Siemens Rapidlab 1200 - Po 2;F I O 2; Calcium Adjustment for Ph; Anion Gap

Rapidlab 1200 Operator’s Guide: System Overview and Intended Use 1-59
02087462 Rev. V
Estimated oxygen saturation [O
2
SAT(est)] does not account for variations in
2,3
DPG levels, carbon monoxide levels, or the presence of other
dyshemoglobins. Therefore, clinically significant errors can result from
incorporating an estimated value for oxygen saturation into further calculations,
such as oxygen content and pulmonary shunt, or by assuming that the value
obtained is equivalent to fractional oxyhemoglobin.
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pO
2
/F
I
O
2
The pO
2
/F
I
O
2
ratio is an index of the efficiency of pulmonary oxygen exchange
that relates the arterial pO
2
to the fraction of inspired oxygen.
34
Calcium Adjustment for pH
The ionized calcium concentration is dependent upon sample pH. The calcium
value adjusted to pH of 7.40 [Ca
++
(7.4)] reflects the true ionized calcium
concentration of blood normalized to pH 7.40.
The system adjusts the calcium value according to the following equation:
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Ca
++
(7.4) = Ca
++
× 10
[–0.178 × (7.40–pH(37))]
The calcium value is adjusted only when pH at 37°C is between 7.2 and 7.7,
because no reliable, published clinical data is available for correction at values
outside this
range.
35
Anion Gap
The anion gap (AnGap) is an approximation of the difference between
unmeasured cations and unmeasured anions in the sample and is useful in
determining the cause of metabolic acidosis.
35
An abnormal anion gap indicates electrolyte imbalance or other conditions where
electroneutrality is disrupted, such as diabetes, ingestion of toxins, lactic acidosis,
and dehydration.
The system determines the anion gap as follows:
AnGap = (Na
+
+ K
+
)–(Cl
-
+ HCO
3
–
act)