Chapter 20 Fluid Management
Overview of fluid and electrolyte physiology
1. What is the goal of perioperative fluid management?
2. What percentage of body weight is represented by water?
3. In what two compartments is total body water found?
4. What percentage of extracellular fluid volume is occupied by plasma volume? What are the other constituents of extracellular fluid?
5. How does plasma differ from other components of extracellular fluid?
6. What are the major sources of daily water loss? How does temperature affect daily water loss?
7. What body compartment has the highest concentration of potassium? What electrolytes are found in plasma?
8. Which source produces the greatest volume of gastrointestinal fluid? Which source of gastrointestinal fluid contains the highest concentration of bicarbonate?
Fluid replacement solutions
9. What are the daily water, potassium, and sodium requirements for the average adult?
10. How are crystalloids grouped? How do crystalloid solutions distribute?
11. What is the composition of a balanced salt solution?
12. What occurs when normal saline is used in large volumes?
13. What group of patients routinely receives normal saline during surgery? Why?
14. What is the sodium concentration of hypertonic saline? What are the potential benefits of hypertonic saline?
15. What is the advantage of using 5% dextrose water instead of pure water? What are the clinical indications for use of 5% dextrose water?
16. What are colloids? How should colloids be used to correct blood loss in clinical practice?
17. What are the differences between 5% albumin and 25% albumin?
18. What is dextran? What is the indication for its intravenous administration?
19. What are hydroxyethyl starches?
20. What are some potential adverse effects of using hydroxyethyl starches or dextran for volume replacement?
21. What are the arguments for crystalloids versus colloids for perioperative fluid replacement?
Perioperative fluid strategies
22. What is the 4-2-1 rule of perioperative fluid management?
23. What is compensatory intravenous volume expansion?
24. How is fluid deficit corrected?
25. How is blood loss replaced clinically?
26. What is “third-space loss of fluid”? What is used to replace it?
27. Why might the traditional fluid management strategy cause problems? How might one restrict the fluid administration?
Answers*
Overview of fluid and electrolyte physiology
1. Proper perioperative fluid management requires knowledge of the patients’ surgical procedure, their preexisting disease states, and the physiologic effects of the anesthetic plan. Balancing these three factors will allow the anesthesiologist to maintain the patient’s intravascular volume, cardiac preload, oxygen-carrying capacity, coagulation status, electrolyte balance, and acid-base homeostasis. (364)
2. Total body water represents approximately 60% of the body’s total weight in the average adult. The relative percentage of body water can vary depending on age, gender, and adiposity. The average 70 kg man contains approximately 600 mL/kg or 40 L of total body water. (364)
3. Total body water is found in the intracellular and extracellular compartments. The intracellular fluid volume averages 400 to 450 mL/kg and the extracellular fluid volume averages 150 to 200 mL/kg. (364)
4. The two main components of the extracellular compartment are blood volume, which averages 60 to 65 mL/kg, and the interstitial fluid volume, which averages 120 to 165 mL/kg. The other constituents of extracellular fluid include pleural fluid, peritoneal fluid, aqueous humor, sweat, urine, lymph, and cerebrospinal fluid. (364-365)
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