So while you can save Jenny from being poisoned in a Burrower nest west of the Junkyard (antidote) you cannot save Cliff from subsequently bleeding out-
Except maybe with the Doctor feat?
Since health hypos are automatically used on the PC bandages are the only way to heal NPCs that I'm aware of.
So it seems like Cliff is doomed unless you're a Doctor!
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Also, interestingly: if you save Jenny then finish the 'saving Jenny' conversation you only get monologue from Cliff regardless of who you talk to- but when Cliff bleeds out it switches to Jenny's "you failed to save Cliff" monologue.