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Paediatric Index of Mortality 3 (PIM3)

Yes only when BOTH pupils are fixed and larger than 3 mm to bright light. Fixed pupils caused by drugs, toxins, or local eye injury do not count as yes (exclusion detail is [NEEDS SOURCE] — ANZICS booklet; see notes).

Ventilated at any time during the first hour in ICU. PIM's definition also counts CPAP and BiPAP (mask or endotracheal); a tracheostomy with spontaneous breathing does not count (inclusion/exclusion detail is [NEEDS SOURCE] — ANZICS booklet).

Yes for a planned admission (elective surgery or elective monitoring/procedure). An unexpected admission after elective surgery that could not have been foreseen is not elective (wording is [NEEDS SOURCE] — ANZICS booklet).

The reason for ICU admission, if it is recovery from a procedure. Mutually exclusive; choose 'none' if the admission is not a post-procedure recovery.

Risk tier of the MAIN reason for ICU admission (at most one). Very high-risk includes e.g. cardiac arrest before admission, SCID, leukaemia/lymphoma after first induction, bone-marrow transplant, liver failure. High-risk includes e.g. spontaneous cerebral haemorrhage, cardiomyopathy/myocarditis, hypoplastic left heart, neurodegenerative disorder, necrotising enterocolitis. Low-risk includes e.g. asthma, bronchiolitis, croup, obstructive sleep apnoea, diabetic ketoacidosis, seizure disorder. Choose 'none' if the reason is not on any list.

First systolic BP from first ICU contact to +1 hour. Leave blank if unknown (defaults to 120). For cardiac arrest at admission enter 0; if shocked with an unmeasurable BP enter 30. (Special-value wording is [NEEDS SOURCE] — ANZICS booklet.)

Arterial or capillary base excess in mmol/L. The equation uses its absolute value, so sign does not matter. Leave blank if unknown (contributes 0).

Fraction of inspired oxygen, simultaneous with the PaO₂. Room air is 0.21. If FiO₂ or PaO₂ is unknown, leave both blank — the FiO₂/PaO₂ term then defaults to 0.23 (PIM3's 'normal' value).

Arterial PaO₂, simultaneous with the FiO₂. Accepts mmHg or kPa. If FiO₂ or PaO₂ is unknown, leave both blank — the FiO₂/PaO₂ term then defaults to 0.23.

Independent clinical validation: pending

Two independent clinical validators will be named here once review is complete.

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How it is calculated

PIM3 score (logit) = 3.8233 × pupils − 0.5378 × elective + 0.9763 × ventilated + 0.0671 × |base excess| − 0.0431 × SBP + 0.1716 × (SBP² ÷ 1000) + 0.4214 × (FiO₂/PaO₂ term) − 1.2246 × bypass-cardiac recovery − 0.8762 × non-bypass-cardiac recovery − 1.5164 × non-cardiac recovery + 1.6225 × very-high-risk diagnosis + 1.0725 × high-risk diagnosis − 2.1766 × low-risk diagnosis − 1.7928, where each pupil, ventilation, elective, recovery, and diagnosis indicator is 1 when present and 0 otherwise (Straney 2013). SBP is in mmHg (unknown → 120; cardiac arrest → 0; shocked/unmeasurable → 30) and enters both linearly and as SBP² ÷ 1000; base excess enters as its absolute value in mmol/L (unknown → 0); the FiO₂/PaO₂ term is (FiO₂ × 100) ÷ PaO₂ with FiO₂ a fraction and PaO₂ in mmHg, or 0.23 when either is unmeasured (PIM3's 'normal' substitute, not PIM2's 0). Predicted mortality (probability) = 1 ÷ (1 + e^−logit). Both the logit and the probability (a value from 0 to 1) are reported, each to 4 decimal places; the derivation paper defines no severity bands.

Limitations and notes

PIM3 estimates the probability of death from data collected at first ICU contact. It is a unit-level case-mix / benchmarking tool — summed individual probabilities across a cohort give an expected death count, compared with observed deaths as a Standardised Mortality Ratio (SMR = observed/expected) — and is NOT an individual bedside prediction. The derivation paper (Straney 2013) defines no diagnostic cut-points or risk bands, so this score reports none. Missing-data conventions are load-bearing: unknown systolic BP defaults to 120 mmHg, unknown base excess contributes 0, and an unmeasured FiO₂/PaO₂ sets that term to PIM3's 'normal' value of 0.23 (a correction — PIM2 used 0). SBP coding: cardiac arrest at admission → enter 0; shocked with an unmeasurable BP → enter 30; unknown → leave blank (120). Use the FIRST value of each variable from first ICU contact up to 1 hour after admission (may include ED/retrieval data), not the worst. Calibration drifts by setting and era (external AUC ~0.80–0.90, variable calibration); recalibrate and monitor locally before comparative interpretation. [NEEDS SOURCE] (all depend on the ANZICS PIM2/PIM3 Information Booklet, which returned HTTP 404 at verification): the pupil-exclusion clause (fixed pupils from drugs/toxins/local eye injury not scored), the mechanical-ventilation CPAP/BiPAP inclusion and tracheostomy-while-spontaneously-breathing exclusion, the elective 'could not have been foreseen' exclusion wording, and the exact verbatim SBP special-value wording (the values cardiac arrest→0 and shocked/unmeasurable→30 are widely repeated but no quotable full-text source was fetched). Per-region calibration statistics and the exact ANZPIC diagnosis-code mappings for each risk tier are also [NEEDS SOURCE].

Accepted input ranges

  • Pupils fixed to bright light
  • Mechanically ventilated in the first hour
  • Elective ICU admission
  • Recovery from a procedure
  • Main-reason risk category
  • Systolic blood pressure — 0–300 mmHg
  • Base excess — -40–40 mmol/L
  • FiO₂ at the time of the PaO₂ — 0.21–1 fraction
  • Arterial PaO₂ — 20–600 mmHg

References

  1. Straney L, Clements A, Parslow RC, et al; ANZICS Paediatric Study Group and PICANet. Paediatric index of mortality 3: an updated model for predicting mortality in pediatric intensive care. Pediatr Crit Care Med. 2013;14(7):673–681.PMID 23863821DOI 10.1097/PCC.0b013e31829760cf
  2. ANZICS Centre for Outcome and Resource Evaluation. PIM2 & PIM3 for the ANZPIC Registry — Information Booklet (Version Jan 2019). Authoritative source for variable coding rules (SBP special values, pupil/ventilation definitions, first-hour timing).Source
  3. Lee OJ, Jung M, Kim M, Yang HK, Cho J. Validation of the Pediatric Index of Mortality 3 in a Single Pediatric Intensive Care Unit in Korea. J Korean Med Sci. 2017;32(2):365–370.DOI 10.3346/jkms.2017.32.2.365

Version and changelog

v1.0.0 · Mortality and severity

  • 2026-07-25 v1.0.0 — Initial release: PIM3 logistic model → predicted mortality probability, with corrected FiO₂/PaO₂ missing-value default of 0.23.

Important

For use by qualified health professionals as an informational and educational aid. It supports clinical judgment and does not replace it. Verify every result independently before making a clinical decision. This is not a medical device.