Nutrition Management of Fluid Intake and Hydration
Manual of Clinical Nutrition Management A- 34 Copyright © 2013 Compass Group, Inc.
- Adults (4,5)
Weight (kg) Fluid Requirement (ml/kg/day)
First 10 kg of body weight 100
Second 10 kg of body weight 50
Each additional kilogram 20 mL/kg(<50 years of age)
15 mL/kg(>50 years of age)
*In obese patients, actual weight for height is used
Other Suggested Methods:
RDA Method: 1 milliliter (mL) per kilocalorie (Kcal) (Grade V) (2)
Fluid Balance Method: Urine output + 500 milliliter (mL) per day (Grade V)(2)
Adults between 18 55 years: 35 ml/kg per day (4,5)
Adults between 55-75: 30 ml/kg per day (5)
Adults age > 75 years: 25 ml/kg per day (5)
Fluid restriction: < 25 ml/kg per day (renal and cardiac disease, fluid overload status) (5)
Patients receiving mechanical ventilation or other source of humidified oxygen can absorb up to an
additional 1000 ml of fluid daily, whereas unhumidified oxygen therapy can result in a net loss of fluid (6).
Patients treated on air-fluidized beds set at higher temperatures are at greater risk of dehydration due to
an increase in insensible water loss associated with the warmer bed temperatures. Patients who require
air-fluidized beds set at a higher temperature will need additional fluids, estimated to be approximately
10 to 15 mL/kg (7,8). For beds set at temperatures (86°F), fluid loss is similar to that on a conventional bed
(480 ml/m2/24 h). However, when the bed temperature is high (94°F), fluid loss may increase up to 80%
(938 ml/m2/24 h) in a 70-kg person (7). (Bed temperatures are adjustable and usually set between 88°
and 93°F.)
Assessment of Fluid Status
The clinical assessment of total body water (TBW) is generally inaccurate (Grade II) (2). A body mass loss of over
3% is a good indicator of dehydration (Grade II) (2). More than 10% of TBW may be lost before evidence of
hypovolemia appears. The thirst mechanism is activated when the decrease in TBW reaches approximately
2%. Serial assessment of body weight is probably the most reliable parameter, especially because water
makes up such a large proportion of total body weight ( 2 ). Along with serial assessment, the following
physical alterations can be assessed to help determine hydration status ( 9 ).
Volume deficit
Decreased moisture in the oral cavity
Decreased skin and tongue turgor (elasticity); skin may remain slightly elevated after being pinched
Flattened neck and peripheral veins in supine position
Decreased urinary output (<30 ml/h without renal failure)
Acute weight loss (>1 lb /day)
Volume excess
Clinical apparent edema is usually not present until 12 15 L of fluid has accumulated
1 L fluid = 1 kg weight
Pitting edema, especially in dependent parts of the body (e.g., feet, ankles, and sacrum)
Distended peripheral and neck veins
Symptoms of heart failure or pulmonary edema
Central venous pressure >11 cm H 20
Laboratory values used to evaluate fluid status include urine specific gravity, urine osmolality, serum
electrolytes; serum osmolality; hematocrit; blood, urea nitrogen (BUN); and urine specific gravity. Serum
sodium is the best indicator of intracellular fluid disorders. The hematocrit reflects the proportion of blood
plasma to red blood cells. Fluid loss causes hemoconcentration and serum osmolality; fluid gain causes
hemodilution and decreases serum osmolality. A rise in BUN level frequently reflects a fluid deficit state and
a fluid deficit causes urine to be concentrated (specific gravity >1.030); a fluid excess dilutes urine (specific
gravity <1.010) ( 6 ).
Aging increases the risk for dehydration based on the physical and psychological changes. The elderly often