Total Body Water and Electrolyte Management

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Questions and Answers

What percentage of total body water (TBW) typically constitutes a person's total body mass?

75–90%

40–60%

50–75% (correct)

25–50%

Which of the following correctly describes the composition of intracellular fluid (ICF)?

Primarily contains extracellular ions

High in protein but low in phosphates

Rich in potassium and magnesium (correct)

Rich in sodium and chloride

Which fluid compartment constitutes 1/3 of total body water (TBW)?

Extracellular fluid (ECF) (correct)

Interstitial fluid (ISF)

Plasma

Intracellular fluid (ICF)

What is a primary characteristic of interstitial fluid (ISF) compared to plasma?

Lacks significant amounts of protein Signup and view all the answers

Which of the following is NOT a principal constituent of plasma?

Potassium Signup and view all the answers

What is the total maintenance fluid requirement for a patient weighing 28 kg?

1660 mL Signup and view all the answers

For a 15 kg patient, what is the calculated maintenance fluid requirement?

1250 mL Signup and view all the answers

What is the maintenance fluid calculation method for a patient over 20 kg?

20 mL/kg for every kg above 20 kg Signup and view all the answers

What is typically included in the deficit calculation for a patient?

Replacement of prior loss Signup and view all the answers

If a patient has lost significant fluids, which component is crucial for maintaining homeostasis?

Water plus electrolytes Signup and view all the answers

What percentage of weight loss indicates moderate dehydration?

6 - 10% Signup and view all the answers

Which of the following symptoms indicates severe dehydration?

Tachycardia Signup and view all the answers

What formula is used to calculate sodium deficit in hyponatremic dehydration?

(desired sodium - observed sodium) X bodyweight (kg) X 0.6 Signup and view all the answers

What is the sodium level range for isonatremic dehydration?

137 – 148 mEq/L Signup and view all the answers

For a patient weighing 20 kg with a sodium level of 127 mmol/L, what is the sodium deficit?

120 mmol / 24 hours Signup and view all the answers

What is the osmolarity of the Reduced Osmolarity ORS?

245 mmol/L Signup and view all the answers

In which situation is oral rehydration solution (ORS) recommended?

Mild or moderate dehydration with no vomiting Signup and view all the answers

What might indicate a patient is suffering from hypovolemic shock due to severe dehydration?

Hypotension Signup and view all the answers

What is the maintenance fluid requirement for a child weighing 7 kg?

700 ml / 24 hours Signup and view all the answers

How is sodium maintenance calculated for a child?

Weight x 3 Signup and view all the answers

Which of the following is NOT a potential cause of water deficit?

Excessive fluid intake Signup and view all the answers

Which clinical sign indicates dehydration in children under 1.5 years?

Depressed anterior fontanel Signup and view all the answers

What is the expected heart rate change in a dehydrated individual?

Elevated heart rate Signup and view all the answers

What laboratory indicator might suggest moderate dehydration?

Electrolyte imbalance Signup and view all the answers

Which symptom is indicative of severe dehydration?

Sunken eyes Signup and view all the answers

Which of the following describes decreased skin turgor?

Skin remains elevated when pinched Signup and view all the answers

Study Notes

Total Body Water (TBW)

TBW constitutes 50–75% of total body mass.
Divided into intracellular fluid (ICF) and extracellular fluid (ECF).
ICF accounts for 2/3 of TBW, while ECF makes up 1/3 of TBW.

Fluid Components

ECF is further divided into:
- Plasma (intravascular fluid)
- Interstitial fluid (ISF)
Plasma contains sodium, chloride, bicarbonate, and protein (mainly albumin).
ISF resembles plasma but has minimal protein.
ICF is rich in potassium, magnesium, phosphates, sulfates, and proteins.

Fluid & Electrolyte Management

Treatment focuses on providing:
- Water
- Electrolytes (Sodium chloride and Potassium)
- Glucose (not covered in this unit)

Calculating Fluid Requirements

Maintenance: Daily water and electrolyte requirement to maintain homeostasis.
Deficit: Replacement of lost fluids due to vomiting, diarrhea, or poor intake.

Maintenance Calculation

Water requirements based on body weight:
- 1–10 kg: 100 mL/kg
- 11–20 kg: 50 mL/kg
- 20 kg: 20 mL/kg, max of 2400 mL/day.

Sodium Maintenance

Sodium maintenance calculated as:
- Weight (kg) x 3 mEq/kg/day.

Water Deficit Considerations

Caused by:
- Decreased intake (e.g., elderly)
- Increased loss (diarrhea, vomiting, diabetes)
- Heat or skin loss (insensible loss)

Clinical Signs & Symptoms of Dehydration

Vital Signs:
- Tachycardia: Increased pulse rate due to reduced blood volume.
- Hypotension: Low blood pressure.
Physical Signs:
- Depressed anterior fontanelle in infants.
- Sunken eyes and absent tears.
- Dry mucous membranes and decreased skin turgor.
- Delay in capillary refill time.
- Decreased urine output and weight loss.

Laboratory Indicators

Calculate dehydration percentage based on weight loss.
Examples categorize dehydration severity:
- Mild: Thirst and slight decrease in urine output.
- Moderate: Dry mucous membranes and oliguria.
- Severe: Hypovolemic shock with hypotension and anuria.

Replacement of Water Deficit

Formulas based on dehydration severity:
- Mild (3-5%): Weight (kg) x 3 - 50 mL.
- Moderate (6-10%): Weight (kg) x 60 - 100 mL.
- Severe (9-15%): Weight (kg) x 90 - 150 mL.

Sodium Deficit

Normal sodium levels: 137–148 mEq/L.
Types of dehydration based on sodium levels:
- Isonatremic: Sodium level maintained (137–148 mEq/L).
- Hyponatremic: Sodium level <137 mEq/L.
- Hypernatremic: Sodium level >148 mEq/L.

Treatment of Dehydration

For mild or moderate dehydration without vomiting, oral rehydration solutions (ORS) are recommended.
Composition of Reduced Osmolarity ORS includes:
- Glucose, Sodium, Chloride, and Potassium.
New ORS studies indicate that reduced osmolarity solutions are more effective than standard formulations.

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Description

This quiz focuses on Total Body Water (TBW) and its composition, including intracellular and extracellular fluids. It covers fluid and electrolyte management, daily requirements, and calculation methods for maintenance and deficit. Test your knowledge on how the body maintains homeostasis through proper fluid balance.