Surveillance of Surgical Site Infection Annual Report For procedures carried out from: January 2003 - December 2010 Scottish Surveillance of Healthcare Associated Infection Programme (SSHAIP)
Table of Contents Acknowledgement 5 Glossary 6 Key Points 7 1. Introduction 9 2. Aims and Objectives 10 3. Methods 10 3.1 Surveillance methodology 10 3.2 Post discharge and readmission surveillance 11 3.3 Analysis presented in this report 11 4 Results 13 4.1 Procedures 13 4.2 Patient demographics 13 4.3 Incidence of SSI in 2010 14 4.4 Incidence of SSI from 2003 to 2010 15 4.5 Characteristics of SSI 17 4.6 Inpatient incidence density of SSI, by year of surveillance, 2003 to 2010 17 4.7 Incidence of SSI by risk group 22 4.8 Readmission Surveillance for Hip Arthroplasty Procedures 23 4.9 PDS Surveillance for Caesarean Section 25 4.10 Variation in SSI Rate by NHS board 27 4.11 Compliance with guidelines 29 5. Discussion 33 6. Conclusions 35 7. Developments 35 8. References 36 9. Appendices 37 Appendix I: SSI rates 37 Appendix II: NNIS Risk Score 37 2
List of Tables Table 1: Annual number of operations by procedure category 13 Table 2: Median age and proportion of female patients by procedure category 2003 to 2010 and 2010 13 Table 3: Number of participating boards, procedures, inpatient SSI and inpatient cumulative SSI incidence rate by procedure, 2010 14 Table 4: Number of patient days, inpatient SSI and incidence density of inpatient SSI per 1000 post operative inpatient days with 95% confidence interval, by category of procedure, 2010 15 Table 5: Number of procedures, inpatient SSI and inpatient cumulative incidence SSI rate by procedure, 2003 to 2010 15 Table 6: Inpatient cumulative SSI incidence rate by procedure, 2003-2010 16 Table 7: Incidence density of inpatient SSI per 1000 post operative inpatient days with 95% confidence interval, by category of procedure, 2003 to 2010 16 Table 8: Cumulative incidence of inpatient SSI, by category of surgical procedure, by NNIS risk index for, 2003 to 2009 and 2009 22 Table 9: Number of procedures, SSI and rate of SSI by hip arthroplasty subcategory 2007 to 2010 23 Table 10: Number of procedures, SSI and rate of SSI by hip arthroplasty subcategory for January to December 2010 24 Table 11: SSI rate with 95% confidence interval by caesarean section procedure for inpatient and PDS to day 10 January to December 2010 25 3
List of Figures Figure 1: Infection type by procedure, inpatient SSI 2003 to 2010 17 Figure 2: Infection type by procedure, inpatient SSI 2010 17 Figure 3: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for abdominal hysterectomy, 2003 to 2010 18 Figure 4: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for breast surgery, 2003 to 2010 18 Figure 5: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for caesarean section, 2003 to 2010 19 Figure 6: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for hip arthroplasty, 2003 to 2010 19 Figure 7: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for knee arthroplasty 20 Figure 8: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for major vascular surgery 20 Figure 9: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for open reduction of long bone fracture 21 Figure 10: Method of detection by year for hip arthroplasty to day 30, 2007-2010 23 Figure 11: Method of detection for hip arthroplasty to day 30, January to December 2010 24 Figure 12: Proportion of SSI involving superficial incisions or deep and organ space, January 2007 to December 2010, for hip arthroplasty procedures (inpatient and readmission to day 30) 25 Figure 13: SSI rate for both inpatient and PDS to day 10 by caesarean section procedure January to December 2010 26 Figure 14: Proportion of SSI involving superficial incisions or deep and organ space, January 2010 to December 2010, for caesarean section procedures (inpatient and PDS to day 10) 26 Figure 15: Cumulative incidence (no of SSI per 100 procedures) of SSI rate including inpatient and PDS to day 10 (NNIS = 0) by NHS board in 2010 for caesarean section procedures (n = 12647) 27 Figure 16: Cumulative incidence (no of SSI per 100 procedures) of inpatient and readmissions to day 30 SSI (NNIS = 0) by NHS board in 2010 for hip arthroplasty (n = 4744). 28 Figure 17: Timing of administration of antibiotic prophylaxis for hip and knee arthroplasty surgery in 2010 (n = 9002) 29 Figure 18: Duration of prophylactic antibiotics therapy for caesarean section and orthopaedic procedures in 2010 (n = 24854) 30 Figure 19: Prophylactic antibiotics given in accordance with local guidelines for caesarean section and orthopaedic procedures in 2010 (n = 24854) 30 Figure 20: Antibiotic impregnated cement used for hip arthroplasty procedures in 2010 (n = 6309) 31 Figure 21: Consultant performing procedure or present within theatre for hip arthroplasty surgery in 2010 (n = 9625) 31 Figure 22: Administration of venous thromboembolism prophylaxis for hip and knee arthroplasty procedures in 2010 (n = 14483) 32 4
Acknowledgement The Surgical Site Infection (SSI) surveillance staff, throughout NHS boards, are to be commended for their efforts dedicated to collecting and reporting SSI data to Health Protection Scotland (HPS). Thanks are also extended to the members of the Scottish Surveillance of Healthcare Associated Infection Programme (SSHAIP) team who have contributed to this report and the SSI programme of surveillance in order to make a difference to the care surgical patients receive in NHSScotland. 5
