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    Acid base balane Acid base balane Presentation Transcript

    • Physiology of Acid-Base Balance
      Under the guidance of :
      Dr. Sandeep Tandon
      Professor and Head of Dept. of Pedodontics Dr. Ambika S. Rathore Dr. Rinku Mathur Dr .Shantanu Jain
      Dr. Tripti Sharma Rai
    • 2
      CONTENT:
      • Introduction
      • Acid-Base Balance
      • ph Scale
      • Acidosis and Alkalosis
      • Compensatory Mechanisms
      • Disturbance in acid-base balance
      • Anion Gap
      • Factors affecting acid-base balance in children
      • Infantile metabolic acidosis
    • 3
      Introduction
      • Acid-base homeostasis is the part of human homeostasis concerning the proper balance between acids and bases, in other words, the pH.
      • Chemical and physiologicprocesses responsible for the maintenance of the acidity of body fluids.
    • Acid Base Homeostasis
      • Chemical processes:
      • extracellular
      • intracellularbuffers
      • The physiologic processes: the excretion of volatile acids by the lungsand fixed acids by the kidneys
      4
    • 5
      ACID-BASE BALANCE
    • 6
      ACIDS
      OH-
      OH-
      OH-
      OH-
      • Acids can be defined as a proton (H+) donor
      • Hydrogen containing substances which dissociate in solution to release H+
      H+
      H+
      H+
      H+
    • 7
      ACIDS
      Physiologically important acids include:
      Carbonic acid (H2CO3)
      Phosphoric acid (H3PO4)
      Pyruvic acid (C3H4O3)
      Lactic acid (C3H6O3)
      Phosphoric acid
      Lactic acid
      Pyruvic acid
      Carbonic acid
    • 8
      BASES
    • 9
      OH-
      OH-
      OH-
      OH-
      BASES
      • Bases can be defined as:
      • A proton (H+) acceptor
      • Molecules capable of accepting a hydrogen ion (OH-)
      H+
      H+
      H+
      H+
    • 10
      BASES
      Physiologically important bases include:
      Bicarbonate (HCO3- )
      Biphosphate (HPO4-2 )
      Biphosphate
      Bicarbonate
    • 11
      pH SCALE
    • 12
      pH SCALE
      pH refers to Potential Hydrogen
      Expresses hydrogen ion concentration in water solutions.
      Water ionizes to a limited extent to form equal amounts of H+ ions and OH- ions
      H2OH+ + OH-
      H+ion is an acid
      OH-ion is a base
    • 13
      H+
      H+
      OH-
      H+
      OH-
      OH-
      H+
      H+
      OH-
      H+
      H+
      H+
      H+
      OH-
      H+
      OH-
      OH-
      H+
      OH-
      H+
      OH-
      H+
      OH-
      OH-
      H+
      OH-
      H+
      OH-
      OH-
      pH SCALE
      Pure water is Neutral
      • ( H+ = OH-)
      pH = 7
      Acid
      • ( H+ > OH- )
      pH < 7
      Base
      • ( H+< OH-)
      pH > 7
      Normal blood pH is 7.35 - 7.45
      pH range compatible with life is 6.8 - 8.0
      ACIDS, BASES OR NEUTRAL???
      3
      1
      2
    • 14
      pH SCALE
      Normal hydrogen ion concentration in ECF= 38-42 nM/L.
      Ph scale- simplify the mathematical handling of large numbers.
      • Unit changes in pH represent a tenfold change in H+ concentrations
      pH = log 1 / H+ concentration
    • 15
      pH SCALE
      Ph of the ECF: 7.40
      NORMAL
      ACIDOSIS
      ALKALOSIS
      DEATH
      DEATH
      7.3
      7.5
      7.4
      6.8
      8.0
      Venous Blood
      Arterial Blood
    • 16
      Determination of Acid Base Status
      • pH = pK + log HCO3
      CO2
      Henderson-Hasselbalch equation
      Normal acid-base ratio= 1:20
      ph of arterial blood= indirect method
    • 17
      ACIDOSIS / ALKALOSIS
    • 18
      ACIDOSIS / ALKALOSIS
      Acidosis
      • A condition in which the blood has too much acid (or too little base), frequently resulting in a decrease in blood pH
      Alkalosis
      • A condition in which the blood has too much base (or too little acid), occasionally resulting in an increase in blood pH
    • 19
      Acidosis / Alkalosis
      • Acidosis
      H+
      OH-
      • Alkalosis
      H+
      OH-
    • 20
      ACIDOSIS / ALKALOSIS
      pH changes have dramatic effects on normal cell function
      1)Changes in excitability of nerve and muscle cells
      2) Influences enzyme activity
      3) Influences K+ levels
    • 21
      Changes in Cell Excitability
      • pH decrease (more acidic) depresses the central nervous system
      • Can lead to loss of consciousness
      • pH increase (more basic) can cause over-excitability
      • Tingling sensations, nervousness, muscle twitches
    • 22
      Influences on Enzyme Activity
      • pH increases or decreases can alter the shape of the enzyme rendering it non-functional.
