As part of the v2-to-FHIR project we are mapping commonly used fields in key v2 messages to FHIR resources so that messages can be transformed into bundle of FHIR resources. PID-34 is the Last Update Facility field but there is no cognate existing data element in FHIR. We suggest that a standard extension to Patient be created to allow exchange of this concept. 

We suggest a Reference to an Organization as the value.

A portion of the v2 description can be reused as part of the extension narrative:

This extensive identifies the facility of the last update to a patient's/person's identifying and demographic data.