CH 13 - Shock

Afterload

The force or resistance against which the heart pumps

Anaphylactic shock

Severe shock caused by an allergic reaction

Anaphylaxis

An extreme, life-threatening, systemic allergic reaction that may include shock and respiratory failure

Aneurysm

A swelling or enlargement of part of an artery, resulting from weakening of the arterial wall

Autonomic nervous system

The part of the nervous system that regulates involuntary activities such as heart rate, blood pressure, and digestion

Cardiac tamponade

Compression of the heart from a buildup of blood or other fluid in the pericardial sac, leading to decreased cardiac output

Cardiogenic shock

A state in which not enough oxygen is delivered to body tissues because of low blood output from the heart; can be a severe complication of a large acute myocardial infarction or other conditions

Compensated shock

The early stage of shock, in which the body can still compensate for blood loss

Cyanosis

A blue skin discoloration caused by a reduced level of oxygen in the blood; may show as ashen/gray skin or be checked via mucous membranes and capillary refill in people with dark skin

Decompensated shock

The late stage of shock, when blood pressure is falling

Dehydration

Loss of water from the tissues of the body

Distributive shock

A condition that occurs when there is widespread dilation of the small arterioles, small venules, or both

Edema

The presence of abnormally large amounts of fluid between cells in body tissues, causing swelling

Homeostasis

A balance of all systems of the body

Hypothermia

A condition in which the internal body temperature falls below 95°F (35°C)

Hypovolemic shock

A condition in which low blood volume, due to massive internal or external bleeding or extensive loss of body water, results in inadequate perfusion

Irreversible shock

A condition defined by the inability to successfully achieve resuscitation regardless of the methods employed

Myocardial contractility

The ability of the heart muscle to contract

Neurogenic shock

Circulatory failure caused by paralysis of the nerves that control the size of the blood vessels, leading to widespread dilation; seen in patients with spinal cord injuries

Obstructive shock

Shock that occurs when there is a block to blood flow in the heart or great vessels, causing an insufficient blood supply to the body's tissues

Perfusion

The flow of blood through body tissues and vessels

Pericardial effusion

A collection of fluid between the pericardial sac and the myocardium

Preload

The precontraction pressure in the heart as the volume of blood builds up

Pulmonary embolism

A blood clot that breaks off from a large vein and travels to the blood vessels of the lung, causing obstruction of blood flow

Pulse pressure

The difference between the systolic and diastolic pressures

Sensitization

Developing a sensitivity to a substance that initially caused no allergic reaction

Septic shock

Shock caused by severe infection, usually a bacterial infection

What is shock, in the broadest sense?

A state of collapse and failure of the cardiovascular system, or any of its components (heart, vasculature, blood volume), leading to inadequate perfusion of the body's cells and tissues

What is the "perfusion triangle," and what happens when one part fails?

The three components of the cardiovascular system: the heart (pump), blood vessels (container), and blood (content); shock occurs when one or more of these parts isn't working properly

What four components make up blood?

Red blood cells, white blood cells, platelets, and plasma

What three things does adequate perfusion require?

Adequate oxygen exchange in the lungs, nutrients (glucose) in the blood, and waste removal, primarily through the lungs

What is diffusion, and how does it relate to gas exchange?

A passive process in which molecules move from an area of higher concentration to an area of lower concentration; it's how oxygen and carbon dioxide cross the walls of the alveoli

In what three ways is carbon dioxide transported from the tissues back to the lungs?

Dissolved in plasma, combined with water as bicarbonate, and attached to hemoglobin

Why does poor perfusion cause a dangerous carbon dioxide buildup?

Impaired transport of CO2 out of the tissues causes waste products to build up, which can cause cellular damage

During shock, how does the body redirect blood flow to protect vital organs?

It shunts blood away from organs more tolerant of low flow (skin, intestines) toward organs that cannot tolerate low flow (heart, brain, lungs); if perfusion isn't restored, those tissues can die

Define systolic pressure and diastolic pressure

Systolic pressure is the peak arterial pressure generated when the heart contracts; diastolic pressure is the pressure maintained in the arteries while the heart rests between beats

What regulates blood flow through the capillary beds, and what controls it?

Capillary sphincters (circular muscular walls that constrict and dilate), controlled by the autonomic nervous system and responsive to heat, cold, oxygen need, and waste-removal need

What two systems help compensate to support perfusion when it's threatened?

The autonomic (sympathetic) nervous system and hormones (epinephrine and norepinephrine)

What happens when beta-1, beta-2, and alpha receptor sites are triggered during shock?

Beta-1: increased heart rate and force of contraction; beta-2: bronchodilation, allowing more oxygenated air in; alpha: selective vasoconstriction that redirects blood to essential organs

How quickly do neurohormonal compensatory responses occur compared with renal fluid reabsorption?

