I'm trying to define the first occurrence of a blood transfusion (closest to procedure) after a surgical procedure during the encounter. Since a patient can have multiple transfusions, I'm only wanting the first one after surgery.

I've reviewed the examples posted on cooking with CQL and other measures (VTE2 and AMI8) but I'm still getting an error:

"Member relevantPeriod is not found for tuple of QualifyingEncounter: Encounter, Performed, BloodTransfusion: Procedure, Performed, SurgicalProcedures: Procedure, Performed"

Here is the logic: (see attachment for more info)

"Encounter with Blood Transfusion" QualifyingEncounter
return
First("Blood Transfusion" FirstTransfusion
where FirstTransfusion.relevantPeriod during QualifyingEncounter.relevantPeriod sort by start of relevantPeriod)