Shock

Shock is inadequate cellular perfusion. Cells require oxygen, water, and glucose to produce energy in the form of adenosine triphosphate. As shock progresses from tissues to organ systems and the whole body, blood circulation slows and eventually ceases, which causes organs to fail. Shock can occur because of a heart attack, severe allergic reaction, or bleeding. Perfusion is the circulation of blood to the tissues in adequate amounts to meet the cells’ needs. This includes delivery of oxygen and removal of toxic waste products. There are two circuits in the body: systemic circulation between the heart and the lungs, which carries oxygen-rich blood from the left ventricle through the body and back to the right atrium. It delivers oxygen and nutrients and removes waste products. To protect vital organs from hypoperfusion, the body attempts to compensate by directing blood flow away from organs that are more tolerant of shock (skin and intestines) and toward the heart, brain, and lungs. So look for signs in the skin that the patient is experiencing shock.

The perfusion triangle is the heart, the set of pipes (blood vessels, veins, and arteries), and the container (the blood). When a patient is in shock, one or more of the three parts is not working properly. For blood vessels, if all dilate rapidly, the normal amount of blood volume is not enough to fill the system and provide adequate perfusion to the body — vasodilation. Blood — if there is enough blood or plasma lost, the container is not enough to support the perfusion needs of the body. Plasma contains electrolytes and fluid. Heart — damage to the heart by disease or injury decreases the ability of the heart to properly function as a pump. It cannot pump enough blood through the body to support perfusion.

Blood flow through the capillary beds is regulated by the capillary sphincters controlled by the autonomic nervous system. Regulation of blood flow is determined by cellular need and is accomplished by vessel constriction or dilation and capillary sphincter constriction or dilation. Perfusion is more than just the cardiovascular system working; it also requires adequate oxygen exchange in the lungs, which is why ventilation and oxygenation are one of the EMT’s primary concerns. Epinephrine and norepinephrine are released to support the respiratory and cardiovascular system. They change the heart rate and the strength of cardiac contraction. They also cause vasoconstriction in nonessential areas and help shunt blood to the vital organs.

Cardiogenic shock is caused by inadequate function of the heart or pump failure. After a heart attack, the heart no longer functions well, resulting in buildup that forces fluid out of the capillary beds that surround the alveoli, leading to pulmonary edema. Edema is the presence of large amounts of fluid between cells in body tissues, causing swelling of the affected area. It results in tachypnea (rapid respirations) and crackles or rales (a rattling sound that may be heard during breathing on inhalation). The ability to contract is referred to as myocardial contractility. Pressure is known as preload, which increases the volume of blood within the ventricles, which causes the heart muscle to stretch, which is followed by the afterload, which is the force or resistance against which the heart pumps. High afterload is the reason heart failure develops in patients with hypertension. Cardiogenic shock may result from low cardiac output due to high afterload or low preload, poor contractility, or a combination.

Obstructive shock is caused by an obstruction that prevents an adequate volume of blood from being distributed to the body. Cardiac tamponade is caused by pericardial effusion — the filling of fluid in the pericardial cavity. It could be caused by blunt or penetrating trauma that causes hemorrhage around the heart. It can be seen in patients with cancer and autoimmune diseases. Signs are referred to as Beck triad: presence of jugular vein distention, muffled heart sounds, and a narrowing pulse pressure where systolic and diastolic blood pressures start to merge (systolic pressure decreases and diastolic pressure increases).

Tension pneumothorax allows air that is normally held within the lung to escape into the chest cavity. The lung eventually collapses, causing a pneumothorax, which is when air accumulates within the chest cavity and begins applying pressure to the heart and greater vessels. When trapped air begins to shift the chest organs toward the uninjured side, it is known as a tension pneumothorax — it pushes the mediastinum toward the other side and the vena cava loses its ability to stay fully expanded. Blood pressure drops, and you may notice difficulty when attempting to ventilate the patient with a bag-mask device. The affected side will have absent lung sounds and the patient may become cyanotic. Tracheal deviation is a late sign.

Pulmonary embolism is a blood clot that occurs in the pulmonary arteries and blocks the flow of blood through the lungs. It can prevent blood from being pumped from the right side to the left, resulting in complete backup of blood in the right ventricle and catastrophic obstructive shock.

