Timing in Pharmacy Models
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Introduction
Timed events occur frequently in healthcare where time has to be recorded for clinical, administrative or medico-legal reasons. The following discussion relates to timed events in the medication management domain as represented in the Medication Information model. Additional material on timing is available in the RIM and Data types sections of the HL7 documentation.
In the medication information model the concept of time apply to ACTS (eg. medication prescription, supply and administration) in the various moods of Act (eg. promise, order, event) and to PARTICIPATIONS (e.g. authoring, data entry, verifying, or performing a medication promise, order, event). Not all combinations of these Acts, Moods, and Participations will be relevant to any particular message hence not all potential timed events will be required. Because there are so many potential time related issues following a medication process from prescription through to administration, this discussion has been prepared to enable those implementing Version 3 messages to achieve a clear understanding of the time recording issues. Each of the various HL7 time artifacts has to correspond to the records of timed events in the real world.
Time Data Types
The following data types are used to represent time in medication information model:
•The time stamp (TS) which identifies a particular point in time. It can vary in precision from describing a particular year to a particular millisecond.
•The interval of time stamps (IVL_TS) describes a low value time stamp, which is usually a "start" time, a high value time stamp, which is usually a "stop" or "end" time, and the interval between, either as a "width" (value and units) or centre point time stamp. Any or all of these characteristics might be specified in any interval attribute.
•The Generic Timing Specification (GTS) describes complex patterns of time in terms of interrelated sets of time stamps and/or intervals of time. Within this Pharmacy domain, the most common implementation of this will be the Periodic Interval of Time, the PIVL, which is a generalization of the more complex GTS. Timing Attributes in "Act"
In general, Act classes in HL7 have the following types of timing events:
•The time(s) that the act will occur or has occurred from a clinical effect perspective, is described in the EFFECTIVE TIME. The effective time can describe the time an event started, stopped and its duration (the interval between start and stop) or complex timing sequences which are variations of this. The focus is on the time that is 'biologically relevant' to the patient. In the Pharmacy domain, for the SBADM act, this is therefore closely related to the "when" part of the dosage information; however, because "a substance administration act" may be describing an ongoing process that occurs at many points in time (e.g. "three times a day) within a time period (which may or may not be indefinite, e.g. "for 7 days", or "continuously"), the description of timing is often "nested". For the SPLY act, the effective time is the "when" the supply is to be or was made. (Data Type - GTS)
•The time (s) during which the act will occur or which occurred from an administrative or resource use perspective, is known as the ACTIVITY TIME. This can describe the time an event started, stopped and the interval or complex timing sequences which occurred between. For example this could be the time taken to prepare, commence, monitor, finish and clean up after the administration of an intravenous solution. (Data Type - GTS)
•The time at which the system recorded or became aware of the Act, is known as the AVAILABLITY TIME. This allows for Acts which occurred in the past to be recorded. The availability time will in most cases be the same time as the effective time and is not widely used. But there are some example use cases, such as to describe when the statement that "a particular medication is known to have been administered to a patient at some time in the past" becomes known and recorded. (Data Type - Time Stamp) Note: The context (mood) of the event being described will determine how the timing attributes should be interpreted. Further information is available from the RIM documentation relating to the timing attributes of ACT.
Participation Time Events
An Act is also modified by participations which occur such as authoring, performing, data recording, and verifying. The relevance of these participations will be determined by the story board as in some situations not all of these occur or are recorded as occurring separately.
In the Pharmacy Information model the Authoring (prescribing or ordering) PARTICIPATION TIME is modeled; this is usually the key information about the "when" a prescription is authorised. The data recording, and verifying times may be recorded if necessary. A performer time is not used, because in this domain, this is synonymous with the key attribute of effective time within the act itself.
While Participation Times allow for the interval of time datatype, in pharmacy we will generally only use the Time Stamp data type to signify time that a prescription is written (authored) or transcribed (data enterer etc.). However in the example below we have also used an interval time to demonstrate that it possible to record the duration of this process in some situations.
Storyboard to Illustrate Medication Information Timing
The following limited storyboard covers the timed events which are included in the Pharmacy information model.
•Dr. Hypocrites writes a prescription at 1330 hrs. on January 1, 2003 (time A).
•Dr. Hypocrites' billing system records the time taken to create the prescription (including drug selection, contraindication management and printing) is two minutes (time B).
•The prescription is ordered to commence at noon on January 2nd (time C) , and is to be completed two weeks later on the 16th January (time D).
•The prescription calls for an intravenous drug solution to be administered twice a day (time E) for a period of 30 minutes (time F).
