Cardiovascular Physiology shock Presented by: Dr. Shaimaa Nasr Amin Lecturer of Medical Physiology

Shock Definition : Shock is a clinical syndrome of circulatory failure characterized by a low cardiac output , hypotension and inadequate tissue perfusion resulting in tissue hypoxia .

Causes of shock : Shock occurs as a result of many disorders, they are divided into four main types , according to their causes :

-Types & causes of shock : 1- Hypovolaemic shock (cold shock ) : It is the common type of shock which occurs as a result of severe reduction of the blood volume . It occurs as a result of : a - Loss of large volume of blood , as in traumatic or surgical shock b- Loss of large volume of plasma , as in severe burns . c- Loss of fluids as in severe vomiting & diarrhea .

2- Distributive shock ( warm shock ) : - It occurs as a result of widespread V D . This leads to marked decrease in A B P , resulting in decreased blood flow to a vital organs like heart & brain . Causes of warm shock : a- Exposure to strong emotions ( neurogenic shock ) , such as fear or bad news & severe pain .These lead to marked hypotension due to sympathetic inhibition . b- Allergic reactions ( anaphylactic shock ) : , it occurs as a result of exposure to an antigen . It causes antigen- antibody reactions that causes histamine secretion , which causes marked V D & shock . c- Exposure to bacterial toxins ( Septic shock ) : Bacterial toxins stim. The macrophages that secrete V D cytokines ( interleukin- 1 ) . These substances predispose to shock .

3- Cardiogenic shock ( congested shock ) : This occurs as a result of inadequate pumping action of the heart which leads to reduction of the cardiac output and arterial B P . Causes of cardiogenic shock : A- Myocardial infarction of the left ventricle . B- Heart failure . C- Severe ventricular arrhythmia . D- Acute myocarditis .

4- Obstructive shock : - This occurs as a result of obstruction of blood flow in the lungs or heart . This leads to reduction in the cardiac filing & hypotension . It occurs as a result of : a- Pneumothorax . b- Massive pulmonary embolism . c- Cardiac tamponade ( fluid in the pericardial sac ) . d- Cardiac tumor .

Danger of shock : 1 - Severe shock without a rapid control , may be fatal . It becomes irreversible & end by death . 2 - Death occurs as a result of development of multiple positive feedback cycles .( death cycles ) , which are : a- Marked hypotension → cerebral ischemia → depression of V C C → more V D & bradycardia → more hypotension till death occurs . b- Marked hypotension → myocardial ischemia → low cardiac output → more hypotension & death . c- Pulmonary damage due to pulmonary microembolism by thrombi formed by coagulant agents released from the damaged cells ( acute or adult respiratory distress syndrome (A RD S ) .

Manifestations of shock ( hypovolemic shock ) 1- Cardiovascular effects , in the form of , rapid& weak pulse . 2- Respiratory effects , in the form of tachypnea , due to stim. Of ischemic chemoreceptors that stimulate resp. centers. 3- Skin effects , in the form of intense coetaneous V C . That lead to pale & cold skin . 4- Overstim . Of the sweat glands , resulting in excessive sweating due to sympath. Stimulation.

Manifestations of shock ( hypovolemic shock ) 5- Kidneys effect , in the form of oliguria or anuria due to V C of the renal vessels or P P T of myoglobin resulting from the crushed cells in the renal tubules. 6- C N S effects , in the form of anxiety & restlessness by stim . of reticular formation by catecholamines . While drowsiness due to hypoxia , that inhibits nerve center . 7- Change in PH value ( acidosis) , due to accumulation of lactic acid as a result of anaerobic glycolysis that occurs 2ndry to hypoxia .

Management of hypovolemic shock - Management of shock aims at : a- Restoration of adequate tissue perfusion b- Treating the causes .

Management of hypovolemic shock - The steps of management include the following : 1- Keeping the person in the recumbent position & raising the foot of bed to increase V R & improve the cerebral blood flow . 2- Warm the person by covering him by many layers of blankets to enhance the blood flow to a vital organs . 3- Avoid any oral drinks .

Management of hypovolemic shock 4- Observation of the vital signs such as , pulse , A B P , temperature & respiration . 5- Giving vasopressor drugs to adjust the B P for keeping cerebral blood flow . 6- Rapid hospitalization for treating the causes of shock .

Management of Anaphylaxis

Management of Anaphylaxis 1. Seek emergency care Get immediate help if the person has these symptoms : Difficulty breathing or wheezing ,tightness in the throat or a feeling that the airways are closing,hoarseness or trouble speaking ,swollen lips, tongue, or throat,nausea, abdominal pain, or vomiting ,fast heartbeat or pulse ,skin that itches, tingles, swells, or develops raised red areas (hives), anxiety or dizziness, Loss of consciousness.

Management of Anaphylaxis 2. Inject Epinephrine Immediately If the person has a history of anaphylaxis, don't wait for signs of a severe reaction to inject epinephrine. Inject epinephrine into outer muscle of the thigh. Avoid injecting into a vein or buttock muscles. Do not inject medicine into hands or feet, which can cause tissue damage. If this happens, notify the emergency room staff.

An auto-injector contains a preloaded dose of 0 An auto-injector contains a preloaded dose of 0.3 mg of epinephrine for adults

Management of Anaphylaxis 3. Do CPR if the Person Stops Breathing