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Postoperative wound infection rates: Results of prospective statewide surveillance
SCIENTIFIC PAPERS
Postoperative Wound Infection Rates: Results of Prospective Statewide Surveillance
Bruce F. Farber, MD, Charlottesville, Virginia Richard P. Wenzel, Md, Charlottesville, Virginia
The National Center for Disease Control estimates that 325,000 surgical wound infections occur each year in the United States [I]. Such postoperative wound infections represent approximately 20 percent of all nosocomial infections [I] and cause significant morbidity and added expense. A case-matched study Frr\m tb;O ;natitartinn .hnrrraA that P nnatnnnrdiwn Ll”ll, Ull‘D lllUClLU”l”ll UII”“-zU “..CI” u ~“~““~“.UV..Y
that prospective statewide surveillance will eventually lead to the identification of operations at hospitals associated with unusually high rates of infection. Effort could then be directed toward reducing the rates. This report describes infection rates after 44,687 selected surgical procedures performed in
wound infection doubled the length of postoperative stay in the hospital [2]. Encouraging data on infection control measures are presented by Cruise [3], who demonstrated that prospective postoperative wound surveillance and reporting to clinicians can lead to a 50 percent reduction in the infection rate. In 1976 we reported a system of total hospital surveillance that begins with examination of the nursing care pian (Kardexj in order to identify patients at high risk and those who have undergone general anesthesia [4]. With this system, infection rates for specific surgical operations are calculated monthly and distributed widely throughout the hospital. The University of Virginia system was 82 percent accurate when compared with daily surveillance of all patients, and it saved a considerable amount of time compared with the other methods studied [4]. In 1974 we began teaching the system to infection control practitioners in Virginia and can now compare infection rates for similar procedures in hospitals throughout the state. It is our hypothesis
1979.
From the University of Virginia School of Medicine, Charlottesville. Vlrgin&. Requests for reprints should be adbssad to Richard P. Wenzel, M), Box 473. University of Virginia Medical Center, Charlottesville, Virginia 22908.
Vofuma 140, Seplamber 1980
hnnnitnla --.-wr--
in I- Viruinin . --b-_‘m,.frnm --_--
Jnmxwv 1----J
1 A, 1877 a-.
. tn “., Mav _._SJRl _A,
Material and Methods Hospitals: There are 129 hospitals in Virginia. Thirtyeight (29 percent) of these hospitals reported their prospective surveillance data, which are published in a monthly statewide report for distribution. The hospitals were divided into the following categories: university hospital, 1; community hospitals with less than 100 beds, 7; community hospitals with 100 to 300 beds, 21; community hospitals with greater than 300 beds, 7; and federal (Veterans Administration) hospitals, 2. Surveillance: Infection control practitioners are trained in intensive 2 week courses at the University of Virginia Hospital (8 to 10 students per class). On return to their locality, they adhere to a uniform system of prospective surveillance described earlier [4]. The system begins with n rn.,L,“, r\+-,hn . . .. ..“L.” ,.,.“., ml.-... IU,.“A,-..,h ,F.-..w...x, ..n+:.-...+ a-I~“lcTvT “I u.c AIUJDII~ LuIc- yu.u \s.cuur;a, “I r;vwy pamx,
on the ward. Admission date, diagnoses and dates of commonly performed procedures and. all operations are noted. The practitioner then selects patients ,at high risk for infection based on established criteria and reviewstheir hospital charts. In general, surveillance is performed weekly on all wards and twice weekly in all intensive care areas and on the obstetrics ward. The charts of all patients remaining in the hospital for more than 48 hours after operation were reviewed. Monthly reports from partici-
343
Procedure
l
‘l3 8 7 21 3 5
8162 22/269
17/235
106/514 31100 4167 O/592 131358 3/60 l/36 3165 7/59 3,707
... ...
... ...
Incomplete classification within group.
Total
2 1 10 1 8
g/331 10/251 5/513’ l/IO 41498 lo/l32
4 5 3 5 12
...
5 21
%
161294’ 5124
University Hospital (N = 1) No.
...
