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TYPES OF SHOCK |
Definition
Shock is a life-threatening medical emergency characterized by the
inability of the body to supply enough oxygen to meet
tissue requirements. Most often, shock results from decreased cardiac
output, either from direct pump failure or decreased cardiac preload (i.e., loss
of volume). Rarely, shock can be have a primary neurologic etiology. |
Hypovolemic Shock
Hypovolemic shock results from decreased preload. Since preload is one of the
determinants of stroke volume, cardiac output falls as preload drops.
Hypovolemic shock can be further divided into two broad categories based upon
etiology: hemorrhage and
fluid loss.
Common causes of hemorrhage include trauma, upper and lower gastrointestinal
bleeding, ruptured aortic or ventricular aneurysm, ruptured hematoma,
hemorrhagic pancreatitis, and fractures.
Fluid loss results from of diarrhea, vomiting, heat stroke, inadequate
repletion of insensible losses, burns, and "third spacing" (which can occur in
intestinal obstruction, pancreatitis, and cirrhosis).
The normal compensatory reaction to hypovolemia is increased heart rate. Thus,
hypovolemic shock is typically characterized by
hypotension and tachycardia. |
Septic Shock
Similar to hypovolemic shock, septic shock results in hypotension and
tachycardia. However, the underlying abnormality is decreased systemic vascular
resistance. This leads to an increased cardiac output. However, despite this
increase, the systemic hypotension still results in tissue hypoperfusion. |
Cardiac Shock
Cardiogenic shock results from primary pump failure, manifested
physiologically as decreased systolic function and depressed cardiac output. The
mechanisms of cardiogenic shock are diverse and can be divided into four general
categories: cardiomyopathies, arrhythmias, mechanical abnormalities, and
obstructive disorders. Similar to other types of shock, cardiac shock is
associated with hypotension. However, depending on the etiology, there may be an
associated tachycardia and bradycardia. |
Spinal Shock
Spinal shock is s a state of transient physiological reflex depression of
spinal cord function below the level of injury with associated
loss of all sensorimotor functions. Flaccid paralysis, including of the
bowel and bladder, is observed. These symptoms tend to last several hours to
days until the reflex arcs below the level of the injury begin to function.
Spinal shock is manifested by hypotension and bradycardia.
Shock tends to occur more commonly in injuries above T6, secondary to the
disruption of the sympathetic outflow from T1-L2 and to
unopposed vagal tone, leading to decrease in
vascular resistance with associated vascular dilatation. |
Brain Shock
Brain shock is a condition where the body is unable
to supply enough oxygen to meet the tissue requirements of the brain.
This is most commonly seen in the presence of a mass lesion and increased
intracranial pressure. From the
Monro-Kellie doctrine, the total volume of
the intracranial contents is fixed. An intracranial mass lesion will first
displace CSF and then blood volume. The normal compensatory response is
increased blood pressure. As the rest of the body is being well perfused, there
is usually a reflex bradycardia. The combination of
elevated blood pressure and a decreased pulse should always raise the concern of
intracranial hypertension and lack of adequate blood flow to the brain.
Increased intracranial pressure will eventually lead to
Cushing's triad of hypertension, bradycardia
and apnea. |
Types of Shock
|
Blood Pressure |
Pulse |
Hypovolemia |
Decreased |
Increased |
Septic |
Decreased |
Increased |
Cardiac |
Decreased |
Increased / Decreased |
Spinal |
Decreased |
Decreased |
Brain |
Increased |
Decreased |
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