Download Hemorrhage Physiological Response to Hemorrhage Defining Shock

12/1/2009
Chapter 19:
Hemorrhage
Hemorrhage and Shock
• Occurs when there is a disruption or “leak” in the
vascular system
• External hemorrhage
• Internal hemorrhage
– Associated with higher morbidity and mortality than
external hemorrhage
Physiological Response to Hemorrhage
• The body’s initial response to hemorrhage is to stop
bleeding by chemical means (hemostasis)
• This vascular reaction involves:
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Local vasoconstriction
Formation of a platelet plug
Coagulation
Growth of fibrous tissue into the blood clot that
permanently closes and seals the injured vessel
• If hemorrhage is severe, these mechanisms may fail,
resulting in shock (hypoperfusion)
Defining Shock
• Shock is best defined as inadequate tissue perfusion
– Can result from a variety of disease states and injuries
– Can affect the entire organism or can occur at a tissue or
cellular level
• Shock is not adequately defined by:
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Pulse rate
Blood pressure
Cardiac function
Hypovolemia
Loss of systemic vascular resistance
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Tissue Oxygenation
• Adequate oxygenation of tissue cells (perfusion)
depends on three components of the cardiovascular
system
– Heart
– Vasculature
– Lungs
• When any one of these malfunctions, a decrease in
cellular oxygenation may occur
Cardiac Output
• The amount of blood separately pumped by each
ventricle per minute, usually expressed in liters per
minute
– Determined by multiplying the heart rate by the volume of
blood ejected by each ventricle during each beat (stroke
volume)
• A crucial determinant of organ perfusion
• Depends on:
– Strength of contraction
– Rate of contraction
• Amount of venous return available to the ventricle (preload)
Shock
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Baroreceptor Reflexes
Fick principle
The vasculature
Pressure gradients
P i h l vascular
Peripheral
l resistance
i
((afterload)
f l d)
Viscosity
Microcirculation
Vasomotion
• Help maintain blood pressure by two negative feedback
mechanisms
– By lowering blood pressure in response to increased
arterial pressure
– By increasing blood pressure in response to decreased
arterial pressure
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Chemoreceptor Reflexes
• Low arterial pressure may stimulate peripheral
chemoreceptor cells that lie within the carotid and aortic
bodies
decreases, these cells stimulate the
• When oxygen or pH decreases
vasomotor center of the medulla
Compensatory Mechanisms
• CNS ischemic response
• Hormonal mechanisms
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Adrenal-medullary mechanism
Renin angiotensin aldosterone mechanism
Renin-angiotensin-aldosterone
Vasopressin mechanism
Atrial natriuretic factor
• Reabsorption of tissue fluids
• Splenic discharge of blood
The Lungs
• Adequate cellular oxygenation requires that adequate
oxygen be available to red blood cells at the capillary
membrane in the lungs
– First component of the Fick principle
The Body as a Container
• The healthy body may be viewed as a smooth-flowing
delivery system inside a container
– Container must be filled to achieve adequate preload and
tissue oxygenation
• Made possible by:
– The high arterial pressure of oxygen in inspired air
– Adequate depth and rate of ventilation
– Matching of pulmonary ventilation and perfusion
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The Body As a Container
• The external size of the container of any particular
human body is relatively constant
– The volume of the container is directly related to the
diameter of the resistance vessels
– Any change in vessel diameter changes the volume of the
fluid the container holds, thereby affecting preload
Blood Volume
• The average adult male has a blood volume of 7% of
total body weight
• The average adult female has a blood volume of 6.5%
of total body weight
– Volume increases significantly during pregnancy
• Normal adult blood volume is 4.5 to 5 L
– Remains fairly constant in the healthy body
Blood and its Components
Plasma
• Approximately 92% water
– The liquid portion of blood
• Circulates salts, minerals, sugars, fats, and proteins
throughout the body
• Contains three major proteins
– Albumin
– Globulins (alpha, beta, and gamma)
– Fibrinogen
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Red Blood Cells (Erythrocytes)
• Transport 99% of blood oxygen
– Remaining 1% is carried in plasma
• Make up approximately 45% of the blood
• Most
M t abundant
b d t cells
ll iin th
the b
body
d
• Provide oxygen to tissues and remove carbon dioxide
Platelets.