... 3,484
1::
::: 1 11
3
12 11 3
1::
; 2 4 0.2 10
5 14
171465 t/33 o/39 O/127 21176 l/9 o/9 OJl3
am5
24/506’ Q/64 a/388 91516 131633’ i/28 l/521 7171 o/a o/30 4/33 3126 la/513
5 1 4 1 2 7 7 7 17
136/2,911 5/363 7/185 101993 24/l ,356 91137 a/124 a/111 2/12 20,66 1
4
l
5 28 3 4 2 3 1 13 6 1 11 9 4
5111,177
147/3,075’ 73/257 63/2,126 116/3,098 43/2,36 1 51198 ‘23/2,577 911682 7/123 3/326 20/188 131148 12913,271
Community Hospitals 100-300 Beds (N = 21) No. %
Statewide Postoperative Wound Infection Rates After Selected Surgical Procedures
Appendectomy Ruptured Nonruptured cholecystectomy l-kniorr~phy complicated Uncemplicated Colon resection Splenectomy n‘lyroidectomy Aboveknee amputation Below-knee amputation Total abdominal hysterectomy (abdominal wound infection) Total vaginal hysterectomy (cuff infection) Cessrean section Total hip replacement Total knee replacement Meniscectotny Laminectomy Femoropopl iteal bypass Aortofemoral bypass Nephrectomy Radical neck dissection
TABLE I
16,102
52/1,678 31228 6193 l/500 22/1,406 91196 3/73 4/132 8150
17/720
78/ 1,628’ 481164 2911,301 58/ 2,323 32/2,899’ 71143 2Y/2,179 901745 2199 O/327 IO/l33 16/114 6V2.760
3 16
3 1 7 0.2 2 5
2
14 2
... 8
3 1 5 1 12 2
5 29
>300 Beds (N = 7) No. %
_. _ .._
... ...
8
l/l3 O/20 o/3 l/32 O/l9 o/4 l/21
5
. .“. ..*
... ...
1::
. ..
.,r 3
...
5 11 1
0;ii
733
‘id 9
5
_. .
l/21 o/2 l/l9 a/75 31352’ o/9 01146 l/31 o/2 O/l5 Ill55 4146
Federal Hospitals (N = 2) No. %
44,687
31 l/5,566 121748 78/4i7 1 l/2,232 61/3,299 231434 12/261 15/325 WI42
9312,407
26615,522 1351511 11/4,085 20016343 95/6,77&I 141388 4815,899 199f 1,661 9/232 3/698 45f409 44f398 22816,813
x 13
6 2 4 0.5 2 5
4
a”4 Ii I I 3
12
i
5 26 3 3 1 4
All Hospitals (N = 38) No. %
Statewide Postoperative
pating hospitals were sent to the University of Virginia, and data were tallied for the study period. The accuracy of the data reported in the statewide system has been estimated by comparative daily prospective reviews: the reported data are approximately 70 percent sensitive and 99 percent specific [5]. The hospitals under surveillance had an 85 percent monthly reporting frequency [5].
