Acid base balance
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Acid base balance

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learning aid,teaching aid by Dr.M Ravi chandra

learning aid,teaching aid by Dr.M Ravi chandra

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Acid base balance Presentation Transcript

  • 1. “If one advances confidently in the direction of his dreams, he will meet with a success unexpected in common hours --Henry David Thoreau "Shoot for the moon. Even if you miss it, you will land among the stars….!" - Les Brown 
  • 2. DR.M.RAVICHANDRA,M.SASST. PROFESSOR OF SURGERY RIMS ,SRIKAKULAM
  • 3. Strong and Weak Acids and Bases A strong acid ..rapidly dissociates and releases large amounts of H+ in solution….HCl Weak acids ..less tendency to dissociate their ions … is H2CO3 A strong base … reacts rapidly and strongly with H+ and quickly removes these from a solution… OH- A typical weak base is HCO3- Most of the acids and bases in the extracellular fluid that involved in normal acid-base regulation are weak acids and bases
  • 4.  Volatile acids:  Can leave solution and enter the atmosphere.  H2C03 (carbonic acid).  Pco2 is most important factor in pH of body tissues.  Pco2 is a measurement of tension or partial pressure of carbon dioxide in the blood. The normal arterial pCO2 is 4.1- 5.6 k Pa (31- 42 mmHg)
  • 5.  Fixed Acids:  Acids that do not leave solution.  Sulfuric and phosphoric acids.(H2SO4&H3PO4)  Catabolism of amino acids, nucleic acids, and phospholipids.
  • 6.  Organic Acids:  Byproducts of aerobic metabolism, during anaerobic metabolism and during starvation, diabetes.  LACTIC ACID, KETONES ,PYRUVIC ACID
  • 7. Normal Hydrogen Ion Concentration and pH of Body Fluids the blood H+ concentration is normally maintained within tight limits around a normal value of about 0.00004 mEq/L (40 nEq/L)Ph= log 1/H= -log [H]Ph=7.4
  • 8. pH = pK + log HCO3 CO2
  • 9. DEFENCE MECHANISMSAGAINST pHCHANGES
  • 10. 1.CHEMICAL BUFFER SYSTEMS
  • 11. There are three primary systems that regulate the H+ concentration(1) the chemical acid-base buffer systems of the body fluids(2) the respiratory center(3) the kidneys
  • 12.  a buffer system is a combination of two compounds that minimizes pH changes when acid or base is added to a solution A pair of substance is involved: one substance yield H+ ion when PH is increased the other binds with H+ ion when pH is decreased.
  • 13.  Chemical buffer system  Combination of weak acid and weak base  Binds to H+ as H+ concentration rises  Releases H+ as H+ concentration falls  Can restore normal pH almost immediately  Three major chemical buffer systems  Bicarbonate system  Phosphate system  Protein system
  • 14.  Accomplished by converting:  Strong acid  Weak acid  Strong base  Weak base
  • 15.  bicarbonate/carbonic acid  major plasma buffer phosphate: H2PO4- / HPO42-  major urine buffer ammonium: NH3 / NH4+  also used to buffer the urine proteins: important in ICF Hb: is the main buffer against CO2 changes
  • 16. BICARBONATE BUFFER SYSTEM Carbonic acid (H2CO3)  Weak acid Bicarbonate ion (HCO3-)  Weak base CO2 + H20  H2CO3  H+ + HCO3- Works along with respiratory and urinary system  These systems remove CO2 or HCO3- THE RATIO OF BICARBONATE TO CARBONIC ACID IS NORMALLY 20:1 Alterations in the ratio alters Ph irrespective of absolute concetrations
  • 17. NaOH + H2CO3 H2O + Na HCO3HCl + Na HCO3 NaCl + H2CO3
  • 18. BICACARBONATE BUFFER
  • 19. Bing via Image*
  • 20.  Bing via Image*
  • 21.  pK 6.1 the concentrations of CO2 and HCO3 not great. the most powerful extracellular buffer in the body the two elements of the buffer system are regulated by the kidneys and the lungs
  • 22. PHOSPHATE BUFFER SYSTEM Dihydrogen phosphate ion (H2PO4-)  Weak acid Monohydrogen phosphate ion (HPO42-)  Weak base H2PO4-  H+ + HPO42- More important in buffering kidney filtrate than in tissue
  • 23. The main elements of the phosphate buffer system are H2PO4- and HPO4NaOH + NaH2PO4 H2O+ Na2HPO4HCl + Na2HPO4 NaCl + NaH2PO4
  • 24.  pK 6.8 8 % of the concentration of the bicarbonate buffer the total buffering power less than that of the bicarbonate buffering system.
  • 25.  the phosphate buffer is important in the tubular fluids of the kidney for two reasons(1) phosphate concentrated in the tubules(2) the tubular fluid has lower pH than the extracellular fluid does - bringing the operating range of the buffer closer to the pK (6.8) of the system important in buffering intracellular fluid because the concentration of phosphate in this fluid is many times that in the extracellular fluid
  • 26.  Bing via Image*
