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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