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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Transcript

  • 1. Acid – Base BalanceInstitute of Nephrology and Hypertension Carmel Medical Center
  • 2. Acid – Base BalanceInstitute of Nephrology and Hypertension Carmel Medical Center
  • 3. Acid – base balance
  • 4. Acid – Base Balance Normal concentration of H + in extracellular fluid is 40 nmol/L.
  • 5. Acid – Base Balance Roughly one millionth the concentration of Na , K, Cl and Bicarb.
  • 6. Acid – Base Balance In normal conditions this concentration is very well controlled
  • 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. Acid – Base BalanceTwo kinds of acids1- Carbonic2- Non Carbonic
  • 9. Acid – Base Balance Metabolism results in the generation of approximately 15000 mmol CO2 CO 2 + H2O = H2CO3
  • 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. 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. Acid – Base BalanceIf HCl is addedHCl + Na2HPO4 -----NaCl + NaH2PO4
  • 13. Acid – Base BalanceH CO3 + H+ ------ H2O + CO2
  • 14. Acid – Base Balance HCO3 (Salt)=20 pH= pK + log H2CO3=pCO2 (Acid)=1
  • 15. Acid – Base Balance Stop Think Get anamnesis Physical examination pH Bicarbonate pCO2 Adequacy of compensation
  • 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. 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. 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. Acid – base balance If metabolic acidosis, determine anion gap If metabolic alkalosis, determine volume status
  • 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. Metabolic Alkalosis How do patients become alkalotic? How do patients remain alkalotic?
  • 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. 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. Metabolic Alkalosis Impaired HCO3 excretion with perpetuation of metabolic alkalosis Decreased GFR Volume depletion Increased tubular reabsorption Volume depletion Chloride depletion Hypokalemia Hyperaldosteronism
  • 25. DiagnosisMetabolic alkalosis, determine chloride in urine to differentiate volume dependency or not
  • 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. ExampleNa 140K 3.4Cl 77Bicarbonate 9Anion gap 54pH 7.23pCO2 23Ketonuria: tracesCreatinine 2.3 Why do they remain alkalotics
  • 28. Compensations Metabolic Alkalosis pCO2 = 40+ 0.6 delta BICMetabolic AcidosispCO2 = 2 last numbers of pHpCO2 = 1.5 x ( HCO3) + 8
  • 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. ExampleBUN 100Na 142Cl 120pH 7.4pCO2 20Bicarbonate 13
  • 31. ExampleBUN 15Na 140Cl 105pH 7.02pCO2 40Bicarbonate 10
  • 32. ExampleBUN 12Na 146Cl 100pH 7.60pCO2 37Bicarbonate 35K 3.5
  • 33. ExampleBUN 14Na 140Cl 108pH 7.37pCO2 20Bicarbonate 11K 3.8
  • 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. 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. continuation LESSONS Consider all possibilities Urine Ketones positive in starvation and vomiting Check urine output before giving IV Control your patient often !!!
  • 37. EXERCISE pH 7.49 Bic 35 PCO2 48 Anion Gap16
  • 38. CONTINUATION Compensation – PCO2 40+ 0.6 x Delta bic ( 35 – 24 ) = 8 48mm- The anion gap is normal Simple Metabolic Alkalosis
  • 39. EXERCISE pH 7.68 Bic 40 pCO2 35 Anion Gap 14
  • 40. Continuation pCO2 should be 40+ 0.6 ( 40-24) = 49.6 Anion Gap is |normal Combined Metabolic and Respiratory Alkalosis
  • 41. EXERCISE pH 7.26 pCO2 60 Bic 26
  • 42. CONTINUATION Compensation is +1 mEq/10 mm CO2 Bic is 26 – pCO2 is up 20mm Hg- compensation is adequate for
  • 43. CONTINUATION Acute respiratory Acidosis
  • 44. EXERCISE Complains of difficulty in breathing for the last 4 days pH 7.42 pCO2 30 Bic 19 Anion Gap 16
  • 45. continuationChronic Respiratory Alkalosis
  • 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. EXERCISE pH 7.45 Bic 44 pCO2 65 Anion Gap 14
  • 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. EXERCISE 21 y old IDDM presents with vomiting pH 7.75 pCO2 24 BIC 32 Anion Gap 30
  • 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. CONTINUATION Severe Respiratory Alkalosis + Severe High Anion Gap Metabolic Acidosis+ Severe Metabolic Alkalosis.
  • 52. The End ‫ת ו ד ה‬