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Acid-Base Disorders. Arash Safaie , MD Emergency Physician. Basic Concepts. pH ↓7.36: Acidemia ↑7.44: Alkalemia Physiologic Buffers Bicarbonate Carbonic Acid Systems (RBCs) Phosphate Buffers (Bone). Useful Knowledge. ABG vs. VBG. Role of Temperature. VBG pH: 0.03↓ PCO2: 6.6↑
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Acid-Base Disorders ArashSafaie, MD Emergency Physician
Basic Concepts • pH • ↓7.36: Acidemia • ↑7.44: Alkalemia • Physiologic Buffers • Bicarbonate • Carbonic Acid Systems (RBCs) • Phosphate Buffers (Bone)
Useful Knowledge ABG vs. VBG Role of Temperature • VBG • pH: 0.03↓ • PCO2: 6.6↑ • HCO3: 1.4↑
Respiratory Acidosis • 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 Alkalosis • 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
Pregnancy & Childhood • Pregnancy • pH: 7.46-7.50 • PaCO2: 31-35 • HCO3: 18-22 • Childhood (7-19y) • PaCO2: 37
Metabolic Acidosis • Compensation • ↓HCO3: 1 ↓PCO2: 1.2 • PCO2: (1.5 x HCo3) + 8 • 12-24h for Max. Respiratory Response • Compensation Limit PCO2: 10-15 • 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
Anion Gap & ΔGap • AG: Na – (Cl + HCO3) • > 15 High • < 3 Low • ΔG: (AG – 12) – (24 – HCO3) • >+6: concurrent Metabolic Alkalosis or Respiratory Acidosis • <-6: concurrent Normal AG Metabolic Acidosis or Respiratory Alkalosis
Metabolic Alkalosis • Compensation • ↑HCO3: 1 ↓PCO2: 1.2 • Compensation Limit PCO2: 55-75 • 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
1 • pH: 7.37 • PCO2: 50 • HCO3: 28 • Na: 139 • Cl: 102
2 • pH: 7.44 • PCO2: 46 • HCO3: 34 • Na: 140 • Cl: 100
3 • pH: 7.35 • PCO2: 28 • HCO3: 14 • Na: 140 • Cl: 110
4 • pH: 7.32 • PCO2: 50 • HCO3: 25 • Na: 140 • Cl: 110
5 • pH: 7.43 • PCO2: 30 • HCO3: 22 • Na: 140 • Cl: 108
6 • pH: 7.30 • PCO2: 40 • HCO3: 20 • Na: 140 • Cl: 110
7 • pH: 7.37 • PCO2: 16 • HCO3: 4 • Na: 140 • Cl: 96
8 • pH: 7.30 • PCO2: 16 • HCO3: 4 • Na: 140 • Cl: 106
9 • pH: 7.30 • PCO2: 28 • HCO3: 14 • Na: 140 • Cl: 111
10 • pH: 7.42 • PCO2: 50 • HCO3: 29 • Na: 140 • Cl: 105