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1、Definition,Inadequate perfusion (oxygen supply) of tissues, resulting in: Organ dysfunction Cellular and organ damage And if not quickly corrected Death,Causes of Shock a quick list:,Heart Attack Anaphylaxis Loss of Circulating Blood Volume (bleeding , burns, dehydration) Venous Dilation (allergy, p
2、ain, drugs, heat stroke, infection) High or Low Body Temperature,Signs of Shock,Pulse: Rapid, weak, thready Tachycardia Why? Compensation for decreased MAP sensed by _ Baroreceptors,Signs of Shock,Respirations Shallow, irregular, labored May be tachypnea (increased respiratory rate.) Why? Compensati
3、on for hypoxia sensed by: Chemoreceptors,Signs of Shock: MAP,Blood Pressure Low, Falling Hypotension is a late finding: why? Compensatory mechanisms work at first to maintain MAP,Signs of Shock,Due to hypoperfusion: Decreased “mentation” - confused, sluggish, anxious Skin cold, mottled,Emergency Tre
4、atment,Evaluate vital signs BP, Respiration Rate, Pulse Oximeter, Temp. Control bleeding Prevent loss of body heat,Causes of Shock: Classification (the real list),Low Output Circulatory Failure Hypovolemic shock (too little volume) Cardiogenic shock (pump failure) Obstructive shock Distributive shoc
5、k: Venous pooling High Output Circulatory Failure Distributive Shock: Sepsis, toxic shock, anaphylaxis:,Hypovolemic Shock,CO reduced due to loss of intravascular VOLUME Reduced venous return Causes Most often, blood loss (hemorrhage) Dehydration Burns Fluid lost into peritoneal cavity w/ pancreatiti
6、s MAP = CO * TPR,Hypovolemic Shock,CO reduced due to loss of intravascular VOLUME Reduced venous return Causes Most often, blood loss (hemorrhage) Dehydration Burns Fluid lost into peritoneal cavity w/ pancreatitis MAP = CO * TPR,Cardiogenic Shock,Myocardial Infarction (most frequent cause) Acute Va
7、lvular Dysfunction e.g. papillary muscle rupture post-MI Arrhythmia e.g., heart block, ventricular tachycardia MAP = CO * TPR,Cardiogenic Shock,Myocardial Infarction (most frequent cause) Acute Valvular Dysfunction e.g. papillary muscle rupture post-MI Arrhythmia e.g., heart block, ventricular tachy
8、cardia MAP = CO * TPR,Obstructive Shock,CO reduced by vascular obstruction: Obstruction of Venous return (vena cava syndrome usually neoplasms) Compression of the heart (pericardial tamponade*) Outflow from heart (Massive pulmonary embolism, aortic dissection),Pericardial Tamponade,Life threatening
9、condition caused by fluid (blood, effusion fluid) under pressure around the heart. Decreases CO by decreasing filling Causes include pericarditis and MI,Distributive Shock,Maldistribution of flow Two Categories: Low Output - Venous pooling due to loss of venous tone High Output Circulatory Failure,V
10、enous Pooling,A Low Output Circulatory Failure Often due to spinal shock or drug overdose Behaves like hypovolemic shock CO severely reduced because blood is pooled in peripheral veins, rather than returned to heart,Distributive Shock: High Output,CO is normal or elevated; distribution inappropriate
11、 Shock is due to loss of vascular resistance Examples: Sepsis, Toxic Shock: Bacterial endotoxin triggers vasodilation Anaphylaxis MAP = CO * TPR,Distributive Shock: High Output,CO is normal or elevated; distribution inappropriate Shock is due to loss of vascular resistance Examples: Sepsis, Toxic Sh
12、ock: Bacterial endotoxin triggers vasodilation Anaphylaxis MAP = CO * TPR,Anaphylaxis,Anaphylactic Shock,Histamine triggers vasodilation, increased capillary permeability Can lead to low-output distributive shock,Physiological Response to Shock,MAP = CO * TPR The pressure drop is compensated for by
13、regulatory mechanisms This = “Nonprogressive” / “Compensated” Shock,Additional Compensatory Mechanisms,Renin-Angiotensin Mechanism AII : vasoconstrictor Aldosterone: Water conservation ADH: Water retention and thirst,Progressive Shock,Compensatory mechanisms inadequate to compensate for loss of bloo
14、d volume Cardiac circulation compromised decreased heart function decreased flow Positive feedback cycle: Shock worsens less compensation shock worsens Clotting in small vessels Vessels dilate and permeability increases,Irreversible Shock,Cardiac and other tissue irreversibly damaged Characterized by: Decreasing cardiac function Progressive blood vessel dilation Progressive increase in vessel permeability,