CIRCULATORY SHOCK Dr. AmelEassawi
OBJECTIVES The student should be able to: • Define circulatory shock. • Identify different stages of circulatory shock. • Recognize the different types of circulatory shock. • Understand changes occurring in the different types of shock. • Explain body response to different types of shocks. • Understand the management outline for shock.
Circulatory shock • Circulatory shock is a state of inadequate tissue perfusion with relatively or absolutely inadequate cardiac output. • Depending upon the cause of inability of the heart to pump sufficient blood volume for tissue perfusion circulatory shock can be divided into different types
Circulatory shock Stages of Shock • Non Progressive Stage or Compensated stage: Circulatory compensatory mechanism cause full recovery without help from outside therapy. • Progressive Stage: Decreased blood pressure and cardiac output. In this situation the shock needs intervention of therapy without therapy the shock gets worse. • Refractory Shock or Irreversible Stage: the patient does not respond to treatment.
refractory shock Factors Contributing to Irreversible Shock • Cerebral ischemia • Depression of vasomotor and cardiac areas of the brain (vasodilation , decreased blood pressure, decreased heart rate) • Myocardial depression due to acidosis causes decreased cardiac output. • Respiratory failure • triggered not only by shock but also by lung bruise, other forms of trauma. • Damage to capillary endothelial cells and alveolar epithelial cells, with release of cytokines. • Depression of kidney functions
Circulatory shock Types of Circulatory Shock • Hypovolemic shock • Cardiogenic shock • Vasogenic shock 1. Anaphylactic shock 2. Septic shock 4. Neurogenic shock
Hypovolemic shock • Hypovolemic shock is also called "cold shock." • It is characterized by • Hypotension • Rapid, thready Pulse • Cold, Pale, Clammy Skin • Intense Thirst • Rapid Respiration • Restlessness .
Hemorrhage Decrease blood volume Decrease venous return Decrease stroke volume Decrease cardiac out put Hypovolemic Shock Decrease arterial pressure
Compensatory reactions activated by hemorrhage • Tachycardia • Venoconstriction • Tachypnea→increased thoracic pumping • Restlessness→increased skeletal muscle pumping (in some cases) • Increased movement of interstitial fluid into capillaries • Increased secretion of norepinephrine and epinephrine • Increased secretion of vasopressin • Increased secretion of renin and aldosterone • Increased secretion of erythropoietin • Increased plasma protein synthesis
Cardiogenic shock • Myocardial Infarction(pump failure) • Causes congestion in the lungs ( Pulmonary edema). • In Myocardial Infarction, shock occurs in 10% and has mortality of 60-90%.
Vasogenic Shock Anaphylactic Shock • Anaphylactic shockis rapidly developing, severe allergic reaction that sometimes occurs when an individual who has previously been sensitized to an antigen is exposed to it. • The resultant antigen-antibody reaction releases large quantities of histamine, causing increased capillary permeability and widespread dilation of arterioles and capillaries.
Vasogenic Shock Septic Shock • Usually due to gram-negative bacteria • Endotoxins released by gram-negative bacteria causes vasodilatation. Skin is warm (also, called warm shock). • High fever • Increased capillary permeability with loss of plasma in tissues • Mortality is 30-50%
Neurogenic shock • In Neurogenic shock, there is decreased sympathetic activity, therefore, increased vascular capacity. • Sudden loss of vasomotor tone resulting in massive dilation of veins therefore venous pooling of blood and decreased venous return to heart. • Causes of Neurogenic shock • General Anesthesia • Spinal Anesthesia • Brain damage
Neurogenic shock Fainting Type of distributive shock is neurogenic shock, in which there is sudden autonomic activity producing vasodilation, pooling of blood in the extremities, and fainting. These are called vasovagal attacks,. Other forms of syncope include • postural syncope, fainting due to pooling of blood in the dependent parts of the body on standing. • Micturition syncope, fainting during urination. It is due to the combination of the orthostasis and reflex bradycardia induced by voiding in these patients.
Neurogenic shock • Pressure on the carotid sinus, produced, for example, by a tight collar, can cause such marked bradycardia and vasodilation that fainting results (carotid sinus syncope). • Rarely, vasodilation and bradycardia may be precipitated by swallowing (deglutition syncope). • Cough syncope occurs when the increase in intrathoracic pressure during straining or coughing is sufficient to block venous return
References • Human physiology, Lauralee Sherwood, seventh edition. • Text book physiology by Guyton &Hall,11th edition. • Physiology by Berne and Levy, sixth edition.