Glossary ASA AA BR CABG CEL DG ECDC ECOSS FF FV GR GGC HAI HDL HPA HPS HG ICTs LN LO NHS NNIS NWTC OPCS4 OR PDS SAPG SH SIGN SSHAIP SSI SSIRS TY WI American Society of Anesthesiologists Ayrshire & Arran Borders Coronary arterial bypass grafts Chief Executive Letter Dumfries & Galloway European Centre for Disease Control Electronic Communication of Surveillance in Scotland Fife Forth Valley Grampian Greater Glasgow & Clyde Healthcare associated infections Health Department Letter Health Protection Agency Health Protection Scotland Highland Infection Control Teams Lanarkshire Lothian National Health Service National Nosocomial Infection Surveillance National Waiting Times Centre Office of Population, Censuses and Surveys Classification of Surgical Operations and Procedures (4th revision) Orkney Post discharge surveillance Scottish Antimicrobial Prescribing Group Shetland Scottish Intercollegiate Guideline Network Scottish Surveillance of HAI Programme Surgical site infection Surgical site infection reporting system Tayside Western Isles 6
Key Points Surveillance of Surgical Site Infection data for procedures performed between January 2003 and December 2010 NHS Board participation Health Protection Scotland (HPS) continue to facilitate national surveillance of surgical site infection (SSI). All 15 of the NHS boards in Scotland participated in the SSI programme in the eighth year (2010). In the last year, 2010, 190 inpatient SSI resulting from 34514 procedures have been reported to HPS. In the eight complete years surveillance has been performed (2003 to 2010) 1883 inpatient SSI, resulting from 192007 procedures, have been reported to HPS. The results from the surveillance programme have been used by NHS boards at a local level to review clinical practice and have resulted in improvements in performance, both in terms of the process of care (e.g. antibiotic prophylaxis compliance) and in terms of outcome (i.e. reduction in SSI rates). New developments Within NHSScotland, HPS conducted a pilot study for light SSI surveillance (which represents the minimal data to be collected locally) for non mandatory procedures within participating NHS boards during January and February 2011. Key findings A total of 192007 procedures have been reported to HPS during the period 2003 to 2010 resulting in a total of 1883 inpatient infections. The number of procedures reported to HPS has increased each year, although there has been a decrease in some of the voluntary procedures. In 2010, a total of 34514 procedures were reported to HPS. The inpatient SSI cumulative incidence SSI rates in 2010 varied by surgical procedure and ranged from knee arthroplasty (0.2%) to major vascular surgery (5.4%). Readmission surveillance until day 30 post operatively for hip arthroplasty has resulted in a higher proportion of SSIs being detected following discharge from hospital (44.8%). The proportion of caesarean section SSI detected by post discharge surveillance (PDS) to day 10, not including in patient infections, was 87.9%. The more serious infections for hip arthroplasty were identified in patients readmitted to hospital following discharge. The incidence of SSI increased with the number of risk factors present for the categories of surgery where there were sufficient data to perform these analyses. 7
Trends in rates of SSI The inpatient SSI incidence density rates in NHSScotland over the duration of the SSI surveillance programme (2003-2010) showed a significant linear reduction for breast surgery, caesarean section, hip arthroplasty, knee arthroplasty, major vascular surgery and open reduction of long bone fracture. The SSI rates for the mandatory hip arthroplasty and caesarean section procedures in Scotland over the duration of the SSI surveillance programme have decreased since 2003 but have remained relatively stable over the last three years of reporting, 2008-2010. Variation between NHS Boards The incidence of SSI varied by NHS board performing the surgery. This variation may be attributable to the number of procedures performed, case mix of the patient population and length of stay variations. 8
1. Introduction Surgical site infection (SSI) is one of the most common healthcare associated infections (HAI), estimated to account for 15.9% of inpatient HAI 1 in NHSScotland. SSI have serious consequences for patients affected as they can result in pain, suffering and in some cases require additional surgical intervention 2. The impact on the individual can be difficult to quantify, however a recent study 3 found that following deep SSI, patients experienced pain, isolation, social and economic problems. SSI is the most preventable of all HAI 1,4. SSI cause excess morbidity and mortality and are estimated on average to double the cost of treatment, mainly due to an increase in length of stay 5.The average length of stay in NHSScotland decreased from 6.0 days in 2004 to 5.3 days in 2008 6 ; this may be due to advances in surgical techniques, the introduction of less invasive procedures and the move towards day case surgery. Literature from several countries suggests that between 53% and 84% of SSI may occur following discharge from hospital and as post operative length of stay has decreased more of these infections may occur in the community 7-10. These trends make detection of SSI after discharge, or PDS, increasingly important in identifying the true risk of infection following surgery 10,11. All NHS boards participate in SSI surveillance for at least two procedures from a list of ten 12. Prospective readmission surveillance for hip arthroplasty 30 post operative days and for caesarean section procedures for 10 post operative days is mandatory 13,14. The overarching aim of SSI surveillance is to reduce the incidence of infection following surgical intervention. One factor in achieving this aim is to encourage NHS boards to use local data to evaluate local practice. A quarterly report is produced and distributed by Health Protection Scotland (HPS) to each NHS board showing their results for that quarter broken down by the major reported risk factors for SSI. An electronic reporting tool has been developed by HPS entitled surgical site infection reporting system (SSIRS). This SSIRS tool enables NHS boards to examine local SSI data and produce local reports and also facilitates boards to monitor their SSI rates in real time. Both the quarterly