Arash Safaie, MD Emergency Physician
pH ↓7.36: Acidemia ↑7.44: Alkalemia Physiologic Buffers Bicarbonate Carbonic Acid Systems (RBCs) Phosphate Buffers (Bone) Basic Concepts
Useful Knowledge ABG vs. VBG VBG pH: 0.03↓ PCO2: 6.6↑ HCO3: 1.4↑ Role of Temperature Tempe rature (°C) pH Paco 2 (mm Hg) Pao 2 (mm Hg)
Acute Intracellular Buffering CO2 Narcosis ↑PCO2: 10 ↑HCO3: 1 ↑PCO2: 10 ↓pH: 0.08 Chronic Beyond 6-12h starts 5d completes Hypochloremia ↑PCO2: 10 ↑HCO3: 4 ↑PCO2: 10 ↓pH: 0.03 Respiratory Acidosis
Acute Intracellular Buffering ↓PCO2: 10 ↓HCO3: 2 ↓PCO2: 10 ↑pH: 0.08 Chronic Beyond 6-36h starts 14d completes Hyperchloremia ↓PCO2: 10 ↓HCO3: 3.5 ↓PCO2: 10 ↑pH: 0.03 Respiratory Alkalosis
Pregnancy pH: PaCO2: HCO3: Childhood (7-19y) PaCO2: 37 Pregnancy & Childhood
Compensation ↓HCO3: 1 ↓PCO2: 1.2 PCO2: (1.5 x HCo3) + 8 12-24h for Max. Respiratory Response Compensation Limit PCO2: Normal AG Urine AG: (Urine Na + Urine K) – Urine Cl Positive Urine AG: Altered Urinary Acidification Negative Urine AG: GI Loss Role of NaHCO3 in Rx Metabolic Acidosis
AG: Na – (Cl + HCO3) > 15 High < 3 Low Δ G: (AG – 12) – (24 – HCO3) >+6: concurrent Metabolic Alkalosis or Respiratory Acidosis <-6: concurrent Normal AG Metabolic Acidosis or Respiratory Alkalosis Anion Gap & Δ Gap
Compensation ↑HCO3: 1 ↓PCO2: 1.2 Compensation Limit PCO2: Saline Responsiveness Saline-Responsive: Urine Cl <10 Saline-Resistant: Urine Cl >10 Rx Saline-Responsive: NaCl + KCl Severe: IV Mineral Acids Edematous: Acetazolamide, Dialysis Saline-Resistant: KCl + Mineralocorticoid Antagonist Metabolic Alkalosis
pH:7.37 PCO2:50 HCO3:28 Na:139 Cl:102 1
pH:7.44 PCO2:46 HCO3:34 Na:140 Cl:100 2
pH:7.35 PCO2:28 HCO3:14 Na:140 Cl:110 3
pH:7.32 PCO2:50 HCO3:25 Na:140 Cl:110 4
pH:7.43 PCO2:30 HCO3:22 Na:140 Cl:108 5
pH:7.30 PCO2:40 HCO3:20 Na:140 Cl:110 6
pH:7.37 PCO2:16 HCO3:4 Na:140 Cl:96 7
pH:7.30 PCO2:16 HCO3:4 Na:140 Cl:106 8
pH:7.30 PCO2:28 HCO3:14 Na:140 Cl:111 9
pH:7.42 PCO2:50 HCO3:29 Na:140 Cl:105 10