Tygon S-50-HL can be considered for short term surgical implant:
tygon/Tygon medical tubing.pdf
tygon/Tygon medical tubing properties.pdf
There are a number of medical grades of Tygon that have been used for implant:
Some people mistakenly refer to this following as a disadvantage of Tygon, but it has to do with contamination, not with biocompatability: