Chapter 35 Neil B. Davids and Robert L. Mabry Uncontrolled hemorrhage is the second leading cause of death in the civilian trauma setting [1] and the leading cause of preventable death during armed conflict [2,3]. Traditional methods of hemorrhage control in the prehospital setting were simple dressings, direct pressure, proximal arterial pressure points, elevation of bleeding extremities, and, as a last resort, a tourniquet. These measures are essentially the same as those used in antiquity [4]. Recent military and civilian experiences, as well as technological advances, have made new hemorrhage control tools available to both civilian and military out-of-hospital personnel. Advances in civilian trauma care have often occurred secondary to military conflict. Because hemorrhage is the leading cause of potentially survivable death on the battlefield, researchers and physicians have focused intensely on prehospital management of severe hemorrhage. Within the past 10 years, significant advances have included several hemostatic dressings, ready-to-use tourniquets, and improved training in their use [5]. Some of these experiences have directly translated into saved lives in the civilian setting as well [6]. Death from compressible hemorrhage is rare in civilian settings [7], being, in most instances, entirely preventable with simple first aid measures [8]. Most civilian patients with severe hemorrhage can be rapidly transported to urban or suburban trauma centers while direct pressure is applied by a prehospital provider to an isolated injury. Hemorrhage control techniques commonly used by the military on the battlefield, such as tourniquets and advanced hemostatic agents, may have a role in EMS systems likely to encounter delayed patient transport, such as the rural and wilderness setting, prolonged extraction from a collapsed structure, enclosed space, or wrecked vehicle, and mass casualty incidents (MCI). This is particularly important in a scenario of mass shootings or deliberate bombings, where penetrating injury is the most common pattern and approximates battlefield situations. Traumatic hemorrhage is the acute loss of circulating blood volume as a result of injury [9]. Hemorrhage severity is largely predicated on the volume of blood lost before hemostatic control can be achieved. This volume will vary as a function of vessel defect, vessel size, type, and location. Large defects result in not only greater bleeding but also greater consumption of clotting factors and platelets, increasing the likelihood of coagulopathy. Brisk, pulsatile bleeding and the bright red hue of oxygenated blood identify arterial hemorrhage. Arterial bleeding control will require the application of pressure sufficient to overcome the systolic blood pressure and compress the muscular wall of the vessel. Constant pressure for 20 or more minutes may be required to stop arterial bleeding. Venous bleeding is non-pulsatile, may be brisk if the vessel is large, and may appear darker until exposed to oxygen. Venous bleeding will occlude at much lower pressures, will require less time to control, and is more amenable to the use of hemostatic agents than arterial bleeding. Capillary bleeding is usually much less brisk than arterial or venous bleeding due to the smaller size of the involved vessels but may be difficult to control if the patient has platelet dysfunction or clotting factor deficiency. Hemorrhagic shock is a failure of the cardiovascular system to deliver oxygen and nutrients to tissues due to blood loss and hypovolemia. Hemorrhagic shock recognition has often depended on abnormalities of vital signs, appearance of the skin, urine output, and mental status [10]. Although providing the basis of shock recognition and assessment, these metrics are limited by a number of important factors. Physiological response in patients on antihypertensives and other pharmacological agents is often blunted. Healthy patients in good physical condition may have sufficient physiological reserves to delay alterations in heart rate, blood pressure, and respiratory rate even with significant blood loss [11]. Urine output can rarely be assessed in the prehospital environment and mental status, while sensitive to hypotension due to blood loss, can be clouded by concomitant head trauma, intoxication, hypoglycemia, pain medications, or mental illness. Alternative predictors of the severity of shock include the pulse pressure or shock index, both of which can be calculated from traditional vital signs. Pulse pressure is the difference between systolic and diastolic blood pressures. Use of pulse pressure in trauma is based on the principle that hemorrhage will increase the systemic vascular resistance, thus increasing diastolic pressure. At the same time, decreased preload will subsequently produce a reduction in systolic pressure. Narrowing of pulse pressure occurs before significant decreases in systolic blood pressure. Dynamic changes in pulse pressure have been used as a marker for cardiac output and volume status [12,13]. Shock index is calculated by dividing the heart rate by the systolic blood pressure and has been shown to be more sensitive than either of the vital signs alone. Shock index predicts shock states in multiple trauma patients and is predictive of complications once patients are admitted to the hospital [14]. It can also be adjusted to compensate for age-related differences in physiology, especially in the elderly [15]. Serum lactate measurements may identify hypoperfusion; however, this is a late finding and may not be useful in a prehospital setting [16,17]. Point-of-care testing of serum lactate, however, may be useful during long transports. A novel method for measuring and diagnosing shock is tissue oxygen saturation (which can be measured peripherally); however, it is still undergoing evaluation. Early laboratory studies show it to be an earlier marker than standard vital signs [18,19]. Heart rate variability measurements are able to predict mortality but do not perform better than other common indices, and may not be the best for evaluation of hemorrhagic shock [20]. Sublingual capnography