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42 Cards in this Set
- Front
- Back
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What are the three main types of shock?
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Mechanical (pump failure)
Distributive (significant vasodilation) Hypovolemic (the most common) |
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What can cause mechanical shock?
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-Myocardial Infarction
-Myocardial Contusion -Cardiac Tamponade -Tension Pneumothorax |
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What can cause distributive shock?
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-Neurogenic shock - loss of vascular control by the nervous system
-Spinal shock - a loss of vascular control inferior to a spinal injury -Psychogenic shock - fainting -Septic shock - severe infection causing a lack of control of vessels |
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What can cause hypovolemic shock?
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-Hemorrhagic (Hypovolemic) shock - blood loss
-Septic shock - severe infection causing leaky vessels -Metabolic shock - bodily loss of fluid causing dehydration |
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What are the four intact components required for adequate perfusion of the bodies tissues?
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An intact vascular system
Adequate air exchange in the lungs Adequate fluid volume in the vascular system A functioning heart pump |
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How is blood pressure and cardiac output calculated?
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Blood pressure = cardiac output x peripheral vascular resistance
Cardiac Output = Heart rate x Stroke Volume |
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What is shock?
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A condition that occurs when the perfusion of the body's tissues with oxygen, electrolytes, glucose and fluids becomes inadequate
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How can shock occur?
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Loss of red blood cells in hemorrhaging patients.
Results in less oxygen being transported to body tissues. Decreased circulating blood lowers the glucose, fluid volume and electrolytes to the cells. This results in the cells becoming shocked and grave changes in the body tissue begin to occur. |
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What do cells do when they are deprived of oxygen?
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Cells use backup processes that utilize energy sources less efficiently. This results in the production of lactic acid and disrupts certain cellular fuction such as energy production by mitochondria.
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What does accumulating lactic acid evetually lead to?
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Systemic acidosis caused by accumulating lactic acid in organs and blood.
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What can happen to respiratory muscle function?
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It can weaken leading to respiratory failure worsening the hypoxia.
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How does the body respond to inadequate oxygen delivery?
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Increased activity in the sympathetic nervous system (increased sympathetic tone). The release of catecholamines casues increased rate and strength of the hearts contractions and constriction of peripheral arterial blood vessels.
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How does the midbrain respond?
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The midbrain responds to progressive hypoxia and acidosis with an increase in the respiratory rate.
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What are the signs of Compensated Shock and what are the order in which they occur?
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1) Weakness and lightheadedness - due to decreased blood volume
2) Thirst - caused by hypovolemia 3) Pallor - caused by catecholamine induced vasoconstriction and/or loss of red blood cells 4) Tachycardia - catecholamines on the heart 5) Diaphoresis - catecholamines activating sweat glands 6) Tachypnea - brain elevates due to stress, catecholamines, acidosis and hypoxia 7) Decreased urinary output 8) Weakened peripheral pulses |
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What are the signs of decompensated shock?
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The follow on from compensated shock!
1) Hypotension - caused by hypovolemia (absolute or relative) or by diminished output (obstructive or mechanical shock) 2) Altered mental status - due to decreased cerebral perfusion, acidosis, hypoxia and catecholamine stimulation 3) Cardiac arrest - due to critical organ failure secondary to blood or fluid loss. Sometimes due to arrhythmia. |
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What is early shock?
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Loss of approximately 15-25% of the blood volume. Enough for the following....
-Slight to moderate tachycardia -pallor -narrowed pulse pressure -thirst -weakness -possible delayed cap refill |
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What is late shock?
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Loss of approx 30-45% of the blood volume. Enough to cause the following....
-hypotension -altered LOC -Cardiac arrest |
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How can early shock present?
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A fast pulse with pallor and diaphoresis.
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How can late shock present?
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Weak pulse or loss of the peripheral pulse.
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What blood pressures do the various pulses appear at?
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Radial = 80mgHg
Femoral = 70mgHg Carotid = 60mgHg |
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Why is cap refil not reliable?
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Can be used for infants up to age of 5-6. This is okay for showing late shock but not much good for determining early shock in adults.
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How is tachycardia evaluated?
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Always attempt to explain why a patient has tachycardia.
