Fernando Schiraldi Giovanna Guiotto Equilibrio Acido-Base Fernando Schiraldi Giovanna Guiotto Ospedale San Paolo - Napoli schirald@gmail.com giovannaguiotto@gmail.com

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

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

THE Hb “FLEXIBILITY”

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

H+ vs Ca++ & troponins

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

S VISKIN (1999) Lancet 354;1625-33

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

H+ + HCO3- H2CO3 H2O + CO2 20 = 6.1 + 1.3 HCO3- 24 46 28 38 pK CO2 6.1 6.1 20 = 6.1 + 1.3 HCO3- 24 46 28 38 pH = 6.1 + 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 (1874-1962)

“a too good pH” H+ + HCO3- H2CO3 H2O + CO2 20 = 6.1 + 1.3 HCO3- 24 28 pK CO2 6.1 6.1 20 = 6.1 + 1.3 HCO3- 24 28 46 38 pH = 6.1 + 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 (1874-1962)

“a too good pH” 24 12 pH = 6.1 + log = 7.1 = 7.28 = 7.42 = 7.4 40 19 25 × 0.03

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

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

pH vs PCO2 acute “mixed” chronic pH 7.22 7.25 7.32 PCO2 70 70 70 HCO3 28 30 35

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’

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

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

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

AG = Na – (Cl + HCO3) = 10 ± 2

The 4 HAG Metabolic Acidosis UREMIA DKA HYPOPERFUSION TOXIC

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

THE “MAKE-UP” EFFECT OF METABOLIC ALKALOSIS ON METABOLIC ACIDOSIS pH 7.27 PCO2 25 HCO3 10 BE -13 Na 136 Cl 100 AG 26 pH 7.38 PCO2 38 HCO3 24 BE 0 Na 134 Cl 84 AG 26

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