Shock Flashcards
What are three reasons for hypoperfusion?
Inadequate pump
Inadequate fluid
Inadequate container
What are the five aspects of an inadequate pump that cause hypoperfusion?
Inadequate preload Inadequate stroke volume Inadequate cardiac output Inadequate heart rate Excessive afterload
What is the aspect of inadequate fluid that causes hypoperfusion?
Hypovolemia
What are the two aspects of an inadequate container that cause hypoperfusion?
Inadequate systemic vascular resistance
Over dilation
How does shock affect the cellular level?
It causes a state of acute nutritional insufficiency for oxygen and other essential substrates, resulting in cellular anoxia, cellular dysfunction and eventually, cell death
What is the 60-40-20 rule?
60% of the body weight is water
40% of body weight is intracellular fluids
20% of body weight is extracellular fluid
What is stroke volume?
It is the amount of blood released from the heart per beat
What is the formula for cardiac output?
Cardiac output = stroke volume x heart rate
CO = SV x HR
What is cardiac output?
It is the amount of blood circulated from the heart in a minute
What are three principle factors that affect cardiac output?
Preload
Afterload
Myocardial contractility
What is preload?
It is the amount of blood delivered to the heart during diastole
What is preload dependent on?
Venous return
What happens if there is an increase in preload?
There is an increase in stroke volume
What is afterload?
It is the pressure at which the ventricle pumps against
With afterload, when is blood ejected?
Only after the resistance is overcome
What is afterload dependent on?
The degree of peripheral arterial vasoconstriction
What is myocardial contractility? (2)
The force generated by the myocardium on contraction
Remember Starling’s Law (the rubber band theory)
What is the formula for blood pressure?
Blood pressure = cardiac output x peripheral vascular resistance
What may peripheral vascular resistance be also seen as?
Systemic vascular resistance (SVR)
What is blood pressure?
THe resistance of blood flow by the force of friction between the blood and walls of the vessels
What is blood flow?
Systemic vascular resistance is dependent on the internal diameter of the vessels and viscosity of blood
What two vessels do not significantly change diameter?
Aorta
Arteries
How large can the arterioles change their lumen?
Factor of 5
What are baroreceptors?
They are sensory fibers located in the aortic and carotid tissues
What do the baroreceptors help control?
They help control the BP by using two negative feedback mechanisms
What are the two negative feedback mechanisms used by the baroreceptors?
Lower BP in response to increased arterial pressure
Increase BP in response to decreased arterial pressure
What are two systemic pressures?
Venous
Arterial
What does the venous systemic pressure control?
Venous system constriction increases preload and stroke volume
What does the arterial systemic pressure control?
Arterial system constriction increases afterload and BP
What are the four components of microcirculation?
It is a capillary network
It is responsive to the needs of local tissues
It will adjust to supply/bypass tissues in need/or without need
Utilizes the pre and post capillary sphincters to facilitate these needs
What are ten affects on microcirculation?
Local control by tissues Nervous control of blood flow Baroreceptors Chemoreceptors CNS ischemia response Hormonal response Adrenal-medullary response Renin-Angiotensin-Aldosterone mechanism Vasopressin Reabsorption of tissue fluid
What is the function of oxygen?
It bends to hemoglobin and diffuses across the capillary membrane
What is the normal percentage of hemoglobin that is saturated by oxygen?
97-100%
What is Fick’s principle?
It recognizes the five conditions required for effective movement of oxygen within the body
What are the five conditions of Fick’s principle?
Adequate FiO2 Appropriate O2, diffusion from blood to the capillaries Adequate number of RBC's Proper tissue perfusion Effective tissue offloading
What are the four Weil-Shubin classifications of shock?
Distributive
Hypovolemic
Cardiogenic
Obstructive
What is psychogenic shock? (2)
It is relative hypovolemia due to severe vasodilation
It is caused by sudden and temporary sympathetic nervous system failure
What is neurogenic shock? (5)
AKA Spinal shock
Massive relative hypovolemia due to severe vasodilation
Damage caused to the nervous system inhibiting its involuntary/voluntary control of homeostasis
Sudden loss of sympathetic tone to the smooth muscles of the vessels below the point of injury
Without constant stimulation widespread relaxation of these muscles causes a decrease in PVR and a drop in BP
What is respiratory shock? (6)
Airway obstruction Hypoventilation Toxic inhalation Severe pulmonary edema Exacerbation COPD Multi-lobe bilateral pneumonia
What is hypovolemic shock? (3)
Inadequate perfusion of tissues caused by a volume deficiency other than blood
AKA third space loss
Severe dehydration: diarrhea/vomiting, peritonitis, heat exhaustion, severe burns
What is hemorrhagic shock? (2)
Internal/external hemorrhage resulting in hypovolemia and a systemic reduction in tissue perfusion
Mortality rate dependent on etiology, early recognition, and aggressive intervention
What is cardiogenic shock? (3)
Failure of the pump to supply O2 rich blood to the tissues
Potentially a combination shock, depending on the etiology: Massive AMI, Valvular insufficiency, Lethal dysrhythmia, Cardiac arrest
Has a 60-90% mortality rate
What is metabolic shock?
It is shock that is a result of a change in the chemistry of the endocrine system in the body
What are some causes of metabolic shock? (7)
Insulin shock Diabetic ketoacidosis Adrenal gland failure Thyroid failure Pituitary gland failure Renal failure Toxic ingestion
What is septic shock? (3)
Massive infection and toxin production resulting in the inability of the cell to exchange O2/CO2 resulting in cellular death
Relative hypovolemia due to pool of blood in extremities
1 month morality rate 35-45%
What is the progression of shock? (4)
Follows a sequence of stages related to changes in capillary perfusion and cellular necrosis
Various shock states may interrelate clinically to produce a mixed picture
Hypovolemic shock may lead to acidosis and result in cardiogenic shock
Septic shock may lead to hypovolemia as a result of microbal toxins, cytokines, and capillary permeability
What are the four stages of shock?
Initial stage of shock
Compensatory stage
Progressive stage
Refractory stage
What happens in the initial stage of shock? (3)
Cellular changes occur in response to shock
Anaerobic metabolism due to the lack of oxygen
Clinical signs not detectable
What happens in the compensatory stage of shock? (3)
Neural compensation: baroreceptors in aortic and carotid sinus are stimulated by a drop in MAP, sympathetic nervous system stimulated via vasomotor and cardiac centers of the medulla, catecholamine response causes arteriole constriction, venous reservoir constriction, inotropic and chronotropic effect on the heart
Hormonal compensation causes the RAAS system to start
Chemical compensation, increased respiratory rate to clear CO2
What happens in the progressive stage of shock? (2)
Compensatory mechanisms not effective
Severe hypoperfusion causes MODS