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Hemorrhage is a common cause of shock among trauma victims. Field clinical trials have suggested that volume resuscitation before controlling hemorrhage may be detrimental [36, 49,56–58, 60]. Possible mechanisms for worse outcomes include dislodgement of clot, dilution of clotting factors, decreased oxygen‐carrying capacity of blood, hyperchloremic metabolic acidosis, and exacerbation of bleeding from injured vessels in the thorax or abdomen.

Controlling external hemorrhage is essential for maintaining vascular volume. Direct pressure is usually sufficient to control external bleeding. Military and civilian experience suggests that tourniquets should be used early and liberally [98]. An assortment of topical hemostatic materials to be placed directly on the bleeding wound also exists [98–101] (see Chapter 35).

Studies in Houston and San Diego suggest that mortality following traumatic hemorrhage is not influenced by prehospital administration of fluid [57, 59]. Survival to hospital discharge rates were not significantly different for patients receiving fluids versus patients not receiving fluids in the field. Both studies were performed in systems with relatively short scene and transport times.

As discussed above, currently EMS clinicians are taught to administer only enough IV or IO fluids to restore a peripheral pulse or to reach a systolic blood pressure of 80–90 mmHg. However, the optimum target blood pressure for these patients remains undefined. Trauma victims with isolated head injuries who receive excessive fluids may develop worsened cerebral swelling. In addition, excess fluids may precipitate congestive heart failure in susceptible individuals or lead to impaired immune response following severe injury.

Conversely, the benefit of limited volume resuscitation has been derived from military and urban data with a predominance of penetrating injuries and young, healthy patients. This population may be more tolerant of hypovolemic resuscitation and benefit from relative hypotension while reducing the risk of clot dislodgement.

Tranexamic acid (TXA) is a lysine derivative that blocks fibrinolysis. It has long been used to control hemorrhage during surgery [2]. In a randomized controlled study, TXA reduced mortality from traumatic hemorrhage if administered within 3 hours of the time of injury. Some EMS systems are beginning to use TXA to treat hemorrhagic shock. Evidence for its benefit is found in its early administration and in patients with severe shock or concomitant traumatic brain injury [102]. Late administration of TXA has been associated with worse outcomes [103].

Attempts at establishing intravascular access in critically injured trauma victims may delay time to definitive care, especially in the urban setting [56104–107]. The majority of IV fluid studies have taken place in urban settings primarily with penetrating trauma victims and rapid transport times. The effectiveness of IV fluids for similar patients in the rural and wilderness settings remains undefined. The subject remains controversial, with several studies providing mixed messages [45, 56,98–100,105–108].