1. F. Rashid Farokhi Nephrologist Masih Daneshvari Hospital
ACID base disorders
F. Rashid Farokhi
Nephrologist
Masih Daneshvari Hospital

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

3. 6.8
7.35
7.4
7.45
7.8
Arterial PH

4. How can the body regulate H+ concentration in such a low concentration despite of
Daily production of meq CO2
Daily production of meq nonviolate acids
Entrance of exogenous acids ?

5. circulation
CO2 +H2O H+ + HCO3-

6. HPhosphate- H+ + phosphate -
Buffering systems
H2CO H+ + HCO3-
H2PO H+ +H PO4 2-
HAlb H+ + Alb-
HHgb H+ + Hgb -
HProt H+ + Prot –
HPhosphate H+ + phosphate -

7. K1[CO2] K2[Halb] K3[H2PO4-] Kn[HA] [HCO3-] [alb-] [HPO4-2] [A-]
H2CO H+ + HCO3 –
V1  [H2CO3]
H+ + HCO 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/( ) + [Albumin] ×(0.123×PH ) + [PO4]}×(0.309× PH-0.469)
-PH

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

10. Example 1: PH=7.50 , HCO3 =28 , PCO2=40 PCO2 [H+] = 24 × [HCO3-] 40
? = 24 ×
[HCO3-]

11. [H+] =24× [ HCO3-] [H+] PH 40 1.25  1.25 1.25 = 80 7.1
PCO2
[ HCO3-]
[H+] PH
40 1.25  1.25 1.25 =
40 1.25  1.25 =
40  1.25 =
40  0.8 =
40 0.8  0.8 =
40  0.8  0.8 0.8 =
[H+] =24×

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

13. The effect of respiratory system on acid base balance
C6H12O CO2 +6H2O
CO2 + H2O H2CO 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-

17. Acid base
disorders

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

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

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

21. Respiratory compensation in metabolic acidosis
PH = 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

22. Respiratory compensation in metabolic alkalosis
PH = 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

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

24. PH = 6.1+ log {HCO3- / [0.03 x PCO2]}
Respiratory
Alkaloosis
PCO2
PH = 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

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

26. 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

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

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

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

31. 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

32. anion gap in approach of metabolic acidosis

33. 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

34. 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?

35. High anion gap metabolic acidosis
H+ + HCO H2O + CO2 + A- HA

36. Hyperchloremic metabolic acidosis
H+ + HCO H2O + CO2 + Cl-
HCl

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

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

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

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

41. 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

42. 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= =14
14+5+=19
∆ AG = 19-10= 9
9/15 <1

43. 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?

44. 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 mmHg this calculation is accurate invitro but not invivo, so SBE is calculated

45. Base excess in acid base disorders
Metabolic acidosis: SBE<-5 PCO2 = 40 + SBE
Metabolic alkalosis: SBE>+5 PCO2= 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)

46. 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?

47. 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

48. 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

49. 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

50. Comparison of normal arterial and venous blood gas parameters
ABG mmHg VBG mmHg
Pco
HCO PH

52. Strong Ion Differences

53. 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

54. Strong Ion Differences approach to acid base disorders
Most internists traditional approach to acid base disorders considering : H+ = K× PCO2/HCO3
popularized by Relman and Schwartz in 1960s
Many surgeons, critical care specialists and anesthesiologists are interested in an alternative approach, termed strong ion differerences
introduced by Stewart in 1981

55. Acid is a proton donor Base is a proton acceptor
Definition of Acids and Bases based on
traditional approach
Acid is a proton donor
Base is a proton acceptor

56. Definition of Acids and Bases In Stewart approach:
Acid is as ion that shift the dissociation equilibrium of water to:
higher concentration of H+ and
lower concentration of OH-
Base is as ion that shift the dissociation equilibrium of water to:
lower concentration of H+ and
higher concentration of OH-

57. Pure Water H20 H+ + OH- Body-7 -8
H+ = 4 ×10

58. Strong cations : Na, Ca, Mg, K
Weak cations: H
Strong Anions: Cl, Lactate,
Weak Anions: Albumin, Phosphate, HCO3

59. [ Na + Ca + Mg + K] - [Cl + lactate] = SID( apparent)
SID>40 : metabolic alkalosis
[ Na + Ca + Mg + K] > [Cl + lactate]
OH- H+
H H OH-
H2O

60. [ Na + Ca + Mg + K] - [Cl + lactate] = SID( apparent)
SID<40 : metabolic acidosis
[ Na + Ca + Mg + K] < [Cl + lactate]
OH- H+
H H OH-
H2O

61. [ Na + Ca + Mg + K] - [Cl + lactate] = SID( apparent)
SID<40 : metabolic acidosis
[ Na + Ca + Mg + K] < [Cl + lactate]
OH- H+
H H OH-
H2O

62. According to modified SID theory variables responsible for change in acid base balance are :
PCO2
Nonvolatile weak acids
Strong Ions

63. Strong Cations + weak cations = Strong Anions + Weak Anions
Strong Cations - Strong Anions= Weak Anions - Weak Cations
[ Na + Ca + Mg + K] - [Cl + lactate] = Weak anions

64. K1[CO2] K2[Halb] K3[H2PO4-] Kn[HA] [HCO3-] [alb-] [HPO4-2] [A-]
H2CO H+ + HCO3 –
V1  [H2CO3]
H+ + HCO 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+] = = =

65. [ Na + Ca + Mg + K] - [Cl + lactate] = SID( apparent)
SID app – SID eff = SID gap

66. anion gap and serum albumin in traditional approach
If we consider
anion gap and serum albumin
in traditional approach
stewart approach does not appear a clinically significant advantage