Transcript Shock - Doctors2Be

CIRCULATORY SHOCK
Lecture by
Dr.Mohammed Sharique Ahmed Quadri
Assistant professor ,Physiology
‫بسم هللا الرحمن الرحيم‬
Circulatory shock
Circulatory shock is a state of inadequate
tissue perfusion with relatively or
absolutely inadequate cardiac out put.
Depending upon the cause of inability of
the heart to pump sufficient blood volume
for tissue perfusion circulatory shock can
be divided into different types
Hypovolumic shock
• Hypovolemic shock is also called "cold shock."
• It is characterized by
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Hypotension;
Rapid, thready Pulse;
Cold, Pale, Clammy Skin;
Intense Thirst;
Rapid Respiration;
Restlessness .
Hemorrhagic shock
Hemorrhage
Decrease blood volume
• It illustrate the features of a major
form of hypovolemic shock and the
multiple compensatory reactions
that come into play to defend ECF
volume
Decrease venous return
Decrease stroke volume
Decrease cardiac out put
Decrease arterial pressure
Compensatory response
Compensatory reactions activated by
hemorrhage.
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Vasoconstriction
Tachycardia
Venoconstriction
Tachypnea→increased thoracic pumping
Restlessness→increased skeletal muscle pumping (in
some cases)
Increased movement of interstitial fluid into capillaries
Increased secretion of norepinephrine and epinephrine
Increased secretion of vasopressin
Increased secretion of renin and aldosterone
Increased secretion of erythropoietin
Increased plasma protein synthesis
Effect of hemorrhage on mean arterial
pressure
Anaphylactic Shock
• A good example is anaphylactic shock, a rapidly
developing, severe allergic reaction that
sometimes occurs when an individual who has
previously been sensitized to an antigen is
exposed to it.
– The resultant antigen-antibody reaction releases
large quantities of histamine, causing increased
capillary permeability and widespread dilation of
arterioles and capillaries.
Stages of Shock
1. Non progessive stage or Compensated stage
Here circulatory compensatory mechnism
cause Full recovery without help from
outside therapy
2. Progressive stage-Decreased BP AND COP.
Here without therapy ,shock gets worse
3. Refractory shock or Irreversible stage (called
before)
Here patient does not respond
to Treament .
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Irreversible or refractory shock
Factors contributing irreversible shock
• Cerebral ischemia
– Depression of vasomotor and cardiac areas of the brain
(vasodilatation , decreased BP, decreased HR)
• Myocardial depression due to Acidosis causes decreased
COP
• Respiratory failure (ARDS)
– triggered not only by shock but also by sepsis, lung contusion,
other forms of trauma.
– Damage to capillary endothelial cells and alveolar epithelial cells,
with release of cytokines.
SEPTIC SHOCK
• Usually due to gram-negative bacteria
• Endotoxins released by gram-negative
Bacteria—cause VASODILATATION(Skin is
warmTherefore called WARM SHOCK).
• High fever
• Increased capillary permeability with loss of
plasma in tissues
• Mortality is 30-50%
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Cardiogenic shock
• Cause---Myocardial Infarction(pump failure)
• Causes symptoms of shock and congestion in
the lungs ( Pulmonary oedema).
• Note—In Myocardial Infarction, shock occurs
in 10% and has mortality of 60-90%.
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Neurogenic shock
• In Neurogenic shock, there is decreased
sympathetic activity, therefore, increased
vascular capacity.
• Reason—Sudden loss of Vasomoter Tone
resulting in massive dilation of veins therefore
Venous pooling of blood and decreased venous
return to heart.
• Causes of Neurogenic shock
– -General Anesthesia, Spinal Anesthesia
– -Brain damage
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Fainting
• Type of distributive shock is neurogenic shock, in
which there is sudden autonomic activity
producing vasodilation, pooling of blood in the
extremities, and fainting. These are called
vasovagal attacks,. Other forms of syncope
include
– postural syncope, fainting due to pooling of blood in
the dependent parts of the body on standing.
– Micturition syncope, fainting during urination, It is
due to the combination of the orthostasis and reflex
bradycardia induced by voiding in these patients.
Fainting
– Pressure on the carotid sinus, produced, for
example, by a tight collar, can cause such marked
bradycardia and vasodilation that fainting results
(carotid sinus syncope).
– Rarely, vasodilation and bradycardia may be
precipitated by swallowing (deglutition syncope).
– Cough syncope occurs when the increase in
intrathoracic pressure during straining or coughing is
sufficient to block venous return