Anaesthesia: Blood sampling

You are called to the resuscitation room where an unwell, 34-year-old man is undergoing

assessment. You agree to take the venous blood sample for investigations. The

bottles and syringes required are all listed below. Select the sample that you would

draw and fill THIRD.

a) Standard gold-topped sample bottle containing gel activator (SST) for urea and

electrolytes

b) Standard grey-topped sample bottle containing fluoride oxalate for glucose

c) Standard blue-topped sample bottle containing citrate coagulation screen

d) Standard purple-topped sample bottle containing EDTA for full blood count

e) Blood culture bottles

Answer: a

Typically, a blood culture sample would be drawn and filled first. This is to reduce

the chance of bacterial contamination during sampling. Following that, the clotting

screen in the citrate bottle should be filled next as the minimum amount of time for

the blood to be out of contact with the circulation is ideal. This also reduces the risk of

contamination with coagulants or anticoagulants in other bottles. Next comes the

gold-topped SST bottle. If this is filled after the purple-topped bottle, EDTA contamination

can interfere with biochemistry analysis. Finally the grey-topped oxalate bottle

is filled. SST tubes used to appear higher up in the order of draw but have dropped

down as they are now considered additive tubes, containing silica particles to promote

clotting.

Anaesthesia