Distributive shock results when there is dilation of the small arterioles, small venules, or both; therefore, blood volume pools in the expanded vascular beds and tissue perfusion decreases. Septic shock is where toxins are generated by bacteria which cause damage to the vessel walls; vessel walls leak and are unable to constrict well. In combination with plasma loss, there is dilation, which results in shock. There is insufficient plasma due to fluid leaking; this leaking fluid can collect in the alveoli, interfering with respiration. Larger than normal vascular volume with smaller than normal intravascular fluid leads to shock.

Neurogenic shock occurs when there is damage to the upper cervical levels of the spinal cord, which may cause loss of control to the musculature and vessels below. Brain conditions, tumors, pressure on the spinal cord, and spina bifida can all lead to this as well. Muscles in the walls are cut off from the sympathetic nervous system that causes them to contract, and then all dilate too much. Signs of this type of injury are the absence of sweating below the level of injury, low heart rate in the presence of hypotension, with normal and warm skin. This is the only type of shock that occurs without pale, cool skin because vasoconstriction cannot be triggered through the autonomic nervous system. Body temperature can also fall to match that of the environment — hypothermia occurs, which severely complicates the situation. Maintenance of body temperature is always an important element of treatment for a patient in shock.

Anaphylactic shock occurs when a person reacts quickly to a substance that they are sensitized to. Do not be surprised when a patient reports no history of allergic reaction to a substance on first or second exposure. Each subsequent exposure after sensitization tends to produce a more severe reaction. Exposure falls into four categories — injections, stings, ingestions, and inhalation. Signs are cyanosis and paleness by examining mucous membranes inside the inner lower eyelid and capillary refill. Skin is flushed, itchy, or burning over the face and upper part of the chest, urticaria (hives), edema — buildup of fluid in the face, lips, and tongue especially. The circulatory system shows dilated peripheral blood vessels, increased vessel permeability, and a drop in blood pressure.

Respiratory system signs include sneezing or itching in the nasal passage, stridor, upper airway obstruction, tightness in the chest with a dry cough, wheezing, and dyspnea (difficulty breathing), secretions of fluid and mucus into the bronchial passages, alveoli, and lung tissue, constriction of the bronchi, difficulty drawing air into the lungs, forced expiration accompanied by wheezing, and cessation of breathing. There may be abdominal cramping, nausea/vomiting, altered mental status, dizziness, fainting, and coma. There is widespread vascular dilation, increased permeability, and bronchoconstriction.

Psychogenic shock is a sudden reaction of the nervous system that produces a temporary, generalized vasodilation, resulting in fainting or syncope. An irregular heartbeat or a brain aneurysm could be culprits. However, an unpleasant sight can also be the cause and should receive a full assessment.

Hypovolemic shock is a result of an inadequate amount of fluid in the circulatory system. It can be hemorrhagic where an open wound causes bleeding out. It can also be a result of severe thermal burns; intravascular plasma loss is caused when fluid leaks from the capillaries into the surrounding tissue. Dehydration, loss of water or fluid — vomiting or diarrhea, hot weather.

Compensated shock is when the body can still compensate. Signs include agitation, anxiety, restlessness, feeling of impending doom, weak, rapid pulse, clammy skin, pallor with cyanosis of the lips, shallow rapid breathing, nausea/vomiting, capillary refill longer than 2 seconds, marked thirst, and narrowing pulse pressure (systolic and diastolic merging closer together).

Decompensated shock includes falling blood pressure and declining mental status. Signs include falling blood pressure (systolic 90 mm Hg or lower), declining mental status, altered level of consciousness, labored or irregular breathing, ashen, mottled, or cyanotic skin, thready or absent peripheral pulses, dull eyes, dilated pupils, and poor urinary output.

Irreversible shock is a condition that is the inability to successfully achieve resuscitation regardless of the methods employed. Expect shock in the following: multiple severe fractures, abdominal or chest injury, spinal injury, severe infection, major heart attack, and anaphylaxis.

General shock treatment: control all obvious external bleeding using direct pressure; if that is not successful, apply tourniquets. Make sure the patient has an open airway. Manual in-line stabilization if necessary. Check breathing and pulse. Never allow a patient to eat or drink prior to being evaluated by a physician. Apply spinal motion restriction if there is concern about neck or back injuries. Do not delay transport. Always provide oxygen, assist with ventilations, and use airway control adjuncts as needed and continue to monitor the patient’s breathing. To prevent the loss of body heat, place blankets under and over the patient; do not use external heat sources as they may cause vasodilation and decrease blood pressure even more. Consider ALS rendezvous if possible and aeromedical transport. Accurately record the patient’s vital signs approximately every 5 minutes. Limit on-scene time to 10 minutes or less.