Because the poaching mixed is brought up to a fairly low temp and maintained there for poaching, this could pose safety problems at re-use. The potential for problems could be minimized were you to take the poaching medium up to pasteurization temps when you were finished poaching, then rapidly cool the mixture before chilling thoroughly.
Better, imo, and what I do, is to plan another recipe to be made immediately following poaching. The obvious comes to mind of course if poaching shellfish: a chowder or bisque, especially the latter as there are all those shells waiting to be used. If, instead, the shells get used for the bisque base as soon as they are available, one can easily segue into making the bisque, do the straining/simmering while the poached shellfish is being consumed (pasteurization occurs at that point), then finish the soup after dinner, cool quickly, chill.
If after your cook above you cooled the poaching mixture fairly quickly, it's possible the mixture could be safely used again but there is no way of knowing for sure. I'd say if it was cooled quickly it is likely fine, but there's no 100% certainty. Should you wish to use it again, at the very least take it up to 160, stirring constantly at that point and checking the temp to be sure that all parts of the mixture are at least 160, then cool to your poaching temp. This would decrease the likelihood of vegetative pathogens, but not those, if any (and there might not be), that are heat resistant. If the mixture was not cooled quickly after its first use, discard it.