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What is Shock?
Shock is any condition in which the circulatory system
is unable to provide adequate circulation to the vital
body organs such as the brain, heart and lungs as a
result of a decrease in the blood pressure.
Shock is Profound hemodyamic and metabolic disturbance
characterized by failure of the circulatory system to
maintain adequate perfusion of vital organs
Shock is usually accompanied by renal failure, as a
normal compensatory mechanism, because the blood
flow to the kidney is decreased to keep enough blood
for the vital organs.
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General Symptoms of shock
1. Increase heart rate as a result of the baroreflex:
• Shock will decrease the volume of blood pumped
from the heart and the blood flow to the brain.
• That will activate the baroreceptors in the carotid
bodies to increase HR trying to supply enough blood
to the vital organs.
2. Pale skin:
• As a result of vasoconstriction of the peripheral
vessels, because the skin is the least priority tissue
for blood flow
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General Symptoms of shock
3. Cold and clammy skin :
As a result of vasoconstriction.
• Shock decreases the skin surface temperature as a
result of vasodilatation, which will increase the
internal body temperature.
• Because the skin plays a major role in controlling body
temperature, as it will help in exchanging heat with
the external environment.
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Classification of Shock
Hinshaw & Cox classification
In 1972 Hinshaw and Cox suggested four types of shock:
1) Hypovolemic shock,
2) Cardiogenic shock,
3) distributive shock
4) obstructive shock:
In many patients, shock is a combination of two or more
of these four types of shock.
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(1) Hypovolemic shock
• This is the most common type of shock and based on
insufficient circulating volume.
• Its primary cause is loss of fluid from the circulation
(most often "hemorrhagic shock").
• Causes may include internal bleeding, traumatic bleeding,
or severe burns.
(2) Cardiogenic shock
• This type of shock is caused by the failure of the heart
to pump effectively.
• This can be due to damage to the heart muscle, most
often from a large myocardial infarction.
• Other causes of cardiogenic shock include arrhythmias,
cardiomyopathy, congestive heart failure (CHF), or
cardiac valve problems.
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(3) Distributive shock
• As in hypovolaemic shock there is an insufficient
intravascular volume of blood. Examples of this type:
a) Septic shock
– Caused by an overwhelming systemic infection resulting in
vasodilation leading to hypotension.
– It can be caused by some Gram negative bacteria, Gram-positive
cocci, and certain fungi.
b) Anaphylactic shock
– Caused by a severe anaphylactic reaction to an allergen, antigen,
drug or foreign protein causing the release of histamine which
causes widespread vasodilation, leading to hypotension and
increased capillary permeability.
c) Neurogenic shock
– This is the rarest form of shock. It is caused by trauma to the
spinal cord resulting in the sudden loss of autonomic and motor
reflexes below the injury level leading to vasodilation and
hypotension.
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(4) Obstructive shock
• In this situation the flow of blood is obstructed which
impedes circulation and can result in circulatory arrest.
• Several conditions result in this form of shock.
a) Cardiac tamponade
a)in which fluid in the pericardium prevents inflow
of blood into the heart.
b) Tension pneumothorax
a)Through increased intrathoracic pressure,
bloodflow to the heart is prevented (venous
return).
c) Massive pulmonary embolism
a)is the result of a thromboembolic incident in the
bloodvessels of the lungs and hinders the return
of blood to the heart.
d) Aortic stenosis
a)hinders circulation by obstructing the ventricular
outflow tract
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Signs of severity
The severity of shock can be graded 1-4
Grade 1
Up to about 15% loss of effective blood volume (~750ml
in an average adult who is assumed to have a blood
volume of 5 liters). This leads to a mild resting
tachycardia and can be well tolerated in otherwise
healthy individuals.
Grade 2
Between 15-30% loss of blood volume (750-1500ml) will
provoke a moderate tachycardia and begin to narrow the
pulse pressure.
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Signs of severity
Grade 3
At 30 - 40% loss of effective blood volume (1500 - 2000
ml) the compensatory mechanisms begin to fail and
hypotension, tachycardia and low urine output
(<0.5ml/kg/hr in adults) are seen.
Grade 4
At 40-50% loss of blood volume (2000 -2500 ml)
profound hypotension will develop and if prolonged will
cause end-organ damage and death.