reports and SSIRS can be used to monitor local practice and initiate further investigation and action. In addition to the quarterly reports, supplementary analyses are undertaken by HPS on a quarterly basis to identify any NHS board shown to have a significant change in SSI rates between two quarters or a higher than expected rate within the quarter. These NHS boards are alerted to changes by the production of an individual exception report. NHS boards identified are contacted by HPS to highlight the high rate and are advised to take appropriate action to investigate these changes. HPS facilitates local investigation when requested. An important aspect of SSI surveillance data is to monitor compliance with best practice as defined within clinical guidelines and care bundles as this can assist in reducing infection rates 15. The Scottish Intercollegiate Guideline Network (SIGN) produce evidence based guidelines to promote best clinical practice. SIGN Guideline 104, Antibiotic Prophylaxis in Surgery 16 is aimed at reducing inappropriate prophylactic prescribing and recommends that intravenous prophylactic antibiotics should be given less than or equal to 30 minutes before the skin is incised, the duration of antibiotic prophylaxis should not be more than 24 hours and that antibiotic impregnated cement is used for cemented joint replacement. SIGN Guideline 62, Prophylaxis of venous thromboembolism 17 recommends all general, gynaecological or orthopaedic surgery patients should have mechanical and/or chemical 9
prophylaxis. This report will present compliance throughout NHSScotland with these guidelines. HPS have published guidelines on the prevention and treatment of SSI in the SSI Prevention Bundle http://www.hps.scot.nhs.uk/haiic/ic/ssipreventionbundle.aspx and the SSIRS tool has been developed to support the SSI Prevention Bundle. This report presents the results of the analysis of the cumulative data from 2003 to 2010 and on 2010 data. 2. Aims and Objectives The aim of this report is to estimate the magnitude of SSI risk in surgical patients in NHS Scotland. The objectives of this report are: To describe the characteristics of patients included in the surveillance programme To present the incidence density SSI rates by surgical procedure in the most recent years of surveillance and over the whole period of surveillance To describe the characteristics of inpatient SSI identified within the surveillance programme To identify trends in incidence density SSI rates over the period 2003 to 2010 To describe the variation in incidence density SSI rates between NHS boards and highlight boards with unexpectedly high rates To describe the characteristics of SSI identified by post discharge and readmission surveillance since these components of surveillance were made mandatory To assess compliance with SIGN guidelines at a national level including those pertaining to the prevention of SSI and the administration of prophylactic antibiotics. 3. Methods 3.1 Surveillance methodology Data are collected according to the Scottish Surveillance of HAI Programme (SSHAIP) standardised national protocol 12 to ensure a consistent approach to data collection. The Centers for Disease Control and Prevention case definitions for SSI are used 18. SSI must occur within 30 days of surgery. A list of procedures included in the surveillance programme can be found in the SSI surveillance protocol and resource pack 5th Edition 12 : http://www. hps.scot.nhs.uk/haiic/sshaip/guidelines.aspx As a minimum, where these procedures are performed, NHS boards must continually collect data on hip arthroplasty and caesarean section procedures, in line with the requirements of HDL (2006) 38 13 and CEL (11) 2009 14. 10
3.2 Post discharge and readmission surveillance This report contains rates of SSI for caesarean section procedures detected until day 10 post operatively which was made mandatory from the 1st April 2009. All NHS boards have established networks with community midwives who routinely monitor caesarean section patients for the first 10 days after surgery and all SSI identified through PDS are reported to HPS. Each NHS board has established methods to identify patients readmitted with an SSI within 30 days following hip arthroplasty; thus identifing additional SSI to those found during the inpatient period. The report indicates where caesarean section PDS infections or hip arthroplasty readmission infections are included in analyses. Analyses of caesarean section PDS to day 10 will be limited to 2010. 3.3 Analysis presented in this report This report includes eight years of SSI surveillance data and describes cumulative data from 2003 to 2010 and the most recent years data from 2010. A total of 15 NHS boards, 14 territorial and one special NHS board participated in the mandatory programme of SSI surveillance. The SSI rates described in this report are presented as cumulative incidence SSI rates (number of SSI/number of procedures*100) or as incidence density SSI rates (number of inpatient SSI/number of inpatient post operative days*1000), used where the length of stay may be a confounding factor (Appendix I). All rates described in this report are inpatient SSI rates unless otherwise stated. Patient days are calculated as the number of days from operation until discharge from hospital. Annual rates are presented as inpatient SSI incidence density rates to allow for changes in the inpatient length of stay from 2003 to 2010 and trends in annual rates are assessed through using the linear by linear association chi-square test. This test examines linear changes over time. The National Nosocomial Infection Surveillance (NNIS) risk index allows benchmarking to be carried out whilst accounting for differences in the distribution of risk factors in comparison patient populations (Appendix II). Within this report comparison of SSI rates between NHS boards is performed using only procedures with a NNIS score of 0 to eliminate confounding factors included in the NNIS score, however this does not correct for other possible confounding factors. Comparison of NHS boards inpatient cumulative incidence SSI rates for the latest year are made through the production of funnel plots 19,20 and for caesarean section procedures these comparisons are made separately with inpatient rates and rates including PDS surveillance to post operative day 10. For hip arthroplasty procedures, a comparison is made separately with rates including SSI identified on readmission to hospital within 30 days of the operation. In order to limit the influence of case mix on these comparisons only patients with a NNIS score of 0 have been included in these funnel plots. The funnel 11