An elevated rate is never normal. Anxiety can cause an elevated rate but this returns to normal and is not sustained. Elevated pulse is one of the first signs of shock. Any trauma patient over 100 and especially over 120 should be suspected of having shock. |
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How can some patients not have tachycardia?
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Bradycardia can develop in patients with traumatic hypotension. The absence of tachycardia in the injured patient does not rule out shock.
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How can capnography help monitor shock?
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Patients in shock have decreased oxygen being supplied to their cells. A level of CO2 much under 40 especially in the 20's and below may be an indication of respiratory collapse. This can be a warning sign of worsening shock.
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What is Low-Volume shock or Absolute hypovolemia?
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Loss of blood through injury results in the secretion of catecholamines. These cause vasoconstriction in the peripheral tissues to shunt blood to the vital organs. If the blood loss is enough then this mechanism fails and hypotension is the result.
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What is High-Space shock or relative hypovolemia?
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The volume the blood vessels can hold is much greater than the actual amount of blood in the body. Anything that can result in a loss of control of the vascular system causing vasodilation can cause "vasodilatory shock". There is not enough blood to maintain blood pressure and therefore perfusion in the dilated blood vessels. In trauma this is known as neurogenic shock or spinal shock.
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What is Mechanical (Cardiogenic or Obstructive shock)?
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Any traumatic condition that slows or prevents the venous return of blood can cause shock.
Anything that obstructs the flow of blood to the heart can cause shock. |
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What are some traumatic conditions that can cause mechanical shock?
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Tension pneumothorax - Causes decreased venous return by collapsing the vena cavae causing JVD.
Cardiac Tamponade - Blood fills the space between the pericardium and the heart squeezing it and preventing it from filling. Cardiac output is reduced leading to shock. Myocardial contusion - Heart loses pumping capacity due to an injury to the heart muscle. No way to differentiate from a tamponade. |
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How do mechanical shock patients differ?
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They usually have a different appearance that that of hemorrhagic shock patients.
Mechanical shock patients are usually pale and cyanotic with distended neck veins and tachycardia. |
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What are the general management priciples for shock?
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1) Control Bleeding - either by direct pressure or rapid transport to surgery.
2) Administer high flow O2 - try to keep a pulse oximeter reading above 95% 3) Load and go - Patients in shock are in the load and go catagory - almost all critical interventions should be done in the ambulance. |
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What is cardiogenic shock?
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Occurs when the heart is unable to circulate sufficient blood to maintain adequate peripheral oxygen delivery.
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What can cause cardiogenic shock?
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Many diseases can cause destruction or inflammation of the heart muscle.
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What is the most common cause of cardiogenic shock?
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Extensive infarction of the left ventricle, diffuse ischemia or decompensated congestive heart failure.
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What is obstructive shock?
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This occurs when blood flow in the heart or the great vessels becomes blocked.
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What are examples of obstructive shock?
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Pericardial tamponade - diastolic filling of the right ventricle is impared leading to a decrease in CO.
Obstruction of the superior or inferior vena cava such as in vena cava syndrome in 3rd trimester pregnancy. A large pulmonary embolus A tension pneumothorax causing reduced venous return to the heart. |
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What can hypovolemic shock be split into?
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Exogenous and endogenous.
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What is the most common cause of exogenous hypovolemic shock?
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External hemorrhage.
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What are the causes of endogenous hypovolemic shock?
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The fluid loss is contained within the body such as with
-dehydration -burn -crush injuries -anaphylaxis |
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How can dehydration occur?
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-GI losses through vomiting and diarrhea
-Loss from fever, hyperventilation or high environmental temperatures -Increased sweating -Internal losses as in peritonitis, pancreatitis and ileus -plasma losses from burns |
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What are the three most common types of distributive or high-space shock?
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-septic shock
-neurogenic shock -anaphylactic shock |
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What is septic shock?
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Defined as a presence of sepsis syndrome with a BP less than 90mmHg.
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What happens with septic shock?
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Leaky capillaries, vasodilation and third space fluid shifts. There is not only insufficient volume in the vascular system. Leaking fluid often interferes with the respiratory system. A larger than normal vascular system is asked to contain a smaller than normal volume of fluid.
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