Acid-base and blood gas analysis Zsolt Molnar 2009

H + potency: pH (pondus Hydrogenii) Søren Sørensen, 1909 pH = -lg H + -lg 40 = 7.40 Potency of H + Molnár ‘99 H + nmol/L 40

H + potency: pH (pondus Hydrogenii) Søren Sørensen, 1909 pH = -lg H + -lg 40 = 7.40 Potency of H + Molnár ‘99 H + nmol/L

H + potency: pH (pondus Hydrogenii) Søren Sørensen, 1909 pH = -lg H + -lg 40x10 -9 = lg 100x10 -9 = lg 16x10 -9 = 7.80 Molnár ‘99 H + nmol/L Potency of H +

H + potency: pH (pondus Hydrogenii) Søren Sørensen, 1909 pH = -lg H + -lg 40x10 -9 = lg 100x10 -9 = lg 16x10 -9 = 7.80 Henderson-Hasselbalch: Molnár ‘99 H + nmol/L Potency of H +

Blood gas analysis

pH PaCO 2 actHCO 3 - stHCO 3 - BE BB What does an ABG tell us? Molnár ‘99 - measured: measured: Hgmm - calc: mmol/L - calc: (T, CO 2 ) mmol/L - c: (T, CO 2, pH)  3 mmol/L - c: (össz puffer) ~48 mmol/l

Skandinavian school Sörensen, Astrup, Siggaard-Andersen BE, BB Boston school Henderson, Hasselbalch Use what is measured pH, CO 2, HCO 3 - Skandinavian vs. Boston school Molnár ‘99

1.H + concentration: pH a.> 7.45 = alkalosis b.< 7.35 = acidosis c.7.35 < pH < 7.45 = normal v. compensated 2.Respiratory component: PaCO 2 a.> 45 Hgmm = respiratory acidosis b.< 35 Hgmm = respiratory alkalosis 3.Metabolic component: HCO 3 - a.> 25 mmol/L = metabolic alkalosis b.< 20 mmol/L = metabolic acidosis 4.Compensated changes a.1/c + 2/a + 3/a = respiratory acidosis b.1/c + 2/b + 3/b = metabolic acidosis Analysing algorhythm Molnár ‘99

Concept of electroneutrality  + = 154  - = 154 mmol/L HCO 3 = 26 Organic acids = 6 Protein = 16 HPO 4 = 2 SO 4 = 1 Cl - = 109 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Misc = 1  anions =  kations Anion-gap=(Na+K)-(Cl+HCO 3 )

Metabolic acidosis  + = 154  - = 154 mmol/L HCO 3 = 26 Organic acids = 6 Protein = 16 HPO 4 = 2 SO 4 = 1 Cl + = 109 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Misc = 1 High AG

Metabolic acidosis  + = 154  - = 154 mmol/L HCO 3 = 16 Organic acids = 14 Protein = 16 HPO 4 = 2 SO 4 = 1 Cl + = 109 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Misc = 1 High AG AG

Metabolic acidosis  + = 154  - = 154 mmol/L HCO 3 = 16 Organic acids = 14 Protein = 16 HPO 4 = 2 SO 4 = 1 Cl + = 109 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Misc = 1 High AG AG = 26 mmol/L AG

Metabolic acidosis  + = 154  - = 154 mmol/L HCO 3 = 26 Organic acids = 6 Protein = 16 HPO 4 = 2 SO 4 = 1 Cl + = 109 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Misc = 1 Normal AG

Metabolic acidosis  + = 154  - = 154 mmol/L HCO 3 = 16 Organic acids= 6 Proteins = 16 HPO 4 = 2 SO 4 = 1 Cl + = 119 Na + = 142 K + = 4 Mg 2+ = 2 Ca 2+ = 5 Egyéb = 1 Normal AG

Reasons

High AG a.Lactate acidosis: shock, sepsis, liver failure, etc b.Ketoacidosis c.Acid intake: salicilate toxicity Normal AG a.Intestinal HCO 3 - loss: diarrhea, fistula stb. b.Renal HCO 3 - loss: RTA Metabolic acidosis Molnár ‘99