plots in this report show the upper and lower 95% confidence limits as curved lines. If an individual NHS board s rate was outwith the 95% confidence limit, this is regarded as an outlier, suggesting an SSI rate which was significantly different to other NHS boards. Rates of compliance with relevant recommendations from published SIGN guidelines are shown by procedure category. As all CABG and cardiac procedures reported to the SSI programme were undertaken within one NHS board, analysis of these procedure categories is limited to number of procedures performed, inpatient SSI, inpatient SSI rates and patient demographics and are not included in more detailed analyses. Cranial surgery SSI surveillance has not been selected by any NHS board to be performed during 2008, 2009 and 2010 and therefore was not included in the results. All confidence limits in this report were produced using the Wilson s approximation to the binomial distribution 21. 12
4 Results 4.1 Procedures The annual number of procedures by procedure category are shown in Table 1. Table 1: Annual number of operations by procedure category Procedure 2003 2004 2005 2006 2007 2008 2009 2010 Total Abdominal hysterectomy 774 701 836 922 1107 915 821 845 6921 Breast surgery 576 454 522 424 356 393 798 892 4415 CABG 297 373 298 291 444 669 850 824 4046 Caesarean section 2482 3137 4967 6152 13148 14035 14497 15229 73647 Cardiac surgery 0 18 8 39 47 252 334 406 1104 Hip arthroplasty* 3506 5481 6202 5340 8141 9195 9501 9625 56991 Knee arthroplasty 2154 3329 3734 4178 4499 4699 4901 4858 32352 Major vascular surgery 125 177 213 208 125 162 244 312 1566 Open reduction of long bone fracture** 849 1382 1502 1065 1438 1611 1595 1523 10965 Total 10763 15052 18282 18619 29305 31931 33541 34514 192007 * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur The total number of procedures included in the surveillance programme has increased year on year since 2003, resulting in three times as many procedures included in surveillance in 2010 than there were in 2003. 4.2 Patient demographics The median age and proportion of female patients for each procedure category during 2003 to 2010 and 2010 are described in Table 2. Table 2: Median age and proportion of female patients by procedure category 2003 to 2010 and 2010 Procedure 2003 to 2010 2010 Median age % female patients Median age % female patients Abdominal hysterectomy 47 100.0% 49 100.0% Breast surgery 60 98.5% 61 98.7% CABG 67 22.6% 68 22.7% Caesarean section 32 100.0% 31 100.0% Cardiac surgery 68 47.9% 67 47.5% Hip arthroplasty* 71 62.7% 71 62.5% Knee arthroplasty 70 57.7% 69 57.9% Major vascular surgery 72 28.1% 70 33.4% Open reduction of long bone 81 72.5% 81 73.1% fracture** * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur 13
The median age and percentage of female patients did not significantly change between these time periods for each of the nine procedure categories. For patients undergoing caesarean section, who had their age recorded, the majority were under 35 years old (72.5%) with a further 26.9% aged between 35 and 44 years old. For hip arthroplasty, for those patients who had their age recorded, the majority of patients were 65 years or older (n= 6416, 68.9%). 4.3 Incidence of SSI in 2010 A total of 34514 procedures were reported during 2010. Table 3 shows the inpatient SSI (cumulative incidence) rates by procedure over this period. Table 3: Number of participating boards, procedures, inpatient SSI and inpatient cumulative SSI incidence rate by procedure, 2010 Procedure Number of NHS boards Number of procedures Inpatient SSI Inpatient SSI Rate (%) (95% CI) Abdominal hysterectomy 5 845 9 1.1 (0.6, 2.0) Breast surgery 3 892 5 0.6 (0.2, 1.3) CABG 1 824 26 3.2 (2.2, 4.6) Caesarean section 14 15229 52 0.3 (0.3, 0.4) Cardiac surgery 1 406 6 1.5 (0.7, 3.2) Hip arthroplasty* 15 9625 58 0.6 (0.5, 0.8) Knee arthroplasty 9 4858 9 0.2 (0.1, 0.4) Major vascular surgery 2 312 17 5.4 (3.4, 8.6) Open reduction of long bone fracture** 9 1523 8 0.5 (0.3, 1.0) Total - 34514 190 0.6 (0.5, 0.6) * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur The inpatient cumulative incidence SSI rates ranged from major vascular surgery with a rate of 5.4% to knee arthroplasty with a rate of 0.2%. To allow for differences in post operative length of stay it is possible to calculate a rate of SSI that uses the number of post operative days of follow-up as the denominator rather than the number of procedures. This rate is called the incidence density and is expressed as the number of SSI per 1000 post operative days of follow-up (Table 4). This method is particularly useful when comparing SSI rates over a sustained period of time when practice can change or in comparing between different healthcare systems, e.g. between countries. 14
