Lecture # 39
HEMODYNAMICS - 7
Dr. Iram Sohail
Assistant Professor
Pathology
College Of Medicine
Majmaah University
OBJECTIVES
• Discuss shock
• Correlate in explaining shock with
hemodynamic mechanism
SHOCK
• Shock is a final & common pathway after
hemorrhage, trauma, burn, myocardial
infarction (heart attack), pulmonary embolism
& microbial sepsis.
• Shock gives rise to hypoperfusion, caused by
reduced cardiac output or reduced blood
volume.
• End results are
– Hypotension
– Impaired tissue perfusion
– Cellular hypoxia
3 Main types
1. Cardiogenic shock
– It results from failure of cardiac pump.
2. Hypovolemic shock
– It is caused by loss of blood or plasma.
3. Septic shock
– It results from microbial infections.
(Less common types/causes of shock)
4. Anesthetic shock
5. Neurogenic shock (spinal cord injury)
6. Anaphylactic shock (severe hypersensitivity
reactions)
Pathogenesis of septic shock
• Most of the septic shock caused by endotoxin
released by gram negative bacilli. These
endotoxins are called LPS
(lipopolysaccharides)
• These LPS will bind with proteins in
circulation. This complex will bind to the
macrophages monocytes and neutrophils.
• Cytokines (TNF, IL-1) will release from WBCs.
• These cytokine release will result in
– Vasodilation (hypotension)
– Decreased myocardial contractility
– Endothelial cell injury
– Lung damage
– Activation of coagulation system
• These all things will result in DIC
(disseminated intravascular coagulation) and
multi organ failure.
• If untreated, shock can result in death.
Stages of shock
1. Non-progressive stage
• Some neurohumoral mechanisms work like
– Baroreceptor reflexes
– Release of catecholamine
– Activation of renin angiotensin mechanism
– Release of ADH (antidiuretic hormone)
– Sympathetic stimulation
• The net effects are
– Tachycardia
– Peripheral vasoconstriction
– Renal conservation of fluid
2. Progressive stage
• If the underlying cause in not corrected, the
shock will pass to progressive
• Tissue hypoxia will occur.
• Decrease oxygen ----- anaerobic glycolysis ---lactic acid accumulation ---- low PH ----- dilation
of arterioles ---- pooling of blood in
microcirculation ----- decrease cardiac out put
3. Irreversible stage
• Without any treatment, the shock will go into
irreversible stage.
• Lysosomal enzymes leakage, worsen cardiac
function, renal shut down and death.
Morphology
• Hypoxic injury & failure to many organs
• Fibrin thrombi in tissues
• In adrenal gland, cortical cell lipid depletion
• In kidney , ATN (acute tubular necrosis)
• In GIT, mucosal hemorrhage & necrosis
• In lungs, diffuse alveolar damage
Clinical course
In cardiogenic & hypovolemic shock
• Hypotension
• Weak and rapid pulse
• Tachypnea (increased respiratory rate)
• Cold, clammy, cyanotic skin
In septic shock
• Warm skin
• Decrease renal out put
• Fluid & electrolyte imbalance