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base excess

Reference interval: - adult: -2 to +3 - child: -4 to +2 - infant: -7 to -1 - newborn: -10 to 12 Principle: A calculated value used to estimate the quantity of HCO3- necessary to bring an acidotic patient or, less commonly an alkalotic patient, to a to a pH of 7.40. Base excess (BE) is derived from the Henderson-Hasselbach equation: 7.40 = 6.1 + log ([HCO3- + BE]/ [0.03 x pCO2]) 1.3 = log ([HCO3- + BE]/ [0.03 x pCO2]) 10[exp 1.3] = ([HCO3- + BE]/ [0.03 x pCO2]) 20 = ([HCO3- + BE]/ [0.03 x pCO2]) 20 x [0.03 x pCO2] = [HCO3- + BE] [BE] = (20 x 0.03 x pCO2) - [HCO3-] where [BE] is the base excess in concentration units. Together with the volume of distribution the amount of HCO3- required to bring a patient's pH to 7.4 may be calculated. The equation assumes that pulmonary function remains constant so as not to influence pCO2. Most blood gas instruments perform this calculation & report the calculated value. Increases: - metabolic alkalosis - acute respiratory alkalosis Decreases: - metabolic acidosis - acute respirator acidosis

Related

arterial blood gas (ABG)

General

general chemistry test

References

  1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 152-53
  2. Clinical Guide to Laboratory Tests, 4th edition, HB Wu ed, WB Saunders, Philadelphia, 2006
  3. Berend K Diagnostic Use of Base Excess in Acid-Base Disorders. N Engl J Med 2018;378:1419-1428. April 12, 2018 PMID: 29641969 http://www.nejm.org/doi/full/10.1056/NEJMra1711860