ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES PART 2 Instructor Terry Wiseth - PowerPoint PPT Presentation

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ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES PART 2 Instructor Terry Wiseth PowerPoint Presentation
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ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES PART 2 Instructor Terry Wiseth

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  1. ADVANCED PHYSIOLOGYFLUID & ELECTROLYTESPART 2Instructor Terry Wiseth NORTHLAND COLLEGE

  2. ELECTROLYTE BALANCE • The exchange of interstitial and intracellular fluid is controlled mainly by the presence of the electrolytes sodium and potassium Na+ K+ K+ Na+ Na+ Na+ K+ K+

  3. ELECTROLYTE BALANCE • Potassium is the chief intracellular cation and sodium the chief extracellular cation • Because the osmotic pressure of the interstitial space and the ICF are generally equal, water typically does not enter or leave the cell K+ Na+

  4. ELECTROLYTE BALANCE • A change in the concentration of either electrolyte will cause water to move into or out of the cell via osmosis • A drop in potassium will cause fluid to leave the cell whilst a drop in sodium will cause fluid to enter the cell Click to seeanimation Na+ K+ K+ H2O H2O Na+ H2O H2O K+ Na+ Na+ K+ H2O H2O H2O H2O

  5. ELECTROLYTE BALANCE • A change in the concentration of either electrolyte will cause water to move into or out of the cell via osmosis • A drop in potassium will cause fluid to leave the cell whilst a drop in sodium will cause fluid to enter the cell Click to seeanimation Na+ K+ K+ H2O Na+ H2O H2O H2O Na+ K+ Na+ K+ H2O H2O H2O H2O

  6. ELECTROLYTE BALANCE • Aldosterone, ANP and ADH regulate sodium levels within the body, while aldosterone can be said to regulate potassium Na+ ADH ANP K+ aldosterone

  7. ELECTROLYTE BALANCE Na+ • Sodium (Na+) ions are the important cations in extracellular fluid • Anions which accompany sodium are chloride (Cl-) and bicarbonate (HCO3-) • Considered an indicator of total solute concentration of plasma osmolality Cl- HCO3-

  8. ELECTROLYTE BALANCE • Sodium ions are osmotically important in determining water movements • A discussion of sodium must also include • Chlorine • Bicarbonate • Hydrogen ions • Potassium and calcium serum concentrations are also important electrolytes in the living system H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O

  9. ELECTROLYTE BALANCES • Hypernatremia - elevated sodium levels • Hyponatremia -- lowered sodium levels • Hyperkalemia -- elevated potassium levels • Hypokalemia ---- lowered potassium levels Click • Hypercalcemia - elevated calcium levels • Hypokalcemia -- lowered calcium levels Click

  10. HYPERNATREMIA • Normal range for blood levels of sodium is app. 137 - 143 meq/liter • Hypernatremia refers to an elevated serum sodium level (145 -150 meq/liter) • Increased levels of sodium ions are the result of diffusion and osmosis Na+

  11. SODIUM PRINCIPLES • 1) Sodium ions do not cross cell membranes as quickly as water does H2O H2O H2O H2O H2O Na+ Na+

  12. SODIUM PRINCIPLES • 2) Cells pump sodium ions out of the cell by using sodium-potassium pumps Na+ Na+ Na+ Na+

  13. SODIUM PRINCIPLES • 3) Increases in extracellular sodium ion levels do not change intracellular sodium ion concentration Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

  14. RESULTS OF HYPERNATREMIA • 1) Water is osmotically drawn out of the cells • Resulting in dehydration • 2) Increase in extracellular fluid volume Intracellular fluid volume Extracellular fluid volume

  15. CNS REACTION TO HYPERNATREMIA • In the CNS tight junctions exist between endothelial cells of the capillary walls • These junctions restrict diffusion from capillaries to the interstitium of the brain • blood-brain barrier • Increased levels of sodium ions in the blood does not result in increased sodium ions in brain interstitial fluid

  16. CNS REACTION TO HYPERNATREMIA • As the result of an osmotic gradient, water shifts from the interstitium and cells of the brain and enters the capillaries • The brain tends to shrink and the capillaries dilate and possibly rupture • Result is cerebral hemorrhage, blood clots, and neurological dysfunction H2O

  17. CNS PROTECTIVE MECHANISM • There is an unknown mechanism that protects the brain from shrinkage • Within about 1 day • Intracellular osmolality of brain cells increases in response to extracellular hyperosmolality ?