Definition of infection: Wound infection was defined as the presence of pus at the incision site. Appendicitis was classified as perforated or nonperforated when this information was available. Herniorraphies were classified as complicated or uncomplicated based on whether or not any compromise in intestinal blood supply was observed at the time of surgery. Wound infection after vaginal hysterectomy was defined as the presence of pus at the vaginal cuff. Postoperative wound infection rate: Infection rates represent the total number of postoperative wound infections divided by the total number of procedures. The infections were identified by on-ward surveillance, and the total number of operations was obtained monthly from the operating room log books. Resulis Table I lists the infection rates for selected surgical procedures. A total of 44,667 operations were surveyed during the 29 month study period. Ahnost half of the procedures were performed at the 21 community hospitals with 100 to 300 beds, whereas only 773 (1.7 percent) of the same procedures were performed at federal (Veterans Administration) facilities. Thus the data primarily reflect practices at medium-sized general hospitals in the community. Hysterectomy was the most common procedure studied at the community hospitals, accounting for over 20 percent of the operations reviewed at these institutions. Appendectomies, cholecystectomies and herniorraphies accounted for 12,14 and 15 percent, respectively, of the operations studied. High rates of infection were noted in the following operations: appendectomy for perforated appendicitis (26 percent), colorectal resection (12 percent), radical neck dissection (13 percent) and leg amputations (11 percent). The infection rate after primary appendectomy for nonperforated appendicitis was 3 percent, considerably lower than the 26 percent rate for perforated appendicitis. In addition, complicated herniorraphies had a 4 percent infection rate compared with a 1 percent rate for uncomplicated procedures. Infection rates for cholecystectomy were higher at Veterans Administration hospitals (11 percent) than at other hospitals (2 to 4 percent). Infection rates after cesarean section appeared higher at the University Hospital. Uniformly low rates were seen after meniscectomy (0 to 1 percent) regardless of the type of hospital. vohmo 14o.9eptmbw
1990
Wound Infection Rates
Comments Attempts to reduce the number of postoperative wound infections have focused on a variety of factors such as ultraviolet light in the operating room [b], plastic drapes [ 71, preoperative skin preparations [8] and prophylactic antibiotics [9]. Not all procedures have been standardized, and it is possible that differences in infection rates at similar types of institutions may reflect differences in practice. In assessing this possibility, we agree with Polk [IO] that “ . . . an infection surveillance officer is absolutely critical in achieving objective evaluation of those methods designed to reduce postoperative or any other hospital-acquired infection” [IO]. In this study, we report the only statewide review of postoperative wound infection rates. The statewide surveillance program was carried out by infection control practitioners trained at our institution, thus establishing uniform surveillance methods and definitions of infection. The definition of wound infection (the presence of pus at the incision site) is likely to identify most infections. This program has been shown to be accurate [5], and therefore differences in rates probably reflect variation in the patient populations, the physicians’ skills or both. Since the characteristics of patient populations are an important determinant of risk, one must be careful in drawing conclusions from the data. There are likely to be differences among patients in different hospital categories. In contrast, such differences will probably be minimal when patients in similar categories are compared. For this reason, we purposely did not satistically compare infection rates among different hospital categories. The statewide wound infection rate after cholecystectomy is lower than the 8 percent rate previously reported at our university [ll] and the 6.9 percent rate reported by the U.S. National Research Council and the National Science Foundation Cooperative Study [2]. It is, however, similar to the 2 percent rate reported by Cruise [12] in an 870 bed teaching hospital. The higher rate for federal facilities may reflect an older patient population, more emergency operations and the relatively limited number of procedures performed. Appendectomy rates are uniformly similar to those reported by Cruise [12] and to data from England and Wales [13]. In addition, the overall wound infection rate after cesarean section is identical to the 6 percent rate reported by Sweet and Ledger [14]. It should be pointed out that our data may underreport true infection rates because follow-up stopped when the patient was discharged. Cruise [15] has shown that approximately 11 percent of infec345
Farber and Wenzel
tions may not be recognized until after discharge. We chose not to use the previously established categories of surgical procedures (clean, clean contaminated, contaminated and dirty [6]) in our ongoing surveillance. The clean category is well understood and may be the most accurate reflection of surgical skill because of lack of endogenous contamination [15]. However, we believe that the usefulness of the other categories is limited because of the mixture of so many different procedures and varying interpretations of the criteria. Thus from an epidemiologic point of view the latter classification makes comparisons more difficult and outbreaks may actually be undetected. Even with our system of obtaining crude infection rates by surgical procedures, some refinements are required. We think our classification of appendectomies is important: for example, appendectomies for perforated appendicitis are followed by a high rate of infection caused by endogenous contamination and therefore should be considered differently than appendectomies for uncomplicated appendicitis. As additional data are collected and studied, more subtle divisions will be considered, such as cholecystectomy with and without common duct exploration. In our opinion, a prospective surveillance program for hospital acquired wound infections is the starting point for programs to reduce infection. Monthly reports of current infection rates are now summarized and distributed to all participating hospitals. Surgeons at participating institutions can then compare their own statistics with those tabulated for similar institutions in the rest of the state. With the described surveillance program, data are periodically updated to reflect current surgical practices. By establishing these baseline rates for various procedures, it is also possible that outbreaks will be detected more rapidly. More importantly, the use of centralized infection reporting has exciting future applications. We are now in the process of distributing rank-ordered rates to individual community hospitals in the same size categories. This should encourage hospitals with particularly high rates of infection to examine their techniques in closer detail. We hope that in a manner analogous to the experience of Cruise, such reporting will reduce the rate of infection statewide. Additional research may focus on controlled intervention trials in high risk operations.
