The use of unbalanced and no plasma-adapted solutions leads to one additional day of hospital stay because of the onset of metabolic and acid–base disorders. The overall cost assuming unbalanced solutions as fluid therapy corresponds to (3,063 + 1,000 + 21) = 4,084 €, with a saving of 4,084 − 3,090 = 994 € using balanced and plasma-adapted ones.

The result of cost–benefit analysis on fluid therapy may be summarized into the following formula that can be used by single institutions to evaluate cost saving related with the use of balanced plasma-adapted solutions (Agrò 2013):

Assuming that:

In addition, we can use the following table reposting the maximum ratio (μ) between extra cost and hospital stay cost for each combination of hospital stay length and average amount of fluid therapy per day. Taking into account site-specific average hospital stay length (day) and average amount of fluid therapy per day (liter), we can obtain site-specific μ.

Multiplying μ * site-specific hospital stay cost per day, we obtain the cutoff value of extra cost in order to gain the cost saving (Agrò 2013) (Table 3.2).