Identification and characterisation of the high-risk surgical population in the United Kingdom

Abstract

Introduction: Little is known about mortality rates following general surgical procedures in the United Kingdom. Deaths are most common in the 'high-risk' surgical population consisting mainly of older patients, with coexisting medical disease, who undergo major surgery. Only limited data are presently available to describe this population. The aim of the present study was to estimate the size of the high-risk general surgical population and to describe the outcome and intensive care unit (ICU) resource use.

Methods: Data on inpatient general surgical procedures and ICU admissions in 94 National Health Service hospitals between January 1999 and October 2004 were extracted from the Intensive Care National Audit & Research Centre database and the CHKS database. High-risk surgical procedures were defined prospectively as those for which the mortality rate was 5% or greater.

Results: There were 4,117,727 surgical procedures; 2,893,432 were elective (12,704 deaths; 0.44%) and 1,224,295 were emergencies (65,674 deaths; 5.4%). A high-risk population of 513,924 patients was identified (63,340 deaths; 12.3%), which accounted for 83.8% of deaths but for only 12.5% of procedures. This population had a prolonged hospital stay (median, 16 days; interquartile range, 9-29 days). There were 59,424 ICU admissions (11,398 deaths; 19%). Among admissions directly to the ICU following surgery, there were 31,633 elective admissions with 3,199 deaths (10.1%) and 24,764 emergency admissions with 7,084 deaths (28.6%). The ICU stays were short (median, 1.6 days; interquartile range, 0.8-3.7 days) but hospital admissions for those admitted to the ICU were prolonged (median, 16 days; interquartile range, 10-30 days). Among the ICU population, 40.8% of deaths occurred after the initial discharge from the ICU. The highest mortality rate (39%) occurred in the population admitted to the ICU following initial postoperative care on a standard ward.

Conclusion: A large high-risk surgical population accounts for 12.5% of surgical procedures but for more than 80% of deaths. Despite high mortality rates, fewer than 15% of these patients are admitted to the ICU.

Figures

Figure 1

Mortality rates for general surgical patients identified from the CHKS and ICNARC databases. CHKS database: standard, all patients admitted to hospital for a general surgical procedure with an overall mortality rate of less than 5%; high risk, subpopulation of patients undergoing a procedure with an overall mortality rate of 5% or more. ICNARC database: ICU, general surgical patients admitted directly to the intensive care unit following surgery; ward to ICU, patients admitted to the intensive care unit following initial postoperative care on a standard ward.

Figure 2

Duration of hospital stay for general surgical patients identified from the CHKS and ICNARC databases. CHKS database: standard, all patients admitted to hospital for a general surgical procedure with an overall mortality rate of less than 5%; high risk, subpopulation of patients undergoing a procedure with an overall mortality rate of 5% or more. ICNARC database: ICU, general surgical patients admitted directly to the intensive care unit following surgery; ward to ICU, patients admitted to the intensive care unit following initial postoperative care on a standard ward.