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Emergency bleeding control describes the steps or actions taken to control bleeding from a patient who has suffered a traumatic injury or who has a medical condition which has led to bleeding. Many bleeding control techniques are taught as part of first aid throughout the world, although some more advanced techniques such as tourniquets, are often taught as being reserved for use by health professionals, or as an absolute last resort, in order to mitigate the risks associated with them, such as potential loss of limbs. In order to manage bleeding effectively, it is important to be able to readily identify both types of wounds and types of bleeding.
Wounds are normally described in a variety of ways. These may deal with a description of wound size (length) and thickness, or also with the plainly visible wound characteristics. Wounds may be categorized as open or closed, or as either acute or chronic in origin. The most common descriptors of wounds are these:
External bleeding is generally described in terms of the origin of the blood flow by vessel type. The basic categories of external bleeding are:
The type of wound (incision, laceration, puncture etc.) will have a major effect on the way a wound is managed, as will the area of the body affected and the presence of any foreign objects in the wound. The key principles of wound management are:
Elevation was commonly recommended for the control of haemorrhage, some protocols continue to include it but recent studies have failed to find any evidence of its effectiveness and it was removed from the PHTLS guidance in 2006. 
Placing pressure on the wound will constrict the blood vessels manually, helping to stem any blood flow. When applying pressure, the type and direction of the wound may have an effect, for instance, a cut lengthways on the hand would be opened up by closing the hand into a fist, whilst a cut across the hand would be sealed by making a fist. A patient can apply pressure directly to their own wound, if their consciousness level allows. Ideally a barrier, such as sterile, low-adherent gauze should be used between the pressure supplier and the wound, to help reduce chances of infection and help the wound to seal. Third parties assisting a patient are always advised to use protective latex or nitrile medical gloves to reduce risk of infection or contamination passing either way. Direct pressure can be used with some foreign objects protruding from a wound, and to achieve this, padding is applied from either side of the object to push in and seal the wound - objects are never removed.
In situations where direct pressure and elevation are either not possible or proving ineffective, and there is a risk of exsanguination, some training protocols advocate the use of pressure points to constrict the major artery which feeds the point of the bleed. This is usually performed at a place where a pulse can be found, such as in the femoral artery. There are significant risks involved in performing pressure point constriction, including necrosis of the area below the constriction, and most protocols give a maximum time for constriction (often around 10 minutes). There is particularly high danger if constricting the carotid artery in the neck, as the brain is sensitive to hypoxia and brain damage can result within minutes of application of pressure. Pressure on the carotid artery can also cause vagal tone induced bradycardia, which can eventually stop the heart. Other dangers in use of a constricting method include rhabdomyolysis, which is a build up of toxins below the pressure point, which if released back into the main bloodstream may cause renal failure
Another method of achieving constriction of the supplying artery is via the use of a tourniquet - a tightly tied band which goes around a limb to restrict blood flow. Tourniquets are routinely used in order to bring veins to the surface for cannulation, although their use in emergency medicine is more limited. The use of the tourniquet is restricted in most countries to professionals such as physicians and paramedics, as this is often considered beyond the reach of first aid and those acting in good faith as a good samaritan. A key exception is the military, where many armies carry a tourniquet as part of their personal first aid kit.
Improvised tourniquets, in addition to creating potential problems for the ongoing medical management of the patient, usually fail to achieve force enough to adequately compress the arteries of the limb. As a result, they not only fail to stop arterial bleeding, but may actually increase bleeding due to the impaired venous bloodflow. Some argue that tourniquets should never be used in the pre-hospital setting, not even for amputations.
Some protocols call for the use of clotting accelerating agents, which can either by externally applied as a powder, gel or pre-dosed in a dressing, or as an intravenous injection. These may be particularly useful in situations where the wound is not clotting, which can be due to external factors, such as size of wound, or medical factors such as haemophilia.
rFVIIa is not, as of 2012, supported by the evidence for most cases of major bleeding. There is a significant risk of arterial thrombosis with its use and thus other than in those with factor VII deficiency should only be used in clinical trails.
Internal wounds (usually to the torso) are harder to deal with than external wounds, although they often have an external cause. The key dangers of internal bleeding include hypovolaemic shock (leading to exsanguination, causing a tamponade on the heart or a haemothorax on the lung. The aortic aneurysm is a special case where the aorta, the body's main blood vessel, become ruptured through an inherent weakness. This is one of the most serious medical emergencies a patient can face, as the only treatment is rapid surgery, although exertion, raised blood pressure or sudden movements could cause a sudden catastrophic failure.
In the event of the bleeding being caused by an external source (trauma, penetrating wound), the patient is usually inclined to the injured side, in order to ensure that the 'good' side can continue to function properly, without interference from the blood inside the body cavity.
The treatment of internal bleeding is beyond the scope of simple first aid, and should be considered by any first aider to be potentially life threatening. The definitive treatment for internal bleeding is always surgical treatment, and medical advice must be sought urgently for any victim of internal bleeding.