Acid – Base BalanceInstitute of Nephrology and        Hypertension Carmel Medical Center
Acid – Base BalanceInstitute of Nephrology and        Hypertension Carmel Medical Center
Acid – base balance
Acid – Base Balance Normal concentration of H + in  extracellular fluid is 40 nmol/L.
Acid – Base Balance Roughly one millionth the concentration of  Na , K, Cl and Bicarb.
Acid – Base Balance In normal conditions this concentration is  very well controlled
Acid – Base Balance Three basic steps1 – Chemical Buffering2 - Control of PP of CO 2 ( alveolar  ventilation)3 – Control ...
Acid – Base BalanceTwo kinds of acids1- Carbonic2- Non Carbonic
Acid – Base Balance Metabolism results in the generation of  approximately 15000 mmol CO2 CO 2 + H2O = H2CO3
Acid – Base Balance An acid is a substance that can donate H + A base is a substance that can accept H + H2CO3 , HCl, N...
Acid – Base BalanceNon Carbonic acids are derived from protein  metabolism .50 to 100 meq/day of H + are produced daily  a...
Acid – Base BalanceIf HCl is addedHCl + Na2HPO4 -----NaCl + NaH2PO4
Acid – Base BalanceH CO3 + H+ ------ H2O + CO2
Acid – Base Balance                   HCO3 (Salt)=20 pH= pK + log                 H2CO3=pCO2 (Acid)=1
Acid – Base Balance   Stop   Think   Get anamnesis   Physical examination   pH   Bicarbonate   pCO2   Adequacy of ...
Diagnosis The evaluation always starts with the anamnesis Then determine the pH See if compensation adequate Remember,...
Metabolic Acidosis Characterized by a fall in the plasma  bicarbonate and a low pH Either by bicarbonate loss Or additi...
Metabolic Acidosis Normal anion gap Gastro- intestinal loss of bicarbonate Renal loss:   a. Proximal RTA   b. Distal RT...
Acid – base balance If metabolic acidosis, determine anion gap If metabolic alkalosis, determine volume status
Metabolic acidosis               High anion gap Lactic acidosis Ketoacidosis Renal failure - Organic acids Intoxicatio...
Metabolic Alkalosis How do patients become alkalotic? How do patients remain alkalotic?
Metabolic Alkalosis Results from elevation of plasma  bicarbonate associated with high pH May be due to bicarbonate admi...
Causes of Metabolic Alkalosis Loss of H+: Gastrointestinal loss              Renal loss: Diuretics                       ...
Metabolic Alkalosis       Impaired HCO3 excretion with perpetuation of                  metabolic alkalosis Decreased GFR...
DiagnosisMetabolic alkalosis, determine chloride in urine to differentiate volume dependency or not
Urine Cl- in Metabolic Alkalosis   Less than 25 mEq/l     More than 40 mEq/l Vomiting               Mineralocorticoid D...
ExampleNa 140K 3.4Cl 77Bicarbonate 9Anion gap 54pH 7.23pCO2 23Ketonuria: tracesCreatinine 2.3 Why do they remain alkalotics
Compensations                              Metabolic Alkalosis                              pCO2 = 40+ 0.6 delta BICMetabo...
Compensations?Respiratory Acidosis   Respiratory AlkalosisAcute                  AcuteHCO3 = + 1 mEq/10 mm   HCO3 = - 1-2 ...
ExampleBUN 100Na 142Cl 120pH 7.4pCO2 20Bicarbonate 13
ExampleBUN 15Na 140Cl 105pH 7.02pCO2 40Bicarbonate 10
ExampleBUN 12Na 146Cl 100pH 7.60pCO2 37Bicarbonate 35K 3.5
ExampleBUN 14Na 140Cl 108pH 7.37pCO2 20Bicarbonate 11K 3.8
Example20 y old vomiting, lethargy, tachypnea,  tachycardia BP 150/100. IDDM , no insulin  lately. Almost no food last few...
continuation                               Diabetic ketoacidosis   Treated with insulin,2.5 Lt saline and Potassium     ...
continuation LESSONS Consider all possibilities Urine Ketones positive in starvation and  vomiting Check urine output ...