346
Summary The results of a prospective statewide study of postoperative wound infection rates after 19 selected surgical operations are reported. Rates are based on 44,689 operations performed at 38 hospitals from January 1,1977 through May 31,1979. The data were collected by review of ward charts and are compared with those of earlier reports. Particularly high rates of infection were found after surgery for perforative appendicitis, colorectal resection, radical neck dissection and leg amputations. These rates should serve as a baseline for future comparisons. The potential value of centralized infection reporting is discussed. Acknowledgment: We gratefully acknowledge the kind assistance and review of the manuscript by William R. Sandusky, MD. References 1. Dixon R. Effects of infections on hospital care. Ann Intern Msd 1978;89:749-53. 2. Green JW, Wenzel RP. Postoperative wound infection: a controlled study of the increased duration of hospital stay and direct cost of hospitalization. Ann Surg 1977; 1852868. 3. Cruise P. Surgical wound sepsis. Can Med Assoc J 1970; 102:251-8. 4. Wenzel RP, Dsterman CA, Hunting KJ. Gwaltney JM Jr. Hospital-acquired Infections. I. Surveillance in a university hospital. Am J Epidemloi 1978;103:251-80. 5. Wenzei RP, Dsterman CA, Townsend TR, st al. The deveiopment of a statewide program for surveillance and reporting of hospital acquired infections. J Infect Dls 1979;140: 741-5. 8. Rarker WF, Longmire W, Altemeier WA, et al. Postoperative wound infections: ths jnfluence of ultraviolet radiation of the operating room and of various other factors. Ann Surg 1984;180&ppl 2:l. 7. Paskln D. A prospective study of wound infections. Am Surg 1989;35:827-9. 8. Cruise PJ, Foord R. A five ypar prospective study of 23,849 surgical wounds. Areh Surg 1973;107:208-10. 9. Karl RC, Mertz JJ, Veith FJ, Mnesn P. Prcphylactk antimiaobtal drugs in surgery. N Engl J bled 1988;275:305-8. 10. Polk H. The value of a nurse epldemioiogist in the control of surgical infection. Surg Clln North Am 1975;55: 1277-82. 11. Wenzel RP, Huntlng KJ. Dsterman CA. Postoperative wound infection rates. Surg Gynecol Obstet 1977; 144:749-52. 12. Cruise PJ. IncMence of wound infections on the surgical services. Surg Clin North Am 1975;55:1289-75. 13. incidence of wound infection in England and Wales. Lancet 1980;2:859-83. 14. Sweet R, Ledgsr W. Pusmsml infectkms morbkiii. Am J Dbstet Gynecol1973;117:1093-100. 15. Cruise P. Infection surveillance: identifying the problems and the high risk patient. South Med J 1977;70: Suppl 14-7.
