Overview
Clinical Meaning
Advanced ABG interpretation requires the ability to identify mixed disorders (two or more primary acid base disturbances occurring simultaneously) and calculate the anion gap to...
Advanced ABG interpretation requires the ability to identify mixed disorders (two or more primary acid-base disturbances occurring simultaneously) and calculate the anion gap to narrow the differential diagnosis of metabolic acidosis. Anion Gap (AG): The anion gap represents unmeasured anions in the blood. It helps classify metabolic acidosis into two categories. Formula: AG = Na+ - (Cl- + HCO3-) Normal: 8-12 mEq/L (some labs use 12 ± 4 depending on albumin correction) • Elevated Anion Gap Metabolic Acidosis (AGMA): Accumulation of unmeasured acids. Each acid provides an H+ (which consumes HCO3-) and an unmeasured anion (which increases the gap). MUDPILES: Methanol, Uremia, DKA (beta-hydroxybutyrate), Propylene glycol, Isoniazid/Iron, Lactic acidosis (shock, sepsis, ischemia), Ethylene glycol, Salicylates. • Non-Anion Gap (Normal AG) Metabolic Acidosis (NAGMA): Loss of bicarbonate OR gain of chloride (hyperchloremic). Causes: Diarrhea (loss of HCO3-rich intestinal fluid), Renal Tubular Acidosis, early renal failure, excessive NS infusion (dilutional acidosis), acetazolamide, ureteral diversion. Delta-Delta (Δ/Δ) Analysis: Identifying Hidden Disorders: In elevated AG metabolic acidosis, the delta-delta ratio helps identify coexisting metabolic disorders: Δ Anion Gap = Calculated AG - Normal AG...