theoretically recognizes local tissue hypoxia and microcirculatory injury, but recent studies suggest it is not present earlier than standard vital signs [21]. Applying direct pressure to stop bleeding from a wound is one of the most ancient principles of first aid. Steady, firm pressure using gauze or a large dressing (such as an abdominal pad) directly onto the bleeding site remains the method of choice to control hemorrhage in the civilian prehospital setting. The dressing must be of sufficient thickness so as not to diffuse or reduce the pressure applied to the site of hemorrhage. Once applied, pressure should be continued until the patient arrives at definitive care and is transferred to hospital personnel. The wound should not be periodically examined to see if the bleeding is stopped while en route, as this will result in disruption of the clot and rebleeding. Application of direct pressure requires the full attention of one provider. If there are multiple casualties or the provider is unable to apply continuous pressure, a pressure dressing may be applied. Pressure dressings are effective and reliable for controlling hemorrhage. They can be fabricated with materials at hand, such as elastic bandages and cravats, or with ready-made commercial dressings [22]. When applying a pressure dressing, the principles are essentially the same as when applying direct pressure. A large pledget of gauze should be applied directly to the wound and compressed with an elastic bandage or cravat. Pressure, not the dressing material itself, is the most important part of attaining hemostasis. If pressure fails to control hemorrhage from an extremity injury, a tourniquet should be applied (Figure 35.1). Initially used to curtail bleeding during amputation, the tourniquet was brought to the battlefield in 1674 [4]. Controversy and debate about the appropriateness and circumstances of tourniquet use began soon after and have continued through the current US conflicts in Iraq and Afghanistan [23]. Figure 35.1 The SOF-T tourniquet. Source: www.health.mil/tccc During the Vietnam conflict, Rich described only one case of limb loss secondary to tourniquet use among thousands of casualties with vascular injuries, and Hutton reported that fasciotomies were sometimes needed when tourniquet times were in excess of 2 hours [24]. Over the course of the last decade, the controversy over tourniquet safety and effectiveness has subsided, with almost universal acceptance in severe extremity bleeding or amputation. Every US soldier and Marine carries a tourniquet, and it is used frequently on the battlefield. The most recent review of military use has shown that tourniquets are safe, effective, and have contributed to a significant reduction in deaths from extremity hemorrhage [25,26]. See Video Clip 35.1 for application of a tourniquet. Civilian prehospital studies evaluating tourniquet safety and effectiveness are lacking. Severe peripheral vascular injures are relatively rare in the civilian setting and transport times to medical facilities are usually rapid. In most instances, civilian EMS providers can maintain continuous direct pressure on a bleeding injury until the patient arrives at the hospital. If direct pressure fails, a tourniquet should be applied. Tourniquets may be useful in MCIs related to explosive blasts, terrorism, or criminal violence. In these cases, there will often be more casualties than skilled providers, and evacuation from the scene may be delayed due to tactical concerns or because of collapsed and unstable structures. This was borne out during the Boston Marathon bombing in 2013. Based on bomb placement, a significant number of lower extremity injuries occurred. Early anecdotal reports conclude that the use of tourniquets (mostly field expedient) saved lives [6]. The American College of Surgeons and the FBI consensus statement (the “Hartford Consensus”) recommended tourniquets for life-threatening bleeding from extremity wounds during mass shooting scenarios [27]. The Active Shooter Law Enforcement Rapid Response Training (ALERRT) Center, recognized by the FBI as the national training standard for active shooter response, also recommends the use of tourniquets for extremity hemorrhage. As tourniquet use became the norm in a combat environment and extremity hemorrhage decreased as a cause of death, control of junctional hemorrhage (hemorrhage in potentially compressible areas not amenable to a standard tourniquet) could be initiated in the prehospital environment [28]. Preliminary research into junctional tourniquets (initially, the Combat Ready Clamp in 2010; Figure 35.2) demonstrated their effectiveness [29,30] and ongoing studies into other potential junctional tourniquet devices continue. See Video Clip 35.2 for application of the Combat Ready Clamp. Figure 35.2 The Combat Ready Clamp. Source: www.health.mil/tccc The abdominal aortic tourniquet, a device inflated over the abdomen with enough pressure to compress the abdominal aorta, is under investigation. A preliminary study demonstrated effectiveness in human volunteers where an abdominal tourniquet was used to reduce common femoral artery flow; however, it was extremely uncomfortable for the volunteers [31]. Anecdotal evidence in the lay press suggests it may be useful and trials of this device are being conducted with selected groups of military personnel in Afghanistan [32]. Suturing and surgical stapling are common methods for hemorrhage control, but usually require time and clean fields. A novel device, recently introduced in the literature, the IT Clamp (Innovative Trauma Care, San Antonio, TX) looks like a hair clip and uses the teeth of the clip to grasp each side of the wound while the clamp portion closes over the wound, approximating the edges and allowing a hematoma to form to serve as a pressure dressing (Figure 35.3). An early study shows that it provides hemostasis in a swine groin injury model compared to standard gauze [33].
Hemorrhage control
Introduction
Assessment
Diagnosis of hemorrhagic shock
Treatment modalities
Pressure
Tourniquets
Rapid wound closure
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