lha Amarlcan Journal of Surgery
Postoperative Wound Infection Rates: Results of Prospective Statewide Surveillance
Bruce F. Farber, MD, Charlottesville, Virginia Richard P. Wenzel, Md, Charlottesville, Virginia
The National Center for Disease Control estimates that 325,000 surgical wound infections occur each year in the United States [I]. Such postoperative wound infections represent approximately 20 percent of all nosocomial infections [I] and cause significant morbidity and added expense. A case-matched study Frr\m tb;O ;natitartinn .hnrrraA that P nnatnnnrdiwn Ll”ll, Ull‘D lllUClLU”l”ll UII”“-zU “..CI” u ~“~““~“.UV..Y
that prospective statewide surveillance will eventually lead to the identification of operations at hospitals associated with unusually high rates of infection. Effort could then be directed toward reducing the rates. This report describes infection rates after 44,687 selected surgical procedures performed in
wound infection doubled the length of postoperative stay in the hospital [2]. Encouraging data on infection control measures are presented by Cruise [3], who demonstrated that prospective postoperative wound surveillance and reporting to clinicians can lead to a 50 percent reduction in the infection rate. In 1976 we reported a system of total hospital surveillance that begins with examination of the nursing care pian (Kardexj in order to identify patients at high risk and those who have undergone general anesthesia [4]. With this system, infection rates for specific surgical operations are calculated monthly and distributed widely throughout the hospital. The University of Virginia system was 82 percent accurate when compared with daily surveillance of all patients, and it saved a considerable amount of time compared with the other methods studied [4]. In 1974 we began teaching the system to infection control practitioners in Virginia and can now compare infection rates for similar procedures in hospitals throughout the state. It is our hypothesis
1979.
From the University of Virginia School of Medicine, Charlottesville. Vlrgin&. Requests for reprints should be adbssad to Richard P. Wenzel, M), Box 473. University of Virginia Medical Center, Charlottesville, Virginia 22908.
Vofuma 140, Seplamber 1980
hnnnitnla --.-wr--
in I- Viruinin . --b-_‘m,.frnm --_--
Jnmxwv 1----J
1 A, 1877 a-.
. tn “., Mav _._SJRl _A,
Material and Methods Hospitals: There are 129 hospitals in Virginia. Thirtyeight (29 percent) of these hospitals reported their prospective surveillance data, which are published in a monthly statewide report for distribution. The hospitals were divided into the following categories: university hospital, 1; community hospitals with less than 100 beds, 7; community hospitals with 100 to 300 beds, 21; community hospitals with greater than 300 beds, 7; and federal (Veterans Administration) hospitals, 2. Surveillance: Infection control practitioners are trained in intensive 2 week courses at the University of Virginia Hospital (8 to 10 students per class). On return to their locality, they adhere to a uniform system of prospective surveillance described earlier [4]. The system begins with n rn.,L,“, r\+-,hn . . .. ..“L.” ,.,.“., ml.-... IU,.“A,-..,h ,F.-..w...x, ..n+:.-...+ a-I~“lcTvT “I u.c AIUJDII~ LuIc- yu.u \s.cuur;a, “I r;vwy pamx,
on the ward. Admission date, diagnoses and dates of commonly performed procedures and. all operations are noted. The practitioner then selects patients ,at high risk for infection based on established criteria and reviewstheir hospital charts. In general, surveillance is performed weekly on all wards and twice weekly in all intensive care areas and on the obstetrics ward. The charts of all patients remaining in the hospital for more than 48 hours after operation were reviewed. Monthly reports from partici-
343
Procedure
l
‘l3 8 7 21 3 5
8162 22/269
17/235
106/514 31100 4167 O/592 131358 3/60 l/36 3165 7/59 3,707
... ...
... ...
Incomplete classification within group.
Total
2 1 10 1 8
g/331 10/251 5/513’ l/IO 41498 lo/l32
4 5 3 5 12
...
5 21
%
161294’ 5124
University Hospital (N = 1) No.
...
