Inputevents

The inputevents table

Table source: MetaVision ICU database.

Table purpose: Input data for patients.

Number of rows: 8,978,893

Links to:

• patients on subject_id
• admissions on hadm_id
• icustays on stay_id
• d_items on itemid

Brief example

The original source database recorded input data using two tables: RANGESIGNALS and ORDERENTRY. These tables do not appear in MIMIC as they have been merged to form the INPUTEVENTS table. RANGESIGNALS contains recorded data elements which last for a fixed period of time. Furthermore, the RANGESIGNALS table recorded information for each component of the drug separately. For example, for a norepinephrine administration there would be two components: a main order component (norepinephrine) and a solution component (NaCl). The starttime and endtime of RANGESIGNALS indicated when the drug started and finished. Any change in the drug rate would result in the current infusion ending, and a new starttime being created.

Let’s examine an example of a patient being given norepinephrine.

The starttime for the solution (NaCl) and the drug (norepinephrine) would be 18:20. The rate of the drug is 1 mcg/kg/min, and the rate of the solution is 10 mL/hr. The nurse decides to increase the drug rate at 18:25 to 2 mcg/kg/min. As a result, the endtime for the two rows corresponding to the solution (NaCl and norepinephrine) is set to 18:25. Two new rows are generated with a starttime of 18:25. These two new rows would continue until either (i) the drug rate was changed or (ii) the drug was delivery was discontinued. The orderid column is used to group drug delivery with rate of delivery. In this case, we have NaCl and norepinephrine in the same bag delivered at the same time - as a result their orderid is the same (8003). When the rate is changed, a new orderid is generated (8020). The column linkorderid can be used to link this drug across all administrations, even when the rate is changed. Note also that linkorderid is always equal to the first orderid which occurs for the solution, as demonstrated in the example above.

Important considerations

• For Metavision data, there is no concept of a volume in the database: only a rate. All inputs are recorded with a starttime and an endtime. As a result, the volumes in the database for Metavision patients are derived from the rates. Furthermore, exact start and stop times for the drugs are easily deducible.
• A bolus will be listed as ending one minute after it started, i.e. endtime: starttime + 1 minute

Table columns

Detailed Description

subject_id, hadm_id, stay_id

Identifiers which specify the patient: subject_id is unique to a patient, hadm_id is unique to a patient hospital stay and stay_id is unique to a patient ICU stay.

caregiver_id

caregiver_id uniquely identifies a single caregiver who documented data in the ICU information system.

starttime, endtime

starttime and endtime record the start and end time of an input/output event.

storetime

storetime records the time at which an observation was manually input or manually validated by a member of the clinical staff.

itemid

Identifier for a single measurement type in the database. Each row associated with one itemid which corresponds to an instantiation of the same measurement (e.g. norepinephrine).

amount, amountuom

amount and amountuom list the amount of a drug or substance administered to the patient either between the starttime and endtime.

rate, rateuom

rate and rateuom list the rate at which the drug or substance was administered to the patient either between the starttime and endtime.

orderid, linkorderid

orderid links multiple items contained in the same solution together. For example, when a solution of noradrenaline and normal saline is administered both noradrenaline and normal saline occur on distinct rows but will have the same orderid.

linkorderid links the same order across multiple instantiations: for example, if the rate of delivery for the solution with noradrenaline and normal saline is changed, two new rows which share the same new orderid will be generated, but the linkorderid will be the same.

ordercategoryname, secondaryordercategoryname, ordercomponenttypedescription, ordercategorydescription

These columns provide higher level information about the order the medication/solution is a part of. Categories represent the type of administration, while the ordercomponenttypedescription describes the role of the substance in the solution (i.e. main order parameter, additive, or mixed solution)

patientweight

The patient weight in kilograms.

totalamount, totalamountuom

Intravenous administrations are usually given by hanging a bag of fluid at the bedside for continuous infusion over a certain period of time. These columns list the total amount of the fluid in the bag containing the solution.

isopenbag

Whether the order was from an open bag.

continueinnextdept

If the order ended on patient transfer, this field indicates if it continued into the next department (e.g. a floor).

statusdescription

statusdescription states the ultimate status of the item, or more specifically, row. It is used to indicate why the delivery of the compound has ended. There are only six possible statuses:

• Changed - The current delivery has ended as some aspect of it has changed (most frequently, the rate has been changed)
• Paused - The current delivery has been paused
• FinishedRunning - The delivery of the item has finished (most frequently, the bag containing the compound is empty)
• Stopped - The delivery of the item been terminated by the caregiver
• Flushed - A line was flushed.

originalamount

Drugs are usually mixed within a solution and delivered continuously from the same bag. This column represents the amount of the drug contained in the bag at starttime. For the first infusion of a new bag, originalamount: totalamount. Later on, if the rate is changed, then the amount of the drug in the bag will be lower (as some has been administered to the patient). As a result, originalamount < totalamount, and originalamount will be the amount of drug leftover in the bag at that starttime.

originalrate

This is the rate that was input by the care provider. Note that this may differ from rate because of various reasons: originalrate was the original planned rate, while the rate column will be the true rate delivered. For example, if a a bag is about to run out and the care giver decides to push the rest of the fluid, then rate > originalrate. However, these two columns are usually the same, but have minor non-clinically significant differences due to rounding error.