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Signs relating to different causes:
(a) Hypovolemic shock
Anxiety, restlessness, altered mental state
Hypotension
A rapid, weak, thready pulse
Cool, clammy skin
Rapid and shallow respirations
Hypothermia
Thirst and dry mouth
Fatigue
Cold and mottled skin
staring into space, often with pupils dilated
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(b) Cardiogenic shock
– Similar to hypovolemic shock but in addition:
– Distended jugular veins
– Weak or absent pulse
– Arrhythmia, often tachycardic
(c) Obstructive shock
1) Similar to hypovolemic shock but in addition:
2)Distended jugular veins due to increased jugular venous pressure
3)Pulsus paradoxus in case of tamponade
(d) Distributive
(i) Septic shock
1) Similar to hypovolemic shock except there is:
2)Pyrexia (fever), due to increased level of cytokines
3)Systemic vasodilation resulting in hypotension
4)Warm and sweaty skin due to vasodilation
5)Reduced contractility of the heart
6)disseminated intravascular coagulation
7)Increased levels of neutrophils
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(ii) Neurogenic shock
1) As with hypovolemic shock but in high spinal injuries
may also be accompanied by profound bradycardia
2) The skin is warm and dry or a clear sweat line exists
3) Priapism due to Peripheral nervous system
stimulation
iii) Anaphylactic shock
1) Skin eruptions and large bumps
2) Localised oedema, especially around the face
3) Weak and rapid pulse
4) Breathlessness and cough due to narrowing of
airways and swelling of the throat
16. Clinical Presentation
Clinical signs and symptoms vary
depending on the underlying cause of shock
and the stage of shock in which the patient
presents.
Initial stage: No visible signs and
symptoms are evident from ongoing cellular
changes in this stage.
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17. Compensatory stage
Consciousness: restless, agitated, confused
Blood pressure: normal or slightly low
Heart rate: increased
Respiratory rate: increased (>20)
Skin: cool, clammy, may be cyanotic
Peripheral pulses: weak and thready
Urine output: concentrated and scant (<30
mL/h) 17
19. Peripheral pulses: weak and thready,
may be absent
Urine output: scant (<20 mL/h)
Bowel sounds: absent
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Effects of inadequate Cell perfusion
There are four stages of shock.
(1) Initial Stage
During this stage, the hypoperfusional state causes
hypoxia, leading to the mitochondria being unable to
produce ATP.
Due to this lack of oxygen, the cell membranes become
damaged, they become leaky to extra-cellular fluid, and
the cells perform anaerobic respiration.
This causes a build-up of lactic and pyruvic acid which
results in systemic metabolic acidosis.
No obvious clinical signs and symptoms are apparent during
this stage of shock
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(2) Compensatory (Compensating) Stage
• This stage is characterised by the body employing
physiological mechanisms, including neural, hormonal and
bio-chemical mechanisms in an attempt to reverse the
condition.
• As a result of the acidosis, the person will begin to
hyperventilate in order to rid the body of carbon
dioxide (CO2).
• CO2 indirectly acts to acidify the blood and by removing
it the body is attempting to raise the pH of the blood.
• The baroreceptors in the arteries detect the resulting
hypotension, and cause the release of adrenaline and
noradrenaline.
• Renin-angiotensin axis is activated and arginine
vasopressin (Anti-diuretic hormone; ADH) is released to
conserve fluid via the kidneys.
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(3) Progressive (Decompensating) Stage
• the compensatory mechanisms begin to fail.
• Due to the decreased perfusion of the cells, sodium ions
build up within while potassium ions leak out.
• As anaerobic metabolism continues, increasing the
body's metabolic acidosis, the arteriolar smooth muscle
and precapillary sphincters relax such that blood
remains in the capillaries.
• Due to this, the hydrostatic pressure will increase and,
combined with histamine release, this will lead to leakage
of fluid and protein into the surrounding tissues.
• As this fluid is lost, the blood concentration and
viscosity increase, causing sludging of the micro-
circulation.
• The prolonged vasoconstriction will also cause the vital
organs to be compromised due to reduced perfusion.
• If the bowel becomes sufficiently ischemic, bacteria
may enter the blood stream, resulting in the increased
complication of endotoxic shock.
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(4) Refractory (Irreversible) Stage
• At this stage, the vital organs have failed and the shock
can no longer be reversed.
• Brain damage and cell death have occurred.
• Death will occur imminently.
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Prognosis
The prognosis of shock depends on the underlying cause
and the nature and extent of concurrent problems.
Hypovolemic, anaphylactic and neurogenic shock are
readily treatable and respond well to medical therapy.
Septic shock however, is a grave condition and with a
mortality rate between 30% and 50%.
The prognosis of cardiogenic shock is even worse.
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Management
Correct underlying disorder if possible and then direct
efforts at increasing the blood pressure to increase oxygen
delivery to the tissues.
Maintain a mean arterial pressure of 60 (1/3 systolic +
2/3 diastolic)
Keep O2 levels >92%,
intubate if neccesary
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Correction of hypotension
Normal Saline should be administered anytime a patient
is hypotensive.
If hypotension exists give more NS.
If possible give blood.
Vasopressor medicines like adrenaline
Inotropic agents for cardiogenic shock like Dobutamine
Norepinephrine ,Dopamine, Epinephrine
Intra-aortic Balloon Pump for cardiogenic
