NURS 208: TOPIC 7 - PERFUSION

What is perfusion?

It is the passage of blood from 1 point to another in the body, delivering oxygen-rich blood to tissues & organs through the circulatory system.

What does perfusion accomplish for the cells?

It moves blood with oxygen and nutrients to and from the cells so they can function properly.

Why is perfusion important?

It ensures cells receive oxygen and nutrients and that waste products are removed.

Why is good perfusion essential?

It is necessary to maintain healthy organ and tissue function.

What are the 3 major problem areas that can affect perfusion?

Heart pump, vasculature pipes, and fluid volume.

What conditions can compromise the heart’s ability to pump effectively?

Heart failure, myocardial infarction, & arrhythmias.

What happens when cardiac output is poor?

Reduced blood flow to vital organs leading to inadequate perfusion and possible tissue damage.

What must the vasculature (pipes) be like to maintain normal blood flow?

Open, elastic, & able to regulate resistance.

What can happen to blood vessels that interferes with perfusion?

They can become too constricted, too dilated, or blocked by clots or plaques.

How do hypertension and vascular disease affect the pipes?

They impair the vessels’ ability to regulate blood flow.

What happens when blood vessels are narrowed or obstructed?

Reduced blood flow to tissues leading to inadequate perfusion.

What happens when blood vessels are overly dilated?

Blood pressure drops and circulation becomes insufficient, causing inadequate perfusion.

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What happens in hypovolemia?

Low fluid volume makes blood more concentrated and lowers blood pressure, causing inadequate perfusion.

What happens in hypervolemia?

Blood becomes diluted, causing edema & impaired oxygen delivery to tissues.

What conditions can alter fluid status?

Dehydration, hemorrhage, fluid overload, kidney failure, and heart failure.

What pump-related conditions affect perfusion?

Myocardial infarction, congestive heart failure, and dysrhythmias because they impair the heart’s ability to pump effectively and reduce blood flow.

How does a myocardial infarction affect perfusion?

It damages heart muscle from a blocked artery, preventing the heart from pumping adequately.

How does congestive heart failure affect perfusion?

The heart cannot pump blood effectively, causing poor circulation and fluid buildup in tissues.

How do dysrhythmias affect perfusion?

Abnormal heart rhythms reduce the heart’s ability to pump efficiently, decreasing blood flow to the body.

What pipe-related conditions affect perfusion?

Hypertension, diabetes mellitus, arteriosclerosis, atherosclerosis, and septic or anaphylactic shock because they damage vessels or cause extreme vasodilation.

How does hypertension affect perfusion?

It damages vessel walls, causing arteries to become narrow or less elastic, reducing blood flow.

How does diabetes mellitus affect perfusion?

It contributes to vessel damage and decreases efficient circulation.

How do arteriosclerosis and atherosclerosis affect perfusion?

Arteries become stiff or develop fatty plaques that narrow the vessel and restrict blood flow.

How do septic and anaphylactic shock affect perfusion?

They cause severe vasodilation, leading to a major drop in blood pressure and impaired perfusion.

What fluid-related conditions affect perfusion?

Hypovolemia from low oral intake, vomiting, diarrhea, hemorrhage, & dehydration; hypervolemia from increased oral intake, rapid IV infusions, CHF, & CKD.

How does hypovolemia affect perfusion?

Low fluid volume decreases blood volume, leading to lower blood pressure and inadequate tissue perfusion.

How does hypervolemia affect perfusion?

Excess fluid increases blood volume and can overwhelm the heart, especially in CHF or CKD, affecting circulation.

How does hemorrhage affect perfusion?

Severe blood loss decreases blood volume, causing inadequate perfusion.

How does dehydration affect perfusion?

It lowers total body fluid, decreasing blood volume & blood pressure, which reduces tissue perfusion.

What is the importance of proper fluid balance?

Ensures homeostasis, allows organs to function effectively, & helps the body adapt to internal & external changes.

What must be true about body fluid for balance to be maintained?

There must be enough fluid and it must be in the right concentration.

What happens when fluid volume is too low?

Blood becomes thicker & less mobile, & nutrients/electrolytes become more concentrated.

What is an example of an electrolyte change seen with low fluid volume?

Sodium (Na⁺) levels become high.

What happens when fluid volume is too high?

Nutrients and electrolytes become diluted, increasing the risk of fluid volume overload.

What is an example of an electrolyte change seen with high fluid volume?

Sodium (Na⁺) levels become low.

Do healthy adults typically have stable or unstable fluid levels?

Stable, with a consistent fluid level.

How much do fluid levels normally fluctuate in a healthy adult per day?

No more than 0.2 kg (0.5 lb).

What does water transport to and from the cells?

Nutrients to cells; wastes from cells.

How does water help with waste elimination?

Fluids, urine, and sweat remove toxins, excess salts, and excess nutrients.

What substances does water help transport in the bloodstream besides nutrients?

Hormones, enzymes, blood platelets, RBCs, WBCs.

How does water support cellular metabolism?

Facilitates chemical reactions and proper cellular functioning.

What role does water play as a solvent?

Dissolves electrolytes and nonelectrolytes.

How does water help maintain blood volume and pressure?

Through plasma volume.

How does water help maintain normal body temperature?

Sweating and evaporation cool the body and stabilize internal temperature.

How does water assist digestion and elimination?

Saliva and gastric juices help break down food and promote elimination.

How does water act as a tissue lubricant?

Provides lubrication such as synovial fluid in joints.

What are the two main compartments of body fluid?

Intracellular fluid (ICF) and extracellular fluid (ECF)

Where is intracellular fluid (ICF) located?

Inside the cells

What is the main function of intracellular fluid?

