- The cascade of events that occurs when cells or tissues are deprived of an adequate energy source due to oxygen deprivation

Chapter 1 - Shock Flashcards by Brenda Righter

Define Shock

The cascade of events that occurs when cells or tissues are deprived of an adequate energy source due to oxygen deprivation

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Shock occurs as the result of what? What effects does it lead to (5)

Inadequate tissue perfusion
Buildup of waste products
Failure of energy dependent functions
Release of cellular enzymes
Accumulation of calcium
Accumulation of reactive oxygen species (ROS)

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True/False: the lack of an adequate Energy Supply leads to the build up of waste products, failure of energy dependent functions, release of cellular enzymes, and accumulation of calcium and ROS

True

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What cascades can be activated during shock (3)

Inflammatory
Coagulation
complement

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The 3 cascades activated during shock result in ___________ and ________.

Further cellular injury
Microvascular thrombosis

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What does shock ultimately lead too? (think cellular level) (3)

SIRS, MODS, and death

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Tissue perfusion is most fundamentally dependent on what?

Blood flow

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Name 3 factors that affect blood flow to tissues

Circulating volume
Cardiac pump function
Vasomotor tone/peripheral vascular resistance

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Name 3 things that affect stroke volume

Ventricular preload (amount of blood returning from the body and entering the heart)
Myocardial contractility (systolic cardiac function)
Ventricular afterload (force heart must overcome to push blood across the aortic and pulmonic valves into the peripheral or pulmonary vasculature

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Name 4 things that can lead to decreased preload

Hypovolemia (hemorrhage, dehydration)
Decreased ventricular filling time (tachycardia)
Impaired ventricular relaxation
Decreases in vasomotor tone and vasodilation (pooling of blood in capacitance vessels)

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What factor directly affects preload?

The circulating blood volume or amount of blood returning to the heart

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Define myocardial contractility

The rate of cross-bridge cycling between actin and myosin filaments within cardiomyocytes

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What factor(s) directly affects afterload?

Vasomotor tone or vascular resistance

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True/False: If peripheral vascular resistance increases, afterload decreases and there is an increase in cardiac output and perfusion.

False, if resistance increases, afterload increases, decrease in CO

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Shock is treated by the restoration and maintenance of what? What are the 4 ways it can be manipulated?

Cardiac Output
Preload
Afterload
Myocardial contractility
Heart rate

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Name the 3 primary types of shock

Hypovolemic
Cardiogenic
Distributive

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Name 3 causes of hypovolemic shock

Blood loss
Third spacing (such as colon volvulus)
Severe dehydration

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Define cardiogenic shock

Pump failure, occurs when the cardiac muscle cannot pump out adequate SV to maintain perfusion

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Define distributive shock

When vasomotor tone is lost. Also known as microcirculatory failure.

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Name 3 common causes of distributive shock

Neurogenic shock
Septic shock
Anaphylactic shock

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True/False: fluid therapy can help treat hypovolemic and cardiogenic but not distributive shock

False, fluid therapy can worsen cardiogenic shock

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What is the 4th, ‘additional’ category of shock (ultimately a combination of the other 3 categories)? Describe it.

Obstructive shock
The underlying mechanism is the obstruction of ventilation or of cardiac output

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What are 4 common causes of obstructive shock?

Tension pneumothorax (resulting in decreased venous return)
Pericardial tamponade
Diaphragmatic hernia
Severe abdominal distention causing vena cava obstruction (leading to inadequate ventricular filling, decreased reload, and consequently, decreased SV and CO)

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True/False: compensatory shock is an early phase of shock and the body is able to restore homeostasis

True

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In compensatory shock, baroreceptors and stretch receptors detect what as blood volume is depleted?

- A fall in pressure

Where are baroreceptors and stretch receptors located? (3)

- Carotid sinus - Right atrium - Aortic arch

What is autonomic traffic?

