For those whose cost of medical treatment or maintenance outweighs their total future economic value (because they are terminally ill, are no longer productive, and have no reasonable chance of becoming productive or happy in the foreseeable future), it is economically efficient to free up medical resources by not treating them.
As an example of this logic, every nurse who cares for a terminally ill Alzheimer's or cancer patient, a comatose individual, or an individual in a vegetative state, is one less nurse to take care of a sick baby or a 12-year-old gunshot victim. See opportunity cost.
Therefore, the benefits Utilitarian Bioethics include increased medical expenditure on other patients with a higher chance of survival and return to a productive and/or happy status. This would ideally lead to an overall net increase in wealth and happiness.
The perceived downsides of Utilitarian Bioethics include : potential justifications for physicians to kill patients, a gravitation towards acceptance of mortality and death, lack of medical progress (as the treatment of severe injuries would not be explored), the uncertainty in measuring 'happiness', and the possibility of classification of many disabled or old people as "nonpersons".