ATI Fluid and Electrolytes Module Exam Review | 2026/2027
ATI Fluid and Electrolytes Module
Exam Review
70 Questions with Correct Answers and Rationales | 2026/2027 Edition
Elsevier ATI Content Mastery Series® | NGN-Integrated
Instructions:
1. Read each question carefully before selecting your answer. All questions are in NCLEX/ATI exam style with
clinical scenarios.
2. Select the single best answer (A, B, C, or D) for each question. Each question has one clearly correct answer.
3. After completing all questions, review the Correct Answer and Rationale for each question to reinforce your
understanding.
4. Use the Quick Reference Appendix at the end of this document for normal lab values, ABG interpretation, and
IV fluid references.
5. Time yourself: aim for approximately 1.5 minutes per question to simulate NCLEX pacing. Total recommended
time: 105 minutes.
6. Focus on safety-first prioritization, clinical reasoning, and ATI content alignment when reviewing rationales.
Section I: Fluid Compartments and Movement
1. A nurse is reviewing the body's fluid distribution with a nursing student. The nurse explains that approximately
two-thirds of the body's total water is found in which compartment?
A) Intracellular fluid B) Intravascular fluid C) Interstitial fluid D) Transcellular fluid
(ICF)
Correct Answer: A) Intracellular fluid (ICF)
Rationale: Approximately 40% of total body weight, or about two-thirds of total body water, is contained within the
intracellular fluid (ICF) compartment. The extracellular fluid (ECF), which includes intravascular and interstitial fluid,
comprises the remaining one-third. ATI emphasizes that ICF is the largest fluid compartment.
2. A client with heart failure develops significant peripheral edema and a weight gain of 4 kg over 2 days. The
nurse recognizes that this weight gain most likely represents fluid retention of approximately how many liters?
A) 1 liter B) 2 liters C) 4 liters D) 6 liters
Correct Answer: C) 4 liters
Rationale: One liter of fluid weighs approximately 2.2 lb (1 kg). A weight gain of 4 kg therefore represents
approximately 4 liters of retained fluid. This is a critical assessment finding in clients with heart failure and indicates
1
, ATI Fluid and Electrolytes Module Exam Review | 2026/2027
significant third-spacing or fluid volume excess. ATI teaches that daily weights are the most reliable indicator of fluid
balance.
3. A nurse is caring for a client who has experienced a major burn injury covering 40% of total body surface area.
The nurse understands that fluid shifts during the first 24 hours post-burn are primarily driven by which
mechanism?
A) Active transport of B) Increased hydrostatic C) Increased capillary D) Decreased oncotic
sodium across the cell pressure within the permeability leading to pressure from protein loss
membrane capillaries third-spacing
Correct Answer: C) Increased capillary permeability leading to third-spacing
Rationale: Major burns cause a massive systemic inflammatory response that increases capillary permeability,
allowing proteins and fluid to escape into the interstitial space (third-spacing). This shift reduces intravascular volume
and can lead to hypovolemic shock. The Parkland formula guides fluid resuscitation in burn patients. While oncotic
pressure does decrease, the primary driver is increased capillary permeability.
4. A nurse is administering an intravenous (IV) solution of 0.9% sodium chloride to a client. The nurse correctly
identifies this solution as which of the following?
A) Hypotonic B) Isotonic C) Hypertonic D) Colloid
Correct Answer: B) Isotonic
Rationale: 0.9% sodium chloride (normal saline) is an isotonic solution with an osmolality of approximately 308
mOsm/L, which is nearly equal to that of plasma. Isotonic solutions remain within the intravascular compartment and
are used for volume expansion without causing significant fluid shifts between compartments. ATI highlights this as a
foundational concept for IV therapy management.
5. A client is admitted with fluid volume deficit secondary to prolonged vomiting. Which assessment finding
would the nurse most likely observe?
A) Crackles auscultated in B) Bounding peripheral C) Decreased skin turgor D) Increased blood pressure
the lung fields pulses and dry mucous and jugular venous
membranes distention
Correct Answer: C) Decreased skin turgor and dry mucous membranes
Rationale: Fluid volume deficit (FVD) leads to decreased extracellular fluid, manifesting as decreased skin turgor, dry
mucous membranes, concentrated urine, and weak/thready pulses. Crackles, bounding pulses, and JVD are findings
associated with fluid volume excess (FVE). ATI prioritizes skin turgor and mucous membrane assessment as early
indicators of dehydration.
