Most street medics would agree that one of their most valuable assets in the field is the help of affinity group medics (also referred to as "medical monitors" or AGMs). The street medic is often limited by their inablity to be directly inside a group of at-risk protesters. The medical monitor, on the other hand, not only operates among such groups, but as a member of them is familiar with those they are most likely to be called on to treat. So while the medical aspects of these two street first-aider roles are essentially identical, the social aspects are quite different.
Beacuse the purpose of direct action is to obtain an objective goal (be it a blockade, a banner-hang, or any other tactical aim), the main focus of the affinity group (AG) performing the action is outside of the group itself, at least throughout most of an action. This puts an important burden on one of the group's most important members: the medic. As an AGM, it is your duty to insure the health and safety of what is by definition a collective of people looking for trouble. And in most affinity groups, there is only one person to do the job.
If you are without an assistant, or cannot remove yourself too far from a scene of injuries, you may not have any other medically-trained "buddy" to watch your back or aid you in treating your affinity group mates. This is not stated to concern you about your ability to carry out the job. Instead you must remedy these and other shortcomings of your role by communicating with the rest of your AG very thoroughly before entering the field for an action. Your whole collective should consider your role at least as important as any other, and integral to their success in action.