The amount of blood required to prime the extracorporeal circuit of a heart-lung bypass machine can be estimated from several features of the patient and the circuit.



(1) patient's hematocrit prior to surgery

(2) target hematocrit for surgery (taking into account hemodilution)

(3) hematocrit of blood being used to prime the circuit

(4) patient's circulating blood volume in mL

(5) volume of the extracorporeal circuit in mL


volume in mL required to prime the extracorporeal circuit =

= (((target hematocrit in percent) * ((blood volume) + (EC circuit volume))) - ((patient hematocrit in percent) * (blood volume))) / (patient hematocrit)



• For the implementation estimation of the blood volume from height, weight or other measures was not included because of the variation between infants, children and adults. Refer to Chapter 2 for means of estimating the blood volume for a patient.

• The equation does not take into account any hemodilution associated with cardioplegia.


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