Physiology of Shock.pdf

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1. Physiology of
Shock
DR.NITIN KHAJOTIA
22thAUG 2022

2. Learning objectives
▪What is a Shock ?
▪What are the different types to shock ?
▪Causes of different types of shock.
▪Effect of progressive shock on body.
▪Symptoms and General management.

3. WHAT is Shock ?
-A physiologic state characterized by systemic
reduction in tissue perfusion , resulting in
decreased tissue oxygen delivery
-Circulation fails to meet the metabolic need of the
tissue
-Circulation Fails to remove the metabolic waste
products. Which accumulates and causes more
tissue injury.

4. Shock -Classification
-Hypovolemic shock –aka. Cold shock
-Distributive shock or Vasogenic shock
-Distributive shock
-Cardiogenic shock
-Obstructive shock
-Refractory shock or Irreversible shock

5. Shock -Classification

6. Shock
Hypovolemic Shock
-Hemorrhage is the most common
cause of hypovolemic shock
-Hemorrhage decreases the filling
pressure (decreases venous return)
-About 10 percent of the total blood
volume can be removed with almost
no effect on either arterial pressure
or cardiac output
-Both of which fall to zero when
about 40 to 45 percent of the total
blood volume has been removed

7. Shock
Hypovolemic Shock
Decrease in arterial pressure cause powerful sympathetic
reflexes via baroreceptors and stretch receptors
It Causes 3 Important effects
-Arterioles constrict, increasing the total peripheral resistance.
-Veins and venous reservoirs constrict, and maintain adequate
venous return
-HR increases to as high as 160 to 180 beats/min.
Sympathetic reflexes affect arterial pressure more than cardiac
output.

8. Shock
Hypovolemic Shock
CharacteristicsFeatures
-Hypotension
Rapid Pluse
Cold, pale and moist skin
Thirst
Lethargic
Prone to Vomiting
SUBDIVISION
-Hemorrhagic Shock
-Traumatic Shock
-Surgical Shock
-Dehydration

9. Hypovolemic Shock
Hemorrhagic Shock
-Caused Due to huge rapid
Blood loss
-For losses up to 30%
Compensatory mechanism
will take place to restore
normal Condition
-loss up to 40% of total
blood volume) it may lead to
circulatory collapse and
death.

10. Hypovolemic Shock
Hemorrhagic Shock –Compensatory mechanism
1. Rapid Compensatory Mechanism
-Generalized Vasoconstriction
-Release of catecholamines
-Activation of reticular activation System
-Renal ischemia release Angiotensin 2
which act on sub fornicalorgan to
increase thirst.
-Constriction of afferent and efferent
arteriolscauses low GFR
-Which causes oliguria, sodium retention,
metabolites in blood
-Progression to Acute renal failure.

11. Hypovolemic Shock
Hemorrhagic Shock –Compensatory mechanism
1.Long-Term Compensatory Mechanism
-Plasma gets restored within 12-72hrs
-Restoration of plasma protein in 3-4 days
-Restoration of RBC in 4-8 weeks
-Restoration of BP over several months

12. Hypovolemic Shock
Other types
Traumatic Shock
-Due to injury causing 'severe' damage to muscle and bone.
-Frank bleeding into injured areas results in shock.
-Crush injury, myoglobin gets clogged in renal tubules, causes
renal damage.
Surgical Shock
-External or internal blood loss caused by ruptured blood vessels
Dehydration Shock
-prolonged vomiting or diarrhoea, diabetes, Adrenal insufficiency
-Burn, heat stress

13. Distributive Shock
Aka. Warm Shock
It Includes
-Syncope
-Anaphylactic Shock
-Septic Shock

14. Distributive Shock
Syncope
Types
-Vaso-Vagal Syncope
-Postural Syncope
-MicturationSyncope
-Carotid sinus Syncope
-Cough Syncope
-Effort Syncope
-Deglutition Syncope
-Neurocardiogenic Syncope

15. Distributive Shock
Anaphylactic
•Severe allergic reaction when an individual who has
previously been sensitive to an antigen is re-exposed to it.
•Generalized antigen-antibody reaction causes release of large
quantities of histamine and other substances in blood.
•Increased capillary permeability, decreased blood volume
•Arteriolar dilation decreases peripheral resistance and BP
falls.

16. Distributive Shock
Septic Shock
Release of bacterial endotoxin by gram negative bacteria
which get absorbed into systemic “ circulation.
It results in -
•High fever
•Peripheral arteriolar paralysis causing marked vasodilation
Depresses myocardium
•Increase capillary permeability, plasma leaks into the tissues
and BP falls

17. Cardiogenic Shock
DECREASED CARDIAC OUTPUT
Two types of factors can severely reduce
cardiac output
➢Cardiac abnormalities that decrease the
ability of the heart to pump blood.
➢Factors that decrease venous return also
decrease cardiac output

18. Cardiogenic Shock
predisposing factors
➢Myocardial infarction (release of certain chemicals,
via Bezold-Jarischreflex apnoea, marked bradycardia
and hypotension. This makes the shock, worse.
➢Congestive cardiac failure
➢Arrhythmias

19. Obstructive Shock
Mechanical obstruction of left or right ventricular filling.
Causes-
▪Tension pneumothorax with kinking of the great veins.
▪Massive pulmonary emboli.
▪Cardiac tamponade i.e. bleeding into the pericardium
with external pressure on the heart.
▪Post end-expiratory pressure respiration

20. NEUROGENIC SHOCK
increasedVASCULAR CAPACITY
Vascular capacity increases so much that even the normal amount of
blood is incapable in filling the circulatory system adequately
sudden loss of vasomotor tone throughout the body, resulting especially
in massive dilation of the veins.
reduces the mean systemic filling pressure, which reduces venous return
Causes of Neurogenic Shock
▪Deep general anesthesia
▪Spinal anesthesia
▪Brain damage is often a cause of vasomotor paralysis.

21. REFRACTORY SHOCK or IRREVERSIBLE SHOCK
Causes-
▪Tension pneumothorax with kinking of the great veins.
▪Massive pulmonary emboli.
▪Cardiac tamponade i.e. bleeding into the pericardium with
external pressure on the heart.
▪Post end-expiratory pressure respiration

22. Stages of Shock
-A nonprogressive stage
Normal circulatory compensatory mechanisms
eventually cause full recovery without help from outside
therapy
-A progressive stage
Without therapy, the shock becomes steadily worse
-irreversible stage
All forms of known therapy are inadequate to save the
person’s life

24. The Vicious Cycle of
Progressive Shock
-Cardiac Depression. Coronary blood flow
decreases below that required for adequate
nutrition of the myocardium.
-Vasomotor Failure. In the early stages, circulatory
reflexes cause intense activity of the sympathetic
nervous system. By the end of 10 to 15 minutes,
the vasomotor center becomes so depressed that
no further evidence of sympathetic discharge can
be demonstrated.

25. The Vicious Cycle of
Progressive Shock
-Blockage of Very Small Vessels -local blood
agglutination due to excess metabolic waste and
increase in pH.
-Increased Capillary Permeability–permeability
of the capillaries gradually increases, and large
quantities of fluid begin to transude into the tissue
-Generalized Tissue deterioration and necrosis

27. Shock -General
Clinical manifestation
➢Tachycardia and tachypnea
➢Weak, thready pulses
➢Hypotension
➢Cold & clammy skin
➢Decreased urine output: dark & concentrated

28. Shock
General Management
➢Control hemorrhage
➢Check for Temperature
➢Restore circulating volume
➢Optimize oxygen delivery
➢Vasoconstrictor if BP still
low after volume loading

29. Thank You

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