  18. CNS PROTECTIVE MECHANISM • Idiogenic osmoles accumulate inside brain cells • K+, Mg+ from cellular binding sites and amino acids from protein catabolism • These idiogenic osmoles create an osmotic force that draws water back into the brain and protects cells from dehydration H2O

  19. CAUSES OF HYPERNATREMIA • 1) Water loss • 2) Sodium ion overload • Most cases are due to water deficit due to loss or inadequate intake • Infants without access to water or increased insensible water loss can be very susceptible to hypernatremia

  20. WATER LOSS • Diabetes insipidus caused by inadequate ADH or renal insensitivity to ADH results in large urinary fluid loss • Increased fluid loss also occurs as the result of osmotic diuresis (high solute loads are delivered to the kidney for elimination)

  21. WATER LOSS • Diabetes mellitus results in loss of fluids as well by creating an osmotic pull (increased urine solute concentration) on water into the tubules of the kidney H2O H2O H2O Glucose Glucose Glucose H2O Glucose H2O Click to animate H2O Glucose Glucose H2O H2O Glucose Glucose H2O H2O Glucose Glucose H2O H2O Glucose

  22. WATER LOSS • High protein feedings by a stomach tube create high levels of urea in the glomerular filtrate producing an osmotic gradient the same as glucose does and increased urinary output results

  23. SODIUM EXCESS • Occurs less frequently than water loss • Retention or intake of excess sodium • ex: IV infusion of hypertonic sodium ion solutions • Aldosterone promotes sodium and water retention by the kidney • High levels of aldosterone may result in mild hypernatremia

  24. CAUSES OF HYPERNATREMIA

  25. TREATMENT OF HYPERNATREMIA • Re-hydration is the primary objective in most cases • Decreases sodium concentrations • A point of concern is whenand how rapid there-hydration occurs

  26. TREATMENT OF HYPERNATREMIA • After 24 hours the brain has responded by producing idiogenic osmoles to re-hydrate brain cells • If this adaptation has occurred and treatment involves a rapid infusion of dextrose for example • There is danger of cerebraledema with fluid beingdrawn into brain tissues

  27. TREATMENT OF HYPERNATREMIA • Treatment is best handled by giving slow infusions of glucose solutions • This dilutes high plasmasodium ion concentrations

  28. TREATMENT OF HYPERNATREMIA • Ideally the goal is to avoid overloading with fluid and to remove excess sodium • Diuretics can be used to induce sodium and water diuresis • However if kidney function is not normal peritoneal dialysis may be required

  29. HYPONATREMIA • Defined as a serum sodium ion level that is lower than normal • Implies an increased ratio ofwater to sodium in extracellularfluid • Extracellular fluid is more dilute than intracellular fluid • Results in a shift of water into cells Na+

  30. CNS RESPONSE TO HYPONATREMIA • Brain cells lose osmoles creating a higher extracellular solute concentration • Effect is to protect against cerebral edema by drawing water out of the brain tissue

  31. GENERAL RESPONSE TO HYPONATREMIA • Suppression of thirst • Suppression of ADH secretion • Both favor decreasing wateringestion and increasingurinary output

  32. SYMPTOMS OF HYPONATREMIA • Primarily neurological (net flux of water into the brain) • Sodium ion levels of 125 meq / liter are enough to begin the onset of symptoms • Sodium ion levels of less than 110meq / liter bring on seizures and coma

  33. H O 2 HYPONATREMIA Na+ • Produced by: • 1) A loss of sodium ions • 2) Water excess • Water excess can be due to: • Ingestion • Renal retention

  34. DILUTIONAL EFFECT • 1) Isotonic fluid loss • 2) Antidiuretic hormone secretion • 3) Acute or chronic renal failure • 4) Potassium ion loss • 5) Diuretic therapy H2O H2O H2O Na+ Na+ H2O H2O H2O H2O Na+ H2O H2O H2O H2O H2O H2O Na+ Na+ Na+ Na+ H2O H2O H2O H2O H2O H2O Na+

