| Highest heart rate (beats per minute) | Integer (0–450) | Highest heart rate from the first 24 hours following admission to the critical care unit |
| Lowest SBP (mmHg) | Integer (0–400) | Lowest SBP from the first 24 hours following admission to the critical care unit |
| Highest temperature (°C) | Real (0.0–46.0) | Highest central temperature from the first 24 hours following admission to the critical care unit. If no central temperature recorded, use highest non-central temperature + 0.5 °C |
| Lowest respiratory rate (breaths per minute) | Integer (0–100) | Lowest rate (either ventilated or non-ventilated) from the first 24 hours following admission to the critical care unit |
| Lowest PaO2 (kPa) | Real (1.0–100.0) | Lowest PaO2 from an arterial blood gas using blood sampled during the first 24 hours following admission to the critical care unit |
| Associated FiO2 | Real (0.21–1.00) | FiO2 associated with the arterial blood gas with the lowest PaO2 |
| Lowest arterial pH | Real (6.10–9.00) | Lowest arterial pH from blood sampled during the first 24 hours following admission to the critical care unit |
| Associated PaCO2 (kPa) | Real (0.0–50.0) | PaCO2 from the arterial blood gas with the lowest arterial pH |
| Highest blood lactate concentration (mmol/l) | Real (0.1–35.0) | Highest blood lactate concentration from the first 24 hours following admission to the critical care unit |
| Total urine output (ml) | Integer (0–99999) | Total urine output from the first 24 hours following admission to the critical care unit. For admissions with a length of stay less than 24 hours, the total over the entire stay is recorded and scaled to represent a 24-hour equivalent |
| Highest urea level (mmol/l) | Real (0.0–300.0) | Highest serum urea concentration from the first 24 hours following admission to the critical care unit |
| Highest creatinine level (µmol/l) | Integer (9–5000) | Highest serum creatinine concentration from the first 24 hours following admission to the critical care unit |
| Highest sodium level (mmol/l) | Integer (40, 260) | Highest serum sodium concentration from the first 24 hours following admission to the critical care unit |
| Lowest WBC count (× 109/l) | Real (0.0–9999.9) | Lowest WBC count from the first 24 hours following admission to the critical care unit |
| Lowest platelet count (× 109/l) | Integer (0–9999) | Lowest platelet count from the first 24 hours following admission to the critical care unit |
| Sedation/paralysis | Categorical | Sedation/paralysis during the first 24 hours following admission to the critical care unit, categorised as: sedated for the entire of the first 24 hours; paralysed and sedated for the entire of the first 24 hours; or neither sedated nor paralysed and sedated for the entire of the first 24 hours |
| Lowest total GCS score | Integer (3–15) | Lowest total GCS score from the first 24 hours following admission to the critical care unit if neither sedated nor paralysed and sedated |
| Age (years) | Integer (0–125) | Age in whole years at admission to the critical care unit |
| Severe liver disease in past medical history | Boolean (yes/no) | Biopsy-proven cirrhosis, portal hypertension or hepatic encephalopathy, evident during the 6 months prior to admission to the critical care unit and documented prior to or at admission to the unit |
| Metastatic disease | Boolean (yes/no) | Distant metastases documented by surgery, imaging or biopsy, evident during the 6 months prior to admission to the critical care unit and documented prior to or at admission to the unit |
| Haematological malignancy | Boolean (yes/no) | Acute or chronic myelogenous leukaemia, acute or chronic lymphocytic leukaemia, multiple myeloma or lymphoma, evident during the 6 months prior to admission to the critical care unit and documented prior to or at admission to the unit |
| Dependency prior to admission | Categorical | Dependency prior to admission to acute hospital, assessed as the best description for the dependency of the patient in the two weeks prior to admission to acute hospital and prior to the onset of the acute illness
Categorised as: able to live without assistance in daily activities; some (minor or major) assistance with daily activities; or total assistance with all daily activities. Daily activities include bathing, dressing, going to the toilet, moving in/out of bed/chair, continence and eating |
| CPR prior to admission | Categorical | CPR (internal or external cardiac massage) received within 24 hours prior to admission to the critical care unit, categorised as: in-hospital CPR (administered by an in-hospital resuscitation team or equivalent); community CPR (not administered by an in-hospital resuscitation team or equivalent); or no CPR. Where a patient received CPR both in the community and in-hospital, this is recorded as community CPR |
| Source of admission | Categorical | The location of the patient immediately prior to admission to the critical care unit, categorised as: emergency department or not in hospital; other acute hospital; Other critical care unit; theatre; or ward or intermediate care area. For patients whose location immediately prior to admission was a transient location of clinic, imaging department, recovery (used as a temporary critical care area) or specialist treatment area, their last non-transient location is recorded |
| Urgency of surgery | Categorical | For patients whose location immediately prior to admission was theatre, the urgency of surgery, categorised as: elective/scheduled; or emergency/urgent (according to the classification of the National Confidential Enquiry into Patient Outcome and Death) |
| Planned admission to the critical care unit | Categorical | Planned admission to the critical care unit, categorised as: planned; unplanned; or, for transfers from another critical care unit only, repatriation. For admissions from theatre, planned admission is defined as acceptance by the critical care unit prior to induction of anaesthesia. For medical admissions, a planned admission is a pre-arranged admission for a planned investigation or high-risk medical treatment. For transfers from another health-care provider, a planned admission is a pre-arranged admission after treatment or initial stabilisation but requiring specialist or higher-level critical care that cannot be provided at the source. Repatriation is defined as a planned transfer because the patient either originated from that critical care unit (i.e. returning after specialist treatment elsewhere) or from that hospital or local area |
| Primary reason for admission | String (13) | Primary reason for admission to the critical care unit, coded using the ICNARC coding method (www.icnarc.org/Our-Audit/Audits/Cmp/Resources/Icm-Icnarc-Coding-Method) |
| Mechanical ventilation | Boolean (yes/no) | Mechanical ventilation at any time during the first 24 hours following admission to the critical care unit |
