Anion Gap

From Anvita Health Wiki

Contents 1 More Specific Terms 2 Introduction 3 Reference-interval 4 Principle 5 Increases 6 Decreases 7 Notes 8 More General Terms 9 Additional Terms 10 References

More Specific Terms

• anion gap 3
• anion gap 4

Introduction

• [Na+] - ([[[Cl-]]] + [[[Hco3- | HCO3-]]])

Reference-interval

• 10-17 mmol/L (both sexes, all ages)

Principle

• when the primary disturbance is a metabolic acidosis, a high anion gap indicates the presence of unmeasured anions
• when the primary disturbance is other than metabolic acidosis, an increased anion gap reveals a hidden metabolic acidosis
• in anion gap acidosis, the expected ratio between the change in anion gap to the change in plasma [[[Hco3- | HCO3-]]] is 1/1 - 2/1;

• a ratio of < 1 suggests non- anion gap acidosis;
• a ratio of > 1 suggest concurrent metabolic alkalosis [3]

Increases

• increase in unmeasured anions

• uremia with increased phosphate & sulfate
• ketotic states with increased organic acids

• diabetes
• alcoholism
• starvation
• hyperemesis

• lactic acidosis
• toxin ingestion

• methanol
• salicylate
• ethylene glycol
• paraldehyde
• iron
• isoniazid
• cyanide
• toluene

• increased albumin as in dehydration

• decrease in unmeasured cations

• metabolic alkalosis leads to decrease in globulin charge
• hypocalcemia

Decreases

• increase in unmeasured cations

• Li+ intoxication
• hypercalcemia
• hypermagnesemia
• multiple myeloma
• polyclonal gammopathy
• polymixin B therapy (polycationic agent)
• increased NH4+ (early phase of chronic renal failure)

• decrease in unmeasured anions

• hypoalbuminemia
• bromide intoxication (interference with Cl- determination)
• hyponatremia with normal or increased extracellular fluid leads to loss of unmeasured cations

Notes

• unmeasured cations Ca+2, Mg+2 & globulins average 14 meq/L
• unmeasured anions, H2PO4-, SO4-2, albumin & organic acids average 24 meq/L

More General Terms

• general chemistry test

Additional Terms

• urinary anion gap

References

1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 151
   - Henry's Clinical Diagnosis & Management by Laboratory Methods, 21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co., Philadelphia, PA. 2007, pg 84
2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1161
3. Medical Knowledge Self Assessment Program (MKSAP) 14, 15, American College of Physicians, Philadelphia 2006, 2009

anion gap