  35. DILUTIONAL EFFECT • 1) Isotonic fluid loss • Burns, fever, hemorrhage • Indirect cause of hyponatremia • Any volume loss stimulates thirst and leads to increased water ingestion • Thus isotonic fluid loss can cause hyponatremia not because of sodium loss but because of increased water intake

  36. DILUTIONAL EFFECT • 2) Antidiuretic hormone secretion • Enhances water retention • 3) Acute or chronic renal failure • The kidney fails to excrete water • Can lead to hyponatremia

  37. DILUTIONAL EFFECT • 4) Potassium ion loss • Potassium ions are the predominant intracellular cations • When they are lost they are replaced by diffusion of intracellular potassium into extracellular fluid • Electrical balance is maintained by the diffusion of sodium ions into the cells in exchange for potassium ions • Thus a loss of extracellular sodium is realized and hyponatremia may ensue

  38. 1) extracellular potassium loss 3) intracellular electrical balance is maintained by diffusion of sodium ions into cells 2) diffusion of potassium ions into extracellular compartments POTASSIUM ION LOSS K+ Na+ Na+ cell K+ K+ K+ interstitial fluid plasma

  39. POTASSIUM ION LOSS Na+ Na+ K+ Cell Na+ K+ K+ Click to seeanimation K+ K+ K+ Interstitial fluid Plasma

  40. DILUTIONAL EFFECT • 5) Diuretic therapy • Common cause of hyponatremia • Loss of sodium and potassium often occurs in addition to fluid loss

  41. CAUSES OF HYPONATREMIA

  42. REACTIONS TO HYPONATREMIA Increased ADHrelease Increased Thirst Decreased urinary H2O loss Increased H2O gain Osmoreceptorsstimulated Click to viewincreased Na+ Increased Na+ Additional H2Odilutes Na+ HomeostasisNormal Na+ H2O lossconcentrates Na+ Decreased Na+ Click to viewdecreased Na+ Decreased ADHrelease Decreased Thirst Increased urinary H2O loss Decreased H2O gain Osmoreceptorsinhibited

  43. HYPERKALEMIA • Normal serum potassium level(3-5 meq / liter) • As compared to Na+ (142 meq / liter) • Intracellular levels of potassium(140-150 meq / liter) • This high intracellular level is maintained by active transport by the sodium-potassium pump K+

  44. Na+ / K+ Pump • Cells pump K+ ions in and Na+ ions out of the cell by using sodium-potassium pumps K+ K+ Na+ K+ K+ Na+ Na+ Na+

  45. HYPERKALEMIA • Hyperkalemia is an elevated serum potassium (K+) ion level • A consequence of hyperkalemia is acidosis • an increase in H+ ions in body fluids • Changes in either K+ or H+ ion levels causes a compartmental shift of the other K+

  46. HYPERKALEMIA • When hyperkalemia develops potassium ions diffuse into the cell • This causes a movement of H+ ions out of the cell to maintain a neutral electrical balance • As a result the physiological response to hyperkalemia causes acidosis H+ K+ HYPERKALEMIA H+ K+ H+ K+ H+ K+ H+ H+ K+ H+ H+ K+ H+

  47. HYPERKALEMIA • The reverse occurs as well • The body is protected from harmful effects of an increase in extracellular H+ ions (acidosis) • H+ ions inside the cells are tied up by proteins (Pr-) • This causes a shift of potassium ions out of the cells H+ H+ ACIDOSIS K+ H+ K+ H+ K+ H+ K+ H+ H+ K+ H+ H+ K+

  48. H+ H+ H+ H+ K+ K+ H+ K+ K+ H+ H+ K+ H+ K+ K+ K+ HYPERKALEMIA • Summarized: • Hyperkalemia causes acidosis • Acidosis causes hyperkalemia HYPERKALEMIA ACIDOSIS

  49. H+ H+ H+ H+ K+ K+ H+ K+ K+ H+ H+ K+ H+ K+ K+ K+ HYPERKALEMIA • Summarized: • Hyperkalemia causes acidosis • Acidosis causes hyperkalemia HYPERKALEMIA ACIDOSIS

  50. SYMPTOMS OF HYPERKALEMIA • Muscle contraction is affected by changes in potassium levels • Hyperkalemia blocks the transmission of nerve impulses along muscle fibers • Causes muscle weakness and paralysis • Can cause arrhythmia's and heart conduction disturbances