NISS — New Injury Severity Score
Modification of the Injury Severity Score (Osler 1997). Sum of squares of the AIS scores of the three most severe injuries regardless of body region. Range 0–75 (any AIS 6 → automatic 75). Better predictor of mortality than ISS in penetrating and blunt trauma.
Score interpretation
→ ED management ± short observation; no trauma centre transfer required if ISS criteria not met.
→ Admit for observation; trauma team reassessment at 6 h; secondary survey documented.
→ Activate major-trauma pathway; transfer to major trauma centre per regional network protocol; FAST + CT trauma series; group + crossmatch; tranexamic acid within 3 h if bleeding.
→ Damage-control resuscitation: 1:1:1 blood products, permissive hypotension (target SBP 80–90 mmHg until haemorrhage controlled), early TXA, surgical / IR haemorrhage control. ICU admission.
Interpretation bands for the NISS. Apply clinical judgement and local guidance.
References
Related
Curated clinical cross-links plus same-class fallbacks.
- Paracetamol overdose · TOXBASE/NPIS; MHRA DSU 2012/2024; SNAP regimen (Lancet 2014)
- TCA overdose · TOXBASE/NPIS; AACT/EAPCCT position statements; Resuscitation Council UK ALS
- Opioid overdose · TOXBASE/NPIS; Resuscitation Council UK
- Anticholinergic toxidrome · TOXBASE/NPIS; AACT/EAPCCT
- Benzodiazepine overdose · TOXBASE/NPIS; AACT/EAPCCT
- β-blocker overdose · TOXBASE/NPIS; AACT/EAPCCT; ESC
Featured in these MRCEM clinical pathways
The NISS is covered in detail — with RCEM/NICE evidence base, indications and pitfalls — in the following exam-focused pathways on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.