In shock, there is progressive failure of the circulatory system.
There is something wrong with the pump (heart), the pipes (blood vessels), the fluid (blood volume), or it becomes obstructed (impedes blood flow).
Shock is not a single specific clinical condition.
Shock results in hypoperfusion at the cellular level with resultant cellular hypoxia (cells run out of energy).
The body attempts to compensate by a progression of physiologic mechanisms to correct the cellular hypoxia / hypoperfusion.
In trauma the most common cause of shock is blood loss in which the vascular space is depleted and cannot recover fluid from the interstitial space.
| Blood loss |
| Decreased venous return |
| Decreased Cardiac Output |
| Compensation with increased Systemic Vascular Resistance |
| Increased tissue hypoxia |
| Acidosis |
Mechanisms for inadequate tissue blood flow (perfusion) include:
- Volume loss
- Pump failure
- Vasodilatation
- Obstruction