This document discusses shock, which is defined as cardiovascular collapse and systemic hypoperfusion that impairs the body's ability to adequately perfuse tissues. Shock can be caused by reductions in cardiac output or circulating blood volume and clinically presents as hypotension, impaired tissue perfusion, organ dysfunction, and hemodynamic disturbances. The causes of shock include cardiogenic shock, distributive shock such as septic or anaphylactic shock, hypovolemic shock from bleeding or fluid loss, and obstructive shock from pulmonary embolism or cardiac tamponade. Shock progresses through compensated, decompensated, and irreversible stages if left untreated and can result in multiple organ failure and death.
3. Shock
• Caused by reduction either in cardiac output or in
effective circulating blood volume
• Hypotension, impaired tissue perfusion & cellular
hypoxia
• Clinically manifested by
– Hemodynamic disturbances
– Organ dysfunction
• Reversible => irreversible cellular injury
• Shock is likely to deteriorate into a vicious cycle
of organ failure and subsequent exacerbation of
shock
5. Causes of shock
2. LOSS OF VASCULAR TONE (Distributive)
• Septic shock (i.e., from bacterial breakdown
products and especially cytokine production by
way of nitric oxides)
• Anaphylaxis: IgE mediated hypersensitivity
response (generalized mast-cell degranulation)
• Neurogenic: certain poisons (notably war gases),
Profound anaesthesia, Spinal cord injury,
Vasovagal (i.e., extreme pain, emotion)
6. Causes of shock
3. Hypovolemic shock
• Bleeding: Externally or Internally
(GI bleeds, hemoperitoneum)
• Other fluid loss: sweating, vomiting,
diarrhea, Burns
• Third-space losses (i.e., into
effusions or ileus)
8. Effects shock
• Regardless of etiology, hypoperfusion of the whole
body produces common problems
• A variety of other secondary mediators of shock
are produced by hypoperfused tissues to further
exacerbate the problem
• Histamine, serotonin, leukotrienes, TNF, IL1, C3a,
C5a, etc dilate vessels, inviting blood to pool in
venules and/or make small vessels permeable,
causing blood to leak out
• With widespread anaerobiosis, lactic acidosis is
likely to develop, and pH goes way down
• When endothelial cells are damaged or
thromboplastin enters the circulation, DIC may
result
9. Stages of shock
• Shock is a progressive disorder if uncorrected leads to
death
• Three phases
1. Nonprogressive phase (compensated shock): reflex
compensatory mechanism activated & perfusion of vital
organs maintained
Baroreceptor reflexes, release of catecholamines,
activation of renin angiotensin axis, antidiuretic hormone
release, & generalized sympathetic stimulation
Blood is shunted away from the kidneys, salivary glands,
gut, skin, and muscles in order to perfuse the brain and
heart. Blood pressure is maintained
Patients may be oliguric from reduced blood flow to the
kidneys ("prerenal azotemia"), and have dry mouth and skin
from reduced blood flow to these organs
10. Stages of shock
2. Progressive stage (decompensated shock):
tissue hypoperfusion & onset of worsening
circulatory & metabolic imbalances, blood
pressure and cardiac output decline
• Lactic acidosis lowers the tissue pH &
aretriolar dilatation => blood pools in
microcirculation => decrease CO &
endothelial injury => DIC
• Survivors typically have reversible
necrosis of the renal tubules
• "shock lung" or "adult respiratory distress
syndrome”
11. Stages of shock
3. Irreversible stage: severe cellular injury
(lysosomal enzyme leakage) & myocardial
contractile function worsens & ischemic
bowel allows bacteria to enter circulation
Correction of the deficient cardiac output
and volume deficit by any means fail to
reverse shock
Blood pressure and pH continue to drop
Death due to multiple organ failure (MOF)
13. Hemorrhagic Shock
Parameter I II III IV
Blood loss (ml) <750 750–1500 1500–2000 >2000
Blood loss (%) <15% 15–30% 30–40% >40%
Pulse rate (beats/min) <100 >100 >120 >140
Blood pressure Normal Decreased Decreased Decreased
Respiratory rate (bpm) 14–20 20–30 30–40 >35
Urine output (ml/hour) >30 20–30 5–15 Negligible
CNS symptoms Normal Anxious Confused Lethargic
14. Septic shock
• Systemic microbial infection e.g gram
negative infections (endotoxic shock),gram
positive and fungi
• 25-50% mortality
• Results from spread of localized infection
e.g abscess, peritonitis, pneumonia into
blood stream
• Endotoxins are bacterial wall
lipopolysaccharides (LPSs)
15. Morphology
• Tissue injury is hypoxic injury
• Any tissue
• Diffuse hypoxic injury to the brain ("respirator
brain")
• Subendocardial necrosis (ed part of the heart)
• Widespread contraction band necrosis in the heart
• Acute tubular necrosis of the kidneys
• Stressed adrenals, i.e., cortical hyperplasia, lipid
depletion
• Bleeding points ("stress ulcers") in the stomach and
duodenum
• Necrosis of, and bleeding into, portions of the
small intestine (especially when dopamine has been
administered)
• fatty change of the liver and centrilobular necrosis
18. HEMORRHAGE
• Hemorrhage: Blood cells that have escaped
from a vessel
• The significance of hemorrhage depends on
"where" and "how much"
• Hematomas: Enough blood in the tissues to
create a palpable mass
• Hemothorax: Blood in a pleural cavity.
Hemopericardium: Blood in the pericardial
cavity
Hemoperitoneum: Blood in the peritoneal
cavity
Hemarthrosis: Bleeding into a joint
21. HEMORRHAGE
• Purpura: < 1cm hemorrhages in the
tissues
• Ecchymoses: >1cm hemorrhage in the
tissues; An ecchymosis in a normal
person is probably a bruise, also
called a "contusion"
• Petechiae: <3mm hemorrhages in the
tissues
27. Thrombocytopenia
• <100,00/µl
• Prolonged bleeding time & normal PT & PTT
• Hemorrhage in Skin, GIT & GUT
• Causes
1. Decreased production: aplastic anemia &
leukaemias, etc
2. Decreased survival: immunologic autoimmune
(idiopathic, drug, HIV) or nonimmunologic
(mechanical)
3. Sequestration: hypersplenism
4. Dilutional
28. Abnormality in clotting factors
• Ecchymoses or prolonged bleeding
after trauma, petechiae are absent
• Hereditary (hemophilia, Von
Willebrand disease) or acquired (Vit.
K deficiency, Liver disease)
