Danish to English Medical Medical (general) Patient records - hospita

Hi - this phrase appears several times in a patient's medical records and concerns catheter insertion/IV access - does "sub" here mean "collapse"?
It appears as follows:

Begge IV-adgange går sub og må genanlægges v anæstesien.

and

PVK gået sub x2 -> anlagt 20G 51 mm PVK UL vejledt venstre antebrachium skyllet 10 mL NaCl x2 ukompliceret.

Thanks for your help!