The nervous/hormonal response occurs within seconds; reabsorption of fluid by the kidneys to boost circulating blood volume occurs more slowly

According to Table 13-1, what type of shock results from pump failure, poor blood vessel function, low fluid volume, and obstructed blood flow?

Pump failure -> cardiogenic shock; poor blood vessel function -> distributive shock (septic, neurogenic, anaphylactic); low fluid volume -> hypovolemic shock (hemorrhagic, nonhemorrhagic); obstructed blood flow -> obstructive shock (tension pneumothorax, cardiac tamponade, pulmonary embolism)

What three factors determine cardiac output?

Myocardial contractility, preload, and afterload

What is pulmonary edema, and why does it cause hypoxemia in cardiogenic shock?

A backup of fluid into the pulmonary vessels/alveoli caused by severe heart failure; oxygen can't diffuse across the fluid-filled alveoli, causing hypoxemia

How does cardiac tamponade impair the heart, and what is the only definitive treatment?

Blood or fluid accumulates in the pericardial sac and compresses the heart's outer walls, preventing it from fully refilling; surgery is the only definitive treatment (field care focuses on increasing cardiac output and giving oxygen)

What is the Beck triad, and what does it indicate?

Jugular venous distention, narrowing pulse pressure, and muffled heart tones — signs of cardiac tamponade

How does a tension pneumothorax progress to obstructive shock, and how is it treated in the field?

Lung damage lets air escape into the chest cavity and the lung collapses; as air keeps accumulating it presses on the heart and great vessels; treat with high-concentration oxygen and chest decompression (an ALS skill) without delaying transport

How does a pulmonary embolism cause obstructive shock?

A blood clot in the pulmonary arteries blocks blood flow through the lungs, preventing blood from moving from the right side of the heart to the left and causing blood to back up in the right ventricle

What causes septic shock, and what does the immune system do to the blood vessels?

A severe, usually bacterial, infection generates toxins; the immune system makes vessels larger and more permeable so white blood cells can reach the tissue, which causes plasma to leak out (hypovolemia) and fluid to collect in the alveoli

In septic shock, what happens to plasma and where does the leaked fluid tend to collect?

Plasma leaks from the blood vessels causing hypovolemia; the leaked fluid often collects in the alveoli, interfering with respiration, while vasodilation increases the vascular volume — together causing dangerously low blood pressure

What causes neurogenic shock, and what happens to the blood vessels below the injury?

Usually a high spinal cord injury; the vessel wall muscles are cut off from sympathetic nerve impulses, so vessels below the level of injury dilate widely and blood pools

Why does neurogenic shock typically present without tachycardia, unlike other types of shock?

Because the sympathetic nervous system and its epinephrine/norepinephrine release are disrupted, so the usual compensatory heart rate increase and vasoconstriction don't occur — expect bradycardia or a normal rate instead

What is anaphylactic shock, and how quickly can it develop?

A severe allergic reaction that occurs after a person is re-exposed to a substance they've become sensitized to; each subsequent exposure tends to be more severe, and reactions can develop within minutes

What are the two categories of hypovolemic shock causes, with examples?

Hemorrhagic (bleeding) and nonhemorrhagic (e.g., severe thermal burns, dehydration from vomiting/diarrhea)

Why is blood pressure a late and unreliable indicator of shock, especially in children?

BP may be the last measurable factor to change, so by the time it drops shock is well developed; children can maintain BP until they've lost more than half their blood volume, so a BP drop in a child means they are close to death

List the conditions under which you should anticipate or expect shock

Massive external bleeding or suspicion of major internal bleeding, spinal cord injury, chest or abdominal injury, major heart attack, anaphylaxis, multiple severe fractures, severe infection, and significant burns

During the primary assessment, what takes priority over opening the airway in a shock patient?

Controlling massive/exsanguinating hemorrhage (tourniquet or wound packing); once bleeding is controlled, proceed with the ABCs (or CAB if cardiac arrest is suspected, since circulation via chest compressions comes first)

What two things are assessed during scene size-up for a possible shock patient?

Scene safety and the mechanism of injury/nature of illness

What should you determine and obtain during history taking for a shock patient?

The chief complaint, and a SAMPLE history

When should you perform a full secondary (head-to-toe) assessment on a shock patient?

If they're a trauma patient with a significant mechanism of injury or multiple injuries, give a poor initial general impression, had problems found in the primary assessment, have a medical problem but are unresponsive, or have problems not noted in the primary assessment

What four things should you reassess in a shock patient, and what should treatment focus on?

