HTHSCI 1H06 B Lecture 6: Shock Module Notes
22 Jun 2018
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Department
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Professor
SHOCK
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Shock
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(deft failure of cardiac system to deliver sufficient oxygen and nutrients to meet the metabolic demands of the tissues in the body
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results in widespread impairment of cellular metabolism and tissue function
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Although shock is classified into different types (cardio genlc ,hypovolemic ,obstructive and distributive ),all types of shock are characterized by decreased
oxygen delivery and 1or increased tissue for oxygen Primary function of cardiovascular system
is to deliver oxygen and
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death may occur at a result of multiple organ failure nutrients to tissue .
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t's accomplished by generating co which supports
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Shock can be seen as an imbalance In oxygen supply vs tissue demand BP ,and ultimately tissue perfusion
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Challenge Is recognizing cause and selecting appropriate intervention
hat Determines 02 Delivery ?
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Blood Pressure
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to perfuse tissue wl blood you need 9BP to keep blood moving
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Bp =Cox SVR
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Without afunction gheart you have no CO ;and it no vascular resistance there's no pressure
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too much SVR can generate huge BP + as blood vessels constrict
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less of it gets to the tissues
2Systemic Vascular Resistance -radius contribute most to SVR
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SVR =(Viscosity xlength)/Radl@ it Ris halved .WR increases by afactor of 16
3Cardiac Output
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ldett Volume of blood pumped out of the heart each minute
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(o=svx HR
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HI #of beats /minute
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which is regulated by autonomic input
4Stroke volume
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ldett amount of blood pumped out of the heart Ibeat which is regulated by preload ,at Hnoad ,and contractility
>Preload :the amount of Alling of ventricles during diastole
•Stretching stimulates contraction ,which
TSV
•Preload is low in hypwolemic shock ,resulting in tSV and CO
>Ater load :Pressure ventricles must overcome before blood can be injected into the aorta or pulmonary trunk
•As after load 4Ihypertension),Svt
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Contractility :the forcefulness at which the heart beats
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the move forceful ,the more pressure ,the more blood ejected ,:.PSV
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ropes :any factor that TCat entry into cardio myocytes which Improve contractility 1epinephrine ,TH ,glucagon )
5Oxygen Content
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contributing factors include partial pressure of oxygen and [hemoglobin]
>differences in partial pressure more 02 from airway to blood ,and from blood to tissue
>98.5% of 02 are bound to arythwcyks ,and 1.5% is dissolved in the liquid medium
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Iv In hemoglobin levels Ianemia ),to Oxygen carrying capacity of blood
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respiratory disorders tpartial pressure
in lungs resulting in lv oxygen content + ablood How to lungs toxygen content
hat Increases Oz Demand ?
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Increased Basal Metabolic Rate
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BMR governs rate at which oxygen is consumed by cells
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regulated by thyroid hormone
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BMR In with hyperthyroidism ,exercising ,have fever
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Infection IFever
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Immune Cell signaling molecules ,tell hypothalamus to change set point for core temperature ,which causes immune cells Abecome move
metabolically active
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4also affects other tissues causing them to consume more oxygen at rest
•Increased work of organs 1heart + lungs)
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kidneys tbrain consume lots of oxygen at rest ,which is necessary to generate ATP to Keep ion pumps running In neurons and renal
tubular cells so that he can generate electrical impulse and get rid of waste
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Skeletal muscle consumes lots of oxygen when its being used
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Cardiac muscle Heart )+skeletal muscle (lungs )consume asignificant amount of oxygen at rest
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Agitation or Pain
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Increase in HR ,RR ,clenched skeletal muscles which 4oxygen consumption at rest
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what about the heart ?
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Increased workload HNS,Tpreload /after load ,physical activity ,stress etc )=Increased oxygen demand
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4Oxygen demand in aheart that is damaged or experiencing Poor perfusion may further damage it
Cellular alterations in Mock Inadequate blood flow
•aerobic respiration :breaking down glucose in presence of oxygen /to organs \
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yell As 36 ATP /glucose
Cardiac depression
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anaerobic respirators :ATP is generated from glucose in the absence of oxygen ^
THSUY hypoxia
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YLHAJ ZATPI glucose tlactic acid |^
Atp deficit as it is consumed more than generated and cells begin to run down Metals ""9¥
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the vicious Cycle in Shock Lactic acid accumulation +fall in pH
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•The heart itself must be adequately perused to stay alive
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If cycle is not interrupted death will occur
Body Responses to Shock
Initial stage of shock
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1oxygen delivery or 4in tissue demand =Cellular alterations resulting in the accumulation of lactic acid
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May or may not be any overt signs or symptoms Ot shock
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Compensatory stage of shock
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Neural ,hormonal and chemical responses designed to improve tissue perfusion and oxygen perfusion
3Progressive stage of shuck
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Occurs It compensatory mechanisms are unsuccessful at Improving perfusion
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multi organ failure Ikidney ,liver ,Gl tract )
4Refractory stage of shock
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As organ damage has become extensive and significant ,permanent damage to myocardium and other tissues occurs
