Coda is a musical term used to denote a short extra passage added to the end of a musical composition, unrelated to the structure and themes of the main musical material. The title of this episode is used to describe the short limbo "afterlife" Janeway experiences, indicating that this "coda" may suspiciously not be related to her life at all.
The visual effect for the anomaly Janeway and Chakotay see from the shuttle craft is a re-use of the anti-time anomaly encountered by the USS Enterprise-D in All Good Things... (1994).
The shuttle leaks hydrazine. Chemists have been playing with hydrazine since the late 1800s. It is very toxic and, when exposed to an iridium catalyst, breaks down into ammonia, nitrogen and hydrogen gasses. NASA has used hydrazine as a low power fuel on several spacecraft maneuvering thruster systems.
This was made just 3 years after the movie Groundhog Day (1993) set the standard for repeat-the-day-till-you-get-it-right time loop narratives. Trek had done it previously in Cause and Effect (1992).
This takes place in 2373.