  • 27. PROTEIN BUFFER SYSTEM Proteins are more concentrated than bicarbonate and phosphate buffers Accounts for ~75% of all chemical buffering of body fluids Buffering ability due to certain functional groups of amino acid residues
  • 28.  except for the red blood cells, the slowness with which H+ and HCO3 move through the cell membranes often delays the maximum ability of the intracellular proteins to buffer extracellular acid-base abnormalities. the pKs of many of these protein systems close to 7.4.
  • 29. The buffer system buffers each other by shifting hydrogen from buffer to other
  • 30.  Exhalation of carbon dioxide Powerful, but only works with volatile acids Doesn’t affect fixed acids like lactic acid CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3- Body pH can be adjusted by changing rate and depth of breathing
  • 31.  the overall buffering power of the respiratory system is one to two times as great as the buffering power of all other chemical buffers in the ECF combined
  • 32.  Bing via Image*
  • 33.  Bing via Image*
  • 34.  Alkalosis →↑urinary HCO3- (base) Acidosis →↓urinary HCO3- new HCO3- production
  • 35.  pH< 7.35 acidosis pH > 7.45 alkalosis
  • 36.  A CONDITION WHERE THE PCO2 IS ABOVE THE NORMAL RANGE  MORE THAN 5.6 kilopascals  (or) more than 42mmof hg
  • 37. *Image via Bing 
  • 38. *Image via Bing 
  • 39. *Image via Bing 
  • 40. *Image via Bing 
  • 41. *Image via Bing 
  • 42. compensatory mechanisms in respiratory acidosis compensatory mechanisms in respiratory acidosis*Image via Bing 
  • 43.  Inadequate ventilation of anaesthetized patient When the effects of muscle relaxants have not worn off or been fully reversed at the end of anaesthesia Risk increases when the patient has pre existing pulmonary disease like ch. Bronchitis or emphysema Thoracic & upper abdominal incisions
  • 44.  A CONDITION WHERE THE ARTERIAL PCO2 IS BELOW THE NORMAL RANGE  LESS THAN 31 MM OF HG  (OR) LESS THAN 5.6 KILO PASCALS
  • 45. *Image via Bing 
  • 46.  Excessive pulmonary ventilation during ANAESTHAESIA (Hyperventilation) High altitudes Hyperpyrexia Hypothalamic lesions Hysteria
  • 47.  A condition where there is a deficit of base or excess of acid other than carbonic acid(H2CO3)
  • 48. Ulcerative colitisGastro colic fistulaHigh intestinal fistula Prolonged  intestinal aspiration
  • 49. *Image via Bing 
  • 50. *Image via Bing 
  • 51. *Image via Bing 
  • 52.  This is a calculated estimation of the undetermined or unmeasured anions in the blood This is some times used to establish the cause of metabolic acidosis ANIONGAP= (Na) _ (HCO3+Cl) NORMAL ANION GAP IS 10-16 mmol / L
  • 53. *Image via Bing 
  • 54. *Image via Bing 
  • 55. *Image via Bing 
  • 56.  KETOACIDOSIS LACTIC ACIDOSIS SALICYLATES POISONING SPIRITS –ETHANOL & METHANOL ALDEHYDES RENAL FAILURE
  • 57.  DIARRHOEA RENAL TUBULAR ACIDOSIS URETEROSIGMOIDOSTOMY TOTAL PARENTARAL NUTRITION ACETAZOLAMIDE INTESTINAL OBSTRUCTION INTESTINAL FISTULA
  • 58.  Increased ventilation Renal excretion of hydrogen ions if possible K+ exchanges with excess H+ in ECF ( H+ into cells, K+ out of cells)
  • 59.  A CONDITION WHERE THERE IS BASE EXCESS OR DEFICIT OF ANY ACID OTHER THAN CARBONIC ACID
  • 60. Cortisone excessCushings syndrome
  • 61. CHEYNE STOKES RESP TETANY*Image via Bing 
  • 62. *Image via Bing 
  • 63. *Image via Bing 
  • 64.  RESPIRATORY- RETENTION OF CARBONDIOXIDE BY THE LUNGS RENAL – EXCRETION OF BICARBONATE BY THE KIDNEYS
  • 65. Changes in Arteial Concentrations of H + , HCO 3 - & CO 2 in Acid-Base Disorders Primary HCO 3 Cause of HCO3- Cause of CO2 H + CO 2 Disorder - Change ChangeRespiratory Acidosis ↑ ↑ ↑ Renal Primary Compensation AbnormalityRespiratory Alkalosis ↓ ↓ ↓MetabolicAcidosis ↑ ↓ ↓ Reflex Primary Ventilatory AbnormalityMetabolic CompensationsAlkalosis ↓ ↑ ↑
  • 66.  Respiratory Acidosis ; ↑PCO2 & [H+] Respiratory Alkalosis ; ↓PCO2 & [H+] Metabolic Acidosis ; compensatory reflex hyperventilation ⇒ ↓PCO2 1. Tubular acidosis; ↓HCO3- reabsorption & H+ secretion 2. Diarrhea & Vomiting(intestinal); ↓HCO3- 3. Diabetes Mellitus; ↑acetoacetic acid (ketone body) 4. Ingestion of acids; aspirin, methyl alcohol 5. Chronic renal failure; ↓acid excretion 6. Hypoxia (severe exercise); ↑lactic acid
  • 67.  Metabolic Alkalosis ; compensatory reflex hypoventilation ⇒ ↑PCO2 1. Diuretics; ↑distal tubule flow ⇒↑Na+ reabsorption & H+ secretion 2. Excess Aldosterone; ↑H+ secretion 3. Vomiting; ↓H+ (upper gastric content) 4. Ingestion of alkaline drugs; sodium bicarbonate
  • 68. Summary of Acid-Base Disturbances Uncompensated Compensated pH [HCO 3 - ] P CO2 pH [HCO 3 - ] P CO2 24 40 Normal 7.4 mEq/L mmHgRespiratory Acidosis ↓ - ↑ ↓ ↑ ↑Respiratory Alkalosis ↑ - ↓ ↑ ↓ ↓MetabolicAcidosis ↓ ↓↓ - ↓ ↓↓ ↓MetabolicAlkalosis ↑ ↑↑ - ↑ ↑↑ ↑
  • 69. HAVE A NICE DAYHAVE A NICE DAY *Image by 8771253@N06 via Flickr