FORMULA FOR CALCULATION
OF CONSTANT RATE
INFUSIONS
This may be useful when using dobutamine, sodium nitroprusside and lignocaine. Also
see Chapter 21,
Table 21.2
(CR1 for lignocaine), and
Table 21.3
(CR1 for dobutamine), and Macintire (1995).

To make up an infusion that will last for 6 hours: choose the volume of fluid
required for 6 hours,
and set the drip rate.
Body weight (kg) x dose (u/kg/min) x 0.36
= total dose in mg to be added to fluid for infusion
to be given over 6 hours.

The following formula is more versatile and allows the clinician to work out
any combination. Quantity of drug (mg) to be added to the fluids for infusion
=
Dose rate of drug (ug/kg/min) x body weight (kg) x volume of fluid
(ml)
delivery rate (ml/mm) x 1000
or
Delivery rate (ml/mm) of the infusion =
Dose rate of drug (ug/kg/min) x body weight (kg) x volume of fluid
(ml)
quantity of drug (mg) added to fluids x 1000