Table 4: Number of patient days, inpatient SSI and incidence density of inpatient SSI per 1000 post operative inpatient days with 95% confidence interval, by category of procedure, 2010 Procedure Patient days Inpatient SSI Inpatient SSI Rate (%) (95% CI) Abdominal hysterectomy 3748 9 2.4 (1.3, 4.6) Breast surgery 2174 5 2.3 (1.0, 5.4) CABG 7506 26 3.5 (2.4, 5.1) Caesarean section 48868 52 1.1 (0.8, 1.4) Cardiac surgery 3681 6 1.6 (0.7, 3.6) Hip arthroplasty* 70966 58 0.8 (0.6, 1.1) Knee arthroplasty 27294 9 0.3 (0.2, 0.6) Major vascular surgery 4206 17 4.0 (2.5, 6.5) Open reduction of long bone fracture** 15313 8 0.5 (0.3, 1.0) Total 183756 190 1.1 (0.9, 1.2) * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur The highest incidence density SSI rate was reported in major vascular surgery at 4.0 SSI per 1000 patient days and the lowest rate was reported in knee arthroplasty at 0.3 SSI per 1000 patient days. 4.4 Incidence of SSI from 2003 to 2010 A total of 192007 procedures were reported during the surveillance period 2003 to 2010. Table 5 shows the inpatient SSI (cumulative incidence) rates by procedure over this period. Table 5: Number of procedures, inpatient SSI and inpatient cumulative incidence SSI rate by procedure, 2003 to 2010 Procedure Number of NHS boards Number of procedures 2003 to 2010 Inpatient SSI Inpatient SSI Rate (%) (95% CI) Abdominal hysterectomy 10 6921 110 1.6 (1.3, 1.9) Breast surgery 4 4415 34 0.8 (0.6, 1.1) CABG 1 4046 161 4.0 (3.4, 4.6) Caesarean section 15 73647 603 0.8 (0.8, 0.9) Cardiac surgery 1 1104 20 1.8 (1.2, 2.8) Hip arthroplasty* 15 56991 578 1.0 (0.9, 1.1) Knee arthroplasty 12 32352 139 0.4 (0.4, 0.5) Major vascular surgery 3 1566 107 6.8 (5.7, 8.2) Open reduction of long bone fracture** 12 10965 131 1.2 (1.0, 1.4) Total - 192007 1883 1.0 (0.9, 1.0) * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur 15
The highest overall inpatient SSI rate over this period was in major vascular surgery at 6.8% and the lowest inpatient SSI rate was found in knee arthroplasty at 0.4%. The annual inpatient SSI rate by procedure category is shown in table 6. Table 6: Inpatient cumulative SSI incidence rate by procedure, 2003-2010 Procedure Inpatient SSI Rate (%) 2003 2004 2005 2006 2007 2008 2009 2010 Abdominal hysterectomy 2.5% 1.4% 1.9% 2.0% 1.1% 1.2% 1.8% 1.1% Breast surgery 1.6% 1.8% 1.0% 0.2% 0.3% 0.3% 0.5% 0.6% CABG 5.4% 5.1% 1.3% 2.1% 1.4% 6.6% 4.7% 3.2% Caesarean section 2.3% 2.1% 1.5% 1.7% 0.9% 0.5% 0.4% 0.3% Cardiac surgery - 0.0% 0.0% 0.0% 0.0% 3.6% 1.5% 1.5% Hip arthroplasty* 2.1% 1.6% 1.3% 1.1% 0.9% 0.8% 0.8% 0.6% Knee arthroplasty 1.1% 0.9% 0.7% 0.3% 0.3% 0.2% 0.3% 0.2% Major vascular surgery 11.2% 10.2% 9.9% 8.7% 2.4% 4.9% 3.3% 5.4% Open reduction of long bone fracture** 2.2% 2.1% 1.7% 2.6% 0.3% 0.5% 0.6% 0.5% * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur For each procedure category there has been a reduction in the SSI rate since the introduction of surveillance. The incidence density SSI rates for the whole period of surveillance (2003 to 2010) are shown in Table 7. Table 7: Incidence density of inpatient SSI per 1000 post operative inpatient days with 95% confidence interval, by category of procedure, 2003 to 2010 2003 to 2010 Procedure Patient days Inpatient SSI Inpatient SSI Rate (%) (95% CI) Abdominal hysterectomy 33842 110 3.3 (2.7, 3.9) Breast surgery 13078 34 2.6 (1.9, 3.6) CABG 35570 161 4.5 (3.9, 5.3) Caesarean section 252557 603 2.4 (2.2, 2.6) Cardiac surgery 9567 20 2.1 (1.4, 3.2) Hip arthroplasty* 440327 578 1.3 (1.2, 1.4) Knee arthroplasty 212398 139 0.7 (0.6, 0.8) Major vascular surgery 19546 107 5.5 (4.5, 6.6) Open reduction of long bone 114201 131 1.1 (1.0, 1.4) fracture** Total 1131086 1883 1.7 (1.6, 1.7) * includes those procedures that would have previously been included within hip arthroplasty category but are now categorised as repair of neck of femur ** includes those procedures that would have previously been included within the open reduction of long bone fracture category but are now categorised as repair of neck of femur The highest SSI rate was in major vascular surgery at 5.5 SSI per 1000 patient days and the lowest rate was in knee arthroplasty with 0.7 SSI per 1000 patient days. 16
4.5 Characteristics of SSI The distribution of the type of SSI detected during the inpatient stay for the periods 2003 to 2010 and for 2010 are presented in Figure 1 and Figure 2 respectively. 100% Figure 1: Infection type by procedure, inpatient SSI 2003 to 2010 90% 80% 70% Percentage 60% 50% 40% Not recorded Organ/Space Deep Superficial 30% 20% 10% 0% Abdominal hysterectomy Breast surgery Caesarean section Hip arthroplasty Procedure Knee arthroplasty Major vascular surgery Reduction of long bone fracture Figure 2: Infection type by procedure, inpatient SSI 2010 100% 90% 80% Percentage 70% 60% 50% 40% Not recorded Organ/Space Deep Superficial 30% 20% 10% 0% Abdominal hysterectomy Breast surgery Caesarean section Hip arthroplasty Procedure Knee arthroplasty Major vascular surgery Reduction of long bone fracture Changes in the proportions of SSI for the abdominal hysterectomy, breast surgery, major vascular and reduction of long bone fracture procedures should be treated with caution due to the small number of inpatient SSI detected for these procedures. 4.6 Inpatient incidence density of SSI, by year of surveillance, 2003 to 2010 Figures 3 to 9 describe the inpatient SSI incidence density rate from 2003 to 2010 for each procedure. As previously noted CABG and cardiac surgery were performed within one NHS board and are therefore not included. 17
Figure 3 shows the annual inpatient SSI incidence density rate with 95% confidence intervals for abdominal hysterectomy procedures. Figure 3: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for abdominal hysterectomy, 2003 to 2010 7.0 IP Incidence Density SSI rate (SSI/1000 patient days) 6.0 5.0 4.0 3.0 2.0 1.0 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year The confidence intervals around these rates are wide due to the relatively small number of procedures reported each year and therefore should be treated with caution. There was no significant annual linear trend in the inpatient SSI rate (c2 = 9.630, df = 7, p = 0.211). The annual inpatient SSI incidence density rates for breast surgery from 2003 to 2010 are shown in Figure 4. Figure 4: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for breast surgery, 2003 to 2010 12.0 IP Incidence Density SSI rate (SSI/1000 patient days) 10.0 8.0 6.0 4.0 2.0 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year There was a significant downward linear trend in the annual SSI rate (c2 = 16.154, df = 7, p = 0.024). Since 2006 there has been a non-significant increase noted in the annual SSI rate. The annual inpatient SSI incidence density rates for caesarean section procedures are shown in Figure 5. 18
