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Acid And Base

Home > PowerPoint Slides > Acid And Base
Published in: Bio Chemistry | MBBS Tuition | NEET
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Pathophysiology of Acid-Base imbalance.

Ashutosh S / Lucknow

5 years of teaching experience

Qualification: M.S/M.D (SGPGIMS(LUCKNOW) - 2018)

Teaches: UPPSC Exam, UPSC Exam, MBBS Tuition, MCI Exam, JIPMER

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  1. Acid and Base Balance and Imbalance
  2. pH Review ' pH = - log [H+] 1--1+ is really a proton Range is from 0- 14 If [H+] is high, the solution is acidic; pH < 7 If [H+] is low, the solution is basic or alkaline ; pH > 7
  3. Copyright e The McGraw-Hill Companies. Ine, Permission req(ired for reproduction ot display. Acidi Acidic app' concentration increases cow's milk 60 com 8.4 sodium bicarbonate 8.0 white IOS milk of magnesia 7.0 distilled water 10 11 11.5, household ammonia 12 13 14 Neutral OH- concentration increases Basic (alkaline)
  4. Copyright O The McGraw-Hill Companies. Inc. Permission required for reproduction or display. Hydrogen Ion Concentrations {2.5 and pH Grams of H+ per Liter 0.00000000000001 0.0000000000001 0.000000000001 0.00000000001 0.0000000001 0.000000001 0.00000001 0.0000001 0.000001 0.00001 0.0001 0.001 0.01 0.1 1.0 pH 14 13 12 11 10 9 8 7 6 5 4 3 2 Increasingly basic Neutral—neither acidic nor basic Increasingly acidic 4
  5. Acids are 1--1+ donors. Bases are 1-1+ acceptors, or give up OH- in solution. Acids and bases can be: —Strong — dissociate completely in solution ' HCI, NaOH —Weak — dissociate only partially in solution Lactic acid, carbonic acid
  6. The Body and pH Homeostasis of pH is tightly controlled Extracellular fluid = 7.4 , Blood = 7.35 - 7.45 < 6.8 or > 8.0 death occurs Acidosis (acidemia) below 7.35 Alkalosis (alkalemia) above 7.45
  7. Copyright O The McGraw-Hill Companies. Inc. Permission required foe reproduction or pH of arterial blood Normal pH range Acidosis Alkalosis pH scale 6.8 7.0 7.35 7.45 Survival range 7.8 8.0
  8. Small changes in pH can produce major disturbances Most enzymes function only with narrow pH ranges Acid-base balance can also affect electrolytes (Na+, 1
  9. The body produces more acids than bases Acids take in with foods Acids produced by metabolism of lipids and proteins Cellular metabolism produces C02. ' C02 + 1-120 H2C03 H + + HC03-
  10. Control of Acids 1. Buffer systems Take up H+ or release H+ as conditions change Buffer pairs — weak acid and a base Exchange a strong acid or base for a weak one Results in a much smaller pH change 10
  11. Bicarbonate buffer Sodium Bicarbonate (NaHC03) and carbonic acid (H2C03) Maintain a 20:1 ratio : HC03- : H2C03 I-ICI + NaHC03
  12. Phosphate buffer Major intracellular buffer ' H + + HPO 2- ' OH- + H2P04- H 2 p04- 1-120 + H 2 p042- 12
  13. Protein Buffers Includes hemoglobin, work in blood and ISF Carboxyl group gives up 1--1+ Amino Group accepts 1-1+ Side chains that can buffer 1-1+ are present on 27 amino acids. 13
  14. 2. Respiratory mechanisms Exhalation of carbon dioxide Powerful, but only works with volatile acids Doesn't affect fixed acids like lactic acid ' C02 + 1-120 H2C03 H + + HC03- Body pH can be adjusted by changing rate and depth of breathing 14
  15. 3. Kidney excretion Can eliminate large amounts of acid Can also excrete base Can conserve and produce bicarb ions Most effective regulator of pH If kidneys fail, pH balance fails 15
  16. Rates of correction Buffers function almost instantaneously Respiratory mechanisms take several minutes to hours Renal mechanisms may take several hours to days 16
  17. Copyright O The McGraw-Hill Companies. Inc. Permission required foe reproduction or First line of defense against pH shift Second line of defense against pH shift Chemical buffer system Physiological buffers Bicarbonate buffer system Phosphate buffer system Protein buffer system Respiratory mechanism (C02 excretion) Renal mechanism (H+ excretion)
  18. Circulation + Tco Lungs Carbonic anhydrase Respiratory center in brain stem TRespi ation rate and de th TC02 given off Erythrocyte H2C03-----> H+ + HCOJ Kidney JpH t Rate of H+ secretion 18 From Thibodeau GA, Patton KT: Anatomy & physiology, ed 5, St Louis, 2003, Mosby Mosby items and derived items copyright @ 2004.2000 by Mosby. Inc.