... 3,484
1::
::: 1 11
3
12 11 3
1::
; 2 4 0.2 10
5 14
171465 t/33 o/39 O/127 21176 l/9 o/9 OJl3
am5
24/506’ Q/64 a/388 91516 131633’ i/28 l/521 7171 o/a o/30 4/33 3126 la/513
5 1 4 1 2 7 7 7 17
136/2,911 5/363 7/185 101993 24/l ,356 91137 a/124 a/111 2/12 20,66 1
4
l
5 28 3 4 2 3 1 13 6 1 11 9 4
5111,177
147/3,075’ 73/257 63/2,126 116/3,098 43/2,36 1 51198 ‘23/2,577 911682 7/123 3/326 20/188 131148 12913,271
Community Hospitals 100-300 Beds (N = 21) No. %
Statewide Postoperative Wound Infection Rates After Selected Surgical Procedures
Appendectomy Ruptured Nonruptured cholecystectomy l-kniorr~phy complicated Uncemplicated Colon resection Splenectomy n‘lyroidectomy Aboveknee amputation Below-knee amputation Total abdominal hysterectomy (abdominal wound infection) Total vaginal hysterectomy (cuff infection) Cessrean section Total hip replacement Total knee replacement Meniscectotny Laminectomy Femoropopl iteal bypass Aortofemoral bypass Nephrectomy Radical neck dissection
TABLE I
16,102
52/1,678 31228 6193 l/500 22/1,406 91196 3/73 4/132 8150
17/720
78/ 1,628’ 481164 2911,301 58/ 2,323 32/2,899’ 71143 2Y/2,179 901745 2199 O/327 IO/l33 16/114 6V2.760
3 16
3 1 7 0.2 2 5
2
14 2
... 8
3 1 5 1 12 2
5 29
>300 Beds (N = 7) No. %
_. _ .._
... ...
8
l/l3 O/20 o/3 l/32 O/l9 o/4 l/21
5
. .“. ..*
... ...
1::
. ..
.,r 3
...
5 11 1
0;ii
733
‘id 9
5
_. .
l/21 o/2 l/l9 a/75 31352’ o/9 01146 l/31 o/2 O/l5 Ill55 4146
Federal Hospitals (N = 2) No. %
44,687
31 l/5,566 121748 78/4i7 1 l/2,232 61/3,299 231434 12/261 15/325 WI42
9312,407
26615,522 1351511 11/4,085 20016343 95/6,77&I 141388 4815,899 199f 1,661 9/232 3/698 45f409 44f398 22816,813
x 13
6 2 4 0.5 2 5
4
a”4 Ii I I 3
12
i
5 26 3 3 1 4
All Hospitals (N = 38) No. %
Statewide Postoperative
pating hospitals were sent to the University of Virginia, and data were tallied for the study period. The accuracy of the data reported in the statewide system has been estimated by comparative daily prospective reviews: the reported data are approximately 70 percent sensitive and 99 percent specific [5]. The hospitals under surveillance had an 85 percent monthly reporting frequency [5].
Definition of infection: Wound infection was defined as the presence of pus at the incision site. Appendicitis was classified as perforated or nonperforated when this information was available. Herniorraphies were classified as complicated or uncomplicated based on whether or not any compromise in intestinal blood supply was observed at the time of surgery. Wound infection after vaginal hysterectomy was defined as the presence of pus at the vaginal cuff. Postoperative wound infection rate: Infection rates represent the total number of postoperative wound infections divided by the total number of procedures. The infections were identified by on-ward surveillance, and the total number of operations was obtained monthly from the operating room log books. Resulis Table I lists the infection rates for selected surgical procedures. A total of 44,667 operations were surveyed during the 29 month study period. Ahnost half of the procedures were performed at the 21 community hospitals with 100 to 300 beds, whereas only 773 (1.7 percent) of the same procedures were performed at federal (Veterans Administration) facilities. Thus the data primarily reflect practices at medium-sized general hospitals in the community. Hysterectomy was the most common procedure studied at the community hospitals, accounting for over 20 percent of the operations reviewed at these institutions. Appendectomies, cholecystectomies and herniorraphies accounted for 12,14 and 15 percent, respectively, of the operations studied. High rates of infection were noted in the following operations: appendectomy for perforated appendicitis (26 percent), colorectal resection (12 percent), radical neck dissection (13 percent) and leg amputations (11 percent). The infection rate after primary appendectomy for nonperforated appendicitis was 3 percent, considerably lower than the 26 percent rate for perforated appendicitis. In addition, complicated herniorraphies had a 4 percent infection rate compared with a 1 percent rate for uncomplicated procedures. Infection rates for cholecystectomy were higher at Veterans Administration hospitals (11 percent) than at other hospitals (2 to 4 percent). Infection rates after cesarean section appeared higher at the University Hospital. Uniformly low rates were seen after meniscectomy (0 to 1 percent) regardless of the type of hospital. vohmo 14o.9eptmbw
1990
Wound Infection Rates