      • Changes in enzyme structure can result in accelerated or depressed metabolic actions within the cell.
    • 23
      Influences On K+ Levels
      • When reabsorbing Na+ from the filtrate of the renal tubules K+ or H+ is secreted (exchanged).
      • Normally K+issecreted in muchgreater amountsthan H+
      K+
      K+
      K+
      K+
      K+
      K+
      Na+
      Na+
      Na+
      Na+
      Na+
      Na+
      H+
      K+
    • 24
      Influences On K+ Levels
      • If H+ concentrations are high (acidosis) than H+ is secreted in greater amounts.
      • This leaves less K+ than usual excreted.
      • The resultant K+ retention can affect cardiac function and other systems.
      K+
      K+
      K+
      K+
      K+
      K+
      K+
      K+
      Na+
      Na+
      Na+
      Na+
      Na+
      Na+
      H+
      H+
      H+
      H+
      H+
      H+
      H+
    • 25
      SOURCE OF HYDROGEN ION
      CO2 + H2O H2CO3 H+ + HCO3-
      H+
      H2CO3
      HCO3-
    • 26
      Regulation of Acid Base Balance
      Two types of acids are produced in the body:
      • Volatile acids :CO2 produced
      during the metabolism of
      carbohydrates and lipids
      • Non-volatile acids:metabolism of
      protein e.g. sulphuric acids
    • Compensatory mechanisms
      1)Chemical Buffers
      • React very rapidly(less than a second)
      2)Respiratory Regulation
      • Reacts rapidly (seconds to minutes)
      3)Renal Regulation
      • Reacts slowly (minutes to hours)
      4) Intracellular Shifts of Ions
      27
    • Acid-base buffer system
      • Maintains the pH by binding with free hydrogen ions.
      • Combination of weak acid and a base (unprotonated compound).
      • Three major chemical buffer systems
      • Bicarbonate system
      • Phosphate system
      • Protein system
      28
    • 29
      BICARBONATE BUFFER SYSTEM
      This system is most important because the concentration of both components can be regulated:
      • Carbonic acid by the respiratory system
      • Bicarbonate by the renal system
    • 30
      H+
      • H2CO3H+ + HCO3-
      • Hydrogen ions generated by metabolism or by ingestion react with bicarbonate base to form more carbonic acid
      H2CO3
      HCO3-
    • 31
      BICARBONATE BUFFER SYSTEM
      H+
      • Equilibrium shifts toward the formation of acid
      • Hydrogen ions that are lost (vomiting) causes carbonic acid to dissociate yielding replacement H+ and bicarbonate
      H2CO3
      HCO3-
    • 32
      BICARBONATE BUFFER SYSTEM
      H+
      HCO3-
      H2CO3
      H2O
      CO2
      +
      +
      Addition of lactic acid
      Exercise
      Loss of HCl
      Vomiting
    • 33
      PHOSPHATE BUFFER SYSTEM
      Na2HPO4 + H+ NaH2PO4+ Na+
      • Most important in the intracellular system
      Na2HPO4
      +
      H+
      +
      Na+
      NaH2PO4
    • 34
      PHOSPHATE BUFFER SYSTEM
      • Regulates pH within the cells and the urine
      • Phosphate concentrations are higher intracellular and within the kidney tubules.
