FLUID THERAPY

1. How is water distributed throughout the body?
Total body water comprises 60% of body weight in males and 50% of body weight in females.
The distribution of this water is 40% in intracellular space (30% in females because of
larger amounts of subcutaneous tissue and smaller muscle mass) and 20% in extracellular
space. The extracellular fluid is broken down into 15% interstitial and 5% plasma. Total body
water decreases with age; 75% to 80% of a newborn infant’s weight is water.
2. What are sensible and insensible fluid losses? How are maintenance fluid
requirements calculated?
n Insensible losses (nonmeasurable)
□ Skin: 600 mL
□ Lungs: 200 mL
n Sensible losses (measurable)
□ Fecal: 200 mL
□ Urine: 800-1500 mL
□ Sweat: Variable
These losses account for 2000 to 2500 mL/day, giving a 24-hour fluid requirement of 30 to
35 mL/kg to maintain normal fluid balance.
3. What are fluid maintenance requirements for children?
Twenty-four–hour fluid requirements for children have been formulated on the basis of weight:
n 4:2:1 rule: 4 mL/kg per hour for the first 10 kg
n Then add additional 2 mL/kg per hour for the next 10 kg to 20 kg
n Then add 1 mL/kg per hour for every kilogram after that
EXAMPLE: 30-kg child
40 þ 20 þ 10 ¼ 70 mL/hr maintenance
4. Describe the clinical features of volume deficit and volume excess.
n Deficits (low volume)
□ Central nervous system: decreased mentation in severe cases
□ Cardiovascular: tachycardia, hypotension (in later stages)
□ Skin: decreased turgor in subacute volume loss
□ Renal: decreased urine output
n Excesses (volume overload)
□ Distended neck veins
□ Pulmonary edema
□ Peripheral edema
5. What are the classes of hemorrhagic shock, and what fluid should be
administered in each class?
See Table 7-1.

6. What is the 3:1 rule in fluid therapy after acute blood loss?
Three milliliters of crystalloid is given for each milliliter of blood loss to compensate for
administered fluid that is lost into the interstitial and intracellular spaces. This is a starting dose.
Most patients need more than this and will need 5:1 to restore normovolemia. Please see
Chapter 54 for description of blood replacement in patients who require massive transfusions
(greater than 10 U of packed red blood cells).
7. What empiric replacement fluids can be used for fluid losses?
n Sweat: 5% dextrose (D5) ¼ normal saline solution with 5 KCl/L
n Gastric, colon: D5 ½ normal saline solution with 30 KCl/L
n Bile, pancreas, small bowel: lactated Ringer’s solution
n Third space (interstitial loss): lactated Ringer’s solution
8. What is the difference between crystalloids and colloids? Give examples of each.
n Crystalloids: Crystalloids are mixtures of sodium chloride and other physiologically
active solutes. The distribution of sodium will determine the distribution of the infused
crystalloid. Examples are normal saline solution, lactated Ringer’s solution, and hypertonic
saline solution.
n Colloids: High-molecular-weight substances that stay in the vascular space and exert an
osmotic force are colloids. Examples are albumin, hetastarch, dextran, and blood.
9.Describe the composition of normal saline and lactated Ringer’s solution. Which
should be used for acute resuscitation?
Table 7-2 summarizes the composition of normal saline and lactated Ringer’s solution.
Lactated Ringer’s solution is preferable for acute volume replacement because normal saline
solution can result in hyperchloremic metabolic acidosis.

10. What evidence-based data exist to support the use of various
resuscitation fluids?
n Lactated Ringer’s solution: This remains the least expensive and best fluid for trauma
resuscitation.
n Albumin, hetastarch and other colloids: No evidence from randomized controlled trials
exists to demonstrate that resuscitation with colloids reduces the risk of death, pulmonary
edema, or hospital stay compared with resuscitation with crystalloids in patients with trauma
or burns, or after surgery. Because colloids are more expensive, it is difficult to justify their
continued use in this setting.
n Hypertonic saline solution: The only benefit is shown in patients with head trauma–cerebral
edema.
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