- The interplay between the parasympathetic and sympathetic nervous systems

In early compensatory shock, baroreceptors act to (increase/decrease) inhibition of (sympathetic/parasympathetic) tone. This (increases/decreases) inhibition of vagal activity, resulting in an (increase/decrease) in release of atrial natriuretic peptide (ANP). This results in (vasoconstriction/vasodilation)

- Decrease - Sympathetic tone - Increases - Decrease - Vasoconstriction

A decrease in renal perfusion stimulates the secretion of ___________ from the juxtaglomerular cells located in the wall of the afferent arteriole. This stimulates the production of _______ which is then converted to ________.

- Renin - Angiotensin I - angiotensin II

Name 2 effects of angiotensin II

- Increases sympathetic tone on the peripheral vasculature - Promotes aldosterone release from the adrenal cortex

What is the effect of aldosterone

- Restores circulating volume by increasing renal tubular sodium and water resorption

True/False: vasopressin is released from the anterior pituitary in response to decreased plasma volume and results in vasoconstriction.

- False, posterior pituitary,

Vasopressin is released from what gland in the body?

- The posterior pituitary

Vasopressin is released from the __________ in response to __________ and results in _________ and _______(actions).

- Posterior pituitary - Decreased plasma volume - Vasoconstriction - Increased water reabsorption in the renal collecting ducts

Vasopressin stimulates (increased/decreased) water reabsorption in the renal tubules

- Increased

Compensatory responses for shock result in what physical responses

- Increased thirst - Craving for salt

Name 4 clinical signs of uncompensated shock, even though blood pressure may still be maintained at this time.

- Resting tachycardia - Tachypnea - Poor peripheral pulses - Cool extremities

The compensatory responses for an increase in thirst and a craving for salt are mediated by what 2 things?

- The renin-angiotensin-aldosterone system (RAAS) - A fall in Atrial Natriuretic Peptide (ANP)

Define uncompensated aka hypodynamic shock

- When compensatory mechanisms become insufficient to maintain arterial blood pressure and perfusion of vital organs

Name 3 cellular consequences of decreased oxygen and accumulation of metabolic waste

- Loss of enzymatic activities - Loss of membrane pumps - Loss of midochondrial activity * Results in cellular swelling and release of intracellular calcium stores

Name 3 things damaged cells release in shock.

- Cytotoxic lipids - Enzymes - ROS

Release of cytotoxic lipids, enzymes and ROS by shock damaged cells further damages cells, the resulting inflammation causes ________ and ______ influx into the tissue, the formation of _____, and activation of the ____________ and ______ cascades.

- Inflammatory cell - Platelet - Neutrophil extracellular traps (NETS) - Arachidonic acid cascade - Complement cascade

Name 3 things that can increase the production (and decrease scavenging) of ROS from cells

- Mitochondrial failure - Calcium release - Reperfusion

Influx of inflammatory cells during uncompensated shock results in the activation of what cascades? (2)

- Arachidonic acid cascade - Complement cascade

What impedes blood flow to local tissues during uncompensated shock?

- formation of microthrombi and coagulopathy

What is the main consequence of loss of GIT function during shock? (4)

- protein loss - fluid loss - endotoxin absorption - bacterial translocation

Define Class I shock

- Mild blood loss, <15% of total volume - Body is capable of restoring volume deficits, may be no symptoms other than a drop in urine output

Define Class II shock

- 15-30% blood loss - Onset of hyperdynamic shock - Agitation or anxiety is present, compensation can normalize blood pressure, but perfusion deficits will persist

Define class III shock

- Profound tachycardia and tachypnea, anxiety, agitation - Urine output may cease, jugular filling and CRT are prolonged, pulses are weak, extremity temperatures are decreased, lactic acid builds up - Blood pressure will drop in spite of increasing heart rate, cardiac contractility, and total peripheral resistance

Define class IV shock

- Uncompensated, life-threatening hemorrhagic shock - Bradycardia, obtundation, anuria, profound hypotension, circulatory collapse, and death

What is the most common cause of shock in adult horses

- Hypovolemia

What is the purpose of fluid therapy in the treatment of shock?

