Anatomy and Physiology Review
The cardiovascular system
Pathophysiology
- Bleeding removes critical components of the blood (such as oxygen-carrying hemoglobin) from circulation and can impair the ability of the body to perfuse its cells.
- Massive bleeding causes extraordinary blood loss in a very brief amount of time.
- Bleeding can be external (leaking to the outside of the body) or internal (bleeding into body cavities, often with little or no external evidence).
- Blood loss through hemorrhage is a function of the size (diameter) and internal pressure of the leaking blood vessel.
- High-risk areas include “junctional” regions at the neck, armpits, and groin.
- Arteries are often large and carry highly pressurized blood. When damaged, they frequently cause massive hemorrhage.
- Capillaries are the smallest blood vessels and tend to leak slowly (oozing bleeding).
- Veins can be large or small but are less pressurized compared with arteries. Even so, violation of a large vein can cause massive hemorrhage.
- Shock occurs when the cells of the body cannot be supplied adequately with oxygen and nutrients, and when waste products cannot be removed. Shock in its most basic sense is the hypoperfusion of cells.
- Shock is most commonly caused by four mechanisms:
- Failure of the pump (as in cardiogenic shock): The heart fails to deliver adequate supplies of blood to the cells.
- Hypovolemia (as in hypovolemic shock): There is not enough blood to carry oxygen and nutrients to the cells. This can result from absolute hypovolemia (bleeding) or relative hypovolemia (losing the liquid portion of the blood in dehydration).
- Failure of blood vessel tone (as in distributive shock): If blood vessels cannot maintain a normal diameter and dilate inappropriately, pressure within those vessels falls and blood cannot be pumped to the body cells.
- Obstruction of blood flow (as in obstructive shock): The flow of blood is blocked by a secondary condition (as with a massive pulmonary embolism).
- The body can compensate for shock by increasing heart rate and strength of contraction, by breathing faster, and by constricting blood vessels (shunting to the core). This state is referred to as compensated shock.
- The mechanisms of compensation require oxygen and nutrients, which frequently are in short supply in a shock state. As a result, these efforts can fail and cause decompensated (hypotensive) shock.
Signs and Symptoms
- Use mechanism of injury to predict injuries and anticipate the possibility of internal hemorrhage.
- Massive hemorrhage is often obvious, but not all bleeding is easily recognized.
- Arterial bleeding typically is bright red and spurting. However, spurting stops as mean arterial pressure falls.
- Venous bleeding typically is slower and darker but can be massive in a large vein.
- Capillary bleeding commonly results from abrasion and oozes blood slowly.
- Bleeding can be hidden in bulky clothing or appear to be less in low light conditions.
- Internal bleeding commonly is recognized by considering mechanism of injury and recognizing patterns of compensated shock.
- Internal bleeding may also be indicated by bruising, localized pain and tenderness, abdominal distension and/or rigidity, and blood present in stool or vomit.
- Signs and symptoms of shock include:
- Altered mental status (including the spectrum from anxious to unconscious).
- Increased heart rate.
- Signs of vasoconstriction, such as pale skin, delayed capillary refill time, sweating, narrowing pulse pressures (systolic BP – diastolic BP = Pulse pressure).
- Falling blood pressure (late sign).
- Nausea and vomiting.
- It is important to remember that specific causes of shock may demonstrate unique signs and symptoms. For example, anaphylactic shock commonly is associated with edema and skin rash. These findings are detailed more specifically in other sections.
Treatment
- Consider the need for personal protective equipment, including gloves and eye protection, when managing hemorrhage.
- Assess mechanism of injury to identify the potential for internal hemorrhage.
- Identify and stop massive hemorrhage immediately.
- Compress the wound (apply direct pressure). Compress with palm pressure toward a bone when possible.
- Maintain pressure and expose the wound (if possible)
- If bleeding can be localized, apply point pressure to bleeding area and pack the surrounding cavity with standard or hemostatic gauze. Reapply direct pressure.
- If direct pressure fails, or if direct pressure is not possible and the wound is in an extremity, apply a tourniquet.
- Apply the tourniquet “high and tight” on the extremity and tighten until a distal pulse is lost (or until the tourniquet cannot be tightened further).
- Commercial tourniquets perform better, but if a tourniquet must be improvised, ensure that it is at least 1 to 2 inches wide and can be tightened with mechanical force (as with a windlass system).
- If a single tourniquet fails, consider applying a second proximal tourniquet.
- Manage the airway and consider the need for high-concentration oxygen (in cases of hypoxia).
- Consider the need for immediate transport to an appropriate trauma center destination.
- Dress and bandage nonmassive hemorrhage.
- Place the patient in a supine position (if possible)
- Keep the patient warm; consider adding heat (such as hot packs around the trunk)
- Splint fractures, especially pelvic fractures.
Key Concepts
- Truly massive hemorrhage is a rare event. Learn to distinguish moderate to severe bleeding from life-threatening exsanguinating hemorrhage. When in doubt, however, treat aggressively.
- In trauma care, no treatment priority is more important than stopping massive hemorrhage.
- Often, relatively minor external hemorrhage can distract attention from more significant life threats, such as airway or breathing problems.
- Do not fear tourniquets. When applied properly, complication rates are very low and lifesaving benefits far outweigh the risks.
- Internal hemorrhage and shock patients are a surgical priority. Transport must be an immediate priority.
- Warmth = life in trauma patients. Be aggressive in maintaining body temperature.
- Compensated shock can be challenging to recognize. Consider all unexplained tachycardia and rapid breathing to be shock until proven otherwise.
- Do not wait for hypotension to diagnose shock