22
  22. 22.  (3% NS)  > concentration of solutes as plasma  Causes H2O to draw out of cell (shrink)  Mannitol –treatment of cerebral edema. Dr. N. Sivaranjani 23
  23. 23. Dr. N. Sivaranjani 24
  24. 24. ELECTROLYTES  Substances whose molecules dissociate into ions (charged particles) when placed into water Cations: positively-charged Anions: negatively-charged  Sodium – major cation of ECF  Chloride - major anion of ECF  Potassium – major cation of ICF  Phosphate – major anion of ICF Dr. N. Sivaranjani 25
  25. 25. ELECTROLYTE Composition Electrolyte Conc Plasma (mEq/L) ICF Sodium, Na+ 142 10 Potassium, K+ 5 150 Calcium, Ca++ 5 2 Magnesium, Mg++ 3 40 (155) Chloride, Cl- 103 2 Bicarbonate, HCO3 - 27 10 Biphosphate, HPO4 - 2 140 Sulfate, SO4 -2 1 5 Protein 16 40 Organic acids 6 5 (155) Dr. N. Sivaranjani 26
  26. 26. Functions of Electrolytes  Promote neuromuscular irritability  Regulate acid and base balance  Regulate distribution of body fluids among body fluid compartments Dr. N. Sivaranjani 27
  27. 27.  are regulated together  kidneys play a predominant role  major regulatory factors are the hormones - Aldosterone, ADH and Renin angiotensin Atrial natriuretic peptide  Hypothalamic regulation - Stimulates thirst and ADH release  Pituitary regulation - Releases ADH  Adrenal cortical regulation – Releases Aldosterone  Renal regulation - Primary organs for regulating fluid and electrolyte balance Selective reabsorption of water and electrolytes Renal tubules are sites of action of ADH and aldosterone Electrolyte and water balance Dr. N. Sivaranjani 28
  28. 28. Synthesis Action Action on sodium and water Aldosterone secreted by the zona glomerulosa of the adrenal cortex regulates the Na+ → K+ exchange and Na+ → H+ exchange at the renal tubules. Sodium and water retention Anti-Diuretic Hormone (ADH) Under control of hypothalamus, posterior pituitary releases ADH increase the water reabsorption by the renal tubules. Retention of water Renin- Angiotensin System release of renin by the juxtaglomerular cells Angiotensin-II BP by vasoconstriction of the arterioles. It also stimulates aldosterone production Retention of sodium and water Atrial natriuretic peptides stimulation of atrial stretch receptors Inhibit renin and aldosterone secretion – cause elimination of sodium Increases urinary excretion of sodium.Dr. N. Sivaranjani 29
  29. 29. DECREASED FLUID VOLUME Stimulation of thirst center in hypothalamus Increase in thirst ↑ intake of water INCREASES PLASMA OSMOLALITY Dr. N. Sivaranjani 30
  30. 30. Posterior pituitary gland Osmoreceptors in hypothalamus +↑Osmolarity ↑ADH Kidney ↑H2O reabsorption ↑vascular volume and ↓osmolarity Stress, hypoglycaemia, Anesthetic agents, Heat, Nicotine, Antineoplastic agents, Narcotics, Surgery ANTIDIURETIC HORMONE REGULATION MECHANISMS Fluid volume Increase permeability of renal collecting ducts to water by binding to V2 receptors – cause insertion of water channels to luminal membrane
  31. 31. Juxtaglomerular cells↓Serum Sodium ↓Blood volume ↓Blood Pressure ↓renal blood flow Angiotensin I Distal renal tubules Angiotensin II Adrenal Cortex↑Sodium reabsorption (H2O resorbed with sodium) Angiotensinogen in plasmaRENIN Angiotensin- converting enzyme ALDOSTERONE Via vasoconstriction of arterial smooth muscle ALDOSTERONE-RENIN-ANGIOTENSIN SYSTEM Increases Blood Pressure
  32. 32. INCREASED BLOOD VOLUME , INCRESED BLOOD PRESSURE ATRIAL NATRIURETIC PEPTIDE RELEASE Reduces in thirst Decreased intake of water STIMULATION OF ATRIAL STRETCH RECEPTORS Inhibits release of ADH Diuresis – increase urine output Inhibits release of Aldosterone Decreases Na reabsorption Natriuresis – Na excretion
  33. 33. Dr. N. Sivaranjani 34
  34. 34. Volume Disorders 2° Alteration in Sodium Balance ECF Expansion Isotonic Inc N N Water and Na retention – Edema- 2̊ Cardiac failure 2̊ Hyper- aldosteronism due to hypoalbunemia. Hypertonic Inc Dec Inc Na retention due to excess mineralocorticoid – cushing’s syndrome or conn’s syndrome Hypotonic Inc Inc Dec water retention due to ADH excess or Glomerular dysfuncion Volume ECF ICF Conditions Disorder Vol. Vol. Osmolality
