NURS 2090 Lecture Notes - Peripheral Edema, Vasodilation, Low-Density Lipoprotein
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Published on 16 Apr 2013
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Altered Perfusion
Perfusion - Forcing blood or other fluid to flow through a vessel and into the vascular bed of
tissue to provide oxygen *affects every system of the body
Requirements for Effective Perfusion
Adequate ventilation and diffusion: ability to breathe in and transport O2
Intact pulmonary circulation: lower part of lung – low surface tension/max blood flow/O2
Perfusion cannot occur without inhalation/diffusion of O2.
O2 enters lungs – crosses alveolar cap junction – pulm circ
∆ requires ventilation (intake of O2), Perfusion (movement of O2).
Ventilation-perfusion ratio (0.8:0.9) indicates that the rate of ventilation is slightly less
than the rate of perfusion
The largest volume of ventilation- perfusion is the lower lungs where they are most easily
inflated due to the low surface tension of the alveoli, which allows ventilation, and
where the perfusion is best due to BP allowing max blood flow (also has gravity
working for it!)
Adequate blood volume and components
Adequate cardiac output: optimal SV, HR, heart rhythm
Intact cardiac control center: needed to regulate HR and force of contractions
Intact receptors: for feedback
Intact parasympathetic and sympathetic nervous systems
Intact cardiac conduction
Intact coronary circulation: maintains perfusion to cardiac structures RCA
Intact systematic circulation
Adequate tissue uptake of oxygen
Types of circulation:
Circulation: effective circulation depends on patency (the condition of not being blocked or obstructed)
of the blood vessels and on the adjustments of the microcirculation to meet the demands of the tissues.
1. Pulmonary- circulation through the lungs provides the ability to transfer O2 from the
environment to the body
includes the right side of the heart and pulmonary arteries/capillaries and veins
pulmonary veins carry oxygenated blood to the left side of the heart
pulmonary artery carries deoxygenated blood to the lungs
Pulmonary circ works at a lower pressure than systemic b/c it moves blood slower
through the lungs for maximal gas exchange
2. Systemic–distributed to body tissues
this system involves all of the arteries and veins except ones in the pulmonary
circulation.
Functions at a higher pressure to work against resistance to get to peripheral tissues
Monitored by the left side of heart (esp. left ventricle which has strongest pumping)
3. Cardiac– this system includes the right coronary artery (RCA), the left coronary artery (LCA)
and the left anterior descending coronary artery (LAD) which perfuse the right and left sides of
the myocardium (muscle) of the heart.
Coronary arteries:
1. RCA: supplies blood to the right ventricle
supplies 25-35% of blood to the left ventricle
supplies the SA node
2. LAD: branches off of the LCA
supplies 45-55% of blood to the left ventricle/provides much of the blood flow to the left
ventricle which enables the propulsive force of ejection
known as the “widow-maker” because blockage of this artery is particularly associated
with mortality
3. LCA: main coronary artery
feeds blood to the left side of the heart
Pericardium: outer covering of the heart
holds heart in place/contains receptors that help regulate BP and HR
1st line of defense against infection and inflammation
contains pericardial fluid (lubrication)
Myocardium: thick muscular layer
thickest at left ventricle (works the hardest – systemic circulation)
hypertrophy occurs here as workload increases
Endocardium: inner lining of the heart, continuous layer of endothelium
Cardiac Cycle – one contraction (systole: begins with closure of AV valve, ventricles have greater
pressure and eject blood, lub) and one relaxation (diastole: ventricles relax, pressure greater in
aorta/pulm artery, Aortic/pulm valves close and make the dub)
AV Valves: bicuspid (mitral), tricuspid
Contractions – rely on the passage of ions and electrical impulses from one myocardial cell to another.
These are generated through action potentials. Two major types of action potentials; slow and fast, work
in an organized manner
Phases of action potential:
1. Rapid depolarization: fast Na channels open and the rapid influx of Na into the cell cause it to
become positively charged
2. Early repolarization: fast Na channels close
3. Plateau – slow Na and Ca channels open and Na and Ca slowly enter the cell
4. Rapid repolarization: a regrouping phase in which the cell membrane becomes polarized with a
positive charge on the outside of the cell and a negative charge inside the cell. The cell also
becomes permeable to K and it exits the cell.
5. Resting phase
PQRSTU Waves: electrical activity imposed by ions on cardiac cells can be measured using ECG/EKG
P = depolarization of atria via SA node
PQ interval = depolarization of AV nodes + bundle fibers
QRS = depolarization of ventricles
T = repolarization of ventricles
U = repolarization of Purkinje fibers
SA Node: pacemaker/ generates rhythmic impulses in atria/stimulated by slow response to NA and Ca
channels opening
AV Node: connects impulses between atria and ventricles/slow to allow atria to empty blood into
ventricle/generates impulses that travel to bundle of His and culminate in Purkinje fibers
Cardiac Output: depends on stroke volume (SV) and heart rate (HR)
CO = SV x HR
average CO is 3.5 – 8.0 L/min (can increase 4x during exercise)
Document Summary
Perfusion - forcing blood or other fluid to flow through a vessel and into the vascular bed of tissue to provide oxygen *affects every system of the body. Adequate ventilation and diffusion: ability to breathe in and transport o2. Intact pulmonary circulation: lower part of lung low surface tension/max blood flow/ o2. Perfusion cannot occur without inhalation/diffusion of o2. O2 enters lungs crosses alveolar cap junction pulm circ. Requires ventilation (intake of o2), perfusion (movement of o2). Ventilation-perfusion ratio (0. 8:0. 9) indicates that the rate of ventilation is slightly less than the rate of perfusion. Adequate cardiac output: optimal sv, hr, heart rhythm. Intact cardiac control center: needed to regulate hr and force of contractions. Intact coronary circulation: maintains perfusion to cardiac structures rca. Pulmonary veins carry oxygenated blood to the left side of the heart. Pulmonary artery carries deoxygenated blood to the lungs. Functions at a higher pressure to work against resistance to get to peripheral tissues.