Shock Flashcards
Definition of shock?
Acute generalized failure of the circulatory system resulting from blood volume that is too low to fill the vascular system or insufficient cardiac output
General characterization of shock?
Hypotension + Hypoperfusion –> Impaired perfusion+Hypoxia
BP =
CO X Peripheral Resisitance (PR)
Three causes of shock?
Decreased Cardiac Fxn
Decreased Blood Volume
Decreased Peripheral resistance
Causes of decreased peripheral resistance
Systemic inflammation (Septic Shock)
Systemic mast cell activation (Anaphylaxis)
Systemic loss of vascular tone (Neurogenic shock)
End result of shock
Cellular Hypoxia
Failure to transport CO2, Toxic substances away from cells
Cell Death/Tissue Dysfunction
Five types of shock
Cardiogenic Hypovolemic/Hemorrhagic Spetic Anaphylactic Neurogenic
Causes of cardiogenic shock
Myocardial infarction
Ventricular arrythmias
Cardiac tamponade
Saddle Embolism
Causes of hypovolemic shock?
Hemorrhage, Burns, Dehydration
What is septic shock?
Systemic inflammatory reaction from bacteremia with an organism expressing LPS or LOS
What is Systemic Inflammatory Response Syndrome (SIRS)?
LPS activation of macrophages, endothelial cells. Overproduction of inflammatory cytokines and mediators. Decreased PR, BV loss throughout the peripheral.
Most common cause of mortality in ICU
Septic Shock
Central feature of Septic Shock
LPS activation of inflammation
Activated endothelial cells, monocytes, macrophages, and compliment
What do activated endothelial cells in septic shock do? (Molecular)
Decrease production of tissue factor pathway inhibitor (TFPI) and thrombomodulin
How does LPS activate Monocytes/Macrophages?
LPS/LPS BP complex binds CD14 on cell surface.
Signalling mediated thru TLR4, NFkB transcription
Cytokine storm
Triggers NO release and systemic inflammatory effects
Effects of Endothelial cell activation?
Increased vascular permeability, adhesion molecule expression. Inhibition of anti-coagulation properties. Switch to pro-coagulation phenotype.
Describe initial stages of sepsis.
Widespread systemic inflammatory response
systemic vasodilation, diminished contractility.
Widespread adhesion + capillary damage.
Coagulation and DIC
Describe the later stages of sepsis.
Burned out inflammatory and immune responses.
Immune hypo-reactiveness and immune paralysis
What happens in the non-progressive stage of shock?
Compensatory mechanisms maintain cardiac output and blood pressure, perfusion of vital organs.
Examples of compensatory mechanisms that play a role in the non-progressive stage of shock
Baroreflexes Sympathetic NS, Catecholamine release Renin-Angiotensin Axis ADH Tachy, Peripheral Vasoconstriction, Pallor H2O Conservation
What happens in the progressive phase
Anerobic Glycolysis –> Metabolic Acidosis –> low pH retards vasomotor response –> arterial dilation –> blood pooling in microvasculature –> decreased CO
What happens in the irreversible phase of sepsis?
Survival not possible
Lysosomal Enzyme release
NO synthesis causes low myocardial contractility
Ischemic bowel and release of gut bacteria into bloodstream
Most commonly seen symptoms of hypovolemic and cardiogenic shock
Hypotension
Weak, Rapid Pulse
Tachypnea
Cool, Clammy, Cyanotic Skin
Most commonly seen symptoms of septic shock
Warm, Flush skin from peripheral vasodilation
Most commonly seen symptoms of anaphylaxis
Bronchoconstriction and Edema
Urticaria
Which two kinds of shock are most reversible?
Hypovolemic and Anaphylactic
Which is least reversible?
Cardiogenic
What is DIC?
Sudden or insidious development of numerous fibrin thrombi within the microvasculature. Consumption of clotting components later leads to widespread hemorrhaging.
Mechanism of DIC
Rapid consumption of platelets, prothrombinen, f, actors V, VIII, X, platelets and fibrin.
Fibrin –> Anoxia/Hypoxia –> Coagulation Necrosis
No platelets –> Hemorrhage
Synonym for DIC
Consumption Coagulopathy
Pathologic findings of DIC
Widespread Fibrin Thrombi
Diffuse Circulatory Insufficiency
Brain, Lungs, heart, Kidneys
Inc. D Dimer and Hemorrhage
Difference between Septic Shock vs. DIC
- Degree of Activation of Endothelial Cells
- Degree of activation of coagulation cascade
- Severe septic shock –> DIC
Clinical Settings to look for Shock in.
Sepsis, Trauma, Malignancy, Obstetric calamities, vascular abnormalities, hepatic failure, severe toxic or immunologic reactions
Severe toxic or immunologic reactions associated with shock
Snake Bites
Transfusion reactions
Recreational drugs