      • More phosphate ions
      are found in tubular fluids
      • More powerful than
      bicarbonate buffer system
      HPO4-2
    • 35
      PROTEIN BUFFER SYSTEM
      Proteins are excellent buffers because they contain both acid and base groups that can give up or take up H+
      Proteins are extremely abundant in the cell
      The more limited number of proteins in the plasma reinforce the bicarbonate system in the ECF
    • 36
      • Hemoglobin buffers H+ from metabolically produced CO2 in the plasma only
      • As hemoglobin releases O2 it gains a great affinity for H+
      H+
      O2
      O2
      Hb
      O2
      O2
    • 37
      H+ generated at the tissue level from the dissociation of H2CO3 produced by the addition of CO2
      Bound H+ to Hb(Hemoglobin) does not contribute to the acidity of blood
      H+
      O2
      O2
      Hb
      O2
      O2
    • 38
      As H+Hb picks up O2 from the lungs the Hb which has a higher affinity for O2 releases H+ and picks up O2
      Liberated H+ from H2O combines with HCO3-
      HCO3-H2CO3CO2(exhaled)
      O2
      O2
      H+
      Hb
      O2
      O2
    • 39
      RESPIRATORY CENTRE
      Pons
      Respiratory centers
      Medulla oblongata
    • 40
      CHEMOSENSITIVE AREAS
      • Chemo sensitive areas of the respiratory center are able to detect blood concentration levels of CO2 and H+
      • Increases in CO2 and H+ stimulate the respiratory center
      • The effect is to raiserespiration rates
      • But the effectdiminishes in1 - 2 minutes
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
    • 41
      cell production of CO2 increases
      CO2 + H2O H2CO3
      H2CO3 H+ + HCO3-
      H+ acidosis; pH drops
      H+ stimulates respiratory center in medulla oblongata
      rate and depth of breathing increase
      CO2 eliminated in lungs
      pH rises toward normal
      RESPIRATORY CONTROL OF pH
    • 42
      RENAL RESPONSE
      The kidney compensates for Acid - Base imbalance within 24 hours and is responsible for long term control
      The kidney in response:
      To Acidosis
      Retains bicarbonate ions and eliminates hydrogen ions
      To Alkalosis
      Eliminates bicarbonate ions and retains hydrogen ions
    • 43
      H+
      K+
      cell
      H+
      K+
      cell
      ELECTROLYTE SHIFTS
      Acidosis
      Compensatory Response
      Result
      - H+ buffered intracellularly
      - Hyperkalemia
      -Diabetic ketoacidosis
      Alkalosis
      Result
      Compensatory Response
      - Tendency to correct alkalosis
      - Hypo kalemia
    • 44
      DISTURBANCE OF ACID BASE BALANCE
      • Four general categories, depending on the source and direction of the abnormal change in H+ concentrations:
      • Respiratory Acidosis
      • Respiratory Alkalosis
      • Metabolic Acidosis
      • Metabolic Alkalosis
    • 45
      RESPIRATORY ACIDOSIS
    • 46
      RESPIRATORY ACIDOSIS
      Caused by hyperkapnia due to hypoventilation
      Characterized by a pH decrease and an increase in CO2
      pH
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      pH
      CO2
      CO2
    • 47
      RESPIRATORY ACIDOSIS
      • Respiratory acidosis develops when the lungs don't expel CO2 adequately
      • Emphysema, chronic bronchitis, severe pneumonia, pulmonary edema, and asthma
    • 48
      RESPIRATORY ACIDOSIS
      • Decreased CO2 removal can be the result of:
      Obstruction of air passages
      Decreased respiration (depression of respiratory centers)
      Decreased gas exchange between pulmonary capillaries and air sacs of lungs
      Collapse of lung
    • 49
      4) Collapse of lung
      • Compression injury, open thoracic wound
      Left lung collapsed
    • 50
      RESPIRATORY ACIDOSIS
      CO2
      CO2
      HCO3-
