Quick and Dirty Guide to Shock
Shock is a complex group of physiological abnormalities that comes from a variety of diseases and injuries. It is best defined as inadequate perfusion/blood flow to the body’s peripheral tissues causing life-threatening hypoperfusion (not enough O2 reaching the cells). Perfusion requires an intact cardiovascular system and a functioning respiratory system. The shock cascade can progress quickly if it is not recognized, understood, and properly managed early!
The Rapid Progression of Shock
Shock is caused by three major problems that occur within the body:
- Problems with the heart's functioning: Cardiogenic shock can be caused by any disease, or event, which prevents the heart muscle from pumping strongly and consistently enough to circulate the blood normally. Heart attack, conditions which cause inflammation of the heart muscle (myocarditis), disturbances of the electrical rhythm of the heart, any kind of mass or fluid accumulation and/or blood clot which interferes with flow out of the heart can all significantly affect the heart's ability to adequately pump a normal quantity of blood.
- The total circulating blood is low: Hypovolemic shock occurs when the total volume of blood in the body falls well below normal. This can occur when there is excess fluid loss, as in dehydration due to severe vomiting or diarrhea, diseases which cause excess urination (diabetes insipidus, diabetes mellitus, and kidney failure), extensive burns, blockage in the intestine, inflammation of the pancreas (pancreatitis), or severe bleeding of any kind.
- Overwhelming infection, usually caused by bacteria: Septic shock can occur when an infection (usually bacterial) is allowed to progress. Bacteria often produce toxins which can cause injury throughout the body. When large quantities of bacteria/toxins, begin circulating in the bloodstream, every organ is at risk. The most damaging consequences include:- Poor functioning of the heart muscle - Widening of the diameter of the blood vessels - Drop in blood pressure - Activation of the blood clotting system, causing blood clots and a risk of uncontrollable bleeding - Damage to the lungs, causing acute respiratory distress syndrome - Liver failure - Kidney failure - Coma
There are 3 separate stages of shock:
- Stage I: Compensated Shock: When low blood flow (perfusion) is first detected by the body.A number of systems are activated in order to maintain/restore perfusion. The heart beats faster, the blood vessels become smaller in diameter, and the kidney works to retain fluid in the circulatory system to maximize blood flow to the most important organ systems of the body. The patient in this stage of shock has very few symptoms, and aggressive treatment may slow or stop progression to stage II shock.
- Stage II: Decompensated Shock: When the methods of compensation begin to fail. The systems are unable to maintain perfusion any longer. Oxygen deprivation in the brain causes the patient to become confused and disoriented.
- Stage III: Irreversible Shock: The length of time that poor perfusion has existed begins to take a permanent toll on the body's organs and tissues. The heart's functioning continues to spiral downward, and the kidneys usually shut down completely. Cells in organs and tissues throughout the body are injured and dying. The endpoint of Stage III irreversible shock, is patient death.
- Hypovolemic shock: decreased blood volume. A type of hypovolemic shock is hemorrhagic shock, which results from blood loss.
- Obstructive shock: something blocks perfusion to the heart. For example, pulmonary embolism, tension pneumothorax, or cardiac tamponade.
- Distributive shock: abnormal blood distribution that leads to inadequate blood reaching the heart.
- Neurogenic shock: nervous system injury leading to vasodilation in the periphery causing inadequate perfusion to the vital organs.
- Anaphylactic shock: severe allergic reaction that leads to vasodilation and bronchoconstriction.
- Cardiogenic shock: inadequate pumping of the heart. Can be due to heart disease or heart attack.
Remember, most types of shock (hypoperfusion) are caused by dysfunction in one or more parts of the perfusion triangle: 1. The pump (the heart) 2. The pipes, or container (blood vessels) 3. The content, or volume (blood)
Hypovolemic shock is an emergency condition in which severe blood and fluid loss make the heart unable to pump enough blood to the body. This type of shock can cause many organs to stop working. Losing about 1/5 or more of the normal amount of blood in your body causes hypovolemic shock. Blood loss can be caused by:
- Bleeding from cuts
- Bleeding from other injuries
- Internal bleeding, such as in the gastrointestinal tract
The amount of circulating blood may drop from the patient losing too much body fluid, which can occur with:
- Excessive perspiration
As in hypovolemic shock there is an insufficient volume of blood. This form of relative hypovolemia is the result of dilation of blood vessels. Examples of this form of shock are:
- Septic shock: Caused by overwhelming infection leading to vasodilation. It is treated in hospital by antibiotics, fluid replacement, and vasoconstrictors.
