base excess
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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 [[[A352863|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
Decreases
- metabolic acidosis
- acute respirator acidosis
More general terms
Additional terms
References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 152-53
- ↑ Clinical Guide to Laboratory Tests, 4th edition, HB Wu ed, WB Saunders, Philadelphia, 2006
- ↑ Berend K Diagnostic Use of Base Excess in Acid-Base Disorders. N Engl J Med 2018;378:1419-1428. April 12, 2018 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/29641969 <Internet> http://www.nejm.org/doi/full/10.1056/NEJMra1711860