EXERCISE pH 7.49 Bic 35 PCO2 48 Anion Gap16
CONTINUATION Compensation – PCO2 40+ 0.6 x Delta bic ( 35 – 24 ) = 8 48mm- The anion gap is normal Simple Metabolic Al...
EXERCISE pH 7.68 Bic 40 pCO2 35 Anion Gap 14
Continuation pCO2 should be 40+ 0.6 ( 40-24) = 49.6 Anion Gap is |normal Combined Metabolic and Respiratory  Alkalosis
EXERCISE pH 7.26 pCO2 60 Bic 26
CONTINUATION Compensation is +1 mEq/10 mm CO2 Bic is 26 – pCO2 is up 20mm Hg-  compensation is adequate for
CONTINUATION Acute respiratory Acidosis
EXERCISE Complains of difficulty in breathing for the  last 4 days pH 7.42 pCO2 30 Bic 19 Anion Gap 16
continuationChronic Respiratory Alkalosis
Continuation Adequate compensation is ( - ) 5 mEq Bicarbonate / 10 mm Hg If acute, Bic should be 23 Since it is Chroni...
EXERCISE pH 7.45 Bic 44 pCO2 65 Anion Gap 14
CONTINUATION For Met Alk pCO2 should be                40  = 0.6( 44-24)= 52 pCO2 is to high ( 65 ), so Metabolic Alkal...
EXERCISE 21 y old IDDM presents with vomiting pH 7.75 pCO2 24 BIC 32 Anion Gap 30
CONTINUATION Adequate Compensation : pCO2 should be 40+ 0.6 ( 32-24 )= 44.8, so Respiratory Alkalosis. Anion Gap is 30...
CONTINUATION Severe Respiratory Alkalosis + Severe High  Anion Gap Metabolic Acidosis+ Severe  Metabolic Alkalosis.
The End          ‫ת ו ד ה‬
Icm acid base 304
Icm acid base 304
Icm acid base 304
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Icm acid base 304

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  • 1. Buffering\n2. Lungs\n3. through the kidneys\n
  • every day create enormous amounts of carbonic acid\n- eliminated by breeating\n
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  • weak acid: acid able to get the H and that will keep it there (bc not well ionized)\n
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  • HH equation\n\nmore salt: pH goes up\nmore acid: pH goes down\n
  • 1. check pt\n2. check blood gases\na. pH (compensation is never complete)\n\n\n
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  • pH goes down- resp center works more bc of receptors that sense pH\n\n- always have same amount of - and + charges all over\n- anion gap: other things we dont measure in the blood that contribute \n- Na: 140 (positive)\n- Cl: 100 (negative)\n- bicarb: 22/23 (negative)\n- cl and bicarb should equal na, but it doesnt bc of other things affecting it\n- normal anion gap: 14-16\n- created when pt loses bicarbonate\n- met acidosis, w normal anion gap: means pt lost bicarb\n- lose bicarb: GIT or renal losses\n
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  • high anion gap: \n- when add acid\n\nadd acid:\n1. severe prolonged exercise: lactic acidosis\n2. diabetes: great amount of ketones in the body\n3. renal failure: kidneys cant eliminate the end product of metabolism: acids\n4. Intoxications\n- methanol dx: have severe optic nerve neuritis- disc is very fuzzy\n- salicilate: combo of metabolic acidosis and resp alkalosis: aspirate\ncreatinine- component of the muscle\n- have about 1\n- useful to measure kidney fnxn in steady state\n- takes time to rise\n- of take out 2 kidneys: and measure:\n- cr = normal (takes time to accum)\n- GFR = 0\n\n
  • add acid- get met acidosis\nadd base- no problem\nwhay?\nbc bicarb: peed out\n- this is how all bicarb, w normal kidneys, gets out\nmost common acid/base problem in the hospital = metabolic alkalosis\nmet alkalosis:\n-get bicarb\n- impede bicarb excretion\n\n1) excess of suprarenal homones\n2) dehydration\n- GFR go down, bicarb reabsorbed, bicarb of blood increases\n
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  • - can lose H whenever H goes into the cells\n\n
