Shock and Hypoperfusion Flashcards
How can the size of blood vessels cause shock?
If blood vessels become too dilated, the normal blood volume cannot adequately perfuse the body because systemic pressure becomes too low.
How many litres of blood does the average person have circulating in their body at any given time? (assume adult human, not pregnant)
5-6L of blood per person.
How much blood can an adult patient lose before we might notice a change in blood pressure? What stage of shock would this indicate?
An average adult patient can lose up to 30% of their total blood volume before they can no longer maintain their BP and they begin to show signs of decompensated shock.
What is the difference between compensated shock and decompensated shock?
Compensated: The Pt is still able to maintain their BP through increased HR
Decompensated: The Pt can’t maintain their BP anymore and will begin to experience decreased LOC and other symptoms trending towards cardiac arrest
A child has lost a fair amount of blood and is now presenting with shortness of breath, cool and clammy skin, and delayed capillary refill. Their LOC is normal. Are they in compensated or decompensated shock?
Compensated shock
An adult patient has lost a fair amount of blood and is now presenting with laboured breathing, dilated pupils, and pale/clammy skin. When you assess their GCS you find they are 2-4-5: 11. Are they in compensated or decompensated shock?
Decompensated shock
An adult patient has lost a fair amount of blood and is now presenting with nausea, thirst, and weak radial pulses. They appear cognitively normal but anxious. Are they in compensated or decompensated shock?
Compensated shock
What is cardiogenic shock? Give at least one example of a mechanism which would cause this.
The heart fails to pump out enough blood. This could be for a variety of reasons including (but not limited to):
- Inadequate perfusion of the heart muscles (M.I.)
- Chest trauma
- Pulmonary embolism (can also be obstructive shock)
What is obstructive shock? Give at least one example of a mechanism which would cause this.
The heart is pumping but blood flow is obstructed. This could be for a variety of reasons including (but not limited to):
- Pericardial tamponade
- Tension pneumothorax
- Embolism
- Aortic stenosis
- Tumours
What is hypovolemic shock? Give an example of a mechanism which would cause this.
The heart pumps blood, but there is not enough blood volume to perfuse the body. This could be a result of:
- Traumatic injury causing blood loss from vascular system
- Dehydration (Ex: excessive diarrhea, sweating, etc.)
What is distributive shock? Give at least one example of a mechanism which would cause this.
The heart pumps blood, but excessive vascular dilation lowers BP and impairs perfusion to the body. This could be for a variety of reasons including (but not limited to):
- Sepsis
- Anaphylaxis
- Neurogenic shock
- Endocrine shock
- Sometimes burns
Injury to which part of the spine can cause neurogenic shock. Why?
Cervical vertebrae 3, 4, and 5. The brain can no longer communicate with the heart, diaphragm and vascular system to maintain homeostasis.
What simple equation allows us to calculate a person’s blood pressure?
Cardiac output x peripheral resistance = blood pressure
What does the term “afterload” mean in the context of the heart and vascular system?
The amount of pressure the heart needs to exert in order to eject blood from the ventricles.
How are afterload and blood pressure related? Are they directly correlated? Inversely correlated?
Afterload and blood pressure are directly correlated because as afterload increases, BP also increases. The inverse is also true so that when afterload decreases, BP also decreases.
True or False: Blood pressure can only decrease if both cardiac output and/or peripheral resistance decrease.
True. For blood pressure to decrease there needs to be a decrease in either or both of cardiac output and peripheral resistance. This is because Blood Pressure = Cardiac Output x Peripheral Resistance
What is the difference between “Cold” shock and “Hot” shock? Answer in terms of cardiac output and peripheral resistance.
Cold: low cardiac output causes peripheral cyanosis
Hot: low peripheral resistance maintains warm extremities despite shock symptoms
How long can the central nervous system survive without adequate perfusion?
The brain and spine can only survive approximately 4-6 minutes without adequate perfusion.
What is the function of baroreceptors in the vascular system? Where are they primarily found?
Baroreceptors detect pressure and pressure changes in circulation. They are primarily found in the aortic arch and carotid arteries.
What is the function of chemoreceptors in the vascular system? Where are they primarily found?
Chemoreceptors detect changes in pH throughout the circulatory system. They are primarily found in the aortic arch and carotid arteries.
Give at least 2 examples of patient demographic categories which would be at especially high risk of developing shock.
Any of:
- Trauma PTs
- Elderly
- Pediatric
- Pregnant
- Pts experiencing massive M.I.
+ Any more you can justify!
Why are the acids and waste products which accumulate in the late stages of shock especially harmful?
Because they can act as potent vasodilators, decreasing the perfusion of vital tissues such as the brain and heart.
The Weil-Shubin classification of shock divides the 4 primary mechanisms of shock into peripheral and central shock. Which mechanisms fit into each category?
Peripheral shock: Hypovolemic, Distributive
Central shock: Cardiogenic, Obstructive
By what 2 mechanisms does the Renin-Angiotensin Aldosterone system attempt to increase blood pressure?
- Vasoconstriction
- Fluid reabsorption