  19. Acid-Base Imbalances pH< 7.35 acidosis pH > 7.45 alkalosis The body response to acid-base imbalance is called compensation May be complete if brought back within normal limits Partial compensation if range is still outside norms. 19
  20. Compensation If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation. If problem is respiratory, renal mechanisms can bring about metabolic compensation. 20
  21. Acidosis Principal effect of acidosis is depression of the CNS through I in synaptic transmission. Generalized weakness Deranged CNS function the greatest threat Severe acidosis causes — Disorientation —coma —death 21
  22. Alkalosis Alkalosis causes over excitability of the central and peripheral nervous systems. Numbness Lightheadedness It can cause . — Nervousness — muscle spasms or tetany — Convulsions — Loss of consciousness — Death 22
  23. Copyright O The McGraw-Hill Companies. Inc. Permission required foe reproduction or Accumulation of acids Loss of bases Acidosis pH scale Increased concentration of H+ pH drops 7.4 Alkalosis pH rises Decreased concentration of H+ Loss of acids Accumulation of bases
  24. Respiratory Acidosis Carbonic acid excess caused by blood levels of C02 above 45 mm Hg. Hypercapnia — high levels of C02 in blood Chronic conditions: — Depression of respiratory center in brain that controls breathing rate — drugs or head trauma — Paralysis of respiratory or chest muscles — Emphysema 24
  25. Respiratory Acidosis Acute conditons: — Adult Respiratory Distress Syndrome — Pulmonary edema — Pneumothorax 25
  26. Compensation for Respiratory Acidosis Kidneys eliminate hydrogen ion and retain bicarbonate ion 26
  27. Signs and Symptoms of Respiratory Acidosis Breathlessness Restlessness Lethargy and disorientation Tremors, convulsions, coma Respiratory rate rapid, then gradually depressed Skin warm and flushed due to vasodilation caused by excess C02 27
  28. Treatment of Respiratory Acidosis Restore ventilation IV lactate solution Treat underlying dysfunction or disease 28
  29. a) Metabolic balance before onset of acidosis b) Respiratory acidosis C02 C02 C02 Breathing is suppressed, holding C02 in body c) Bodys compensation d) Therapy required to restore metabolic balance 2C0 2 go 2 2C0 2 HCOi 20 20 HC03 30 H2C03 : Carbonic acid HCOS: Bicarbonate ion (Na+• HCO;) (K+ • HCOE) (Mg++• HCO;) (Ca++• HCO;) Primary change pH — decreases PC02 — • Increases HCO; no change - + HCOi Body's correction H2C03 HC0ä {Acidic urine Kidneys conserve HCOö ions and eliminate H + ions in acidic urine HC0ä 20 Lactate Lactate- containing solution Lactate solution used in therapy is converted to bicarbonate ions in the liver 29 From Thibodeau GA, Patton KT: Anatomy & physiology, ed 5, St Louis, 2003, Mosby. Mosby items and derived items copyright @ 2004. 2000 by Mosby. Inc.
  30. Respiratory Alkalosis Carbonic acid deficit pC02 less than 35 mm Hg (hypocapnea) Most common acid-base imbalance Primary cause is hyperventilation 30
  31. Respiratory Alkalosis Conditions that stimulate respiratory center: — Oxygen deficiency at high altitudes — Pulmonary disease and Congestive heart failure — caused by hypoxia — Acute anxiety — Fever, anemia — Early salicylate intoxication — Cirrhosis — Gram-negative sepsis 31
  32. Compensation of Respiratory Alkalosis Kidneys conserve hydrogen ion Excrete bicarbonate ion 32
  33. Treatment of Respiratory Alkalosis Treat underlying cause Breathe into a paper bag IV Chloride containing solution — CI- ions replace lost bicarbonate ions 33
  34. a) Metabolic balance before onset of alkalosis b) Respiratory alkalosis C02 o +1-120 Hyperactive breathing "blows of?' C02 c) Bodys compensation d) Therapy required to 2C0 0.5 2Co 0.5 HC05 20 20 HC03 15 H2C03 : Carbonic acid HCOä: Bicarbonate ion (Na+ • HCO;) (K+ • HCO;) (Mg++• HCO;) (Ca++• HCO;) Primary change pH — increases PC02 — decreases HCOä---- no change Bodys correction Alkaline urine Kidneys conserve H + ions and eliminate HCOä in alkaline urine restore metabolic balance 2C0 0.5 Chloride- containing coi —Cl- solution 10 HCOä ions are replaced by Cl— ions 2003, 34 From Thibodeau GA, Patton KT: Anatomy & physiology, ed 5, St Louis, Mosby items and derived items copyright @ 2004. 2000 by Mosby. Inc.
