106
p r i n c i p l e s o f o p e r a t i o n / t h e o r y
r
HCO
3
-
The following equation is used to calculate the bicarbonate concentra-
tion
1
:
where: log [HCO
3
-
] = pH - 7.608 + log PCO
2
HCO
3
-
is expressed in mmol/L
BE
b
The base excess of blood, or in vitro base excess, is calculated using
the following equation
1
. This parameter is defined as the titratable base
of blood which may be determined by titration with strong acid or base
to (plasma) pH = 7.400 and PCO
2
= 40 mmHg at 37.0°C.
BE
b
= (1 - 0.014 [Hb]) ([HCO
3
-
] - 25 + (1.43 [Hb] + 7.7) (pH - 7.4))
where: Hb is expressed in g/dL
HCO
3
-
is expressed in mmol/L
BE
b
is expressed in mmol/L
The hemoglobin value used is either preset (14.5 g/dL), entered or
calculated. When entered, the value is input from the PATIENT
INFORMATION screen.
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