Acid loss a.NG aspirate b.Diuretics - hypokalemia Excessive alkalinization a.HCO 3 - b.Citrate, lactate (Ringer), acetate Metabolic alkalosis Molnár ‘99

Altered level of consciousness Overdose: opiates, sedatives Trauma: head, i.c. bleeding Muscle weakness Guillain-Barré, myastenia, muscle relaxant effect Type II respiratory failure COPD, acute exacerbation Inadequate IPPV Respiratory acidosis Molnár ‘99

Pulm. emb. CNS excitation Meningitis, encephalitis I.c. bleeding Asthma Iatrogen Inadekvate IPPV Respiratory alkalosis Molnár ‘99

Acidosis a.Shock: septic, cardiogen+pulm oedema b.St. post CPR Alkalosis a.Hyperventilation + NG aspirate (vomiting) b.Liver failure + diuretics Mixed disorders Molnár ‘99

Examples

48 y old woman, admitted with shock: BP 90/50, HR 130, Dg: UTI pH:7.36 CO 2 :29 HCO 3 - :16 Na + :134 K + :4.8 Cl - :98 AG:34.8 Dg: compensated metabolic acidosis Treatment: O 2, fluid, vasopressors, AB Practice – case 1 Molnár ‘99

53 y old man, cirrhotic, bleeding from eoph. varices: BP 70/.., HR 130 pH:7.28 CO 2 :33 HCO 3 - :17 Na + :134 K + :5.4 Cl - :103 AG:19.4 Dg: decompensated metabolic acidosis Treatment: O 2, fluid, blood, endoscopy+ligation Practice – case 2 Molnár ‘99

53 y old man, IDDM, admitted with coma pH:7.05 CO 2 :23 HCO 3 - :6.5 Na + :139 K + :5.4 Cl - :104 AG:34.4 Dg: severe decompensated metabolic acidosis Treatment: ETT-O 2, fluid (NS+bicarb), insulin i.v. bolus+cont. Practice – case 3 Molnár ‘99

68 y old man, colon cancer, postop day 3, unwell, GCS: 12 pH:7.60 CO 2 :43 HCO 3 - :43 Na + :144 K + :2.8 Cl - :102 AG:1.8 Dg: decompensated metabolic alkalosis Treatment: O 2, fluid (NS, RL), K + (max: 50 mmol/h) Practice – case 4 Molnár ‘99

70 y old man, COPD, admitted with acute flareup of cold pH:7.48 CO 2 :72 HCO 3 - :54 Na + :148 K + :3.4 Cl - :96 AG:1.4 Dg: compensated respiratory acidosis Treatment: O 2, fluid (NS, RL), observation on medical ward, ?AB Practice – case 5 Molnár ‘99

75 y old man, COPD, admitted with vomiting+diarrhoea for days pH:7.24 CO 2 :72 HCO 3 - :28 Na + :148 K + :5.7 Cl - :96 AG:29.7 Dg: decompensated metabolic acidosis Treatment: O 2, fluid (NS, RL), ?dialysis, ?AB Practice – case 6 Molnár ‘99

62 y old woman, post op acute gastric perforation pH:7.57 CO 2 :26 HCO 3 - :24 Na + :148 K + :3.8 Cl - :104 AG:23.8 Dg: decompensated respiratory alkalosis Treatment: O 2, morphine+ whatever Practice – case 7 Molnár ‘99

17 y old girl, admitted from a disco in coma, otherwise stable: pH:7.06 CO 2 :80 HCO 3 - :25 Na + :148 K + :4.4 Cl - :105 AG:22.4 Dg: decompensated respiratory acidosis Treatment: ETT, ?antidote, …give her time Practice – case 8 Molnár ‘99

Differentiate between fact (measurement) and fiction (calculation)! Look at the whole picture not just the „deep picture” Treat the patient not the figures! Summary Molnár ‘99