ITC IRMA TruPoint Blood Analysis System - Manual (Page 148)

C.4
Base Excess of Blood 4,12
Base excess of blood, (BEb), also called in vitro or actual base excess, is the
difference in concentration of strong base in whole blood and in the same
blood titrated with strong acid or base to pH=7.40/pCO
2
=5.33kPa at 37°C.
Two formulas are available for the calculation of base excess: Severinghaus/
NCCLS or Siggaard-Andersen. Refer to Section 7- Calculations for instruc-
tions on formula selection.
Severinghaus/NCCLS formula:
BEb = (1-0.014 x Hb) [HCO
3
- -24.8 + (1.43 x Hb+7.7)(pH-7.4)]
› Hb is the hemoglobin value entered
Siggaard-Andersen formula:
BEb = 0.5(8a’-0.919) + 0.5[(0.919-8a’) 2 - 4(24.47- HCO
3
-{5.33})] 1/2
a’ a’ a’
› a’ = 0.00404 + 0.000425 x Hb
› HCO
3
- (5.33) = 0.230 x 5.33 x antilg[(pH(st) - 6.161) / 0.9524]
› pH(st) = pH + lg(5.33 /pCO
2
) x [pH(Hb) - pH] / [lg(pCO
2
(Hb)) -
lg(7.5006 x pCO
2
)]
› pH(Hb) = 0.0406 x Hb + 5.980 - 1.920 x antilg(-0.16169 x Hb)
› lg(pCO
2
(Hb)) = -0.017674 x Hb + 3.4046 + 2.12 x antilg(-0.15158 x Hb)
Base Excess of Extracellular Fluid 5,11
Base excess of extracellular fluid (BEecf), also called in vivo base excess, or
standard base excess, is a quantity that reflects only the non-respiratory
component of pH disturbances. Two formulas are available for the calculation
of base excess: Severinghaus/NCCLS or Siggaard-Andersen. Refer to
Section 7-Calculations for instructions on formula selection.
Severinghaus/NCCLS formula:
BEecf = [HCO
3
-] - 24.8 + 16.2(pH - 7.4)
Siggaard-Andersen formula:
BEecf = BEb for Hb = 3 mmol/L