Figure 5: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for caesarean section, 2003 to 2010 7.0 IP Incidence Density SSI rate (SSI/1000 patient days) 6.0 5.0 4.0 3.0 2.0 1.0 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year The number of procedures reported for this category increased from 2007, when reporting became mandatory and this is reflected in the narrower confidence intervals since 2006.There was a significant decrease noted in the annual SSI rates from 2003 to 2010 (c2 = 312.057, df = 7, p < 0.0005). When procedures carried out from the introduction of mandatory surveillance in caesarean sections are considered, i.e. 2007 to 2010, a significant reduction in the annual SSI rate over this period is found (c2 = 40.604, df = 3, p < 0.0005). The annual inpatient SSI incidence density rates for hip arthroplasty from 2003 to 2010 are shown in Figure 6. Figure 6: Annual rate of inpatient SSI per 1000 patient days (incidence density) with 95% CI for hip arthroplasty, 2003 to 2010 3.0 IP Incidence Density SSI rate (SSI/1000 patient days) 2.5 2.0 1.5 1.0 0.5 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year 19
There was a significant reduction in this rate over the period 2003 to 2010 (c2 = 91.019, df = 7, p < 0.0005). When procedures from the introduction of mandatory surveillance are considered i.e. 2007 to 2010, there is no significant linear reduction in the SSI rate (c2 = 4.263, df = 3, p = 0.234). Figure 7 presents the annual inpatient SSI incidence density rates from 2003 to 2010 for knee arthroplasty procedures. Figure 7: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for knee arthroplasty IP Incidence Density SSI rate (SSI/1000 patient days) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year This rate decreased significantly over the period 2003 to 2010 (c2 = 59.959, df = 7, p <0.0005). The annual inpatient SSI incidence density rates from 2003 to 2010 for major vascular surgery are presented in Figure 8. Figure 8: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for major vascular surgery 20.0 IP Incidence Density SSI rate (SSI/1000 patient days) 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year 20
There was a significant reduction in the SSI rate during this period for this procedure (c2 = 21.541, df = 7, p = 0.003). A large decrease in the inpatient SSI incidence was observed between 2006 and 2007. The annual inpatient SSI incidence density rates from 2003 to 2010 for open reduction of long bone fracture surgery are presented in Figure 9 Figure 9: Trends in rate of inpatient SSI per 1000 patient days (incidence density) with 95% confidence intervals for open reduction of long bone fracture 3.5 IP Incidence Density SSI rate (SSI/1000 patient days) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 2003 2004 2005 2006 2007 2008 2009 2010 Year The SSI rate fell significantly from 2003 to 2010 (c2 = 64.091, df = 7, p < 0.0005), the largest individual decrease in inpatient SSI incidence was observed between 2006 and 2007. The SSI rate has remained stable from 2008 to 2010. 21
4.7 Incidence of SSI by risk group Table 8 describes the number of procedures and inpatient cumulative incidence SSI rates by NNIS risk index for the periods 2003 to 2010 and for 2010. Table 8: Cumulative incidence of inpatient SSI, by category of surgical procedure, by NNIS risk index for, 2003 to 2009 and 2009 Procedures 2003-2010 Risk Index 0 Risk Index 1 Risk Index 2 Risk Index 3 Not Recorded Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures SSI Rate Abdominal hysterectomy 4574 48 1.0% 863 33 3.8% 108 10 9.3% 2 0 0.0% 1374 19 1.4% Breast surgery 2930 17 0.6% 553 9 1.6% 2 0 0.0% 0 0-930 8 0.9% Caesarean section 48546 362 0.8% 6412 91 1.4% 177 8 4.5% 2 1 50.0% 18510 141 0.8% Hip arthroplasty 24667 125 0.5% 20381 311 1.5% 2412 52 2.2% 130 5 3.8% 9401 85 0.9% Knee arthroplasty 17760 49 0.3% 8862 53 0.6% 923 12 1.3% 36 1 2.8% 4771 24 0.5% Major vascular surgery 110 6 5.5% 769 52 6.8% 404 29 7.2% 2 0 0.0% 281 20 7.1% Open reduction of long bone 2635 18 0.7% 6485 86 1.3% 276 9 3.3% 2 0 0.0% 1567 18 1.2% fracture 2010 Procedures Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures SSI Rate Number of procedures Abdominal hysterectomy 608 4 0.7% 149 4 2.7% 26 1 3.8% 0 0-62 0 0.0% Breast surgery 765 4 0.5% 103 1 1.0% 0 0-0 0-24 0 0.0% Caesarean section 12647 41 0.3% 1525 9 0.6% 45 0 0.0% 0 0-1012 2 0.2% Hip arthroplasty 4744 12 0.3% 3696 38 1.0% 337 4 1.2% 18 1 5.6% 830 3 0.4% Knee arthroplasty 3012 3 0.1% 1290 4 0.3% 140 1 0.7% 4 0 0.0% 412 1 0.2% Major vascular surgery 18 1 5.6% 174 10 5.7% 98 6 6.1% 1 0 0.0% 21 0 0.0% Open reduction of long bone fracture 361 1 0.3% 966 5 0.5% 29 0 0.0% 1 0 0.0% 166 2 1.2% SSI Rate During the period 2003 to 2010 and 2010 the cumulative incidence inpatient SSI rate increased with an increasing NNIS score for all procedures. In total there were 24 procedures (18 hip arthroplasty procedures, four knee arthroplasty procedures, one major vascular procedure and one open reduction of long bone fracture procedure) carried out during 2010 where all three of the NNIS risk index risk factors were present. This is in part due to the small numbers of procedures with contaminated or dirty wound classes recorded. In the last year of reporting (2010), for the seven procedures in Table 8, a total of 7.6% of procedures could not be classified due to missing NNIS data, this is a decrease from 11.1% reported in 2009. HPS continually encourage staff throughout NHS boards to improve compliance with reporting NNIS risk index data and are in the process of introducing mandatory recording of data contributing to the NNIS risk index. 22
