The Role II mission in combat care is often described as damage control. It is resuscitation and immediate surgical stabilization of life and limb threatening hemorrage in order to reverse the physiologic "death spiral". It is not necessarily definitive care or recovery.
The golden hour concept stems from the fact that irreversible physiologic changes can occur within the first hour of profound shock. There are three elements of the physiologic change, also known as the lethal triad. These are acidosis, hypothermia, and coagulopathy.
Acidosis, or increasing acidity of the blood, occurs as individual cells throughout the body stop receiving blood supply and nutrients which disrupts normal metabolism. Hypothermia occurs due to exposure and loss of blood. Coagulopathy, or impaired blood clotting, leads to further blood loss. These elements beget the other making a vicious circle, which we sometimes refer to as "circling the drain."
The concept of the FST is to place emergency surgical and resuscitative capabilities close enough to the battlefield so that care is within reach in the golden hour. Although this is more a conceptual time frame than a strict sixty minutes, it is a period during which the death spiral can hopefully be reversed. When a patient arrives, we turn on the room heaters even on hot days to warm up the patient, push fluids and blood to stop acidosis, and thaw plasma to replenish depleted clotting elements.
Unfortunately, this is still not always possible. We had a case a couple weeks ago in which the patient received a gunshot wound to the arm but because of weather, MEDEVAC was not possible. Furthermore, the only road to his location was heavily laid with IEDs. There was no way out. The medics on site had to provide care for about 36 hours until the weather cleared. The good news is that the tourniquet prevented blood loss and initiation of the lethal triad across the patient's entire body. The bad news is that his arm was lost. Sometimes there are tradeoffs that we have no choice but to accept.