Surgery>>>>>Fluid and Electrolyte Management of the Surgical Patient
Question 9#

Water constitutes what percentage of total body weight? 

A. 30-40%
B. 40-50%
C. 50-60%
D. 60-70%

Correct Answer is C

Comment:

Water constitutes approximately 50 to 60% of total body weight. The relationship between total body weight and total body water (TBW) is relatively constant for an individual and is primarily a reflection of body fat. Lean tissues, such as muscle and solid organs, have higher water content than fat and bone. As a result, young, lean men have a higher proportion of body weight as water than elderly or obese individuals. An average young adult male will have 60% of his total body weight as TBW, while an average young adult female's will be 50%. The lower percentage ofTBW in women correlates with a higher percentage of adipose tissue and lower percentage of muscle mass in most. Estimates of TBW should be adjusted down approximately 10 to 20% in obese individuals and up by 10% in malnourished individuals. The highest percentage of TBW is found in newborns, with approximately 80% of their total body weight composed of water. This decreases to about 65% by 1 year and thereafter remains fairly constant.