Population-based cohort study comparing 30- and 90-day institutional mortality rates after colorectal surgery

Abstract

Background: Surgical mortality results are increasingly being reported and published in the public domain as indicators of surgical quality. This study examined how mortality outlier status at 90 days after colorectal surgery compares with mortality at 30 days and subsequent intervals in the first year after surgery.

Methods: All adults undergoing elective and emergency colorectal resection between April 2001 and February 2007 in English National Health Service (NHS) Trusts were identified from administrative data. Funnel plots of postoperative case mix-adjusted institutional mortality rate against caseload were created for 30, 90, 180 and 365 days. High- or low-mortality unit status of individual Trusts was defined as breaching upper or lower third standard deviation confidence limits on the funnel plot for 90-day mortality.

Results: A total of 171 688 patients from 153 NHS Trusts were included. Some 14 537 (8·5 per cent) died within 30 days of surgery, 19 466 (11·3 per cent) within 90 days, 23 942 (13·9 per cent) within 180 days and 31 782 (18·5 per cent) within 365 days. Eight institutions were identified as high-mortality units, including all four units with high outlying status at 30 days. Twelve units were low-mortality units, of which six were also low outliers at 30 days. Ninety-day mortality correlated strongly with later mortality results (rs = 0·957, P < 0·001 versus 180-day mortality; rs = 0·860, P < 0·001 versus 365-day mortality).

Conclusion: Extending mortality reporting to 90 days identifies a greater number of mortality outliers when compared with the 30-day death rate. Ninety-day mortality is proposed as the preferred indicator of perioperative outcome for local analysis and public reporting.

Fig. 1

Funnel plot of risk-adjusted postoperative mortality against total caseload by Trust from 0 to 30 days (90-day mortality outliers marked). HMU, high-mortality unit; LMU, low-mortality unit

Fig. 2

Funnel plot of risk-adjusted postoperative mortality against total caseload by National Health Service (NHS) Trust from 0 to 90 days (90-day mortality outliers marked). HMU, high-mortality unit; LMU, low-mortality unit

Fig. 3

Funnel plot of risk-adjusted postoperative mortality against total caseload by National Health Service (NHS) Trust from 0 to 180 days (90-day mortality outliers marked). HMU, high-mortality unit; LMU, low-mortality unit

Fig. 4

Funnel plot of risk-adjusted postoperative mortality against total caseload by National Health Service (NHS) Trust from 0 to 365 days (90-day mortality outliers marked). HMU, high-mortality unit; LMU, low-mortality unit