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CIRCULATORY SHOCK

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CIRCULATORY SHOCK Lecture by Dr.Mohammed Sharique Ahmed Quadri Assistant professor ,Physiology – PowerPoint PPT presentation

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Title: CIRCULATORY SHOCK


1
CIRCULATORY SHOCK
  • Lecture by
  • Dr.Mohammed Sharique Ahmed Quadri
  • Assistant professor ,Physiology

2
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3
Objectives
  • Define shock.
  • Recognize types of shock haemorrhagic,
    anaphylactic, septic, and cardiogenic.
  • Understand the shock by discussing changes
    occurring in haemorrhagic shock.
  • Explain compensatory response of body to shock.
  • Identify the concept of irreversible
    (unresponsive) shock.

4
Circulatory shock
  • Is acute failure of circulatory system to supply
    the peripheral tissues and organs of the body
    with adequate blood supply, resulting in cellular
    hypoxia.

5
TYPES OF SHOCK
  • HYPOVOLEMIC
  • CARDIOGENIC
  • OBSTRUCTIVE
  • DISTRIBUTIVE

6
DISTRIBUTIVE SHOCK
7
Hypovolaemic
  • Volume Loss
  • Blood loss -Haemorrhage
  • Plasma Loss -Burns
  • ECF Loss - Vomiting Diarrhoea

8
Hypovolumic shock
  • Is most widely studied shock often used as
    prototype in discussion of manifestations of
    shock
  • Hypovolemic shock is also called "cold shock."
  • It is characterized by
  • Hypotension
  • Rapid, thready Pulse
  • Cold, Pale, Clammy Skin
  • Intense Thirst
  • Rapid Respiration
  • Restlessness .

9
Hemorrhagic shock
  • It illustrate the features of a major form of
    hypovolemic shock and the multiple compensatory
    reactions that come into play to defend ECF volume

10
Compensatory response
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12
Compensatory reactions activated by hemorrhage.
  • 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

13
Points to Ponder
  • Goal of compensatory mechanisms is to maintain
    cerebral and cardiac perfusion
  • Vasoconstriction of splanchnic, and renal blood
    flow
  • Compensatory mechanisms are not effective over
    the long term and fails when shock state is
    prolonged.

14
Effect of hemorrhage on mean arterial pressure
15
Stages of Shock
  1. Non progressive stage or Compensated stage in
    this circulatory compensatory mechanism cause
    Full recovery without therapy
  2. Progressive stage Decreased BP AND COP. Here
    without therapy ,shock gets worse.
  3. Refractory shock or Irreversible stage Here
    patient does not respond to Treatment .

16
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.

17
Cardiogenic
  • Pump Failure
  • May be due to
  • Inability of heart to Contract or
  • Inability of heart to pump blood
  • Myocardial damage ( M.I)
  • Arrhythmias
  • Valvular damage
  • Symptoms are those of shock and heart failure
    ( pulmonary oedema)

18
Distributive
  • Decreased Peripheral Vascular Resistance (blood
    volume is normal but vascular capacity increases,
    i.e. relative hypovolemia)
  • Septic Shock (inflammatory mediators)
  • Neurogenic Shock (loss of sympathetic control on
    vascular tone)
  • ANAPHYLACTIC shock (presence of vasodilator
    substances like histamine)

19
Anaphylactic Shock
  • Systemic response to the inflammatory
    mediators released in type I
    hypersensitivity
  • Histamine, acetylcholine, kinins, leukotrienes,
    and prostaglandins all cause vasodilation and
    increase capillary permeability
  • What will happen when arterioles vasodilate
    throughout the body?
  • What will happen when there is increase vascular
    permeability
  • Acetylcholine, kinins, leukotrienes, and
    prostaglandins all can cause bronchoconstriction

20
SEPTIC SHOCK
  • Usually due to gram-negative bacteria
  • Endotoxins released by gram-negative
    Bacteriacause VASODILATATION(Skin is warm
    therefore called WARM SHOCK).
  • High fever
  • Increased capillary permeability with loss of
    fluid in tissues
  • Mortality is 30-50

21
Neurogenic shock
  • In Neurogenic shock, there is decreased
    sympathetic activity, therefore, increased
    vascular capacity.
  • ReasonSudden 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
  • Brain injury
  • Depressant action of drugs
  • General anesthesia (barbiturate)

22
Fainting and Syncope
  • Fainting--Feeling of dizziness due to decreased
    cerebral perfusion but not sufficient to cause
    loss of consciousness.
  • SyncopeTemporary impairment of consciousness due
    to reduction in cerebral blood flow

23
Vasovagal syncope
  • Vasovagal attacks---Increased Vagal activity,ANS
    Disturbance
  • -- It causes vasodilatation due to sympathetic
    inhibition therefore pooling of blood in
  • extermities and Fainting.
  • --Bradycardia
  • --It is short lived and Benign.
  • Causes-----overwhelming Fear, or severPain

24
Fainting/ syncope
  • Other forms of syncope include
  • postural syncope, due to pooling of blood in the
    dependent parts of the body on standing from
    lying down or sitting possition .
  • Micturition syncope, during urination, occurs in
    patients of orthostatic hypotension It is due to
    the combination of the orthostasis and reflex
    bradycardia induced by voiding in these patients.

25
Fainting/ syncope
  • 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

26
References
  • Human physiology by Lauralee Sherwood, seventh
    edition
  • Text book physiology by Guyton Hall,11th edition
  • Text book of physiology by Linda .s
    contanzo,third edition
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