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Acid-Base Disorders- A Quick Revision
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Summary Table of Acid-Base Disorders
| Primary Disorder | Defect | Causes | Effect on pH and Bicarbonate: Carbonic Acid Ratio | Compensatory Responses |
| Metabolic Acidosis | HCO3⁻ Deficiency | High Anion Gap (Acid Gain): – Ketoacidosis (Diabetes, Alcoholism, Malnutrition, Fasting) – Lactic Acidosis (Shock, Hypoxia, Seizures) – Renal Failure – Toxins (Alcohol, Methanol, Salicylates) Normal Anion Gap (HCO3⁻ Loss – Hyperchloremic Acidosis): – GI HCO3⁻ Loss (Diarrhea, Colostomy, Enteric Fistulas, Ileostomy) – Renal HCO3⁻ Loss (Renal Tubular Acidosis, Acetazolamide) | ↓ pH, ↓ Ratio | Respiratory: Hyperventilation (↓ PaCO₂) Renal: 1. ↑ H⁺ Excretion 2. ↓ K⁺ Excretion in Distal Tubules 3. ↓ Bicarbonate Excretion 4. ↑ Ammonia Formation 5. ↑ Acid Phosphate Excretion |
| Metabolic Alkalosis | HCO3⁻ Excess | Chloride-Responsive: – Gastric Secretion Loss (Vomiting, NG Suction) – Colonic Secretions Loss – Diuretics (Post-discontinuation) – Cystic Fibrosis – Excessive Antacid Use Chloride-Resistant: – Primary Hyperaldosteronism, Cushing Syndrome – Glucocorticoid/Mineralocorticoid Use – Reno-Vascular Hypertension – Renin-Secreting Tumors – Milk-Alkali Syndrome | ↑ pH, ↑ Ratio | Respiratory: Hypoventilation (↑ PaCO₂) Renal: 1. ↓ H⁺ Excretion 2. ↑ K⁺ Excretion 3. ↑ Bicarbonate Excretion 4. ↓ Ammonia Formation 5. ↓ Acid Phosphate Excretion |
| Respiratory Acidosis | CO₂ Retention (↑ PaCO₂) | Central Causes: – CNS Depression (Sedatives, Alcohol, Anesthetics) – Infections, Head Trauma, Tumors – Sleep-Disordered Breathing Airway Obstruction: – Severe Asthma, Anaphylaxis, Inhalation Injury, Laryngeal Obstruction Parenchymal Damage: – Emphysema, Bronchitis, ARDS, Pleurisy Neuromuscular Causes: – Poliomyelitis, Kyphoscoliosis, Myasthenia Gravis, Muscular Dystrophy Other: – Congenital Heart Disease, Mechanical Ventilation, Rebreathing | ↓ pH, ↓ Ratio | Renal: 1. ↑ H⁺ Excretion 2. ↓ Bicarbonate Excretion 3. ↑ Ammonia Formation 4. ↑ Acid Phosphate Excretion |
| Respiratory Alkalosis | CO₂ Washout (↓ PaCO₂) | CNS Causes: – Pain, Anxiety, Hyperventilation Syndrome – Psychosis, Fever, CVA, Meningitis, Encephalitis, Tumor, Trauma Hypoxia: – High Altitude, Severe Anemia Drugs: – Salicylates, Catecholamines Endocrine: – Pregnancy, Hyperthyroidism Pulmonary Causes: – Pneumothorax, Pneumonia, Edema, PE, Asthma, COPD Other: – Sepsis, Liver Failure, Mechanical Ventilation, CHF Recovery from Metabolic Acidosis | ↑ pH, ↑ Ratio | Renal: 1. ↓ H⁺ Excretion 2. ↑ Bicarbonate Excretion 3. ↓ Ammonia Formation 4. ↓ Acid Phosphate Excretion |
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