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NURS 347 Study Guide Questions And Answers Latest Update
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- Nursing.
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- Chamberlain College Nursing
NURS 347 Study Guide Questions And Answers Latest Update
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Solution 2024/2025Pepper
NURS 347 Study Guide Questions And Answers
Latest Update
Week 1 Content
Homeostasis, Body Fluid Shifts, Regulation of Water Balance
Review special gerontologic considerations related to fluid and electrolyte
balance.
the older adult has normal physiologic changes that increase susceptibility
to fluid and electrolyte imbalances. Structural changes to the kidneys and a
decrease in the renal blood flow lead to decreased glomerular filtration rate
and loss of the ability to concentrate urine and conserve water. Hormonal
changes include a decrease in renin and aldosterone and an increase in
ADH and ANP. Subcutaneous tissue loss and thinning of the dermis lead to
increased moisture lost through the skin and an inability to respond quickly
to heat or cold. Do not automatically attribute older patients' fluid and
electrolyte problems to the natural processes of aging. Throughout this
chapter are suggestions for adapting your assessment and nursing
interventions when caring for the older adult.
Understand how protein impacts fluid shifts. What would you expect to see
if a patient had a protein deficit?
Decrease in Plasma Oncotic Pressure
Fluid stays in the interstitial space if the plasma oncotic pressure is too low
to draw fluid back into the capillary. Low plasma protein content decreases
oncotic pressure. This can result from excess protein loss (renal disorders),
deficient protein synthesis (liver disease), and deficient protein intake
(malnutrition).
Elevation of Interstitial
Oncotic Pressure
Trauma, burns, and inflammation can damage capillary walls and allow
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plasma proteins to accumulate in the interstitial space. This increases
interstitial oncotic pressure, draws fluid into the interstitial space, and holds
it there.
Understand difference between hydrostatic pressure and oncotic pressure.
Hydrostatic pressure is the force of fluid in a compartment pushing
against a cell membrane or vessel wall. In the blood vessels, hydrostatic
pressure is the BP generated by the heart’s contraction. Hydrostatic
pressure in the vascular system gradually decreases as the blood moves
through the arteries until it is about 30 mm Hg in the capillary bed. At the
capillary level, hydrostatic pressure is the major force that pushes water out
of the vascular system and into the interstitial space.
Oncotic pressure (colloidal osmotic pressure) is the osmotic pressure
caused by plasma colloids (large molecules) in solution. The major colloids
in the vascular system contributing to osmotic pressure are proteins, such
as albumin. Plasma has large amounts of protein, while the interstitial space
has very little. Plasma protein molecules attract water, pulling fluid from the
tissue space to the vascular space. Under normal conditions, plasma oncotic
pressure is about 25 mm Hg. The small amount of protein found in the
interstitial space exerts an oncotic pressure of about 1 mm Hg.
Understand how the body regulates water balance.
Regulation of Water Balance
Many factors are involved in maintaining the finely tuned balance among
water intake, use, and excretion. For proper fluid balance, an average
healthy adult needs a daily water intake between 2000 and 3000 mL (Table
16.2). This amount replaces what the body loses in urinary output and
insensible losses. Oral fluid intake accounts for most of the water intake.
Water intake also includes water from food metabolism and water present in
solid foods.
Insensible water loss, which is invisible vaporization from the lungs and skin,
helps regulate body temperature. Accelerated body metabolism, which
occurs with increased body temperature and exercise, increases the amount
of water lost and may result in the need for additional water replacement.
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Do not confuse water loss through the skin with the vaporization of water
excreted by sweat glands. Insensible perspiration causes only water loss.
Excess sweating (sensible perspiration) caused by exercise, fever, or high
environmental temperatures may lead to large losses of water and
electrolytes.
Hypothalamic-Pituitary Regulation Water ingestion equals water loss in the
person who has free access to water, intact thirst and ADH mechanism, and
normally functioning kidneys. A body fluid deficit or increase in plasma
osmolality activates osmoreceptors in the hypothalamus. This stimulates
thirst and the release of ADH from the posterior pituitary gland. ADH acts on
the distal tubules and collecting ducts in the kidney by making them more
permeable to water. The result is increased water reabsorption from the
tubular filtrate into the blood and decreased excretion in the urine. Because
ADH is only able to regulate how much water the body holds onto, an intact
thirst mechanism is our main protection against developing dehydration or
hyperosmolality. Thirst causes us to increase the amount of water we drink.
Together these result in increased free water in the body, decreasing
plasma osmolality and restoring fluid volume. Many factors influence ADH
secretion and thirst. Decreased BP, nausea, pain, hypoglycemia, and
hypoxemia stimulate ADH release. In the postoperative patient, the stress
response to surgery and receiving analgesics and anesthesia cause ADH
release and decreased osmolality. The unconscious or cognitively impaired
patient is at increased risk for fluid deficit and hyperosmolality because of
an inability to express thirst and act on it. A dry mouth will cause a person
to drink, even when there is no body water deficit.
Renal Regulation
The primary function of the kidneys is to regulate fluid and electrolyte
balance by adjusting urine volume and the excretion of most electrolytes
(see Chapter 44). The kidneys filter the total plasma volume many times
each day. In the average adult, the kidneys reabsorb 99% of this filtrate,
producing around 1.5 L of urine per day. Under the influence of ADH,
aldosterone, and other hormones, selective reabsorption and secretion of
water and electrolytes in the renal tubules result in urine that is different in
composition and concentration from plasma. This process helps maintain
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normal plasma osmolality, electrolyte balance, blood volume, and acid-base
balance.
With severely impaired renal function, the kidneys cannot maintain fluid and
electrolyte balance. This condition results in edema, potassium and
phosphate retention, acidosis, and other electrolyte imbalances (see
Chapter 46).
Adrenal Cortical Regulation
Glucocorticoids and mineralocorticoids secreted by the adrenal cortex help
regulate water and electrolyte balance. The glucocorticoids (e.g., cortisol)
primarily have an antiinflammatory effect and increase serum glucose
levels. The mineralocorticoids (e.g., aldosterone) enhance sodium retention
and potassium excretion (Fig. 16.9). When sodium is reabsorbed, water
follows because of osmotic changes.
Aldosterone is a mineralocorticoid with strong sodium-retaining and
potassium-excreting capabilities. Decreased renal perfusion or decreased
sodium in the distal part of the renal tubule activates the renin-angiotensin-
aldosterone system (RAAS), resulting in aldosterone secretion. In addition to
the RAAS, increased serum potassium, decreased serum sodium, and
adrenocorticotropic hormone (ACTH) stimulate aldosterone secretion.
Aldosterone increases sodium and water reabsorption in the renal distal
tubules, decreasing plasma osmolality and restoring fluid volume. Cortisol is
the most abundant glucocorticoid. In large doses, cortisol has both
glucocorticoid (glucose-elevating and antiinflammatory) and
mineralocorticoid (sodium-retention) effects. Normally cortisol secretion is in
a diurnal or circadian pattern. Increased cortisol secretion occurs in
response to physical and psychologic stress. This affects many body
functions, including fluid and electrolyte balance (Fig. 16.10).
Cardiac Regulation
Natriuretic peptides, including atrial natriuretic peptide (ANP) and b-type
natriuretic peptide (BNP), are hormones made by cardiomyocytes. They are
made in response to increased atrial pressure (increased volume, such as
occurs in heart failure) and high serum sodium levels. They are natural
antagonists to the RAAS and suppress secretion of aldosterone, renin, and
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