In the child coming for elective surgery who has been given a clear fluid drink up to two hours before anaesthesia, the deficit can be considered to be negligible, and does not need replacing.

In the child fasted for 6-8 hours, the deficit can be calculated from the following formula:

Deficit = normal maintenance fluid rate x number of hours starved

In the first hour of surgery 50 % of the deficit should be replaced, and 25 % during each of the second and third hours.

The fluid used should be isotonic.