      CO2
      CO2
      H2CO3
      :
      2
      20
      • breathing is suppressed holding CO2 in body
      • pH = 7.1
    • 51
      H2CO3
      HCO3-
      HCO3-
      HCO3-
      H2CO3
      +
      H+
      :
      2
      30
      BODY’S COMPENSATION
      • kidneys conserve HCO3- ions to restore the normal 40:2 ratio (20:1)
      • kidneys eliminate H+ ion in acidic urine
      acidic urine
    • 52
      Lactate
      LIVER
      H2CO3
      HCO3-
      Lactate
      HCO3-
      :
      2
      40
      • therapy required to restore metabolic balance
      • lactate solution used in therapy is converted to bicarbonate ions in the liver
    • 53
      H2CO3
      HCO3-
      HCO3-
      H2CO3
      :
      20
      RESPIRATORY ALKALOSIS
      • Normal 20:1 ratio is increased
      • pH of blood is above 7.4
      7.4
      7.4
      =
      =
      :
      0.5
      20
    • 54
      RESPIRATORY ALKALOSIS
      • Cause is Hyperventilation
      • Leads to eliminating excessive amounts of CO2
      • Increased loss of CO2 from the lungs at a rate faster than it is produced
      • Decrease in H+
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
      CO2
    • 55
      RESPIRATORY ALKALOSIS
      Can be the result of:
      1) Anxiety, emotional disturbances
      2) Respiratory center lesions
      3) Fever
      4) Salicylate poisoning (overdose)
      5) Assisted respiration
      6) High altitude (low PO2)
    • 56
      • Kidneys compensate by:
      • Retaining hydrogen ions
      • Increasing bicarbonate excretion
      HCO3-
      HCO3-
      H+
      H+
      HCO3-
      HCO3-
      H+
      H+
      H+
      HCO3-
      H+
      HCO3-
      HCO3-
      H+
      H+
      HCO3-
      HCO3-
      H+
      H+
      HCO3-
      H+
    • 57
      RESPIRATORY ALKALOSIS
      Cl-
      H2CO3
      HCO3-
      Chloride containing solution
      :
      0.5
      10
      • therapy required to restore metabolic
      balance
      • HCO3- ions replaced by Cl- ions
    • 58
      HCO3-
      H2CO3
      HCO3-
      =
      7.4
      =
      7.4
      H2CO3
      :
      :
      1
      20
      1
      10
      METABOLIC ACIDOSIS
      • Occurs when there is a decrease in the normal 20:1 ratio
      • Decrease in blood pH and bicarbonate level
      • Excessive H+ or decreased HCO3-
    • 59
      METABOLIC ACIDOSIS
      • Acidosis results from excessive loss of HCO3- rich fluids from the body or from an accumulation of acids.
      • Accumulation of non-carbonic plasma acids uses HCO3- as a buffer for the additional H+ thus reducing HCO3- levels
      Muscle Cell
      Lactic Acid
      HCO3-
    • 60
      METABOLIC ACIDOSIS
      • Metabolic acidosis is always characterized by a reduction in plasma HCO3- while CO2 remains normal
      Plasma Levels
      HCO3-
      CO2
    • 61
      METABOLIC ACIDOSIS
      • The causes of metabolic acidosis can be grouped into five major categories;
      1) Ingesting an acid or a substance that is metabolized to acid
      2) Abnormal Metabolism
      3) Kidney Insufficiencies
      4) Strenuous Exercise
      5) Severe Diarrhea
    • 62
      METABOLIC ACIDOSIS
      • Treating the underlying cause of metabolic acidosis is the usual course of action
      • Control diabetes with insulin or treat poisoning by removing the toxic substancefrom the blood
      • Occasionallydialysis is neededto treat severeoverdoses andpoisonings
    • 63
      METABOLIC ACIDOSIS
      • Metabolic acidosis may also be treated directly
      • If the acidosis is mild, intravenous fluids and treatment for the underlying disorder may be all that's needed
    • 64
      METABOLIC ACIDOSIS
      • When acidosis is severe, bicarbonate may be given intravenously
      • Bicarbonate provides only temporary relief.