6. A nurse is reviewing laboratory results for a client and notes a serum osmolality of 260 mOsm/kg. The nurse
understands that this value indicates which of the following?
A) Fluid volume excess B) Fluid volume deficit C) Overhydration D) Hyponatremia or
dilutional state
Correct Answer: D) Hyponatremia or dilutional state
Rationale: Normal serum osmolality ranges from 275 to 295 mOsm/kg. A value of 260 mOsm/kg is decreased and most
commonly indicates a dilutional state, such as hyponatremia or relative water excess (overhydration). While fluid
volume excess can contribute, the specific low osmolality points to dilution. ATI links osmolality changes directly to
sodium concentration abnormalities.
2
, ATI Fluid and Electrolytes Module Exam Review | 2026/2027
7. A client with cirrhosis of the liver presents with ascites and peripheral edema. The nurse understands that this
fluid accumulation is primarily caused by which of the following?
A) Increased antidiuretic B) Decreased albumin C) Excessive sodium intake D) Increased capillary
hormone (ADH) secretion synthesis leading to exceeding renal excretion hydrostatic pressure from
reduced oncotic pressure portal hypertension
Correct Answer: B) Decreased albumin synthesis leading to reduced oncotic pressure
Rationale: In cirrhosis, the damaged liver cannot synthesize adequate amounts of albumin. This hypoalbuminemia
decreases plasma oncotic pressure, reducing the force that holds fluid within the vasculature and causing fluid to leak
into the interstitial space and peritoneal cavity. While portal hypertension contributes, the primary mechanism is
reduced oncotic pressure. ATI emphasizes albumin's role in fluid balance.
8. The nurse is teaching a nursing student about active transport mechanisms in the body. Which of the following
is the best example of an active transport process?
A) Oxygen moving from B) Glucose moving from C) Water moving across a D) Sodium and chloride
the alveoli into the blood the intestinal lumen into semipermeable membrane moving between interstitial
enterocytes via SGLT1 and intravascular spaces
Correct Answer: B) Glucose moving from the intestinal lumen into enterocytes via SGLT1
Rationale: Active transport requires energy (ATP) to move substances against their concentration gradient. The
sodium-glucose cotransporter (SGLT1) uses secondary active transport by harnessing the sodium gradient maintained
by the Na+/K+ ATPase pump. Osmosis and diffusion are passive processes. ATI highlights the Na+/K+ pump as the
body's most important active transport mechanism.
9. A client who is postoperative following abdominal surgery is experiencing decreased urine output despite
adequate IV fluid intake. The nurse suspects third-spacing. Which of the following findings would support this
suspicion?
A) Central venous pressure B) Hematocrit of 55% C) Weight loss of 1 kg D) Serum sodium of 146
(CVP) of 10 mmHg since surgery mEq/L
Correct Answer: B) Hematocrit of 55%
Rationale: Third-spacing refers to the shift of fluid from the intravascular compartment into the interstitial or
transcellular space. This reduces circulating volume despite total body fluid remaining the same or increasing. An
elevated hematocrit (hemoconcentration) occurs because fluid leaves the vascular space while blood cells remain
concentrated. CVP would be decreased, not elevated. ATI emphasizes that third-spacing can mask true hypovolemia.
10. A nurse is caring for a client receiving a hypertonic saline infusion (3% NaCl). The nurse understands that
hypertonic solutions will cause which of the following fluid shifts?
A) Fluid to shift from the B) Fluid to shift from the C) Fluid to shift equally D) Fluid to shift from the
intracellular compartment intravascular space into the across all compartments interstitial space into the
into the intravascular interstitial space cells
compartment
Correct Answer: A) Fluid to shift from the intracellular compartment into the intravascular compartment
Rationale: Hypertonic solutions, such as 3% NaCl (osmolality > 308 mOsm/L), create an osmotic gradient that draws
water out of the cells and interstitial space into the intravascular compartment. This is therapeutically useful in treating
3
ATI Fluid and Electrolytes Module
Exam Review
70 Questions with Correct Answers and Rationales | 2026/2027 Edition
Elsevier ATI Content Mastery Series® | NGN-Integrated
Instructions:
1. Read each question carefully before selecting your answer. All questions are in NCLEX/ATI exam style with
clinical scenarios.