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Part of the body's defense mechanism
Help stop escaping blood
Formed in red bone marrow
W k by
Work
b swelling
lli and
d adhering
dh i together
h to fform sticky
i k
plugs (initiating the clotting phenomenon)
White Blood Cells (Leukocytes).
• Defend the body against various pathogens (bacteria,
viruses, fungi, and parasites)
• Produced in bone marrow and lymph glands
– A reserve of white blood cells is constantly produced and
maintained, but not many are present in a healthy blood
stream
– Reserves are released when pathogens invade the body
Capillary-Cellular.
Relationship in Shock
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Stage 1: Vasoconstriction
Stage 2: Capillary and venule opening
Stage 3: Disseminated intravascular coagulation
S
Stage
4
4: M
Multiple
l i l organ ffailure
il
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Classifications of Shock.
• Hypovolemic shock
• Distributive shock
– Neurogenic shock
– Anaphylactic
Anaph lactic shock
– Septic shock
Compensated Shock.
• Characterized by signs and symptoms of early shock
• Arterial blood pressure is normal or high
• Treatment at this stage will typically result in recovery
• Cardiogenic shock
• Obstructive shock
Uncompensated Shock.
• Characterized by signs and symptoms of late shock
• Arterial blood pressure is abnormally low
• Treatment at this stage will sometimes result in recovery
Irreversible Shock.
• Characterized by signs and symptoms of late shock
• Arterial blood pressure is abnormally low
• Even aggressive treatment at this stage does not result
in recovery
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Management and Treatment Plan for the Shock Patient.
– Ensure a patent airway
– Provide adequate oxygenation and ventilation
– Restore perfusion
Differential Shock.
Assessment Findings
• Shock is assumed to be hypovolemic until proven
otherwise
• Cardiogenic shock
– Differentiated from hypovolemic shock by one or more of
the following:
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Chief complaint (chest pain, dyspnea, tachycardia)
Heart rate (bradycardia or excessive tachycardia)
Signs of congestive heart failure (jugular vein distention, rales)
Dysrhythmias
Initial Assessment.
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Airway
Breathing
Circulation
Di bili
Disability
Expose body surfaces
Differential Shock.
Assessment Findings
• Distributive shock
– Differentiated from hypovolemic shock by presence of one
or more of following:
• Mechanism that suggests
gg
vasodilation,, e.g.,
g , spinal
p
cord injury,
j y, drug
g
overdose, sepsis, anaphylaxis
• Warm, flushed skin (especially in dependent areas)
• Lack of tachycardia response (not reliable)
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Differential Shock.
Assessment Findings
• Obstructive shock
– Differentiated from hypovolemic shock by presence of
signs and symptoms suggestive of:
• Cardiac tamponade
p
• Tension pneumothorax
• Pulmonary embolism
Resuscitation.
• Resuscitation is aimed at restoring adequate peripheral
tissue oxygenation as quickly as possible
• This is accomplished by:
– Ensuring adequate oxygenation
– Maintaining an effective ratio of volume to container size
– Rapidly transporting the victim to an appropriate medical
facility
Detailed Physical Examination.
• Vital signs
– Pulse
– Blood pressure
– Orthostatic vital signs
• Evaluate patient’s ECG
Red Blood Cell Oxygenation.
• First requirement for adequate tissue oxygenation
• For adequate red blood cell oxygenation:
– The patient must have a patent airway
– Ventilation m
must
st be ssupported
pported with
ith high FiO2
– If necessary, ventilations should be assisted with positive
pressure
– Correct any airway abnormalities that interfere with
adequate ventilation
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Ratio of Volume.
to Container Size
• Adequate oxygen-carrying capacity requires that the
container be full of fluid
• May be accomplished by:
Fluid Resuscitation in Shock.
