Several chemical hemostatic agents have been tested in animals and are used in battlefield operations. These agents are of two primary classes: minerals and chitosan. Mineral formulations work by two primary methods; they absorb water rapidly, thus concentrating platelets and clotting factors and inducing rapid clotting. They also form a barrier over severed blood vessels that provides strength to in vivo clot. Minerals used include zeolite, magnesium, and potassium silicates. The major drawback of these compounds is the local heat generated which can raise wound temperature as high as 53.5 °C. These formulations have been removed from use and should be removed from equipment caches. Chitosan formulations bind to RBC’s due to their negative charge and activate the intrinsic pathway of clotting. They do not generate as much heat as some of the mineral formulations. Most of the hemostatic agents now come packaged in a dressing or porous bag, which helps contain the compound and facilitates operative repair by not contaminating the wound with powder.

Research groups have developed several animal models for investigation of effectiveness of these dressing materials. They range from low-flow venous bleeding to large arterial high-flow bleeding states. All hemostatic agents performed well and in one study were associated with improved survival.

In case series of human use, primarily on the battlefield of Iraq, these dressings appear effective at hemorrhage control. In one series of 103 patients treated with hemostatic agents, bleeding was controlled in 92 % of patients. In another review of 64 uses by the military, bleeding was controlled in 97 % of cases.

Prehospital systems could consider these agents; however, there use would likely be infrequent as the battlefield injuries caused by explosive devices and high-velocity missiles are markedly different than the typical injuries of the civilian world. Their use should be considered a low frequency event and receive special training or be limited to a select team of paramedics, such as a tactical medic group. Other special training should include wound packing for EMS providers.

Exsanguinating hemorrhage from injured extremities is a rare occurrence in civilian trauma, but still remains one of the leading causes of preventable death during wartime, typically as a result of explosions.

The US Army Institute of Surgical Research published an observational study of trauma patients who had tourniquets applied and were cared for at the combat support hospital in Baghdad. They documented 232 patients who had 428 tourniquets applied to 308 injured limbs. The overall mortality was 13 %, with a marked difference in mortality when the tourniquet was placed before the development of hemorrhagic shock. Patients in shock when the tourniquet was applied had a mortality of 90 % compared to 10 % for those patients not in shock. Prehospital use was also associated with better survival: 11 % mortality in patients with tourniquet placed prehospital compared to 24 % mortality when placed in the emergency department. The authors were able to identify a matched cohort of patients who meet criteria for tourniquet use but did not have one applied and compared to a group of similar injury pattern and severity who did receive a tourniquet for hemorrhage control. Mortality was 23 % in the later group compared to 100 % for those without a tourniquet applied. They also report only four transient nerve palsies for the entire cohort.

Based on this new data, tourniquets should be employed to control life-threatening exsanguination from severe extremity wounds as a result of explosions or high-velocity missiles. Tourniquets are now well accepted in the civilian trauma setting in other populations to confirm effectiveness and safety.