•The prescription also indicates that the first allowed fill (dispense) date is January 2nd (time G) and the last allowed fill date (expiry date) is January 16 (time H), with dispensing to occur on a daily interval (time I).
•The pharmacy receives the prescription, and Suzy Supply takes 10 minutes (time J) to mix and prepare the i.v. solution.
•She dispenses it to the Coronary Care Unit at 10am (time K).
•Florence Nightingale prepares to give the infusion at 10.50am on 2nd January (set up the i.v tubing etc) and commences the infusion at 11am (time L) and it is complete by 11.30am (time M).
•She removes the iv and cleans up and finishes at 11.40am. The total nursing time involved (including setup, monitoring and completion) is 50 minutes (time N) . Note: Times A to I refer to the "prescription", which in this example is a combined substance administration and supply order, where the focal act(s) are in the mood RQO.
Time Topic Notes
A Description Time a script was written (date prescribed or ordered), date written on the prescription
Model Mapping Participation.time end time on the 'Author' participation for an Order
Data Types IVL(TS) (end) or TS (if no interval is required - usual situation)
B Description Time taken to write the prescription (tracked for billing purposes)
Model Mapping Length of Participation.time duration on the 'Author' participation for an Order
Data Types IVL(TS) (width)
C Description Part of the dosage instructions: the medication process start date (first time patient should be administered the drug under the course of treatment covered by the prescription)
Model Mapping Outer boundary start on the phase of PIVL within the in EffectiveTime attribute in the SubstanceAdministrationProcess act.
Data Types Phase attribute of a bounded PIVL in GTS
D Description Part of the dosage instructions: the medication process end date (last time patient should be administered the drug under the course of treatment covered by the prescription)
Model Mapping Outer boundary end on the phase of PIVL within the Effective Time attribute in the SubstanceAdministrationProcess act
Data Types Phase attribute of a bounded PIVL in GTS
E Description Part of the dosage instructions - the dosage frequency - twice a day
Model Mapping The Frequency attribute of PIVL within the EffectiveTime attribute in the SubstanceAdministrationProcess act
Data Types Frequency attribute within (a bounded) PIVL (see datatypes R2)
F Description Part of the dosage instructions - the duration of each actual administration - 30 minutes
Model Mapping The amount of time of the Period attribute in (a bounded) PIVL within the Effective Time attribute in the SubstanceAdministrationProcess act
Data Types PQ in Period of PIVL in GTS
G Description Supply start date - the first day the medication can be dispensed
Model Mapping Outer boundary start on the phase of PIVL within the in the Supply Process effectiveTime
Data Types Phase attribute of PIVL in GTS
H Description Supply end date - last day the medication can be dispensed
Model Mapping Outer boundary end on the phase of PIVL within the in the SupplyProcess effectiveTime
Data Types Phase attribute of PIVL in GTS
I Description Part of the supply instructions - the Dispense interval
Model Mapping The Frequency attribute of PIVL within the effectiveTime attribute in the SupplyProcess act
Data Types Frequency attribute within PIVL (see datatypes R2
Note: Times J to K refer to the "dispense", which in this example is a combined supply with substance administration , where the focal act (SPLY) is in the mood EVN.
J Description Administrative time to dispense (time taken to prepare the medication for supply)
Model Mapping Duration of the activityTime for the Supply process event
Data Types Width attribute of the IVL in the IVL part of a bounded PIVL in GTS
K Description The actual time of (one of the) dispense act(s)
Model Mapping The High attribute of the IVL in the IVL part of a bounded PIVL in the effective Time of the SupplyProcess
Data Types The High attribute of the IVL in the IVL part of a bounded PIVL in GTS
Note: Times L to N refer to the "administration", which in this example is a substance administration so the focal act (SBADM) is in the mood EVN.
L Description The infusion administration start time
Model Mapping The inner boundary start on the phase of PIVL within the in EffectiveTime attribute in the SubstanceAdministrationProcess
Data Types Phase attribute of a bounded PIVL in GTS
M Description The infusion administration end time
Model Mapping The inner boundary end on the phase of PIVL within the in EffectiveTime attribute in the SubstanceAdministrationProcess
Data Types Phase attribute of a bounded PIVL in GTS
N Description Administrative time to perform the administration (retrieve drug from cart, prep injection site, perform injection, dispose of remains) start, stop and width 50min
Model Mapping Duration of the activityTime attribute of the SubstanceAdministrationProcess
Data Types Width attribute of the IVL in the IVL part of a bounded PIVL in GTS
For further information on how to describe timing of dosage, please see the Dosage Instructions document in the Appendix to the Pharmacy ballot.
