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ACID base disorders

F. Rashid Farokhi Nephrologist Masih Daneshvari Hospital. ACID base disorders. - 6. - 9. Extra cellular fluid H+ concentration [H +] = 40  10 meq/lit = 40  10 Eq/lit PH = - log [H+] PH = 7.35 - 7.45. meq. - 7. 7.4. 7.35. 7.45. 6.8. 7.8.

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ACID base disorders

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  1. F. Rashid Farokhi Nephrologist MasihDaneshvari Hospital ACID base disorders

  2. - 6 - 9 Extra cellular fluid H+ concentration [H +] = 40  10 meq/lit = 40  10 Eq/lit PH = - log [H+] PH = 7.35 - 7.45 meq - 7

  3. 7.4 7.35 7.45 6.8 7.8 Arterial PH

  4. How can the body regulate H+ concentration in such a low concentration despite of • Daily production of 15000 meq CO2 • Daily production of 50-100 meqnonviolate acids • Entrance of exogenous acids ?

  5. circulation CO2 +H2O H+ + HCO3-

  6. Buffering systems H2CO3 H+ + HCO3- H2PO4 - H+ +H PO4 2- HAlb H+ + Alb- HHgb H+ + Hgb - HProt H+ + Prot – HPhosphate- H+ + phosphate -

  7. H2CO3 H+ + HCO3 – V1  [H2CO3] H+ + HCO3- H2CO3 V2  [H+]  [HCO3-] V1 =V2 [H2CO3] [H+]  [HCO3-] [H+] [HCO3-] [H2CO3] K1[CO2] K2[Halb] K3[H2PO4-] Kn[HA] [HCO3-] [alb-] [HPO4-2] [A-] = K [H+] = = = =

  8. BB= 12.2 × PCO2/(10 ) + [Albumin] ×(0.123×PH-0.0631) + [PO4]}×(0.309× PH-0.469) -PH

  9. H20 + CO2 H2CO3 H+ + HCO3- [CO2] [H+] = K × [HCO3-] PCO2 × 0.03 [H+] = 800 × [HCO3-] PCO2 = 24 × [HCO3-]

  10. Example1: PH=7.50 , HCO3 =28 , PCO2=40 PCO2 [H+] = 24 × [HCO3-] 40 ? = 24 × [HCO3-]

  11. [H+] =24× PCO2 [ HCO3-] [H+] PH 40 1.25 1.25 1.25 = 80 7.1 40 1.25 1.25 = 63 7.2 40 1.25 = 50 7.3 40 7.4 40  0.8 = 32 7.5 40 0.8  0.8 = 26 7.6 40  0.8  0.8 0.8 = 20 7.7

  12. PH=7.50 , HCO3 = 30 , PCO2=40 PCO2 [H+] = 24 × [HCO3-] 40 32 = 24 × 30

  13. The effect of respiratory system on acid base balance C6H12O6 + 602 6CO2 +6H2O CO2 + H2O H2CO3 H+ + HCO3-

  14. Proximal tube NaHCO3 OH- H+ Na+ H+ Proxoimal tubule CO2 + H20 HCO3 +

  15. Distal tubules H+ + HCO3- H2O + CO2 + A- HA H+ + A- HA H+ H+ CO2 OH- HCO3- +

  16. Acid base disorders

  17. What is the difference between acidemia and acidosis, alkalemia and alkalosis?

  18. Metabolic acidosis HCO3 Respiratory Acidosis PCO2 PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Acidemia PH

  19. Metabolic alkalosis HCO3 Respiratory Alkalosis PCO2 PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Alkalemia PH

  20. Respiratory compensation in metabolic acidosis PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Acidemia PH Metabolic acidosis HCO3 PCO2 = (1.5×Hco3) + 8 ± 2 Or 1.25 mmHg fall in the PCO2 for every 1 meq/lit reduction in the bicarbonate

  21. Respiratory compensation in metabolic alkalosis PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Alkalemia PH Metabolic alkalosis HCO3 PCO2 = HCO3 + 15 Or 0.75 mmHg rise in the PCO2 for every 1 meq/lit elevation in the bicarbonate

  22. Respiratory Acidosis PCO2 PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Acidemia PH Acute: HCO3 rises 1meq/lit for every 10 mmHg elevation in PCO2 Chronic: HCO3 rises 4 meq/lit for every 10 mmHg elevation in PCO2

  23. Respiratory Alkaloosis PCO2 PH = 6.1+ log {HCO3- / [0.03 x PCO2]} Alkalemia PH Acute: HCO3 falls by 2 meq/lit for every 10 mmHg decline in PCO2 Chronic: HCO3 falls by 4 meq/lit for every 10 mmHg decline in PCO2

  24. Example 1: PH=7.50 , HCO3 = 30 , PCO2=40 Mixed metabolic and respiratory alkalosis

  25. Examples 2: 1- PH =7.25 ,HCO3=12 , PCO2=25 compensated metabolic acidosis 2-PH=7.1 , HCO3 =12 , PCO2=30 mixed metabolic and respiratory acidosis

  26. Example 3: PH=7.35 , HCO3= 28 , PCO2=60 Acute respiratory acidosis + metabolic alkaosis Chronic respiratory acidosis +metabolic acidosis

  27. In a patient there is following arterial blood values: PH=7.22 , PCO2 =70 , HCO3= 31 What is the acid base disorder?

  28. HCO3 can be measured by adding a powerful acid to serum: HCO3- +H+ H20+CO2+CL 17.9 + 0.03× 41.7= 17.9 + 1.251= 19.151