Reassess vital signs, interventions, chief complaint, and mental status; focus treatment on supporting the cardiovascular system by providing oxygen and keeping the patient warm

List the general emergency care steps for any patient in shock

Take standard precautions; control all obvious external bleeding; open and maintain the airway (with manual in-line spinal stabilization if needed); comfort, calm, and reassure the patient in a supine position; never allow food or drink before physician evaluation; splint on a backboard if spinal motion restriction is indicated; give oxygen and assist ventilations since inadequate ventilation can worsen shock; place blankets under and over the patient to prevent heat loss; transport promptly and treat additional injuries en route; consider ALS rendezvous or aeromedical transport; and record vital signs about every 5 minutes

What are the six critical interventions for shock?

Give epinephrine immediately for anaphylaxis, control external bleeding, place the patient supine unless it compromises breathing, give high-concentration oxygen to reach an SpO2 of 94-98%, prevent heat loss, and provide rapid transport to the appropriate facility

What SpO2 range should you target with oxygen therapy when treating shock?

94% to 98%

What should never be given to a patient in cardiogenic shock, and why?

Nitroglycerin — because by definition these patients are hypotensive

Why should splinting fractures be a low priority for a critically injured trauma patient in shock?

It takes too long and only delays transport; spinal protection, oxygen/ventilation support, thermal management, rapid transport, and early hospital notification take priority instead

According to Table 13-4, what are the signs and symptoms of cardiogenic shock?

Chest pain, irregular pulse, weak pulse, low blood pressure, cyanosis of the lips/under the nails, cool clammy skin, anxiety, delayed capillary refill, rapid breathing, crackles, and pulmonary edema

According to Table 13-4, how do you treat cardiogenic shock in the field?

Position the patient comfortably, give oxygen to target SpO2 94-98%, assist ventilations, transport promptly, and provide ALS assist and/or rapid transport

According to Table 13-4, what are the signs and symptoms of hypovolemic shock?

Rapid weak pulse, low blood pressure, change in mental status, cyanosis of the lips/under the nails, cool clammy skin, and increased respiratory rate

According to Table 13-4, how do you treat hypovolemic shock in the field?

Secure the airway, assist ventilations, give oxygen to target SpO2 94-98%, control external bleeding, keep the patient warm, and provide ALS assist and/or rapid transport

According to Table 13-4, what are the signs and symptoms of septic shock?

Warm skin or fever early on; low blood pressure; pale, gray, mottled skin later; and tachycardia

According to Table 13-4, how do you treat septic shock in the field?

Give oxygen to target SpO2 94-98%, assist ventilations, keep the patient warm, and provide ALS assist and/or rapid transport

According to Table 13-4, what are the signs and symptoms of neurogenic shock?

Bradycardia or a normal heart rate, low blood pressure, baseline skin color/temperature below the level of injury, and signs of neck injury

According to Table 13-4, how do you treat neurogenic shock in the field?

Secure the airway, maintain spinal motion restriction, assist ventilations, give oxygen to target SpO2 94-98%, preserve body heat, and provide ALS assist and/or rapid transport

According to Table 13-4, what are the signs and symptoms of obstructive shock?

Depends on cause: dyspnea, rapid weak pulse, low blood pressure, rapid shallow breaths, decreased lung compliance, unilateral/decreased/absent breath sounds, jugular venous distention, subcutaneous emphysema, cyanosis, and tracheal deviation toward the unaffected side

According to Table 13-4, how do you treat obstructive shock in the field?

Give oxygen to target SpO2 94-98% and provide ALS assist and/or rapid transport; specific treatment otherwise depends on the underlying cause

List the skin signs of anaphylactic shock

Flushed/red or dark skin (especially the face and upper chest), urticaria (hives) that may spread over large areas, edema especially of the face/tongue/lips, pallor (check capillary refill and mucous membranes in patients with dark skin), and cyanosis around the lips

List the circulatory signs of anaphylactic shock

Dilated peripheral blood vessels, increased vessel permeability, a drop in blood pressure, and a weak, barely palpable pulse

List the respiratory signs of anaphylactic shock

Sneezing or itching in the nasal passages, stridor, upper airway obstruction, chest tightness with a persistent dry cough, wheezing and dyspnea, secretions of fluid/mucus into the airways causing coughing, constriction of the bronchi, forced expiration accompanied by wheezing, and cessation of breathing

List other signs of anaphylactic shock besides skin, circulatory, and respiratory signs

Abdominal cramping, nausea, vomiting, altered mental status, dizziness, and fainting or coma

List the signs and symptoms of compensated shock

Agitation, anxiety, restlessness, a feeling of impending doom, weak/rapid (thready) pulse, clammy (pale, cool, moist) skin, pallor with cyanosis about the lips, shallow/rapid breathing, nausea or vomiting, capillary refill greater than 2 seconds in infants/children, marked thirst, and narrowing pulse pressure

List the signs and symptoms of decompensated shock

Falling blood pressure (systolic 90 mm Hg or lower in an adult), declining mental status/altered level of consciousness, labored or irregular breathing, ashen/mottled/cyanotic skin, thready or absent peripheral pulses, dull eyes with dilated pupils, and poor urinary output

What should you follow, in order, when treating any patient suspected of being in shock?