To maintain cell shape and support cellular processes

What are the key electrolytes found in intracellular fluid?

Potassium, magnesium, and phosphorus

What are the functions of the electrolytes in intracellular fluid?

They are necessary for muscle function, nerve signals, and energy production within cells

Where is extracellular fluid (ECF) located?

Outside the cells

What fluids are included in extracellular fluid?

Intravascular fluid (such as cerebrospinal fluid, synovial fluid, digestive secretions), interstitial fluid (fluid surrounding cells in tissues), and plasma (the fluid portion of blood)

What is the main function of extracellular fluid?

To transport nutrients, oxygen, and waste products between the cells and bloodstream

What are the key electrolytes found in extracellular fluid?

Sodium, chloride, and bicarbonate

What are the functions of the electrolytes in extracellular fluid?

They maintain fluid balance, blood pressure, and acid-base balance in the body

Why is fluid balance between ICF and ECF important?

Because it is crucial for maintaining homeostasis

What percentage of a healthy person’s body weight is total body water?

50% to 60%.

Which age group has more body fluid and extracellular fluid compared to adults?

Infants.

Why are infants more prone to fluid volume deficits?

Because they have a higher amount of body fluid & ECF, making them more vulnerable to dehydration & fluid volume disruptions.

How do biologic sex and fat cells affect total body water?

Women and people with more fat cells (including those who are obese) have less body water.

What is the primary solvent in the body?

Water

What is a solvent?

A liquid that dissolves other substances

What is the role of a solvent in the body?

To hold substances in solution

What is a solute?

A substance that is dissolved in a solution

What are common solutes in the body?

Electrolytes, nutrients, vitamins, gases, waste products

What are examples of electrolytes as solutes?

Sodium, potassium, chloride, bicarbonate

What nutrients act as solutes?

Glucose and amino acids

What gases act as solutes?

Oxygen and carbon dioxide

What waste products act as solutes?

Urea and creatinine

What is the function of solutes in fluid balance?

To regulate osmotic pressure and maintain hydration

What is osmosis?

Movement of water from an area of lower solute concentration to higher solute concentration until equilibrium is reached

What is diffusion?

Movement of solutes from an area of higher concentration to lower concentration through a solvent

What is active transport?

Movement of substances across the cell membrane from lower solute concentration to higher concentration using energy

What is capillary filtration?

Movement of fluid through a permeable membrane from an area of higher pressure to lower pressure

What does osmolality deal with?

It deals with the concentration of solute particles that are dissolved in a fluid, such as blood, plasma, or urine.

What does osmolality measure in the body?

It measures the pulling power of solutes on water in the body.

How does osmolality indicate the pulling power of solutes?

It indicates the ability of solutes, like electrolytes and nutrients, to attract water.

What happens when the osmolality of a solution is high?

It means the solution has a greater ability to draw water toward it.

Give an example of osmolality affecting water movement.

A high level of sodium outside the cell causes water from inside the cell to move toward the sodium outside the cell.

What determines the pulling power of a fluid?

It is determined by the total solute concentration within a fluid compartment.

How does water move in relation to osmolality across a semipermeable membrane?

It moves from areas of lower osmolality to areas of higher osmolality to achieve balance.

What does osmolarity measure?

It measures the number of solute particles per liter of solution.

What does the concentration of an osmotic solution, such as IV fluids, indicate?

The osmolarity of the solution.

What characteristic do solutions with osmolarity have?

They have pulling power, meaning they can draw water across semi-permeable membranes.

How does solute concentration affect osmolarity?

The higher the concentration of solutes, the higher the osmolarity.

What happens when IV fluids are administered in terms of fluid movement?

Fluid is pulled into or out of the intravascular space through a cell’s semi-permeable membranes.

What occurs if there is an imbalance of osmotic pressure on either side of a cell membrane?

Osmosis attempts to equalize the osmotic pressure.

What is colloid osmotic pressure (oncotic pressure) and what role does it play in the body?

Colloid osmotic pressure, also called oncotic pressure, influences osmosis and helps maintain fluid balance between blood vessels and surrounding tissues (interstitial space).

Which plasma proteins are primarily responsible for exerting oncotic pressure?

Plasma proteins, mainly albumin, exert colloid osmotic or oncotic pressure in the plasma, pulling water into the circulatory system.

What can result from low oncotic pressure in the blood?

Low oncotic pressure can lead to hypovolemia (low blood volume) or edema (fluid accumulation in tissues).

What is hypoalbuminemia and how does it affect oncotic pressure?

It is low albumin in the blood, which decreases oncotic pressure.

• It can be caused by under-consuming protein in the diet, liver disease, or kidney disease.

How does oncotic pressure prevent excess fluid from accumulating in tissues?

The presence of large protein molecules in the blood creates an osmotic gradient, causing water to move from areas of lower protein concentration (interstitial fluid) to areas of higher protein concentration (blood plasma), preventing excess fluid from leaking into tissues and reducing the risk of edema.

What is the mechanism by which fluids are pulled back into the circulatory system from interstitial spaces?

Oncotic pressure from plasma proteins pulls water from the interstitial spaces back into the vasculature (circulatory system), maintaining fluid balance.

What is diffusion?

It is the movement of ions and molecules from areas of high concentration toward areas of low concentration until equilibrium is reached.

Is diffusion an active or passive process?

It is a passive process.

Give an example of diffusion in the human body.

The movement of oxygen and carbon dioxide during oxygenation.

What is filtration in the context of fluid movement in the body?

It is the process by which water and diffusible solutes move together in response to fluid pressure.

What happens at the arterial end of the capillary during filtration?

Hydrostatic pressure is higher than oncotic pressure, pushing fluids and nutrients out of the capillaries into surrounding tissues.