2. Select the single best answer (A, B, C, or D) for each question. Each question has one clearly correct answer.
3. After completing all questions, review the Correct Answer and Rationale for each question to reinforce your
understanding.
4. Use the Quick Reference Appendix at the end of this document for normal lab values, ABG interpretation, and
IV fluid references.
5. Time yourself: aim for approximately 1.5 minutes per question to simulate NCLEX pacing. Total recommended
time: 105 minutes.
6. Focus on safety-first prioritization, clinical reasoning, and ATI content alignment when reviewing rationales.
Section I: Fluid Compartments and Movement
1. A nurse is reviewing the body's fluid distribution with a nursing student. The nurse explains that approximately
two-thirds of the body's total water is found in which compartment?
A) Intracellular fluid B) Intravascular fluid C) Interstitial fluid D) Transcellular fluid
(ICF)
Correct Answer: A) Intracellular fluid (ICF)
Rationale: Approximately 40% of total body weight, or about two-thirds of total body water, is contained within the
intracellular fluid (ICF) compartment. The extracellular fluid (ECF), which includes intravascular and interstitial fluid,
comprises the remaining one-third. ATI emphasizes that ICF is the largest fluid compartment.
2. A client with heart failure develops significant peripheral edema and a weight gain of 4 kg over 2 days. The
nurse recognizes that this weight gain most likely represents fluid retention of approximately how many liters?
A) 1 liter B) 2 liters C) 4 liters D) 6 liters
Correct Answer: C) 4 liters
Rationale: One liter of fluid weighs approximately 2.2 lb (1 kg). A weight gain of 4 kg therefore represents
approximately 4 liters of retained fluid. This is a critical assessment finding in clients with heart failure and indicates
1
, ATI Fluid and Electrolytes Module Exam Review | 2026/2027
significant third-spacing or fluid volume excess. ATI teaches that daily weights are the most reliable indicator of fluid
balance.
3. A nurse is caring for a client who has experienced a major burn injury covering 40% of total body surface area.
The nurse understands that fluid shifts during the first 24 hours post-burn are primarily driven by which
mechanism?
A) Active transport of B) Increased hydrostatic C) Increased capillary D) Decreased oncotic
sodium across the cell pressure within the permeability leading to pressure from protein loss
membrane capillaries third-spacing
Correct Answer: C) Increased capillary permeability leading to third-spacing
Rationale: Major burns cause a massive systemic inflammatory response that increases capillary permeability,
allowing proteins and fluid to escape into the interstitial space (third-spacing). This shift reduces intravascular volume
and can lead to hypovolemic shock. The Parkland formula guides fluid resuscitation in burn patients. While oncotic
pressure does decrease, the primary driver is increased capillary permeability.
4. A nurse is administering an intravenous (IV) solution of 0.9% sodium chloride to a client. The nurse correctly
identifies this solution as which of the following?
A) Hypotonic B) Isotonic C) Hypertonic D) Colloid
Correct Answer: B) Isotonic
Rationale: 0.9% sodium chloride (normal saline) is an isotonic solution with an osmolality of approximately 308
mOsm/L, which is nearly equal to that of plasma. Isotonic solutions remain within the intravascular compartment and
are used for volume expansion without causing significant fluid shifts between compartments. ATI highlights this as a
foundational concept for IV therapy management.
5. A client is admitted with fluid volume deficit secondary to prolonged vomiting. Which assessment finding
would the nurse most likely observe?
A) Crackles auscultated in B) Bounding peripheral C) Decreased skin turgor D) Increased blood pressure
the lung fields pulses and dry mucous and jugular venous
membranes distention
Correct Answer: C) Decreased skin turgor and dry mucous membranes
Rationale: Fluid volume deficit (FVD) leads to decreased extracellular fluid, manifesting as decreased skin turgor, dry
mucous membranes, concentrated urine, and weak/thready pulses. Crackles, bounding pulses, and JVD are findings
associated with fluid volume excess (FVE). ATI prioritizes skin turgor and mucous membrane assessment as early
indicators of dehydration.