4.8 Readmission Surveillance for Hip Arthroplasty Procedures Table 9 shows the number of procedures performed and SSI rates for hip arthroplasty procedures 2007 to 2010. Table 9: Number of procedures, SSI and rate of SSI by hip arthroplasty subcategory 2007 to 2010 Procedure Number of procedures Inpatient Number of SSI Total SSI rate 95% Readmission Total Confidence to day 30 Interval Primary total hip replacement 23176 85 87 172 0.7% (0.6%, 0.9%) Primary hip hemi arthroplasty 1337 3 1 4 0.3% (0.1%, 0.8%) Revision of total hip replacement 2838 31 16 47 1.7% (1.2%, 2.2%) Revision of hip hemi arthroplasty 135 6 0 6 4.4% (2.1%, 9.4%) Repair of neck of femur* 8713 146 55 200 2.3% (2.0%, 2.6%) Not recorded 263 5 1 6 2.3% (1.0%, 4.9%) Total 36462 276 160 436 1.2% (1.1%, 1.3%) *This only includes procedures which were previously categorised as primary hip hemi arthroplasty The largest proportion of procedures performed was for primary total hip replacement (63.6%) and the lowest proportion of procedures was performed for revision of hip hemi arthroplasty (0.4%). The total SSI rate for hip arthroplasty was 1.2%; however this rate varied depending on which type of hip procedure was performed. The SSI rates for inpatient and readmission to day 30 for each hip procedure category are shown in Figure 10. HPS continually encourage staff through NHS boards to improve collection of data. 5.0% 4.5% Figure 10: Method of detection by year for hip arthroplasty to day 30, 2007-2010 SSI rate 4.0% 3.5% 3.0% 2.5% 2.0% 4.4% 0.6% 0.4% Inpatient Readmission to day 30 1.5% 0.6% 1.0% 1.7% 1.9% 0.4% 0.5% 0.0% 0.4% 0.4% Primary total hip replacement (n=23176) 0.1% 0.2% Primary hip hemi arthroplasty (n=1337) 1.1% Revision of total hip replacement (n=2838) Revision of hip hemi arthroplasty (n=135) Procedure category Repair of neck of femur (n=8713) Not recorded (n=263) 0.8% Total (n=36462) Revision of hip hemi arthroplasty had the highest SSI rate of 4.4% of all the hip arthroplasty procedures however numbers were small for this category and should be interpreted with caution. Primary total hip replacement had the highest proportion of SSI detected on readmission (50.6%) with an SSI rate of 0.4%. 23
Table 10 shows the number of procedures performed and SSI rates for the latest year of surveillance (2010) for hip arthroplasty. Table 10: Number of procedures, SSI and rate of SSI by hip arthroplasty subcategory for January to December 2010 Procedure Number of procedures Inpatient Number of SSI Total SSI rate 95% Readmission Total Confidence to day 30 Interval Primary total hip replacement 6344 15 22 37 0.6% (0.4%, 0.8%) Primary hip hemi arthroplasty 257 1 0 1 0.4% (0.1%, 2.2%) Revision of total hip replacement 668 4 4 8 1.2% (0.6%, 2.3%) Revision of hip hemi arthroplasty 26 1 0 1 3.8% (0.7%, 18.9%) Repair of neck of femur* 2253 36 20 56 2.5% (1.9%, 3.2%) Not recorded 77 1 1 2 2.6% (0.7%, 9.0%) Total 9625 58 47 105 1.1% (0.9%, 1.3%) *This only includes procedures which were previously categorised as primary hip hemi arthroplasty The largest proportion of procedures performed was for primary total hip replacement (65.9%) and the lowest proportion of procedures was performed for revision of hip hemi arthroplasty (0.3%). The total SSI rate for hip arthroplasty was 1.1%; however this rate varied depending on which type of hip procedure was performed. The SSI rates for inpatient and readmission to day 30 for each hip procedure category are shown in Figure 11. Figure 11: Method of detection for hip arthroplasty to day 30, January to December 2010 4.0% 3.5% 3.0% SSI rate 2.5% 2.0% 3.8% 0.9% 1.3% Inpatient Readmission to day 30 1.5% 1.0% 0.5% 0.0% 0.3% 0.2% Primary total hip replacement (n=6344) 0.4% Primary hip hemi arthroplasty (n=257) 0.6% 0.6% Revision of total hip replacement (n=668) Revision of hip hemi arthroplasty (n=26) 1.6% Repair of neck of femur (n=2253) 1.3% Not recorded (n=77) 0.5% 0.6% Total (n=9625) Procedure category Revision of hip hemi arthroplasty had the highest SSI rate of 3.8% of all the hip arthroplasty procedures however numbers were small for this category and should be interpreted with caution. Primary total hip replacement had the highest proportion of SSI detected on readmission (59.5%) with an SSI rate of 0.3%. Figure 12 presents the type of SSI detected by inpatient and readmission surveillance for hip arthroplasty procedures in 2007-2010. 24
Figure 12: Proportion of SSI involving superficial incisions or deep and organ space, January 2007 to December 2010, for hip arthroplasty procedures (inpatient and readmission to day 30) 100% SSI types as proportion of total SSI types 90% 80% 70% 60% 50% 40% 30% 20% 10% Not recorded Organ/Space Deep Superficial 0% Hip arthroplasty inpatient (n=276) 2007-2010 Hip arthroplasty readmission to day 30 (n=160) Data on inpatient SSI for hip arthroplasty procedures, January 2007 and December 2010, indicates that the majority of the inpatient detected infections were superficial (56.2%). Inclusion of SSI detected among patients readmitted to hospital decreased the proportion of SSI that was superficial to 30.6%. This indicates that more serious infections following hip arthroplasty procedures are being identified in patients readmitted to hospital following discharge. 4.9 PDS Surveillance for Caesarean Section Post discharge surveillance (PDS) until day 10 was made mandatory in April 2009 and this section covers the period since this introduction. Table 11 shows the number of procedures performed and SSI rates for the latest year of surveillance (2010) for caesarean section. Table 11: SSI rate with 95% confidence interval by caesarean section procedure for inpatient and PDS to day 10 January to December 2010 Procedure Caesarean section (elective) Caesarean section (non elective) Number of procedures Inpatient SSI Number of SSI PDS to day 10 Total Total SSI Rate % 6456 15 140 155 2.4% 8770 37 237 274 3.1% 95% Confidence interval (2.1%, 2.8%) (2.8%, 3.5%) Not recorded 3 0 0 0 0.0% - Total 15229 52 377 429 2.8% (2.6%, 3.1%) 25
