Background 

There are over 1.4 million annual attendances to Emergency Departments in the UK following head trauma. 1% of patients have life-threatening injuries, whilst most are discharged. National guidelines (NICE and SIGN) were introduced in England and Scotland with the aim of achieving early identification of acute intracranial lesions through increased CT imaging and safely reducing hospital admissions. Later NICE guidelines recommended that patients with severe injuries are manged in specialist centres.

Aims
To evaluate the impact of the NICE/SIGN head injury guidelines on TBI outcomes and hospital admissions.

Methods 
An interrupted time series analysis for the period 1998 to 2017 was completed using Office of National Statistics linked Hospital Episode Statistics and Information Services Division data for all hospitals in England and Scotland. This constitutes complete national NHS administrative data for England and Scotland for the study period.
Time dependent models for the monthly rate of death and hospital admissions for traumatic brain injuries and head trauma were estimated. A change in the level or trend in the model was assessed for at intervention points for each guideline and the introduction of the 4-hour target. All models were adjusted for seasonality and autocorrelation. The time series for the mortality rate for TBI was further adjusted for comorbidity and demographic factors.

Due to the co-introduction of the 4-hour target with the NICE guidelines, the effect of 4-hour target on admissions was assessed using Scottish data.

Findings 
Both Scottish SIGN guidelines were associated with a monthly decreasing trend in total hospital admissions per 100 000 population (Guideline 1:-0.14 (95% CI: -0.27 to -0.01); Guideline 2:-0.09 (95% CI:-0.13 to -0.05)). The introduction of the 4-hour target was associated with increased hospital admissions (0.13 (95% CI: 0.06 to 0.20)). 

The only guideline associated with a reduction in mortality was the 2nd NICE guideline in England (-0.005 95% CI: -0.007 to -0.002). This guideline specifically recommended that patients with severe injuries should be managed in specialist centres. This effect was only observed in the 16-64 age group.

The monthly TBI mortality and admission rate in the 65+ age group in England  increased from 0.5 to 1.5 and 10 to 30 per 100, 000 population respectively. The increasing mortality rate was unaffected by the introduction any of the guidelines.

Conclusion  
Increased CT imaging needs to be coupled with the management of patients with severe injuries in specialist centers to reduce deaths. The 4 –hour target increased admissions with no observed mortality benefit. Although measures that solely increased CT imaging had no effect on mortality, they reduced admissions for head injury. The cause of the observed increased admission and mortality rate in those 65+ and potential treatments for TBI in this age group requires further investigation.

The impact of the NICE/SIGN head injury guidelines on deaths and hospital admissions in England and Scotland: An Interrupted Times Series.