1. Fernando Schiraldi Giovanna Guiotto
Equilibrio Acido-Base
Fernando Schiraldi Giovanna Guiotto
Ospedale San Paolo - Napoli

2. WHICH ARE THE MAIN pH DETERMINANTS ?
Transport & Buffering
H+ PRODUCTION VS
Renal handling
Alveolar ventilation
plus
Alb, Phosf, Sulf, Na, K, Cl, Mg, Ca, Lact, Krebs intermediates and…….fluids

3. IS A NEAR-NORMAL pH IMPORTANT ?
7.7
7.4
6.7 pH Km

4. THE Hb “FLEXIBILITY”

5. IS Acid-Base balance IMPORTANT for HEMODYNAMICS ?
High pH and Low PCO2
*High SVR, *Dyselectrolitemia,
*Relative tissue Hypoxia
Low pH and High PCO2
*High PVR
*Low SVR

6. H+ vs Ca++ & troponins

7. IS A NEAR-NORMAL pH IMPORTANT ?
pH Acid Normal Basic
K =
Ca++ =
Mg++ =

8. S VISKIN (1999) Lancet 354;

9. ABG ESSENTIALS PRIMARY DISORDER “EXPECTED” COMPENSATION
….PLUS ELECTROLYTES

10. H+ + HCO3- H2CO3 H2O + CO2 20 = 6.1 + 1.3 HCO3- 24 46 28 38pK
CO2
6.1
6.1
20 =
HCO3- 24 46 28 38
pH = log
pH = - log 10 [H+]
= 7.16
= 7.1
= 7.38
= 7.29
= 7.4
PCO2
1.2 40 80
× 0.03
Lawrence Joseph Henderson (1878–1942)
Karl Albert Hasselbalch
( )

11. “a too good pH” H+ + HCO3- H2CO3 H2O + CO2 20 = 6.1 + 1.3 HCO3- 24 28pK
CO2
6.1
6.1
20 =
HCO3- 24 28 46 38
pH = log
pH = - log 10 [H+]
= 7.16
= 7.1
= 7.29
= 7.38
= 7.4
PCO2
1.2 40 80
× 0.03
Lawrence Joseph Henderson (1878–1942)
Karl Albert Hasselbalch
( )

12. “a too good pH” 24 12 pH = 6.1 + log = 7.1 = 7.28 = 7.42 = 7.4 40 1925
× 0.03

13. THE EXPECTED COMPENSATION
HCO3-
PCO2
pH ~
HCO3-
PCO2
pH ~
HCO3-
PCO2
pH ~
HCO3-
PCO2
pH ~

14. Diagnostic Strategies
PO2
acute
RESP ALKALOSIS
CNS
RESP ACIDOSIS
“mixed”
Mediators, drugs
chronic

15. pH vs PCO2 acute “mixed” chronic pH 7.22 7.25 7.32 PCO2 70 70 70 HCO328 30 35

16. pH vs PCO2 “mixed” “mixed” pH 7.08 7.47 PCO2 70 70 HCO3 20 46
THINK OF ‘POSTHYPERCAPNIC !!!
and/or DIURETICS !!!
THINK OF ‘EARLY VENTILATION’

17. BGA AND FLUIDS    IVF  IVF  BLOOD pH  URINE pH DEHYDRATION
 URINE Na, Cl
   IVF
DEHYDRATION
+  BLOOD pH

18. Diagnostic Strategies
PO2
acute
RESP ALKALOSIS
CNS
RESP ACIDOSIS
“mixed”
Mediators, drugs
chronic
IVF (US, Clu)
MET ALKALOSIS
IVF

19. Diagnostic Strategies
PO2
acute
RESP ALKALOSIS
CNS
RESP ACIDOSIS
“mixed”
mediators
chronic AG
IVF (US, Clu)
NAG
UAG
MET ALKALOSIS
MET ACIDOSIS
IVF
SID ?

20. AG = Na – (Cl + HCO3) = 10 ± 2

21. The 4 HAG Metabolic Acidosis
UREMIA
DKA
HYPOPERFUSION
TOXIC

22. The 2 NAG Metabolic Acidosis
RENAL LOSSES
ENTERIC LOSSES
…..LOOK at UAG !!!!

24. THE “MAKE-UP” EFFECT OF METABOLIC ALKALOSIS ON METABOLIC ACIDOSISpH
PCO2 25
HCO3 10 BE
Na 136
Cl 100
AG 26
pH 7.38
PCO2 38
HCO3 24 BE
Na 134
Cl 84
AG 26

25. THE CONCEPTUAL MODELS OF
METABOLIC ACIDOSIS
Losses (=AG)
Consumption ( AG)
Blood
Intracellular
Near-normal flow
Low flow