In some cases, such as if a female participant has severe lymphoedema after a mastectomy, a participant may only have one arm available for the iohexol administration and subsequent blood samples.
It is important not to sample from any high risk site. In this particular instance the approach is to use a single site for iohexol administration and blood sampling. The key is to ensure, as in the standard procedure, that the iohexol is completely flushed in; nothing remaining in the line or any multi-way tap. Then as a second precaution, withdraw and discard the first 5ml of blood at the initial 5 minute sample.