- Anaphylactic shock: Caused by allergens that trigger widespread vasodilation and movement of fluid out of the blood into the tissues. This a serious, potentially life-threatening allergic response that is marked by swelling, lowered blood pressure, and dilated blood vessels. In severe cases, a person will go into shock. If anaphylactic shock isn't treated immediately, it can be fatal.
- Neurogenic shock : Caused by the sudden loss of the sympathetic nervous system signals to the smooth muscle in vessel walls. Without this constant stimulation the vessels relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.The rarest cause of shock is acute spinal cord injury leading to neurogenic shock.
Occurs when the normal flow of blood is obstructed. Several conditions result in this form of shock:
- Cardiac tamponade - Blood in the pericardium prevents blood from entering the heart (venous return).
- Pneumothorax - Increased pressure within the thoracic cavity blocks the normal flow of blood to the heart.
- Pulmonary embolism - The result of a blockage (embolus) in the blood vessels of the lungs, blocking the return of blood to the heart.
Cardiogenic shock is literally shock with cardiac origin. It is also the physiologic end point of all other causes of shock. Cardiogenic shock can therefore, regardless of its etiology, be thought of as shock caused by failure of the heart as a forward pump. Modern advances in medical care have made cardiogenic shock less common than it once was, but it is still a life-threatening reality. The most common etiology for cardiogenic shock is a myocardial infarction. Some of the less common causes of cardiogenic shock include infectious cardiac disease processes, such as:
- Acute myocarditis or endocarditis
- Induced heart failure from drugs/medications (i.e., cocaine, beta-blockers, tricyclic antidepressants)
- Trauma-related; such as a myocardial contusion
- Metabolic disorders resulting in cardiac arrhythmia's, such as sustained tachycardia or bradycardia.
- Pulmonary embolism may also produce cardiogenic shock by impeding blood flow in the pulmonary vessels.
Signs and Symptoms of Shock (Hypoperfusion)
Initial symptoms of shock include:
- Cold, clammy hands and feet
- Pale or blue-tinged skin tone (cyanosis)
- Weak, fast pulse rate (tachycardia)
- Fast breathing rate (tachypnea)
- Low blood pressure (hypotension)
A variety of other symptoms may be present, but they are dependent on the underlying cause of the shock state. 1. Mental states
- Altered mental status
2. Peripheral perfusion
- Delayed capillary refill greater than 2 seconds in normal ambient air temperature infant and child patients only
- Weak, thready or absent peripheral pulses
- Pale, cool, clammy skin
3. Vital signs
- Decreased blood pressure (late sign)
- Increased pulse rate (early sign) - weak and thready
- Increased breathing rate (1) Shallow (2) Labored (3) Irregular
4. Other signs and symptoms include
- Dilated pupils
- Nausea and vomiting
- Pallor with cyanosis to the lips
NOTE: Infants and children can maintain their blood pressure until their blood volume is more than half gone, so by the time their blood pressure drops they are close to death. The infant or child in shock has less reserve.
Treatment Goals for Shock
Important goals in the treatment of shock for EMT’s include:
- Quickly diagnosing the patient's state/type of shock
- Intervening to halt the underlying condition(Stop bleeding, re-starting the heart, etc.)
- Treat the effects of shock(High flow O2, keep pt warm, reassure, etc.)
- Supporting vital functions(respiration, blood pressure, heart function).
- Keep the patient warm, with legs raised and head down to improve blood flow to the brain (if no trauma suspected)
- Treat the underlying condition which led to shock.
- Take body substance isolation precautions
- Maintain an open airway
- High concentration oxygen; assist ventilations or administer CPR if indicated
- Control external bleeding
- Elevate legs 8" - 12" if no lower body or spinal injuries
- Splint fractures
- Prevent loss of body heat
- Transport immediately
Normal Saline IV x2 or IO Maintain BP >90 Bolus (Up to 1 liter) *You MUST monitor lung sounds when administering fluid bolus
PHYSICIAN ORDER: Dopamine 5mcg/kg/min via IV/IOAfter 5 minutes, increase if needed to titrate to BP > 90. The outcome for an individual patient in any type of shock depends on the stage of shock when treatment is begun, the underlying condition that is causing shock, and the general medical state of the patient. As always protect the patient’s airway, improve ventilatory status with assisted vents or simply high flow O2 as warranted, and closely monitor the patients circulatory status until definitive care can be initiated!
Don’t forget to check out the Quick Quiz and additional shock resources from MedicTests.com
Check out these 2 videos on Understanding Shock!