– Decreasing the size of the container
• Especially in shock states not associated with hemorrhage
– Possible use of vasoactive medications in some cases of
distributive shock
– Volume replacement may be necessary
Crystalloids.
• Solutions created by dissolving crystals (such as sugars
and salts) in water
– Less osmotic pressure than colloids
– Can be expected to equilibrate more quickly between the
vascular and extravascular spaces
• Two-thirds of infused crystalloid fluid leaves the vascular space
within 1 hour
• 3 mL of a crystalloid solution is needed to replace 1 mL of blood
Hypertonic.
and Hypotonic Solutions
• Hypertonic solutions
– Have a higher osmotic pressure than that of body cells
• 5% dextrose in 0.9% sodium chloride
• 7.5% saline
• 5% dextrose in 0.45% sodium chloride
• Hypotonic solutions.
– Have a lower osmotic pressure than that of body cells
• Distilled water
• 0.45% sodium chloride (0.45% NaCl)
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Isotonic Solutions.
• Lactated Ringer's solution
• Normal saline
• Glucose-containing solutions (e.g., D5W)
Colloids.
• Solutions that contain molecules (usually protein) that
are too large to pass through the capillary membrane
• Exhibit osmotic pressure and remain within the vascular
compartment for a considerable length of time
• Examples
– Whole blood
– Plasma
– Packed red blood cells
Theory of Fluid Flow.
• The flow of fluid through a catheter is directly related to
its diameter (to the fourth power) and inversely related
to its length
• Other factors that affect fluid flow include:
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The diameter and length of the tubing
The size of the vein
The viscosity and temperature of the IV fluid
Viscosity is affected by temperature
Warm fluids generally flow better than cold ones
Key Principles in Managing Shock.
• Establish and maintain an open airway
• Administer high-concentration oxygen and assist
ventilation as needed
• Control external bleeding (if present)
• Initiate IV fluid replacement if appropriate
• Maintain patient's normal body temperature
• Monitor cardiac rhythm and oxygen saturation
• Frequently reassess vital signs
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Hypovolemic Shock.
• Treatment is not considered complete until the
circulatory deficit and its causes are corrected
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Crystalloid fluid replacement for simple dehydration
Volume replacement for hemorrhage
Definitive surgery
Critical care support
Postoperative rehabilitation
Cardiogenic Shock.
• Treatment is directed toward improving the pumping
action of the heart and managing cardiac rhythm
irregularities
– Fluid replacement
– Drug therapy (varies by cause)
– Patients with cardiogenic shock secondary to myocardial
ischemia or infarction require:
• Reperfusion strategies
• Possible circulatory support
– Tension pneumothorax and cardiac tamponade must be
managed immediately
Neurogenic Shock.
• Treatment is similar to treatment for hypovolemia
– Care must be taken during IV therapy to avoid circulatory
overload
– Closely monitor lung sounds for pulmonary congestion
• Use of vasopressors may be indicated
Anaphylactic Shock.
• Subcutaneous administration of epinephrine is
treatment of choice in acute anaphylactic reactions
• Depending on severity, other therapy may include:
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Oral, IV,
Oral
IV or IM administration of antihistamines
Bronchodilators to treat bronchospasm
Steroids to reduce the inflammatory response
Crystalloid volume replacement
Aggressive airway management should be anticipated
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Septic Shock.
• Treatment may include the management of hypovolemia
(if present) and the correction of metabolic acid-base
imbalance
• Prehospital care may include:
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Fluid resuscitation
Respiratory support
Vasopressors to improve cardiac output
A thorough history (to help determine the source of the
sepsis)
Microcirculation in shock. Normal (1, 2), vasoconstriction (3),
capillary opening (4), DIC (5), tissue death (6).
Integration of Patient Assessment and the Treatment Plan.
• The goals of care for the patient with severe
hemorrhage or shock include:
– Rapid recognition of the event
– Initiation of treatment
– Prevention of additional injury
Compensated shock. This stage of shock is reversible.
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Uncompensated shock. This stage of shock is reversible.
Irreversible shock. Death will ensue within 1 day to 3 weeks.
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