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  • - pH low = acidosis\n- bicarb low = met acidosis\n- high anion gap\n- high creatinine \n- you almost ALWAYS get traces of ketones (so prob not ketonuria)\n- is compensation adequate? compensation (low pco2)... next slide\n\n\n\n\n\n\n
  • approximation: level of pco2 should be equal to the last 2 digits of the pH\n(doesnt alway work- bc there is a level of pco2 that you cant reach- cant go below 20)\n... so it IS ADEQUATE\n
  • resp compensation in metabolic problems is immediate\n- metabolic compensations to resp problems is SLOW\n\namount of coompensation by the kidneys- depends on how long the resp problem has been present\n\nacute: less than 24 hours: 1\nchronic: 3.5-5\n\n
  • normal pH - can be due to fact that have 2 alterationds in 2 diff directions\nwhen have high cl- anion gap is prob normal\n- lways check the anion gap! \n\n- when have normal pH- and other problems- must have at least 2 problems- bc compensation is never complete\n\nASPIRIN DOES THAT\n
  • pH low - acidosis\nbicarb low: met acidosis\nanion gap is high\npco2- normal\n- should be low! no compensation\n
  • only calculate anion gap in metabolic acidosis\n\nph high: alkalosis\nbicarb high: met alkalosis\ncompensation: pco2 should be higher- not enough compensation\n\nmet acidosis and resp alkalosis\n
  • ph: lower border of what expect: acidosis\nbicarb: low (by ~ 12) - met acidosis\npco2: low (by 20)\nanion gap: high\ncompensation: not adequate\n\nthere is no such thing as OVER-COMPENSATION\n\n
  • ph: acidosis\nbicarb: low (by 7) - met acidosis\nanion gap: 20: high\ncompensation: about 28, with pco2 of 34 (bc also have vomiting)\nhigh anion gap metabolic acidosis\n\n\nurinary ketones in a person who is not eating- makes sense\n- its enough for a person to get ketones in urine after dont eat for 16 hours\n\n\n\n\n
  • also has renal failure\n\n\nnormal cr = 0.9!- acute renal failure\n\n\ncheck all possibilities- bc certain tx can be problematic\n
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  • ph: high- alkalosis\nbicarb: high- met alkalosis\ncompensation: adequate\n\n\n\n
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  • ph: high= alkalosis\nbicarb: high = met alkalosis\ncompensation: not adequate\n\n(can start by assuming that the pt has two problems in the same direction- bc the ph is so high)\n\n
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  • resp acidosis\npco2: high\n\nacute: bc kidneys havent started to compensate yet-\n- bicarb only changed 2, and pco2 is 20 over the normal \n
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  • ph: high\nbicarb- low: resp alkalosis\npco2- low: \n\nresp alkalosis\n\n\nevery 10 change in pco2: should have:\n- 1 change in bicarb = acute; \n- up to 5= chronic\n
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  • alkalosis\nmetabolic\n\n
  • why not resp acidosis and compensation?\n- bc cant have too much compensation- no such thing- this cant happen- ph is too high\n
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  • Icm acid base 304

    1. 1. Acid – Base BalanceInstitute of Nephrology and Hypertension Carmel Medical Center
    2. 2. Acid – Base BalanceInstitute of Nephrology and Hypertension Carmel Medical Center
    3. 3. Acid – base balance
    4. 4. Acid – Base Balance Normal concentration of H + in extracellular fluid is 40 nmol/L.
    5. 5. Acid – Base Balance Roughly one millionth the concentration of Na , K, Cl and Bicarb.
    6. 6. Acid – Base Balance In normal conditions this concentration is very well controlled
    7. 7. Acid – Base Balance Three basic steps1 – Chemical Buffering2 - Control of PP of CO 2 ( alveolar ventilation)3 – Control of Bicarb concentration ( H excretion ).
