Lecture 8: Shock Flashcards
How many liters of blood is in the body on average?
5L
What is the most common cause of death?
insufficient early resuscitation
The lack of perfusion to cells of the body can produce what?
anaerobic metabolism
Give an overview of shock.
Condition resulting from lack of adequate perfusion at cellular level
most commonly occurs due to circulatory failure
during compensatory phase, body attempts to maintain perfusion using its available compensation mechanism
during decompensation phase, body can’t keep up with demands
systems are sacrificed to maintain O2 supply to brain
initially reversible if treatment provided rapidly to prevent progression to irreversible organ dysfunction
What is the aerobic metabolism?
O2+Glucose ==> energy+ CO2+O2
Principle combustion process is the Krebs cycle (32ATP)
What is the anaerobic metabolism?
energy+ lactic acid + pyruvic acid
short duration/ less efficient
What is Fick’s Principle?
description of components necessary for adequate oxygenation of body cells (perfusion)
1. on-loading of O2 to RBC in the lung
2. Delivery of RBC to tissue cells
3. Off-loading of O2 from RBC to tissue cells
What is the importance of adequate oxygenation?
oxygen required for the majority of cellular energy production derived from krebs cycle and electron transport chain
metabolism with O2 = aerobic metabolism
metabolism without O2 = anaerobic metabolism
What are factors that can affect O2 delivery to tissues?
Cardiac output
available hemoglobin
O2 saturation (SpO2)
What is the metabolic rate of O2 (MRO2)?
Sum total of O2 needed to drive various tissue metabolic processes
metabolic O2 delivery
What is the arterial O2 delivery (DO2)?
Sum total of available oxygen delivery to the tissues
body approx 20-30% effective in extracting circulating O2
Comprised of 2 variables: cardiac output (CO) and arterial oxygen content (CaO2)
What are things that can adversely effect oxygen delivery?
Hypoxia
inadequate circulation
inadequate transport medium
cellular toxins
What leads to shock?
if the metabolic oxygen demands > metabolic oxygen supply = shock
What are the different organs tolerance ot ischemia?
Heart, brain, lungs 4-6minutes
Kidney, liver, GI tract 45-90min
Muscle, bone, skin 4-6hours
What is the progression of shock?
Compensatory defenses work well to a point
when defense mechanism can no longer overcome volume reduction BP decreases, going into decompensation
a patient with signs of compensation is already in shock not going into shock
Next stage after decompensated shock is death (irreversible shock)
What are the different types of shock?
Hemorrhagic
respiratory
neurogenic
psychogenic
cardiogenic
septic
anaphylactic
metabolic
What are the 4 ways that shock can occur in associated with failure of one or more components of the cardio-vascular system?
Hypovolemic (absolute hypovolemia)
Distributive shock (relative hypovolemia)
obstructive shock
cardiogenic shock
What causes hypovolemic shock?
external hemorrhage controlled or uncontrolled
internal hemorrhage
other cause of intravascular volume loss (diarrhea, vomiting, etc…)
Blood loss most common cause of shock in trauma patients
What are the characteristics of hypovolemic shock?
characterized by reduced intravascular volume
may occur with acute blood volume loss due to dehydration (loss of plasma)
Hemorrhage (loss plasma+ RBC), upsets the relationship of fluid volume to size of container balance
What is the difference between absolute hypovolemia and relative hypovolemia?
absolute= hemorrhagic cause, loss of blood
relative= non-hemorrhagic cause, blood volume intact but all vessels dilate so not enough blood to sustain them
What happens to the body with blood loss?
heart is stimulated, increased CO through release of epinephrine from adrenal glands
sympathetic system releases norepinephrine to decrease blood vessel size
this closes peripheral capillaries leading to anaerobic metabolism at cellular level
What can cause distributive shock (relative hypovolemia)?
neurogenic shock
medical causes (anaphylaxis, sepsis, overdose)
What are the characteristics of distributive shock?
vascular container enlarges without proportional increase in fluid volume
relatively less fluid will be available for size of container
the amount of fluid available to the heart as preload decreases and cardiac output falls
resistance to flow is decreased because of increased vessel size leading to decreased diastolic BP, net effect is decreased systolic and diastolic BP
What are the different kinds of distributive shock?
neurogenic shock
septic shock
systemic inflammatory response syndrome (SIRS)
anaphylactic shock
drug and toxin-induced shock
endocrine shock
psychogenic shock
What is neurogenic shock?
can occur when a cervical spine injury damages the spinal cord above where the nerves of the sympathetic nervous system exit
because of loss of sympathetic control vessels dilate below level of injury
What is spinal shock?
injury to the spinal cord that results in temporary loss of sensory and motor function
both neurogenic and spinal shock can happen at the same time
What is septic shock?
exhibits vascular dilation
cytokines, which are locally active hormones produced by WBC responding to infection cause damage to the wall of blood vessels, causing peripheral vasodilation and a leakage of fluid from the capillaries into the interstitial space
What is psychogenic shock?
Mediated through parasympathetic
Nervous system vagal nerve stimulation produces bradycardia
can also lead to transient peripheral vasodilation and hypotension
if severe enough: decrease cardiac output and then vasovagal syncope
What is a mechanical obstructive shock?
valvular disruption from a sudden forceful abdominal blow
What is pericardial tamponade?
fluid in pericardial sac will prevent heart from refilling completely during diastolic phase
What is a tension pneumothorax?
shifting of mediastinum away from injury compresses/kinks superior and inferior vena cava
decreased venous return to the heart
preload pumping efficiency decreases and shock is rapid
What is cardiogenic shock?
intracardiac cause of cardiac pump failure
intrinsic:
- problem within the heart
-cardiomyopathic (MI
- arrhythmic (efficiency of contractions)
- Contusion that may lead to cardiac muscle dysfunction
What are the stages of shock?
Pre-shock (compensated): body’s compensatory mechanisms are able to maintain some degree of tissue perfusion
Shock (decompensated): body’s compensatory mechanisms fail to maintain tissue perfusion (blood pressure falls)
End-organ dysfunction (irreversible): tissue and cellular damage is so massive that the organism dies even if perfusion is restored
What are the S/S you would expect to see when compensatory mechanisms fully engage?
Tachycardia
tachypnea
pupillary dilation
decreased capillary refill
pale cool skin
What S/S would you expect to see when compensatory mechanism fail?
Hypotension
Falling SpO2
Bradycardia
Loss of consciousness
Dysrhythmias
Death
What are complications of Shock?
Acute Respiratory distress syndrome (lung lining damage)
Acute renal failure (ischemic reaction)
Hematologic failure (coagulopathy)
Hepatic failure (liver ischemic reaction)
Multiple organ failure
Failure of 1 major body system
This leads to more shock
if all fail 100% mortality
What are the first symptoms of shock?
Increased heart rate
Increased respiratory rate
What should you do in pre-hospital management of shock?
deliver adequate O2 to produce enough energy to prevent or reverse anaerobic metabolism, thereby avoiding cellular death and ultimately patient death
How should trauma patients in shock be transported?
supine and neutral
Is elevation of feet recommended?
It is contraindicated for many reasons for example it may aggravate impaired ventilatory function by placing weight of abdominal organs on the diaphragm
Summarize Shock Treatment.
treat the underlying cause
establish and maintain airway
ensure adequate breathing
ensure adequate oxygenation
ensure adequate circulation and severe bleeding is stopped
reassure patient and provide warmth
minimize the pain
monitor vital signs
nothing by mouth
arrange rapid transport
