CVS

Shock (circulatory failure)

Shock is a clinical syndrome of circulatory failure characterized by:1. Low cardiac output.2. Hypotension.3. Inadequate tissue perfusion: (Organ Failure)


Objectives:1. Define the term hypotensive shock and give three possible causes.2. Summarize the cardiovascular reflexes elicited following the sudden loss of 1 literof blood (pulse, Bp, PCV …)3. Explain the mechanisms that help compensate for circulatory shock. (hr,stroke v.,vasoconstriction, aldosterone, ADH …


Causes and types: 1. Hypovolaemic shock.2. Distributive shock. 3. Cardiogenic shock. 4. Obstructive shock.


Hypovolaemic shock:Hemorrhagic shock: severe hemorrhage; bleeding.Traumatic shock: (crush syndrome). Burn shock: fluid and protein.Surgical shock: bleeding.Dehydration: (severe diarrhea) Na+ and water loss.


Distributive shock:  (widespread vasodilation) a. Neurogenic shock: emotions, sympathetic tone. b. Anaphylactic shock: histamine. c. Septic shock: cytokines.


Cardiogenic shock:inadequate pumping action of the heart plus systemic congestion.* Extensive myocardial infarction * Heart failure.



Obstructive shock:marked restriction of the diastolic filling of the ventricles. * Large pneumothorax.* Massive pulmonary embolism.* Cardiac tumor. * Cardiac tamponade.

Danger of shock… How does it cause death?

Hypotension→ cerebral ischemia→ depression of the VCC→ VD and bradycardia → more hypotension (and so on till death).2. Hypotension→ myocardial ischemia→ low cardiac output→ more hypotension, and so on till death * late cause of death is pulmonary damage due to pulmonary microembolism by thrombi formed by coagulant agents released from the damaged cells (acute or adult respiratory distress syndrome, ARDS).

Any question?

In summary: Shock is a clinical syndrome of circulatory failure characterized by:1. Low cardiac output.2. Hypotension.3. Inadequate tissue perfusion: (Organ Failure)