Control life-threatening hemorrhage with direct pressure or a tourniquet, open and maintain the airway, give high-concentration oxygen (and bag-mask ventilations as needed), maintain normal body temperature with blankets, provide calm reassurance, and provide prompt transport to the appropriate hospital

What are the most common pediatric causes of shock, by category?

Hypovolemic (traumatic blood loss especially abdominal, dehydration, large burns, inadequate fluid intake), distributive (severe infection, neurologic injury such as head trauma, anaphylaxis), cardiogenic (congenital heart disease, heart muscle infection, diseases that weaken the heart muscle), and obstructive (collapsed lung/tension pneumothorax, blood or fluid around the heart)

Why can even a small amount of blood loss be dangerous in a child?

Children have less circulating blood volume than adults, so a relatively small blood loss can represent a serious threat of shock regardless of what the blood pressure indicates

What five things should you pay attention to when assessing circulation in a pediatric patient?

Pulse (rate, quality, location), skin signs (temperature and moisture), capillary refill time, color, and changes in any of these over time

At what heart rates should you suspect shock in infants/children under 2 years vs. over 2 years?

Under 2 years: a heart rate of 180 beats/min or greater; over 2 years: a heart rate of 160 beats/min or greater

What formula estimates a normal systolic blood pressure in a child aged 1 to 10, and how should the BP cuff be sized?

70 + (2 x age in years) = systolic blood pressure; the cuff should cover two-thirds of the child's upper arm

Why is blood pressure especially difficult to measure and interpret in pediatric patients?

It's the most difficult vital sign to measure in this age group, and appropriately sized equipment is essential for accurate readings

What is the most common cause of pediatric dehydration, and what can it lead to if untreated?

Vomiting and diarrhea; if left untreated it can lead to shock and death

According to Table 13-5, how do pulse and level of activity change across mild, moderate, and severe dehydration?

Mild: normal pulse, normal or slowed activity. Moderate: increased pulse, slowed activity. Severe: marked tachycardia with weak or absent peripheral pulses, and activity ranging from variable to unresponsive

According to Table 13-5, how do urine output and skin findings change across mild, moderate, and severe dehydration?

Mild: decreased urine output, normal skin. Moderate: decreased urine output, cool/mottled skin with poor turgor. Severe: no urine output, cool/clammy skin with poor turgor and delayed capillary refill

According to Table 13-5, how do mouth, eyes, and fontanelle findings change across mild, moderate, and severe dehydration?

Mild: decreased saliva, normal eyes, fontanelle normal to sunken. Moderate: dry mucous membranes, no tears, sunken fontanelle. Severe: dry mucous membranes, sunken eyes, very sunken fontanelle

According to Table 13-5, how do level of consciousness and blood pressure change across mild, moderate, and severe dehydration?

Mild: normal LOC and blood pressure. Moderate: altered LOC, normal blood pressure. Severe: markedly altered LOC and hypotension

When is ALS backup especially needed for a dehydrated pediatric patient?

When dehydration is severe, so IV access can be obtained and rehydration can begin

Why do older adults generally compensate for shock less effectively than younger patients?

Because of the aging process and existing illnesses (such as COPD, heart failure, or dementia) that impair compensatory mechanisms or complicate assessment; medications can also mask or mimic shock signs

What are the treatment priorities for a geriatric patient in shock?

Provide additional padding for comfort (e.g., for arthritis), maintain spinal motion restriction if indicated (otherwise supine, unless it causes breathing difficulty), control life-threatening hemorrhage, suction as necessary, give high-concentration oxygen via a nonrebreathing mask to target SpO2 94-98%, maintain body temperature, and provide rapid transportation

How is most oxygen carried in the blood?

Attached to hemoglobin

Is hemorrhagic shock always hypovolemic, and is hypovolemic shock always hemorrhagic?

Hemorrhagic shock is always a form of hypovolemic shock (it's caused by bleeding), but hypovolemic shock is not always hemorrhagic — it can also result from causes like vomiting, diarrhea, or burns

As a tension pneumothorax progresses, which structures become compressed?

The vena cava, the aorta, the heart, and the opposite (unaffected) lung

What scale is used to assess level of consciousness during the primary assessment?

The AVPU scale