QS Study

Shock can be defined as systemic hypoperfusion owing to reduction either in cardiac output or in the effective circulating blood volume resulting impaired tissue perfusion and cellular hypoxia. It is a disorder that results from systemic hypo-perfusion due to decrease either in cardiac output or in the effective circulating blood volume.

Major types of shock

  • Cardiogenic shock
  • Hypovolemic shock
  • Septic/ endotoxic shock
  • Neurogenic shock
  • Anaphylactic shock

Common Causes of shock are profuse hemorrhage, large myocardial infarction, severe diarrhea, severe vomiting, extensive burn, trauma, bacterial sepsis, and pulmonary embolism.

Fig: Major types of shock

(a) Cardiogenic shock

Principle mechanism: Failure of Myocardial pump owing to intrinsic myocardial damage, extrinsic pressure, or obstruction to outflow. Cardiogenic shock is caused by any form of severe heart failure.

Clinical example-

  1. Myocardial infarction (MI)
  2. Cardiac Tamponade
  3. Pulmonary emboliosm
  4. Ventricular arrhythmia.

(b) Hypovolemic shock

Principle mechanism: Inadequate blood or plasma volume due to hemorrhage in trauma, severe burn etc. Example: Hemorrhage, fluid loss e.g., vomiting, diarrhea, trauma etc.

(c) Septic shock

It is caused by a systemic microbial infection which causes peripheral vasodilation and pooling of blood- leading to stasis of blood > hypoperfusion > shock.

Principle mechanism

  • Peripheral vasodilatation and pooling of blood.
  • Endothelial injury
  • DIC
  • Activation of the cytokine cascade

Example: Endotoxic shock (Due to gram-negative septicemia); Gram-positive septicemia; Fungal sepsis.

(d) Neurogenic shock

It is a distributed type that typically occurs after damage to the pathways of the central nervous system, particularly to the spinal cord. Example- Deep anesthetic accident, brain damage, or spinal cord injury due to loss of vascular tone and peripheral pooling of blood.

(e) Anaphylactic shock

Generalized IgE mediated hypersensitivity response associated with systemic vasodilatation and increased vascular permeability. It is caused by an allergic reaction. Common triggers are medications such as penicillin, latex, bee stings, and foods such as nuts or shellfish.