Chapter 13 Shock Flashcards
perfusion
Perfusion is the means by which blood provides nutrients and removes cellular waste.
Adequate perfusion is required to provide cells oxygen and nutrients and remove waste products.
- Any compromise in perfusion can lead to cellular injury or death.
Poor perfusion (shock)
In cases of poor perfusion (shock), the transportation of carbon dioxide out of the tissues will become impaired, resulting in a dangerous buildup of waste products that may cause cellular damage.
Shock
Shock is a state of collapse and failure of the cardiovascular system that leads to inadequate circulation.
1. To protect vital organs, the body directs blood flow from organs that are more tolerant of low flow (such as the skin and intestines) to organs that cannot tolerate low blood flow (such as the heart, brain, and lungs).
2. Early recognition of the signs and symptoms of shock can save lives.
3. Shock is life threatening and requires immediate recognition and rapid treatment.
perfusion triangle
The heart (pump), blood vessels (container), and blood (content)
The cardiovascular system consists of three parts
The heart (pump), blood vessels (container), and blood (content)
Shock - The cardiovascular system consists of three parts
- The heart (pump), blood vessels (container), and blood (content).
a. These three parts can be referred to as the “perfusion triangle.”
b. When a patient is in shock, one or more of the three parts is not working properly.
Systolic pressure
Systolic pressure is the peak arterial pressure, or pressure generated every time the heart contracts.
Diastolic pressure
Diastolic pressure is the pressure maintained within the arteries while the heart rests between heartbeats.
Pulse
Pulse pressure is the difference between the systolic and diastolic pressures (systolic – diastolic = pulse pressure).
for example 120/80 (Systolic is 120 - Diastolic is 80) Pulse is 120 - 80 = 40
a. It signifies the amount of force the heart generates with each contraction.
b. A pulse pressure of less than 25 mm Hg may be seen in patients with shock.
Blood flow through the capillary beds is regulated by
the capillary sphincters, circular muscular walls that constrict and dilate
capillary sphincters
- These sphincters are under the control of the autonomic nervous system.
- Capillary sphincters also respond to other stimuli such as:
a. Heat
b. Cold
c. The need for oxygen
d. The need for waste removal - Regulation of blood flow is determined by cellular needs.
Perfusion also requires adequate:
- Oxygen exchange in the lungs
- Nutrients in the form of glucose in the blood
- Waste removal, primarily through the lungs
Oxygen, Nutrients, Waste removal
Mechanisms are in place to help support the respiratory and cardiovascular systems when the need for perfusion of vital organs is increase
- Includes the autonomic nervous system and hormones.
a. The sympathetic side of the autonomic nervous system, which is responsible for the fight-or-flight response, will assume more control of the body’s functions during a state of shock.
b. This response by the autonomic nervous system causes the release of hormones such as epinephrine and norepinephrine.
c. Hormones cause an increase in heart rate and in the strength of cardiac contractions, as well as vasoconstriction in nonessential areas, primarily in the skin and gastrointestinal tract (peripheral vasoconstriction).
d. This response causes all the signs and symptoms of shock in a patient.
The autonomic nervous is comprised of two parts
the sympathetic nervous system and the parasympathetic nervous system
sympathetic nervous system (fight-or-flight)
parasympathetic nervous system (coming effect - opposite of the sympathetic)
There are many different types of shock that result from three basic causes – what are the three Causes of Shock
pump failure, poor vessel function, and low fluid volume
What are the four types of Shock
A. Cardiogenic shock
B. Obstructive shock
C. Distributive shock
D. Hypovolemic shock
Cardiogenic shock
- Caused by inadequate function of the heart, or pump failure
- A major effect is the backup of blood into the pulmonary vessels.
- The resulting buildup of pulmonary fluid is called pulmonary edema.
- Cardiogenic shock develops when the heart cannot maintain sufficient output to meet the demands of the body.
a. Cardiac output is the volume of blood that the heart can pump per minute, and it is dependent upon several factors.
i. The heart must have adequate strength for the heart muscle to contract (myocardial contractility).
ii. The heart must receive adequate blood to pump (preload).
iii. The resistance to flow in the peripheral circulation must be appropriate (afterload).
Ventricular contraction
Ventricular contraction, also known as ventricular systole, is a phase of the cardiac cycle where the ventricles of the heart contract and eject blood into the aorta and pulmonary arteries. The process begins with the closure of the mitral and tricuspid valves to prevent backflow of blood into the atria, a phase known as isovolumic contraction. As the ventricles contract, pressure rises rapidly inside them, surpassing the pressure in the aorta and pulmonary arteries, which leads to the opening of the aortic and pulmonary valves, allowing the ejection of blood from the heart