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Course: Medical Surgical Nursing

Topic: Fluid Imbalance

The Nurses International Community

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Module Goals

Learners will be able to:

Review the basic concepts related to fluid imbalance.
Explain the significance of osmolality, osmolarity, blood urea nitrogen, creatinine, and urine-specific gravity related to fluid and electrolyte status.
Describe the clinical presentation of clients with fluid imbalance (dehydration, hypovolemia, hypervolemia).
Describe the management of clients with fluid imbalance.
Discuss the nursing considerations related to clients with fluid imbalance.

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Fluid Imbalance

Fluid and electrolyte balance in the human body ensures proper functioning and homeostasis.

If the imbalance goes untreated, organ systems cannot function properly, resulting in multi-organ failure and, eventually, death.

Nurses assess for subtle imbalances to intervene in a timely manner to save lives.

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Body Fluids

Fluids and electrolytes are constantly being shifted in and out of the cells of the body in order to maintain homeostasis.
Body fluids consist of:

Water
Electrolytes
Blood plasma
Component cells
Proteins
Other solutes

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Body Fluids (Continued)

Body fluids are found in intracellular and extracellular compartments in the body.

Intracellular Fluids (ICF)

They are found inside cells and are made of:

Protein
Electrolytes
Water
Solutes

The most abundant electrolyte is potassium.

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Body Fluids (Continued)

Extracellular Fluids (ECF)

They are found outside cells
The most abundant electrolyte is sodium
Intravascular fluid → fluid inside blood vessels
Interstitial fluid → fluid outside blood vessels and between cells
Transcellular fluid → fluid within organ systems such as cerebrospinal, intrapleural, gastrointestinal, and synovial.

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Critical Thinking Question

Fill in the blanks:

The most abundant intracellular electrolyte is _______
The most abundant extracellular electrolyte is _______
It is found in the vascular system that consists of arteries, veins, and capillary networks: ______ ______
It refers to fluid outside of blood vessels and between the cells: _____ _____
It refers to fluid in areas such as the cerebrospinal, synovial, intrapleural, and gastrointestinal systems: _____ _____

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Fluid Movement

Proper fluid movement in the body depends on the intact vascular lining, protein levels within defined limits in the blood, and adequate pressure inside the blood vessels.
Oncotic pressure is the pressure that holds fluid inside the vasculature.

It is dependent on protein (albumin) content in the blood.

Hydrostatic pressure is the pressure a fluid exerts on what is confining it.

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Fluid Movement (Continued)

Filtration: This occurs due to hydrostatic pressure pushing solutes through a permeable membrane so they can be excreted.

E.g., kidneys removing excess fluid and solutes through urine excretion.

Osmosis: This is the fluid movement through a semipermeable membrane from an area of lesser solute concentration to a greater.

No energy is used → passive transport
Osmolarity (mOsm/L) is the volume concentration of an osmotic solution.

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Solute Movement

Diffusion: The movement of solutes from an area of higher concentration to a lower concentration.

Active transport: The movement of solutes from an area of lower concentration to a higher concentration.

Working against a concentration gradient → needs energy

E.g., a sodium-potassium pump regulating potassium and sodium levels in the intracellular and extracellular levels, respectively.

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Sodium-Potassium Pump

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Fluid and Electrolyte Regulation

The body must regulate fluid accumulation and excretion to prevent fluid excess and deficit and maintain blood pressure.

Fluid intake is regulated by thirst → as fluid is lost, sodium becomes more concentrated in intravascular space.

Increased solutes

= increased serum (blood) osmolality (mOsm/kg)
Osmolality refers to particles in a specific weight of fluid.

Urine-specific gravity (USG) measures the density of urine against the density of water.

Higher density = higher amount of solutes

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Fluid and Electrolyte Regulation (Continued)

Two important solutes in the blood that the kidneys filter are BUN (blood urea nitrogen) and creatinine.

Urea is an ammonia waste product
BUN (blood urea nitrogen) is a measure of the concentration of urea in the blood.
Creatinine is a byproduct of muscle breakdown
If BUN is elevated → dehydration
If both BUN and creatinine are elevated → kidney injury and not filtering properly

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Diagnostic and Lab Values

Serum osmolarity → 275 to 295 mmol/kg
Urine specific gravity → 1.010 to 1.020
BUN → 7 to 20 mg/dL
Creatinine → 0.7 to 1.3 mmol/dL for men

0.6 to 1.1 mmol/dL for women

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Critical Thinking Question

Discuss the main difference between hydrostatic and oncotic pressures, and explain where each takes place.

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Fluid Imbalance

Excessive fluid volume (hypervolemia) occurs when there is an excessive amount of fluid retained in the intravascular space.