  29. What are the problems with PCO2/HCO3 in evaluation of acid base condition It can not determine the: • Severity of metabolic disturbance can not be determined • The etiology of acid base disorder

  30. anion gap in approach of metabolic acidosis

  31. All Anions = All cations Measured Anions +Unmeasured Anions = Measured Cation+Unmeasured Cations M C – MA = UA - UC [Na+] – { [CL-] +[HCO3-] } = UA-UC = AG Anion gap should be corrected with albumin

  32. Example 4:A previously well 55 year old woman is admitted with a complaint of severe vomiting for 5 days. Physical examination reveals postural hypotension, tachycardia and diminished skin turgor. The laboratory findings include: PH=7.23 , PCO2 =22 , HCO3= 9 Na: 140, K: 3.4, Cl: 77, Cr: 2.1, Ketone: trace what is the metabolic disturbances?

  33. High anion gap metabolic acidosis H+ + HCO3- H2O + CO2 + A- HA

  34. Hyperchloremic metabolic acidosis H+ + HCO3- H2O + CO2 + Cl- HCl

  35. [Na+] – { [CL-] +[HCO3-] } = UA-UC = AG HCL + NaHCO3 NaCl +H2O+CO2 HA + NaHCO3 NaA +H2O+CO2 ∆ AG ∆ HCO3

  36. [Na+] – { [CL-] +[HCO3-] } = UA-UC = AG HCL + NaHCO3 NaCl +H2O+CO2 HA + NaHCO3 NaA +H2O+CO2 ∆ AG ∆ HCO3

  37. [Na+] – { [CL-] +[HCO3-] } = UA-UC = AG HCL + NaHCO3 NaCl +H2O+CO2 HA + NaHCO3 NaA +H2O+CO2 ∆ AG ∆ HCO3 AG / HCO3 > 2 : metabolic alkalosis + high anion gap metabolic acidosis

  38. [Na+] – { [CL-] +[HCO3-] } = UA-UC = AG HCL + NaHCO3 NaCl +H2O+CO2 HA + NaHCO3 NaA +H2O+CO2 ∆ AG ∆ HCO3 AG / HCO3 <1 : hyperchloremic metabolic acidosis + high anion gap metabolic acidosis or urine loss of organic anions

  39. Example 4:A previously well 55 year old woman is admitted with a complaint of severe vomiting for 5 days. Physical examination reveals postural hypotension, tachycardia and diminished skin turgor. The laboratory findings include: PH=7.23 , PCO2 =22 , HCO3= 9 Na: 140, K: 3.4, Cl: 77, Cr: 2.1, Ketone: trace what is the metabolic disturbances? ∆ HCO3 = 24-9= 15 ∆ AG ∆ HCO3 AG=140-86=54 ∆ AG = 54-10=44 44/15=3

  40. Example 5: A 58 year old man with a history of chronic bronchitis develop severe diarrhea. The volume of diarrheal fluid is approximately 1 lit/hour. Results of the initial laboratory test is: PH=6.97 , PCO2 =40 , HCO3= 9 Na: 138, K: 3.8, Cl: 115, aibumin: 2 What is the acid base disorder? ∆ HCO3 = 24-9= 15 ∆ AG ∆ HCO3 AG=138-124=14 14+5+=19 ∆ AG = 19-10= 9 9/15 <1

  41. Example 6: A 25 years woman complains of easy fatigability and weakness. She has no other complains. The physical examination is unremarkable, with the blood pressure being normal. The following laboratory data are obtained:plasma [Na+]: 141 meq/lit [K=]: 2.1 meq/lit [Cl-]:85meq/lit [HCo3]: 45 meq/lit urine [Na+]: 80 meq/lit urine [K+]: 170 meq/lit what are your differential diagnosis? What test would you order next?

  42. What is base excess? the amount of base that should be removed from whole blood invitro to restore PH of it to 7.4, while pco2 is held at 40 mmHgthis calculation is accurate invitro but not invivo, so SBE is calculated

  43. Base excess in acid base disorders Metabolic acidosis: SBE<-5 PCO2 = 40 + SBE Metabolic alkalosis: SBE>+5 PCO2= 40+ 0.6 SBE Acute respiratory acidosis: SBE=0 Chronic respiratory acidosis: SBE=0.4(PCO2-40) Acute respiratory alkalosis: SBE=0 Chronic respiratory alkalosis: SBE=0.4(PCO2-40)

  44. Example 7:In a patient there is following arterial blood values: PH=7.22 , PCO2 =70 , HCO3= 31 BE: 5.7 What is the acid base disorder?

  45. Pitfalls of ABG results 1- air bubbles in the syringe • Decreased PCO2 and increased PO2 due to existence of bubbles in the sample Prevention: • gentle removal of bubbles, • rapid sample anaysis

  46. Pitfalls of ABG results 2- the effect of heparin • Dilution of blood parameters , CO2 Prevention: • Use of minimum amount of heparin, • no less than 2 cc of blood should be obtained

  47. Pitfalls of ABG results 3- Specimen transport without ice • Decreased PO2 due to oxygen consumption of leukocytes • Decreased PH and HCO3 due to anaerobic metabolism Prevention: • Rapid cooling of specimen, • rapid sample anaysis

  48. Comparison of normal arterial and venous bloodgas parameters ABG mmHgVBG mmHg • Pco2 35-45 42-50 • HCO3 22-26 23-27 • PH 7.35-7.45 7.32-7.38

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