Shock physiology

1. SHOCK
PRESENTED
BY-
MANDEEP
123

2. CONTENTS
Circulatory shock
Types of shock
Hypovolemic shock
Relationship of bleeding volume to cardiac output and arterial pressure
Sympathetic reflex compensations in shock
Pathophysiology of shock
Distributive shock
Anaphylatic shock
Septic shock
Cardiogenic shock
Obstructive shock

3. CIRCULATORY SHOCK
Shock is a clinical syndrome
characterised by inadequate blood
flow to body tissue primarily due
to low cardiac output.

4. TYPES OF
SHOCK
Hypovolemic
–a cold
shock
Distributive
orVasogenic
or Low
resistance or
Warm shock
Cardiogenic
shock
Obstructive
shock

5. HYPOVOLEMIC
SHOCK
Clinical syndrome
characterised by
inadequate blood flow to
body tissue due to low
cardiac output .
Failure of cardiovascular
system

6. CHARACTERISTIC
FEATURES OF
HYPOVOLEMIC
SHOCK
 Hypotension systolic blood pressure
below 90 mmHg
 Rapid thready pulse
 Rapid shallow breathing
 Cold pale moist skin with greyish ting
[cyanosis ]
 Intense thirst
 ADH and aldosterone release leads to
decreased urine formation
 Lethargic and restless due to cerebral
ischaemia

7. TYPES OF HYPOVOLEMIC SHOCK
Hemorrhagics Traumatics Surgicals Dehydrations

8. HAEMORRHAGIC SHOCK
haemorrhage
Decreasecirculatory
blood volume
Decreased tissue
perfusion
Anaerobic respiration
Increased lactic acid
production
(I) depress the
myocardium(ii)
decreaseperipheral
vascular responsiveness
to catecholamines
Both leads to coma

9. RELATIONSHIP OF BLEEDINGVOLUME
TO CARDIAC OUTPUT
AND ARTERIAL PRESSURE
 shows the approximate effects
on cardiac output and arterial
pressure of removing blood
from the circulatory system
over a period of about 30
minutes.
 About 10 percent of the total
blood volume can be removed
with almost no effect on
either arterial pressure or
cardiac output, but greater
blood loss usually diminishes
the cardiac output first and
later the arterial pressure,
both of which fall to zero
when about 40 to 45 percent
of the total blood volume has
been removed.

10. SYMPATHETIC REFLEX COMPENSATIONS IN SHOCK—THEIR
SPECIALVALUETO MAINTAIN ARTERIAL PRESSURE
 The decrease in arterial pressure after hemorrhage,as well as decreases in pressures in the pulmonary
arteries and veins in the thorax, cause powerful sympathetic reflexes initiated mainly by the arterial
baroreceptors and other vascular stretch receptors
 These reflexes stimulate the sympathetic vasoconstrictor system in most tissues of the body, resulting
in three important effects:
• 1.The arterioles constrict in most parts of the systemic circulation, thereby increasing the
total peripheral resistance.
• 2.The veins and venous reservoirs constrict, thereby helping to maintain adequate venous return
despite diminished blood volume.
• 3. Heart activity increases markedly, sometimes increasing the heart rate from the normal value of 72
beats/min to as high as 160 to 180 beats/min.

11. PATHOPHYSIOLOGY OF HAEMORRHAGIC SHOCK
RAPID
COMPENSATORY
REACTION
LONGTERM
COMPENSATORY
REACTION

12. RAPID COMPENSATORY REACTION
Haemorrhage
Decreased blood
volume
Decreased venous
return
Decreased blood
pressure
Decreased cardiac
output

13. Blood pressure
sympathetic discharge
Decrease baroreceptor activity
Increase chemoreceptor activity
▪ Tachycardia
▪ Generalized vasoconstriction
▪ Stimulates respiration
▪ Renal vasoconstriction

14. LONG TERM COMPENSATORY REACTION
 Restoration of plasma of volume within 12-72 hours
• By mobilization of tissue fluids
• Retention of water and electrolytes by kidney
 Restoration of plasma protiens over a period of 3-4 days [because of activation liver]
 Restoration of RBC mass in 4 –8 weeks [because hypoxia leads to erythropoitin
produced ]
 Restoration of blood pressure over several months via is kidney long term
regulation

15. TRAUMATIC
SHOCK
 Occurs due to injury causing severe damage to muscle and
bone
 1. Frank bleeding into injured areas results in shock.
 2.If there is extensive soft tissue and muscle crushing
(called Crush Syndrome), myoglobin leaks into circulation;
it gets precipitated into renal tubules and clogs them
resulting in renal damage.

17. SURGICAL
SHOCK
 This occurs as a result of external or
internal blood loss caused by ruptured blood
vessels during surgical procedures.

18. DEHYDRATION SHOCK
 It occurs as a result of fluid loss from:
 (1) GIT due to prolonged vomiting or diarrhoea
 (2) Kidneys due to: (i) diabetes mellitus, (ii) diabetes insipidus, (iii) diuretic overdose, (iv) adrenal
insufficiency.
 (3) Skin due to 'burns', heat stress (fever, exposure to heat) results in sweating. Shock due to burns
is characterised with haemoconcentration

19. DISTRIBUTIVE
SHOCK
❑Vasogenic shock
❑Low resistance shock
❑Size of capacitance vessel is increased by
vasodilation leads to decreased cardiac
output inspite of normal blood volume

20. DISTRIBUTIVE
SHOCK
INCLUDES................
 Fainting /syncope
• Sudden transient loss of consciousness due to decrease
in cerebral blood flow
• Also called as neurogenic shock
• Associated with abrupt vasodilation but attack is short
lived and consciousness is restored in few minutes
❑ Types
1. Vasovagal syncope –strong emotion causes vasodilation
2. Postural syncope- pooling of blood in dependent parts of
body
3. Carotid sinus syncope –pressure on carotid sinus
produced by tightcollars marked by bradycardia and
hypotension

22. Anaphylactic shock
• It is rapidly developing severe allergic shock
• Occurs when an individual who has
previously been sensitive to an antigen is re
–exposed to it

23. SEPTIC
SHOCK
Certain infection eg strangulated bowel ,
perforated duodenum
Release of bacterial endotoxin
Absorbed into systemic circulation
High fever and fall in blood pressure

25. MECHANISM OF DISTRIBUTIVE SHOCK
• Genesis of antigen –
antibody reaction
• Release of large
quantities of histamine
Decrease in blood volume
general arteriolar dilatation
Increase in
capillary permeability
decrease in peripheral
resistance
Fall in blood pressure

26. CARDIOGENIC SHOCK
 It is caused when pumping action of the heart is inadequate ; therefore heart fails to pump
out all venous return
Marked decrease in cardiac output shock and congestion of lungs and viscera
[congested shock]
 It can be caused by
1. MI
2. Arrythmia

27. OBSTRUCTIVE SHOCK
Cardiac output is decreased as a result of mechanical obstruction of left or
right ventricular filling
Causes
1. Massive pulmonary embolism
2. Cardiac tamponade [bleeding into the pericardium
with external pressure on the heart]