    • 65
      METABOLIC ALKALOSIS
      • Elevation of pH due to an increased 20:1 ratio
      • May be caused by:
      An increase of bicarbonate
      A decrease in hydrogen ions
      • Imbalance again cannot be due to CO2
      • Increase in pH which has a non-respiratory origin
      7.4
    • 66
      METABOLIC ALKALOSIS
      • A reduction in H+ in the case of metabolic alkalosis can be caused by a deficiency of non-carbonic acids
      • This is associated with an increase in HCO3-
    • 67
      METABOLIC ALKALOSIS
      Can be the result of:
      Ingestion of Alkaline Substances
      2. Vomiting ( loss of HCl )
    • 68
      METABOLIC ALKALOSIS
      Gastric juices contain large amounts of HCl
      During HCl secretion, bicarbonate is added to the plasma
      H+
      K+
      HCl
      HCO3-
      Cl-
    • 69
      METABOLIC ALKALOSIS
      The bicarbonate is neutralized as HCl is reabsorbed by the plasma from the digestive tract
      K+
      HCl
      H+
      Cl-
      H2CO3
      HCO3-
    • 70
      • During vomiting H+ is lost as HCl and the bicarbonate is not neutralized in the plasma
      • Loss of HCl increases the plasma bicarbonate and thus results in an increase in pH of the blood
      K+
      HCl
      Bicarbonate not neutralized
      HCO3-
    • 71
      H2CO3
      HCO3-
      HCO3- + H+
      H+
      +
      CO2
      + H2O
      HCO3-
      :
      1.25
      30
      Alkaline urine
      BODY’S COMPENSATION
      • breathing suppressed to hold CO2
      • kidneys conserve H+ ions and eliminate
      HCO3- in alkaline urine
    • 72
      METABOLIC ALKALOSIS
      Cl-
      H2CO3
      HCO3-
      Chloride containing solution
      :
      1.25
      25
      • Therapy required to restore metabolic
      balance
      • HCO3- ions replaced by Cl- ions
    • 73
      ACID – BASE DISORDERS
    • CLINICAL EVALUATION OF DISTURBANCES IN ACID BASE STATUS
      74
    • ANION GAP
      The term anion gap (AG) represents the concentration of all the unmeasured anions in the plasma.
      The negatively charged proteins account for about 10% of plasma anions.
      Reference range is 8 to 16 mmol/l.
      75
      Anion gap = [Na+] - [Cl-] - [HCO3-]
      AG = [Na+] + [K+] - [Cl-] - [HCO3-]
    • Major Clinical Uses of the Anion Gap
      • To signal the presence of a metabolic acidosis and confirm other findings.
      • Help differentiate between causes of a metabolic acidosis.
      ORGANIC INORGANIC
      • To assist in assessing the biochemical severity of the acidosis and follow the response to treatment .
      76
    • General Factors affecting Acid-Base Balance in Infants
      • Low Bicarbonate depends
      on Gestational Age
      • lower renal threshold
      • lower capacity to reabsorb HCO3-
      • Very low birth weight babies: bicarbonate levels of 12-16 mmoles/l
      • Term babies : levels of 20-22 mmol/l.
      77
    • 78
      The rate of metabolism in infants is twice as great in relation to body mass as in adults
      Twice as much acid is formed which leads to a tendency toward acidosis
      Functional development of kidneys is not complete until the end of the first month
      Renal regulation of acid base may not be optimal.
    • Low Reserve to excrete an Acid Load
      • Term infants, acid excretion is working near maximum capacity and there is little reserve to deal with acidosis.
      • Preterm babies less capacity than a term neonate to buffer an acid load.
      79
    • 80
      Other Factors
      Growth results in deposition of base in new bone as the calcium salts in bone are alkaline salts.
      On a weight basis, fixed acid production is higher than in adults.
      Neonates and children < 12 months
      fixed acid production is 2 to 3 mmol/kg/day).
    • Infantile Metabolic Acidosis 
      • Different inborn errors of metabolism cause a metabolic acidosis:
      • organic acidosis (enzyme defect resulting in accumulation of acidic metabolic intermediates)
      • lactic acidosis
      • hyperchloraemic acidosis
      • Feeding difficulties often in association with tachypnoea
      81
    • Lactic acidosis : enzyme defects and present during childhood.
      • pyruvatecarboxylase deficiency
      • fructose-1,6-diphosphatase deficiency
      • pyruvatedehydrogenase deficiency.
      not an isolated finding as these children have serious dysfunctions of organ systemsesp. affecting brain, liver and muscle.
      82
    • Other Acid-Base Disorders in Children
      Insulin dependent diabetes mellitus usually presents during childhood or adolesence.
      Poisoning in children may cause an acid-base disorder
      83
    • REFERENCES
      Fundamentals of physiology: a human perspective:Lauralee Sherwood; Fluid and acid base balance; page:453-61
      Essentials of medical physiology:
      K Sembulingam; Acid base balance:36-47
      Ganong’s Review of Medical Physiology: Renal physiology: 679-682
      84
    • THANK YOU
      Presented by:
      Dr. Ruby Kharkwal
      1st year postgraduate student
      Department of Pedodontics
      85