The SSI rates for inpatient and PDS to day 10 for each caesarean section procedure category are shown in Figure 13. Figure 13: SSI rate for both inpatient and PDS to day 10 by caesarean section procedure January to December 2010 3.5% 3.0% 2.5% SSI rate 2.0% 1.5% 2.7% 2.5% Inpatient PDS to day 10 2.2% 1.0% 0.5% 0.0% 0.2% Caesarean section elective (n=6456) 0.4% Caesarean section (non-elective) (n=8770) Procedure category 0.3% Total (n=15229)* *Include three not-recorded Methods for detecting SSI in the post operative period were enhanced during 2009 and therefore SSI rates for inpatient and PDS to day 10 can only be compared from April to December 2009 where a similar rate of 2.7% was found. Figure 14 presents the type of SSI detected by inpatient and PDS to day 10 surveillance for caesarean section procedures 2010. Figure 14: Proportion of SSI involving superficial incisions or deep and organ space, January 2010 to December 2010, for caesarean section procedures (inpatient and PDS to day 10) 100% 90% SSI types as proportion of total SSI types 80% 70% 60% 50% 40% 30% 20% 10% Not recorded Organ/Space Deep Superficial 0% Caesarean section inpatient (n=52) Caesarean section PDS to day 10 (n=377) 2010 Data on inpatient SSI for caesarean section procedures, 2010, indicates that the majority of inpatient infections were superficial (92.3%). Inclusion of SSI detected using PDS increased the proportion of SSI that was superficial to 93.9%. 26
4.10 Variation in SSI Rate by NHS board When making comparisons between NHS boards it is important to take into account the precision of the estimated rate of SSI. The precision of the estimate increases with the number of procedures. Figures 15 to 16 indicate the variation in SSI rates by NHS board within selected categories of surgery and represent data from January to December 2010. The case mix of patients undergoing surgery can vary between NHS boards and this can result in NHS boards with a higher proportion of severely ill patients being incorrectly judged to have a high SSI rate. To avoid this influence, only patients with a NNIS score of 0 are included in Figures 15 to 16. The statistical analysis in Figures 15 to 16 was based on an over-dispersed Binomial model. The funnel plots in Figures 15 to 16 shows the SSI rate for the respective procedures within each NHS board plotted against the number of procedures on which the rate is based. The red lines represent the 95% confidence limits. The probability that rates above the high control limit or below the low limit have occurred by chance is low. Nonetheless these results should be interpreted with due caution as not all risk factors including length of stay have been taken account of in these analyses. Not all NHS boards are included in Figures 15 to 16 as some NHS boards did not perform procedures that had a NNIS score of 0 and some NHS boards did not perform certain procedures. As previously noted, HPS operate a quarterly exception reporting system and those boards that have been highlighted have been contacted by HPS. Key to NHS boards: AA Ayrshire & Arran BR Borders DG Dumfries & Galloway FF Fife FV Forth Valley GR Grampian GGC Greater Glasgow & Clyde HG Highland LO Lothian LN Lanarkshire NWTC National Waiting Times Centre OR Orkney SH Shetland TY Tayside WI Western Isles Figure 15 shows a funnel plot of the SSI rate for caesarean section procedures including infections detected by PDS up to the 10th post operative day from 2010. Figure 15: Cumulative incidence (no of SSI per 100 procedures) of SSI rate including inpatient and PDS to day 10 (NNIS = 0) by NHS board in 2010 for caesarean section procedures (n = 12647)* 4 LN TY SSI Percentage (%) 3 2 DG WI BR HG FF FV AA GR LO GGC 1 0 SH OR 0 1000 2000 3000 4000 Number of Procedures *SH and OR rates overlap 27
None of the NHS boards collecting inpatient and PDS to day 10 caesarean section data in 2010 reported an SSI incidence rate that was significantly higher in relation to other NHS boards. Figure 16 shows a funnel plot of the SSI rate for hip arthroplasty including infections detected on readmission until day 30 post operatively. Figure 16: Cumulative incidence (no of SSI per 100 procedures) of inpatient and readmissions to day 30 SSI (NNIS = 0) by NHS board in 2010 for hip arthroplasty (n = 4744). 3.0 2.5 DG SSI Percentage (%) 2.0 1.5 1.0 LN NWTC 0.5 FV AA HG FF LO 0.0 WI BR TY GR GGC 0 200 400 600 800 1000 Number of Procedures None of the NHS boards collecting hip arthroplasty data in 2010 reported an SSI incidence rate including readmissions to day 30 that was significantly higher in relation to other NHS boards. 28
4.11 Compliance with guidelines SIGN Guideline 104, Antibiotic Prophylaxis in Surgery 16 is aimed at reducing inappropriate prophylactic prescribing and recommends intravenous prophylactic antibiotics should be given less than or equal to 30 minutes before skin incision. Figure 17 shows the timing of antibiotic prophylaxis for hip arthroplasty procedures carried out in 2010 where this was recorded. Figure 17: Timing of administration of antibiotic prophylaxis for hip and knee arthroplasty surgery in 2010 (n = 9002) 6000 5000 4000 Number of procedures 3000 2000 1000 0 >30 mins pre-op <30 <30 mins pre-op Peri-op <=3 hours post-op >3 hours post-op Antibiotic timim During this period 62.6% of hip arthroplasty patients received their antibiotic prophylaxis within the recommended period of < 30 minutes before the skin is incised. Data were missing for 623 hip arthroplasty procedures. HPS are working closely with NHS boards to improve recording methods, to reduce the number of not recorded reported to HPS. 29