- Increase circulating volume and improve tissue oxygenation

What determines the amount of oxygen delivered to tissues?

- DO2 = CO x CaO2 - Oxygenation = content of oxygen in the arterial blood as well as the amount of blood perfusing the tissue (cardiac output)

What percentage of crystalloid fluid therapy volume diffuses out of the vasculature into the interstitial space?

- 80%

When giving crystalloid fluids, you must give ____x the blood volume lost in order to restore blood volume

- 4-5x the lost volume

High volume crystalloid fluid therapy resuscitation can result in cell swelling which can trigger a __________ response

- An inflammatory response

Other than cellular swelling, what are 5 potential complications associated with large volume fluid resuscitation?

- Abdominal compartment syndrome - Acute respiratory distress syndrome - Congestive heart failure - Gastrointestinal motility disturbances - Dilutional coagulopathies

True/False: when using crystalloids for fluid resuscitation, you should administer the shock dose and the reassess the patient.

- False, give ¼ to 1/3 shock dose (30mL/kg) and reassess the patient

True/False: isotonic crystalloids are designed as maintenance fluids. The electrolyte composition is designed to approximate the electrolytes of the ECF.

- False, they are replacement fluids

Name 3 types of isotonic crystalloids

- LRS - Normosol-R - Plasmalyte

True/False: Due to dilutional anemia and hypoproteinemia, in cases of moderate to severe blood loss, large volumes of crystalloids alone should be used cautiously.

- False, oxygen carrying capacity will remain unchanged or become improved following fluid therapy, even if dilutional anemia occurs, thus IV crystalloid fluid therapy should never be withheld

Hypertonic saline has an osmoloarity about ___x that of plasma and will expand the vascular space ____x the amount infused

- 8x - 2x

Hypertonic saline principally pulls in volume from what space?

- Intracellular space (not the interstitial space)

Why is the intracellular fluid extraction function of hypertonic saline particularly beneficial in the shock state?

- In the shock state, endothelial cell volume rises with the loss of membrane pump function. The decrease in endothelial cell volume increases capillary diameter and improves perfusion

What is the recommended dose of hypertonic saline?

- 2-4mL/kg (1-2L for a 500kg horse)

What is the mechanism of action of colloids?

- They exert oncotic pressure that opposes the hydrostatic pressure and helps retain water in the intravascular space

What is the oncotic pressure of normal equine plasma?

- 20mmHg

Name 3 natural colloids

- Plasma - Whole blood - Bovine albumin

What are the advantages of natural colloids? (5)

- Provide protein (such as albumin) - Antibodies - Critical clotting factors - Antithrombin 3 - Other plasma constituents

Name 2 synthetic colloids

- Hetastarch - Dextrans

What is the colloid oncotic pressure of hetastarch?

- Average 480kDa (30-2300 kDa)

Name 2 risks of giving hetastarch

- Increase in cutaneous bleeding time/spontaneous bleeding - Kidney damage

By what 2 major mechanisms does the elimination of HES occur?

- Renal excretion - Extravasation

Larger HES molecules are degraded over time by __________

- α-amylase

True/False: the effects of hetastarch can be confirmed by an increase in total protein

- False, COP must be measured directly, TP will be artificially diluted

What type of molecules are in hetastarch?

- Amylopectin molecules

The effects of hetastarch can last up to _____

- 120 hours

What are the benefits of whole blood transfusion as a replacement fluid for shock patients? (4)

- Oxygen carrying capacity - Colloid oncotic support - Platelets - Coagulation factors

The percent blood volume of an adult horse is ____% of total body weight

- 7-9% (8%)

What side effects of large volume resuscitation fluids can be prevented by using whole blood instead?(3)

- dilutional anemia - dilutional coagulopathy - dilutional hypoproteinemia

In situations where bleeding is uncontrolled, why should normalization of blood pressure not be the goal in fluid resuscitation?

