Sat27November0445PM 44

With regard to blood-gas analysis:

True / False

A Clark electrode requires a battery Incorrect answer selected

Too much heparinised saline tends to cause a falsely low reading of the PaCO2 Correct

When alcohol antiseptics are not allowed to dry before venipuncture spurious hyperkalaemia can result Correct

The base excess is the amount of strong acid required to return the pH of 1 litre of blood to 7.40 at a PaCO2 of 5.3 kPa and37°C Correct

Prolonged storage at 4°C may lead to a falsely low value for PaO2 Incorrect answer selected

Explanation

The Clark electrode requires a 0.7 volt battery to function accurately.

Prolonged storage even at 4°C can lead either to a falsely low reading of PaO2 (due to ongoing metabolism in white blood cells) or a falsely high reading (due to bubbles dissolving).

The base excess is used to assess the metabolic component of the blood-gas analysis.

Errors can occur due to excessive heparin either due to the dilutional effect of excessive saline (low PaCO2 and low PaO2, though the pH is little affected).

If ethanol containing antiseptics are not allowed to dry completely before venipuncture, the solution can enter the blood stream and disrupt cell membranes.

Answer Statistics

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Average score: 60.08%

Times answered: 256