Daily Fluid Requirement

Water makes up to around 50 to 70 % of body weight. It is the solution base for all metabolic processes and is important for maintaining blood pressure. Patients receiving TPN should get enough fluid to maintain healthy blood pressure. The daily fluid needs can be calculated using various methods. Two commonly used methods are shown below:

Weight Based: Daily fluid needs for adult patients can be estimated using a factor of 30-35 ml/kg/day

Solved Problem: Calculate the daily fluid requirement range for a patient weighing 150 lb. Approach: Use the factor of 30-35 ml/kg/day to calculate the range. $$ 150\ lb \times {1\ kg \over 2.2\ lb} \times {(30-35)ml \over kg/day} = 2045.5-2386.4\ ml $$ Answer: Range = 2045.5-2386.4 ml

Body Surface Area Based: Daily fluid needs for adult patients can be estimated using a factor of 1500 ml per square meter of body surface area.

Solved Problem: Calculate the daily fluid requirement range for a patient weighing 150 lb and measuring 5 feet 2 inches.. Approach: Convert weight and height to kg and cm, use the Mostellar equation to calculate the BSA. $${ \sqrt{157.48 \times 68.18 \over 3600 } }= 1.73\ m ^ 2 $$ $$ {1500ml \over m ^ 2 / day} \times 1.73 m ^ 2 = 2595\ ml/day $$ Answer: 2595 ml/day