Cumulative sum (CUSUM) analysis: A 10 year experience of outcome monitoring in a regional burn centre

Introduction

Outcome monitoring can identify fluctuations in healthcare. Cumulative sum (CUSUM) analysis can detect when mortality deviates from expected, allowing early intervention through targeted audit. We present a 10-year experience of the prospective use of CUSUM methodology in a regional burn centre.

Method

Prospective outcome monitoring was conducted for all admissions to the intensive care unit between 2012 and 2022. The revised Baux score was used for mortality risk prediction. Risk-adjusted CUSUM charts tracked mortality against that predicted by the revised Baux score. Deviations from expected outcomes triggered detailed structured analysis. Learning outcomes were identified from internal and external governance groups.

Results

CUSUM analysis was triggered on eight occasions: one paediatric (excess deaths), six adult (four excess survivors, two excess deaths) and one elderly (excess survivors). Detailed analysis identified areas for continuous improvement and positive themes from excess survivors.

Conclusion

The use of CUSUM as an early warning trigger stimulates assessment of practice and critical appraisal of factors contributing to unexpected mortality or survival. The revised Baux score at its foundation needs to be carefully considered but remains a valid model. One benefit is positive reinforcement of team cohesion and morale during periods of care excellence leading to excess survivors.