  35. Metabolic Acidosis Bicarbonate deficit - blood concentrations of bicarb drop below 22mEq/L Causes: — Loss of bicarbonate through diarrhea or renal dysfunction — Accumulation of acids (lactic acid or ketones) — Failure of kidneys to excrete H+ 35
  36. Symptoms of Metabolic Acidosis Headache, lethargy Nausea, vomiting, diarrhea Coma Death 36
  37. Compensation for Metabolic Acidosis Increased ventilation Renal excretion of hydrogen ions if possible exchanges with excess 1--1+ in ECF ( 1--1+ into cells, out of cells) 37
  38. Treatment of Metabolic Acidosis IV lactate solution 38
  39. a) Metabolic balance before onset of acidosis 2C0 b) Metabolic acidosis HCOidecreases because of 20 10 HCOi + H c03 10 H2C03 : Carbonic acid HCOS: Bicarbonate ion (Na+• HCOä) (K+ • HCO;) (Mg++• HCO;) (Ca++• HCO;) Primary change excess presence of ketones, chloride, or organic acid ions c) Bodys compensation C02 02 20 co go 0.75 pH — decreases no change PC02 — decreases HCO Body's correction HCOä Acidic urine Hyperactive breathing to "blow off" C02 d) Therapy required to restore metabolic balance 2C0 1 Kidneys conserve HCOi and eliminate H + ions in acidic urine Lactate Lactate- containing solution HCOä 20 Lactate solution used in therapy is converted to bicarbonate ions in the liver 39 From Thibodeau GA, Patton KT: Anatomy & physiology, ed 5, St Louis, 2003, Mosby. Mosby items and derived items copyright @ 2004. 2000 by Mosby. Inc.
  40. Metabolic Alkalosis Bicarbonate excess- concentration in blood is greater than 26 mEq/L Causes: — Excess vomiting = loss of stomach acid — Excessive use of alkaline drugs — Certain diuretics — Endocrine disorders — Heavy ingestion of antacids — Severe dehydration 40
  41. Compensation for Metabolic Alkalosis Alkalosis most commonly occurs with renal dysfunction, so can't count on kidneys Respiratory compensation difficult — hypoventilation limited by hypoxia 41
  42. Symptoms of Metabolic Alkalosis Respiration slow and shallow Hyperactive reflexes ; tetany Often related to depletion of electrolytes Atrial tachycardia Dysrhythmias 42
  43. Treatment of Metabolic Alkalosis Electrolytes to replace those lost IV chloride containing solution Treat underlying disorder 43
  44. a) Metabolic balance before onset of alkalosis 2C0 1 b) Metabolic alkalosis HCOi increases because of loss of chloride ions eco or excess ingestion of sodium bicarbonate c) Body's compensation C02 + H20 C02 H2Co 1 .25 Breathing suppressed to hold C02 d) Therapy required to restore metabolic balance 2C0 1 HCO 3 20 HCO 40 HC03 30 H2C03 : Carbonic acid HCOS : Bicarbonate ion (Na+• HCOE) (K+ • HCOE) (Mg++• HCO;) (Ca++• HCO;) Primary change pH PC02 HCO — increases no change — increases Body's correction HCOö Alkaline urine Kidneys conserve H + ions and eliminate HCOi in alkaline urine 20 From Thibodeau GA, Patton KT: Anatomy & physiology, ed 5, St Louis, Mosby items and derived items copyright @ 2004. 2000 by Mosby. Inc. Chloride- containing solution HCOi ions replaced by Cl— ions 44 2003, Mosby.
  45. Diagnosis of Acid-Base Imbalances 1. Note whether the pH is low (acidosis) or high (alkalosis) 2. Decide which value, pC02 or HC03- , is outside the normal range and could be the cause of the problem. If the cause is a change in pC02 the problem is respiratory. If the cause is HC03- the problem is metabolic. 45
  46. 3. Look at the value that doesn't correspond to the observed pH change. If it is inside the normal range, there is no compensation occurring. If it is outside the normal range, the body is partially compensating for the problem. 46
  47. Example A patient is in intensive care because he suffered a severe myocardial infarction 3 days ago. The lab reports the following values from an arterial blood sample: — pH 7.3 - HC03- = 20 mEq / L ( 22 - 26) -pC02 = 32 mm Hg (35 - 45) 47
  48. Diagnosis Metabolic acidosis With compensation 48
  49. 50 45 40 35 30 — 25 20 g 15 10 5 PC02= 80 60 Metabolic alkalosis Respiratory acidosis x Metabolic acidosis- 7 7.1 7.2 7.3 7.4 7.5 pH 30 20 Respiratory 10 alkalosis , 7.6 7.7 7.8 7.9 49 Mosby items and derived items copyright @ 2004, 2000 by Mosby. Inc.

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