- It may promote continued bleeding (permissive hypotension - >65 MAP vs. >90 MAP)

Name 3 vasopressors that can be used in horses

- Dobutamine - Norepinephrine - Vasopressin

What is the method of action of dobutamine? (3)

- β1-agonist (strong) - β2-agonist (weak) - α-adrenoreceptor affinity (weak)

What is the method of action of norepinephrine? (2)

- β1-agonist - α-adrenoreceptor affinity

What PE parameters may be monitored to assess improvement in cardiac output? (7)

- heart rate - CRT - Jugular venous fill - Extremity temperature - Pulse pressure - Urine output - Mentation

What PE parameters would suggest that a shocky patient has continued blood loss or decompensation is occurring? (5)

- Continued tachycardia - Poor pulse pressure - CRT - Poor jugular fill - Deteriorating mentation

What 2 conditions (other than hypovolemic shock) can result in a prolonged CRT?

- Endotoxemia - Sepsis

3 things that Central Venous Pressure evaluates?

- Cardiac function - Blood volume - Vascular resistance/tone

What is the normal Central venous pressure (CVP) in a standing horse?

- 7-12mmHg

True/False: using a jugular catheter to measure CVP will result in a falsely elevated CVP

- True (should be placed at level of heart base or point of shoulder)

True/False: CVP can be low with hypovolemia or cardiogenic shock. CVP can be elevated due to distributive shock

- False, CVP can be low with hypovolemia or distributive shock. Cardiogenic shock results in an elevated CVP

True/False: the normal urine output of a horse is 0.5mL/kg/hour

- False, 1 mL/kg/h is normal

What is the normal urine output of a horse?

- 1mL/kg/h

Production of urine less than ____ mL/kg/h suggests significant volume depletion.

- 0.5mL/kg/h

During shock, blood pressure does not consistently fall below normal until blood volume is profoundly decreased (_____% or more)

- 30%

L-lactate is the end product of the anaerobic metabolism of what?

- Glucose

What is Type A hyperlactatemia?

- Inadequate oxygen delivery to the tissues causing increased lactate

What is Type B hyperlactatemia?

- Hyperlactemia that develops in spite of appropriate tissue oxygenation

What conditions can cause Type B hyperlactatemia? (5)

- Hepatic dysfunction (impaired clearance) - Pyruvate dehydrogenase inhibition - Catecholamine surges - Sepsis - SIRS

What is the normal oxygen extraction ratio of blood?

- 20-30% - (can increase up to 50-60% in event of decreased perfusion)

True/False: the oxygen extraction ratio can increase up to 50-60% in response to decreased perfusion

- True

What are predictors of survival in patients treated for shock? (4)

- Rapid control of hemorrhage - Restoration of perfusion - Normalization of blood gas values - Prevention of dilutional coagulopathy

What are the 2 phases of the metabolic response to trauma or injury?

- ebb phase - flow phase

When does the flow phase of metabolic response to injury start?

- Once perfusion is restored, lasts over the next few days to weeks

True/False: the flow phase physiologic response to trauma occurs during the first several hours after injury and the ebb phase occurs in the days to weeks after injury

- False. Ebb phase, then flow phase

True/False: the catabolic period of the flow phase mimics clinical signs of shock and the anabolic period is a return to homeostasis.

- True

What initiates the stress response to trauma? (7)

- pain - tissue injury - hypovolemia - acidosis - shock - hypothermia - psychological responses

What stimulates the sympathoadrenal axis in the event of trauma? (5)

- Direct input from nerves - Hypovolemia - Acidosis - Shock - Psychological responses (fear, pain, anxiety)

What 4 substances trigger the release of cortisol in trauma and shock?

- Arginine vasopressin (AVP) - Angiotensin II - Norepinephrine - Endotoxin

Cell membrane injury results in the activation of ____________ and production of ______

- The arachidonic acid cascade - Cytokines

Chapter 1 - Shock Flashcards

(110 cards)