Physiology 2 CARDIOVASCULAR PHYSIOLOGY SHOCK Presented by Dr

Physiology 2 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 2 ndry 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 üIf the person has a history of anaphylaxis, don't wait for signs of a severe reaction to inject epinephrine. üInject epinephrine into outer muscle of the thigh. Avoid injecting into a vein or buttock muscles. üDo 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. 3 mg of epinephrine for adults

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