Theory of shock

Theory of shock

Tissue perfusion is dependent on delivery of adequately oxygenated blood to the tissues. Shock results from a lack of adequate tissue oxygen delivery. Blood delivery is estimated by the patient's cardiac output (CO). The priority is therefore to increase cardiac output and blood pressure (BP). Cardiac output is quantified as the product of heart rate (HR) and stroke volume (SV).

CO = HR x SV

Stroke volume is determined by the haemodynamic parameters of preload, afterload, and contractility. If one of these becomes compromised, cardiac output drops and tissue perfusion will suffer.

It is important to remember that hypovolaemic shock can be caused not only by loss of fluid volume (e.g. acute bleeding), but also by loss of plasma caused by burns or by sequestration into body cavities (also called third spacing).


SVR: systemic vascular resistance


Which kind of receptors do NOT play a role in antihypotensive treatment?


Loss of blood pressure can be due to all of the following EXCEPT