CRASH-2 Trial - Complete Summary

Background

CRASH-2 stands for Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage. It was designed to test whether tranexamic acid (TXA) - an antifibrinolytic drug long used in elective surgery and obstetrics - could reduce mortality in acutely bleeding trauma patients.

TXA works by inhibiting lysine binding sites on plasminogen, thereby reducing plasmin activity and limiting degradation of fibrin clots (antifibrinolytic mechanism).

Trial Design

Feature	Detail
Design	Randomised, double-blind, placebo-controlled trial
Registration	ISRCTN86750102; NCT00375258
Published	The Lancet, July 2010 (full paper DOI)
Sites	274 hospitals across 40 countries
Sample size	20,211 adult trauma patients
Population	Adults with significant haemorrhage or at risk of it, within 8 hours of injury
Analysis	Intention-to-treat

Intervention

TXA group: Loading dose 1 g IV over 10 min, then 1 g IV infusion over 8 hours
Placebo group: Matching placebo infusion (identical appearance)

Primary Outcome

Death in hospital within 4 weeks of injury, categorized by cause:

Bleeding
Vascular occlusion (MI, stroke, PE)
Multi-organ failure
Head injury
Other

Key Results

Outcome	TXA Group	Placebo Group	RR (95% CI)	p-value
All-cause mortality	14.5% (1463/10,060)	16.0% (1613/10,067)	0.91 (0.85-0.97)	0.0035
Death due to bleeding	4.9% (489)	5.7% (574)	0.85 (0.76-0.96)	0.0077
Vascular occlusive events	No significant increase	-	-	NS
Blood transfusion received	No significant difference	-	-	NS

Absolute risk reduction for all-cause mortality: ~1.5% NNT (number needed to treat): ~67 patients to prevent 1 death

Critical Sub-analysis (Timing of TXA)

A key follow-up analysis (The Lancet, 2011 - "The importance of early treatment") showed a strong time-dependent effect:

Time from injury to TXA	Effect on mortality
< 1 hour	Greatest benefit (RR ~0.68)
1-3 hours	Significant benefit (RR ~0.79)
> 3 hours	Increased risk of death from bleeding (RR ~1.44)

This led to the clinical rule: "TXA must be given within 3 hours of injury."

Strengths

Massive sample size (>20,000) giving high statistical power
Truly global (40 countries, 274 sites) - broad generalizability
Double-blind, placebo-controlled design
Intention-to-treat analysis
No increase in thromboembolic events (safety confirmed)

Criticisms / Limitations

No difference in blood transfusion rates - unusual finding that raised questions about mechanism
A relatively modest proportion of patients actually received blood products (below what might be expected)
Did not use viscoelastic testing or modern massive transfusion protocols (MTP ratios)
The 3-hour window was an exploratory sub-analysis, not a pre-specified primary endpoint

Impact and Clinical Practice

TXA is now a standard of care in trauma haemorrhage worldwide
Incorporated into ATLS, TCCC (Tactical Combat Casualty Care), and most national trauma guidelines
The Barash Clinical Anesthesia textbook notes: "administration of tranexamic acid decreased all-cause mortality and death due to bleeding, with no increase in vascular occlusive events" (Barash's Clinical Anesthesia, 9e)
Tintinalli's Emergency Medicine recommends: "Consider tranexamic acid in all patients with traumatic abdominal hemorrhage... risk of death was most reduced with TXA administration within 1 hour" (Tintinalli's, 9e)

Related Trials

Trial	Focus	Key Finding
CRASH-3 (2019)	TBI without major extracranial bleeding (12,000+ patients)	TXA reduced TBI-related death in mild-to-moderate TBI (RR 0.78); no benefit in severe TBI
MATTERs study	Combat trauma (896 patients)	TXA reduced mortality in massively transfused patients despite higher injury severity
PATCH-Trauma (2026)	Prehospital TXA timing - exploratory analysis (PMID 40751727)	Optimal window may be as short as 90 minutes - benefit most pronounced within 90 min, no benefit beyond 90 min in this cohort

2026 Update

A very recent 2026 exploratory analysis of the PATCH-Trauma RCT (Ali et al., Ann Emerg Med 2026) found that:

TXA within 90 minutes significantly reduced 28-day mortality (adjusted RR 0.64, 95% CI 0.50-0.82)
TXA beyond 90 minutes showed no mortality benefit (adjusted RR 1.04, 95% CI 0.74-1.47)

This suggests the traditional "3-hour window" from CRASH-2 may be overly generous, and the optimal therapeutic window could be even tighter at 90 minutes - though this needs further prospective confirmation.

Bottom line: CRASH-2 remains one of the most impactful trauma trials ever conducted. It established TXA as a cheap, safe, and effective life-saving intervention in bleeding trauma - one of the few pharmacological agents proven to reduce trauma mortality in a large global RCT.

Crash 3 trial

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CRASH-3 trial tranexamic acid traumatic brain injury

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