Erik allowed Doreen to explain the situation, impressed at her capacity to keep the patient calm under these circumstances. As she ended her statements, he quickly intervened before Frederick could say anything... "There are no guarantees, sir, but in your condition there are no risks either." - he started chuckling a bit, perhaps in an attempt to reassure the patient - "At worst, you waste half a day of time... at best, you go home in one FULL piece."
He took a seat next to the patient's bed, so as to be on the same level, then continued with a sober tone "The first phase of the procedure is tissue extraction, which I'm sure doctor Naggar can handle. Afterwards, we'll set up the nanites. Once they're ready, we expect the reforming operation to only take about an hour or so."
It took mister Frederick a moment to think. After asking once more if there are any risks, miss Valders stepped in and reassured him once more, explaining how the nanites cannot harm him in any way, and the only wrong that can happen is if they simply can't fulfill the purpose of giving him back his arm. So, the patient nodded in understanding and complied.
With this done, Erik and Samantha excused themselves, since they now needed to prepare the lab while Doreen would've taken care of the sample extraction.