Active
Siemens Critical Care Analysers SOP
Version:
2.00
Author
:
D Harrison
Doc Manager
:
D Harrison
Authorised by
:
Kath Ash
ton
Signature
: .
Ver Date
:
03/08/09
Do not photocopy this document
Page
18
of 24
Last printed:
5 August 2009
( David Harrison )
DMS Ref
:
Document in Microsoft Internet Exp
lorer
Base excess
The c
alculation of the base excess of blood permits the estimation of the number of equivalents of sodium
bicarbonate or ammonium chloride required to correct the blood pH to 7.40
The base excess, in blood, with a pH of 7.40,
-
pCO
2
of 5.33 kPa
-
Hb of 15.0 g/
dl at 37
o
C is zero.
It is calculated as follows
BE(B) = (1
-
0.014 * Hb) [(HCO
3
-
-
24.8) + (1.43 * Hb + 7.7)(pH
-
7.40)]
The Hb may be an assayed value from the associated co
-
oximeter, derived from a measured haematocrit or it
can be an assumed value
entered into the analyser set
-
up.
HCO
3
-
(actual) is derived as follows:
-
log HCO
3
-
=
pH + log(pCO
2
* 0.0307)
-
6.105
(National Committee for Clinical Laboratory Standards Recommendations)
Reference Range
-
2.3
-
+
2.3mmol/l
Turnaround time
Sample
s analysed immediately upon receipt.
Assay characteristics
Precision:
-
pH
=
0.08%
pH 7.1
-
7.6
pC0
2
=
2.3
pC0
2
2.0
-
19.0
p0
2
=
4.1
p0
2
4.0
-
93.0
Reference Range
pH
7.34
-
7.44
pC0
2
4.7
-
6.0
p0
2
1
1.3
-
14.0
Std Bicarbonate 22
-
26
Base Excess.
-
2.3
-
+2.3
Further Information
Maintenance and reagent logs must be completed daily.
Specimens arriving with needle still attached must not
be analysed. The medic who took the sample should be
requested to either come to the laboratory and remove the needle
or
send an alternative specimen.
Calibration is automatic and occurs at pre programmed intervals.
References
1.
Hamilton, L.H. Respiratory and blood gas analysis. Prog Clin P
athol 1969; 9: 284
-
340.
2.
Van Slyke, D.D. Cullen, G.E.
Studies of acidosis J. Biol Chem