  35. 35. ECF Contraction Isotonic Dec N Normal loss of Na & water common cause – loss of GIT fluid SI obstruction, SI fistulae, paralytic ileus Hypertonic Dec Dec Increased water depletion Diarrhea – Commonest cause Diabetes insipidus - rare Hypotonic Dec Inc Decreased sodium depletion infusion of IV fluids with low Na-dextrose aldosterone deficiency- Addison’s disease Volume ECF ICF Conditions Disorder Vol. Vol. Osmolality
  36. 36. • Dehydration • Fluid Overload Dr. N. Sivaranjani 37
  37. 37. Dehydration / water depletion  Pure (tissue) water loss – less common  Depletion of Na and water – more common  and hypovolemia to sodium loss and thus loss of blood volume. Dr. N. Sivaranjani 38
  38. 38. Causes of water depletion :  Decreased intake of water – • Inadequate water supply • Mechanical obstruction for drinking • Impaired response of thirst center – Comatose patient  Increased loss of water – • Increased renal loss of water – RTA, DI • Increased loss of water from skin – Burns, excessive sweating • Increased loss through lungs – hyperventilation • Increased loss of gut – vomiting ,diarrhea Dr. N. Sivaranjani 39
  39. 39. Earliest Detectable Signs  low BP Dry skin and mucous membranes Sunken eye balls, fontanels Circulatory Failure (coolness, mottling of extremities) Loss of skin elasticity Delayed cap refill  lethargy , confusion and coma Dr. N. Sivaranjani 40
  40. 40.  Skin turgor assessment – this assessment can be done on the forearm. Skin that does not flatten immediately after release is called “tenting”, an example of fluid volume deficit.  Dry and cracked lips  Sunken eyes  Thirst and discomfort Dr. N. Sivaranjani 41
  41. 41. Loss of Skin Elasticity due to dehydration Dr. N. Sivaranjani 42
  42. 42. Dr. N. Sivaranjani 43
  43. 43. Manifestations of ECF Deficit (Dehydration) Signs & Symptoms  Weight loss Blood pressure drop Delayed capillary refill Oliguria Sunken fontanel Decreased skin turgor Physiologic Basis Decreased fluid vol. Inadequate circ. Blood Decreased vascular volume Inadequate kidney circ. Decreased fluid volume Decreased interstitial fluid Dr. N. Sivaranjani 44
  44. 44. Degrees of Dehydration Mild Moderate Severe Fluid Vol loss <50ml/kg 50-90ml/kg >100 ml/kg Skin Color Pale Gray Mottled Skin Elasticity Decreased Poor Very Poor M.M. Dry Very Dry Parched U.O. Decreased Oliguria Marked Oliguria BP Normal Normal or lowered Lowered Pulse Normal or Increased Increased Rapid, thready Dr. N. Sivaranjani 45
  45. 45. Biochemical finding :  plasma sodium – increased  urine volume – decreased  urine concentrated Treatment : Aim - Expand ECF volume and improve circulatory and renal function  plenty of water  Treatment of underlying causes  Replacement of fluid deficit – 5% dextrose
  46. 46. Water intoxication / water excess /over hydration  predominant water excess Decrease in serum Na+  Causes : Excessive intake of water  Compulsive drinking of water – psychogenic polydypsia  Excessive administration of fluid through parental route Impaired renal excretion of water  Severe renal failure  SIADH syndrome of inappropriate ADH  Drugs acting as vasopressin agonist Dr. N. Sivaranjani 47
  47. 47. SIADH –  Plasma hypo-osmolality  Normal renal , thyroid, adrenal function  Increased urine Na excretion  Dilutional hyponatremia  Elevated serum ADH Clinical features Behavioral disturbances Confusion Headache Muscle twitching Convulsion Coma
  48. 48. Biochemical finding :  plasma sodium – decreased  decreased plasma osmolality  urine dilated Treatment : Treatment of underlying causes  Fluid restriction SIADH – vasopressin antagonist
  49. 49. 50 Edema the accumulation of fluid within the interstitial space Causes: •increased hydrostatic pressure • venous obstruction, lymphedema, CHF, renal failure •lowered plasma osmotic pressure (protein loss) • liver failure, malnutrition, burns •increased capillary membrane permeability • Inflammation, sepsis Dr. N. Sivaranjani
  50. 50. Dr. N. Sivaranjani 51

Editor's Notes

  • Ostomotic Pressure
    Isotonic (0.9% NS)
    Same concentration of solutes as plasma
  • Hypotonic
  • ×