To the best of my knowledge, there is none. But logically, the situation usually doen't change for the better as there always be some degree of muscle wasting, and diminished venous flow especially in the legs. So I'd advocate the use, as I presume that also with minimal conscious state, the experience of suffocating should be rather distressing. In the end, we finish up with poor evidence in this field. Sorry!
I think you are right. Despite no evidence one tends to continue giving prophylactic LMWH as long as patient is In-patient irrespective of the length of stay.This practice is probably beneficial for the patient but surely safeguards clinicians.
Following transfer to Nursing home, it has been noted that none of them continue with LMWH despite the fact that patient is clinically and neurologically the same as while In-patient in Neuro-rehab unit. Period of stay in Neuro-rehab unit can be as long as 6 months or may be longer in some cases.
I agree with Dirk, because and after three months paralyzed and/or motionless patient (especially in a vegetative state) has a high thromboembolic risk.The other half - financial; maybe Nursing home saves drug costs?