ICU stays

Tracking information for ICU stays including admission and discharge times.

The icustays table

Table source: Hospital database.

Table purpose: Defines each ICU stay in the database using STAY_ID.

Number of rows: 73,181

Links to:

  • patients on subject_id
  • admissions on hadm_id

Important considerations

  • stay_id is a generated identifier that is not based on any raw data identifier. The hospital and ICU databases are not intrinsically linked and so do not have any concept of an ICU encounter identifier.
  • The icustays table is derived from the transfers table. Specifically, it excludes rows in transfers where the ward is not an ICU.
  • Multiple consecutive icu stay entries from transfers are merged into a single entry in transfers.
  • Heart rate measurements are used to determine if an icu stay is valid. If the heart rate measurement for an icu stay in transfers is not available, the icu stay will not be included in icustays (~5%).

Table columns

Name Postgres data type
subject_id INT
hadm_id INT
stay_id INT
first_careunit VARCHAR(20)
last_careunit VARCHAR(20)
intime TIMESTAMP(0)
outtime TIMESTAMP(0)

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 ward stay.


FIRST_CAREUNIT and LAST_CAREUNIT contain, respectively, the first and last ICU type in which the patient was cared for. As an stay_id groups all ICU admissions within 24 hours of each other, it is possible for a patient to be transferred from one type of ICU to another and have the same stay_id.

Care units are derived from the TRANSFERS table, and definition for the abbreviations can be found in the documentation for TRANSFERS.


INTIME provides the date and time the patient was transferred into the ICU. OUTTIME provides the date and time the patient was transferred out of the ICU.


LOS is the length of stay for the patient for the given ICU stay, which may include one or more ICU units. The length of stay is measured in fractional days.