Bleeding and Shock:
As we know, shock is a state of inadequate tissue perfusion, resulting from hypovolemic, cardiogenic, obstructive, or distributive causes. In the case of bleeding, shock is the result of a hypovolemic state. When a vascular injury occurs, the body attempts to maintain hemostasis, through several mechanisms, including vasospasm at the site of injury, activation of the clotting cascade, clot formation, and activation of the CNS and RAAS to maintain MAP. With minor bleeding, control may be possible without significant disruption to circulating fluid volume. Major hemorrhage, however, can lead to depletion of clotting factors, vascular collapse, and death if not treated quickly.
Types of bleeding:
Bleeding can be broken down into either external or internal hemorrhage. External hemorrhage refers to wounds that are the result of a break in the outer skin of the body, causing blood to be lost into the external environment. Internal hemorrhage refers to loss of blood into cavities within the body itself. Bleeding of either type can have 3 possible sources:
Capillary bleeding: Slow bright red, oozing wounds that clot rapidly.
Venous bleeding: Dark red bleeding that flows steadily.
Arterial bleeding: Bright red bleeding that “spurts” along with the pulsation of the heart.
Control of External hemorrhage involves application of direct pressure at the site of the wound. Persistent extremity bleeding may be addressed with a tourniquet or hemostatic dressing. Persistent bleeding in the trunk, axilae, or groin may be addressed with wound packing or a hemostatic dressing. Wounds to the head, or open wounds to the chest should not be packed, and should be instead controlled with only external dressings.
Control of internal hemorrhage cannot be accomplished outside of the surgical setting, so these patients need to be rapidly identified and transported to a trauma centre. You should suspect internal hemorrhage based upon mechanism of injury, vital signs, and patient presentation. Remember to look for evidence of shock (pallor, diaphoresis, tachycardia, and ALOC), and do a full RTS on these patients. Common sites for blood to pool in the body are the thorax (hemothorax/hemomediastinum), abdomen (Cullen sign, and Grey-Turner sign), pelvis, and the femurs.
If internal hemorrhage is suspected, keep the patient supine, maintain warmth, apply supplemental oxygen, and establish large bore IV access.
A NOTE ON FLUIDS: Although the patient in hemorrhagic shock is hypovolemic, we don't want to provide large boluses of isotonic fluids. These fluids do not have the capacity to carry oxygen, and serve only as volume expanders. We do not want to dilute the remaining blood volume any more than we have to. So, as a rule we only want to bolus to maintain a MAP of 65mmHg (or an SBP of 90mmHg). Advanced life support providers may consider the use of vasopressors as directed by local protocols.
Disseminated intravascular coagulation:
When hemorrhage persists for a significant period of time, the body runs out of clotting factors. What this means is, we end up in a situation where we initially have widespread coagulation and bleeding at the same time, followed by sudden uncontrolled bleeding that the body can no longer compensate for.
So, how do we recognize hypovolemic shock in a bleeding patient?
Initially, we will have a mechanism suggestive of potential bleeding (or we will have obvious gross bleeding). The patient will initially compensate through vasoconstriction, elevation of the heart rate, and increased respiratory rate. During the compensatory phase, the SBP may be quite normal. As the patient hemorrhages further, they will begin to decompensate; which will be most noticeable as a sudden drop in SBP. As decompensation progresses further, the patient will have alterations in LOA, tachycardia, tachypnea, pallor, and lethargy. In the terminal phase of shock, the patient may become unresponsive, tachycardia may become bradycardia, and the patient will gradually progress to death. Unlike other types of shock, such as Sepsis, which progress gradually to MODS, hemorrhagic shock has a very rapid downward trajectory to death if not addressed early.
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