    8. 8. Acid – Base BalanceTwo kinds of acids1- Carbonic2- Non Carbonic
    9. 9. Acid – Base Balance Metabolism results in the generation of approximately 15000 mmol CO2 CO 2 + H2O = H2CO3
    10. 10. Acid – Base Balance An acid is a substance that can donate H + A base is a substance that can accept H + H2CO3 , HCl, NH4, H2PO4 can act as acids
    11. 11. Acid – Base BalanceNon Carbonic acids are derived from protein metabolism .50 to 100 meq/day of H + are produced daily and excreted in the urine
    12. 12. Acid – Base BalanceIf HCl is addedHCl + Na2HPO4 -----NaCl + NaH2PO4
    13. 13. Acid – Base BalanceH CO3 + H+ ------ H2O + CO2
    14. 14. Acid – Base Balance HCO3 (Salt)=20 pH= pK + log H2CO3=pCO2 (Acid)=1
    15. 15. Acid – Base Balance Stop Think Get anamnesis Physical examination pH Bicarbonate pCO2 Adequacy of compensation
    16. 16. Diagnosis The evaluation always starts with the anamnesis Then determine the pH See if compensation adequate Remember, compensation is never complete Metabolic acidosis, determine anion gap Metabolic alkalosis, determine volume status
    17. 17. Metabolic Acidosis Characterized by a fall in the plasma bicarbonate and a low pH Either by bicarbonate loss Or addition of acid This results in compensatory decrease of pCO2
    18. 18. Metabolic Acidosis Normal anion gap Gastro- intestinal loss of bicarbonate Renal loss: a. Proximal RTA b. Distal RTA c. Type IV RTA (Hypoaldosteronism) d. Ammonium chloride e. Hyperalimentation
    19. 19. Acid – base balance If metabolic acidosis, determine anion gap If metabolic alkalosis, determine volume status
    20. 20. Metabolic acidosis High anion gap Lactic acidosis Ketoacidosis Renal failure - Organic acids Intoxications a. Salicilate b. Methanol c. Ethylene glycol d. Sulfur Rhabdomyolysis
    21. 21. Metabolic Alkalosis How do patients become alkalotic? How do patients remain alkalotic?
    22. 22. Metabolic Alkalosis Results from elevation of plasma bicarbonate associated with high pH May be due to bicarbonate administration May be due to H+ loss Respiratory compensation consists of hypoventilation and pCO2 elevation
    23. 23. Causes of Metabolic Alkalosis Loss of H+: Gastrointestinal loss Renal loss: Diuretics Mineralocorticoid excess Penicillins Hypercalcemia Hydrogen movement into the cells - Hypokalemia Retention of bicarbonate: Blood transfusion Bicarb administration Contraction alkalosis: Diuretics
    24. 24. Metabolic Alkalosis Impaired HCO3 excretion with perpetuation of metabolic alkalosis Decreased GFR Volume depletion Increased tubular reabsorption Volume depletion Chloride depletion Hypokalemia Hyperaldosteronism
    25. 25. DiagnosisMetabolic alkalosis, determine chloride in urine to differentiate volume dependency or not
    26. 26. Urine Cl- in Metabolic Alkalosis Less than 25 mEq/l More than 40 mEq/l Vomiting  Mineralocorticoid Diuretics excess Cystic Fibrosis  Diuretics (early)  Alkali load  Severe Hypokalemia
    27. 27. ExampleNa 140K 3.4Cl 77Bicarbonate 9Anion gap 54pH 7.23pCO2 23Ketonuria: tracesCreatinine 2.3 Why do they remain alkalotics
    28. 28. Compensations Metabolic Alkalosis pCO2 = 40+ 0.6 delta BICMetabolic AcidosispCO2 = 2 last numbers of pHpCO2 = 1.5 x ( HCO3) + 8
    29. 29. Compensations?Respiratory Acidosis Respiratory AlkalosisAcute AcuteHCO3 = + 1 mEq/10 mm HCO3 = - 1-2 mEq/10 Hg pCO2 mm Hg pCO2Chronic ChronicHCO3 = + 3.5 mEq/10 HCO3 = - 5 mEq/10 mm mm Hg pCO2 Hg pCO2
    30. 30. ExampleBUN 100Na 142Cl 120pH 7.4pCO2 20Bicarbonate 13
    31. 31. ExampleBUN 15Na 140Cl 105pH 7.02pCO2 40Bicarbonate 10
    32. 32. ExampleBUN 12Na 146Cl 100pH 7.60pCO2 37Bicarbonate 35K 3.5
    33. 33. ExampleBUN 14Na 140Cl 108pH 7.37pCO2 20Bicarbonate 11K 3.8
    34. 34. Example20 y old vomiting, lethargy, tachypnea, tachycardia BP 150/100. IDDM , no insulin lately. Almost no food last few days, Na 142, K 3.6, Cl 106, Bic 16, Gluc 230, Urea 190 , Creatinine pending, pH 7.28, PCO2 34. Urine Ketones moderately positive-a couple of hours ago. No urine since.