At-risk patients include:

Heart/ kidney failure
Cirrhosis

Symptoms include:

Pitting edema (swelling in extremities)
Ascites (fluid accumulation in the abdomen)
Dyspnea and crackles from fluid in the lungs

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Fluid imbalance (Continued)

Hypovolemia (Deficient fluid volume) occurs when the loss of fluid volume is greater than the input.

Common causes:

Vomiting
Diarrhea
Excessive sweating
Fever
Poor oral intake

At-risk patients include:

Older adults
Children
Patients with chronic disease

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Fluid imbalance (Continued)

Symptoms

Thirst
Dry mouth
Headache
Dry skin
Dark urine
Dizziness
Elevated heart rate

Dehydration can be mild and treated with increased oral fluids.

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Critical Thinking Question

Which patient is at a greater risk for fluid imbalance?

A patient with heart failure receiving 3 units of blood
A heavier smoker diagnosed with cirrhosis
A 72-yr-old diabetic complaining of nausea and vomiting
An 8-month-old brought to ER with a fever of 101〫F

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Fluid Imbalance Management

Hypervolemia

Sodium and fluid restriction
Diuretics

Hypovolemia

Encouragement fluid intake
Administration of intravenous (IV) solutions

Isotonic, hypotonic, hypertonic
IV fluid restores fluid to the intravascular component; some facilitate the movement of fluid between compartments

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Intravenous Solutions

Isotonic

Has a similar concentration to dissolved particles in blood
E.g., normal saline (0.9% NaCl)

Hypotonic

Has a lower concentration to dissolved particles
Causes the osmotic movement of fluid from intravascular to intracellular space

E.g., 0.45% NaCl

Hypertonic

Has a higher concentration to dissolved particles
Moves fluid from cells to the intravascular compartment

E.g., 3.0% NaCl

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Critical Thinking Question

Which type of IV solution has a similar concentration to dissolved particles in blood?

Hypertonic solution
Hypotonic solution
Isotonic solution
Colloid solution

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Nursing Considerations for Fluid Imbalance

Fluid Imbalance in the Elderly

Aging adults have lower body muscle mass
Decreased thirst receptors in the brain

Putting this population at severe risk for dehydration

Have decreased kidney mass and function
Decreased ability to concentrate urine

Putting this population at severe risk for fluid and electrolyte imbalances

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What Would the Nurse Do?

The nurse is taking care of a patient diagnosed with hepatic cirrhosis. Which of the following interventions should the nurse implement to avoid fluid overload? (Select all that apply).

Monitor weight regularly using the same scale and preferably at the same time every day.
Educate patient and family members on the importance of proper nutrition, hydration, and diet modification.
Monitor input and output closely.
Assess for crackles, changes in respiratory pattern, shortness of breath, and orthopnea.

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Red Flags

Edema
Dyspnea and crackles
Dry mucous membranes
Elevated heart rate
Dry skin
Dark, concentrated urine
Changes in mental status

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Cultural Considerations

Religion, culture, beliefs, and ethnic customs can influence how families understand and use health concepts:

Health beliefs: In some cultures, talking about a possible poor health outcome will cause that outcome to occur.
Health customs: In some cultures, family members play a large role in healthcare decision-making.
Ethnic customs: Differing gender roles may determine who makes decisions about accepting and following treatment recommendations.

AHRQ, 2020

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Cultural Considerations (Continued)

Religion, culture, beliefs, and ethnic customs can influence how families understand and use health concepts:

Religious beliefs: Faith and spiritual beliefs may affect health-seeking behavior and willingness to accept treatment.
Dietary customs: Dietary advice may be difficult to follow if it does not fit the foods or cooking methods of the family.
Interpersonal customs: Eye contact or physical touch may be acceptable in some cultures but inappropriate or offensive in others.

AHRQ, 2020

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References

Agency for Healthcare Research. (2020). Health Literacy Universal Precautions Toolkit, 2nd Edition. https://www.ahrq.gov/health-literacy/improve/precautions/tool10.html

Bak, A., & Tsiami, A. (2016, August 25). Review on mechanisms, importance of homeostasis and fluid imbalances in the elderly. Current Research in Nutrition and Food Science Journal. Retrieved September 8, 2022, from https://www.foodandnutritionjournal.org/vol4nospl-issue-nutrition-in-elderly-2016/review-on-mechanisms-importance-of-homeostasis-and-fluid-imbalances-in-the-elderly/#:~:text=Fluid%20homeostasis%20largely%20depends%20on,stimulation%20and%20activation%20of%20thirst

BBC. (n.d.) Movement across cell membranes. https://www.bbc.co.uk/bitesize/guides/zc9tyrd/revision/5

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References

Fluid. (2012). In Britannica. https://www.britannica.com/science/fluid-biology

Lewis, J. L., III. (June 2020). Volume overload. Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/fluid-metabolism/volume- overload

MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); Dehydration; [updated 2020, Oct 1; reviewed 2016, Apr 15; cited 2020, Aug 5]. https://medlineplus.gov/dehydration.html

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