6. A nurse is reviewing laboratory results for a client and notes a serum osmolality of 260 mOsm/kg. The nurse
understands that this value indicates which of the following?
A) Fluid volume excess B) Fluid volume deficit C) Overhydration D) Hyponatremia or
dilutional state
Correct Answer: D) Hyponatremia or dilutional state
Rationale: Normal serum osmolality ranges from 275 to 295 mOsm/kg. A value of 260 mOsm/kg is decreased and most
commonly indicates a dilutional state, such as hyponatremia or relative water excess (overhydration). While fluid
volume excess can contribute, the specific low osmolality points to dilution. ATI links osmolality changes directly to
sodium concentration abnormalities.
2
, ATI Fluid and Electrolytes Module Exam Review | 2026/2027
7. A client with cirrhosis of the liver presents with ascites and peripheral edema. The nurse understands that this
fluid accumulation is primarily caused by which of the following?
A) Increased antidiuretic B) Decreased albumin C) Excessive sodium intake D) Increased capillary
hormone (ADH) secretion synthesis leading to exceeding renal excretion hydrostatic pressure from
reduced oncotic pressure portal hypertension
Correct Answer: B) Decreased albumin synthesis leading to reduced oncotic pressure
Rationale: In cirrhosis, the damaged liver cannot synthesize adequate amounts of albumin. This hypoalbuminemia
decreases plasma oncotic pressure, reducing the force that holds fluid within the vasculature and causing fluid to leak
into the interstitial space and peritoneal cavity. While portal hypertension contributes, the primary mechanism is
reduced oncotic pressure. ATI emphasizes albumin's role in fluid balance.
8. The nurse is teaching a nursing student about active transport mechanisms in the body. Which of the following
is the best example of an active transport process?
A) Oxygen moving from B) Glucose moving from C) Water moving across a D) Sodium and chloride
the alveoli into the blood the intestinal lumen into semipermeable membrane moving between interstitial
enterocytes via SGLT1 and intravascular spaces
Correct Answer: B) Glucose moving from the intestinal lumen into enterocytes via SGLT1
Rationale: Active transport requires energy (ATP) to move substances against their concentration gradient. The
sodium-glucose cotransporter (SGLT1) uses secondary active transport by harnessing the sodium gradient maintained
by the Na+/K+ ATPase pump. Osmosis and diffusion are passive processes. ATI highlights the Na+/K+ pump as the
body's most important active transport mechanism.
9. A client who is postoperative following abdominal surgery is experiencing decreased urine output despite
adequate IV fluid intake. The nurse suspects third-spacing. Which of the following findings would support this
suspicion?
A) Central venous pressure B) Hematocrit of 55% C) Weight loss of 1 kg D) Serum sodium of 146
(CVP) of 10 mmHg since surgery mEq/L
Correct Answer: B) Hematocrit of 55%
Rationale: Third-spacing refers to the shift of fluid from the intravascular compartment into the interstitial or
transcellular space. This reduces circulating volume despite total body fluid remaining the same or increasing. An
elevated hematocrit (hemoconcentration) occurs because fluid leaves the vascular space while blood cells remain
concentrated. CVP would be decreased, not elevated. ATI emphasizes that third-spacing can mask true hypovolemia.
10. A nurse is caring for a client receiving a hypertonic saline infusion (3% NaCl). The nurse understands that
hypertonic solutions will cause which of the following fluid shifts?
A) Fluid to shift from the B) Fluid to shift from the C) Fluid to shift equally D) Fluid to shift from the
intracellular compartment intravascular space into the across all compartments interstitial space into the
into the intravascular interstitial space cells
compartment
Correct Answer: A) Fluid to shift from the intracellular compartment into the intravascular compartment
Rationale: Hypertonic solutions, such as 3% NaCl (osmolality > 308 mOsm/L), create an osmotic gradient that draws
water out of the cells and interstitial space into the intravascular compartment. This is therapeutically useful in treating
3