    35. 35. continuation Diabetic ketoacidosis Treated with insulin,2.5 Lt saline and Potassium chloride After 3 hours patient lethargic, Met Ac not improved, Gluc 70, jugular ++ reflux++ Rales +++ Anuria At last, Creatinine results………12…..
    36. 36. continuation LESSONS Consider all possibilities Urine Ketones positive in starvation and vomiting Check urine output before giving IV Control your patient often !!!
    37. 37. EXERCISE pH 7.49 Bic 35 PCO2 48 Anion Gap16
    38. 38. CONTINUATION Compensation – PCO2 40+ 0.6 x Delta bic ( 35 – 24 ) = 8 48mm- The anion gap is normal Simple Metabolic Alkalosis
    39. 39. EXERCISE pH 7.68 Bic 40 pCO2 35 Anion Gap 14
    40. 40. Continuation pCO2 should be 40+ 0.6 ( 40-24) = 49.6 Anion Gap is |normal Combined Metabolic and Respiratory Alkalosis
    41. 41. EXERCISE pH 7.26 pCO2 60 Bic 26
    42. 42. CONTINUATION Compensation is +1 mEq/10 mm CO2 Bic is 26 – pCO2 is up 20mm Hg- compensation is adequate for
    43. 43. CONTINUATION Acute respiratory Acidosis
    44. 44. EXERCISE Complains of difficulty in breathing for the last 4 days pH 7.42 pCO2 30 Bic 19 Anion Gap 16
    45. 45. continuationChronic Respiratory Alkalosis
    46. 46. Continuation Adequate compensation is ( - ) 5 mEq Bicarbonate / 10 mm Hg If acute, Bic should be 23 Since it is Chronic Respiratory Alkalosis ( more than 48 hours) Bic should be ( 24- 5)= 19 Anion Gap is normal- there is no hidden Met Ac Simple Chronic Respiratory Acidosis
    47. 47. EXERCISE pH 7.45 Bic 44 pCO2 65 Anion Gap 14
    48. 48. CONTINUATION For Met Alk pCO2 should be 40 = 0.6( 44-24)= 52 pCO2 is to high ( 65 ), so Metabolic Alkalosis + Respiratory Acidosis Why not respiratory acidosis + compensation?
    49. 49. EXERCISE 21 y old IDDM presents with vomiting pH 7.75 pCO2 24 BIC 32 Anion Gap 30
    50. 50. CONTINUATION Adequate Compensation : pCO2 should be 40+ 0.6 ( 32-24 )= 44.8, so Respiratory Alkalosis. Anion Gap is 30 , so Hidden Metabolic Acidosis. Delta Anion Gap 16, Bic should have fallen to + - 6-8, but is 32
    51. 51. CONTINUATION Severe Respiratory Alkalosis + Severe High Anion Gap Metabolic Acidosis+ Severe Metabolic Alkalosis.
    52. 52. The End ‫ת ו ד ה‬

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