Comments Attempts to reduce the number of postoperative wound infections have focused on a variety of factors such as ultraviolet light in the operating room [b], plastic drapes [ 71, preoperative skin preparations [8] and prophylactic antibiotics [9]. Not all procedures have been standardized, and it is possible that differences in infection rates at similar types of institutions may reflect differences in practice. In assessing this possibility, we agree with Polk [IO] that “ . . . an infection surveillance officer is absolutely critical in achieving objective evaluation of those methods designed to reduce postoperative or any other hospital-acquired infection” [IO]. In this study, we report the only statewide review of postoperative wound infection rates. The statewide surveillance program was carried out by infection control practitioners trained at our institution, thus establishing uniform surveillance methods and definitions of infection. The definition of wound infection (the presence of pus at the incision site) is likely to identify most infections. This program has been shown to be accurate [5], and therefore differences in rates probably reflect variation in the patient populations, the physicians’ skills or both. Since the characteristics of patient populations are an important determinant of risk, one must be careful in drawing conclusions from the data. There are likely to be differences among patients in different hospital categories. In contrast, such differences will probably be minimal when patients in similar categories are compared. For this reason, we purposely did not satistically compare infection rates among different hospital categories. The statewide wound infection rate after cholecystectomy is lower than the 8 percent rate previously reported at our university [ll] and the 6.9 percent rate reported by the U.S. National Research Council and the National Science Foundation Cooperative Study [2]. It is, however, similar to the 2 percent rate reported by Cruise [12] in an 870 bed teaching hospital. The higher rate for federal facilities may reflect an older patient population, more emergency operations and the relatively limited number of procedures performed. Appendectomy rates are uniformly similar to those reported by Cruise [12] and to data from England and Wales [13]. In addition, the overall wound infection rate after cesarean section is identical to the 6 percent rate reported by Sweet and Ledger [14]. It should be pointed out that our data may underreport true infection rates because follow-up stopped when the patient was discharged. Cruise [15] has shown that approximately 11 percent of infec345
Farber and Wenzel
tions may not be recognized until after discharge. We chose not to use the previously established categories of surgical procedures (clean, clean contaminated, contaminated and dirty [6]) in our ongoing surveillance. The clean category is well understood and may be the most accurate reflection of surgical skill because of lack of endogenous contamination [15]. However, we believe that the usefulness of the other categories is limited because of the mixture of so many different procedures and varying interpretations of the criteria. Thus from an epidemiologic point of view the latter classification makes comparisons more difficult and outbreaks may actually be undetected. Even with our system of obtaining crude infection rates by surgical procedures, some refinements are required. We think our classification of appendectomies is important: for example, appendectomies for perforated appendicitis are followed by a high rate of infection caused by endogenous contamination and therefore should be considered differently than appendectomies for uncomplicated appendicitis. As additional data are collected and studied, more subtle divisions will be considered, such as cholecystectomy with and without common duct exploration. In our opinion, a prospective surveillance program for hospital acquired wound infections is the starting point for programs to reduce infection. Monthly reports of current infection rates are now summarized and distributed to all participating hospitals. Surgeons at participating institutions can then compare their own statistics with those tabulated for similar institutions in the rest of the state. With the described surveillance program, data are periodically updated to reflect current surgical practices. By establishing these baseline rates for various procedures, it is also possible that outbreaks will be detected more rapidly. More importantly, the use of centralized infection reporting has exciting future applications. We are now in the process of distributing rank-ordered rates to individual community hospitals in the same size categories. This should encourage hospitals with particularly high rates of infection to examine their techniques in closer detail. We hope that in a manner analogous to the experience of Cruise, such reporting will reduce the rate of infection statewide. Additional research may focus on controlled intervention trials in high risk operations.
346
Summary The results of a prospective statewide study of postoperative wound infection rates after 19 selected surgical operations are reported. Rates are based on 44,689 operations performed at 38 hospitals from January 1,1977 through May 31,1979. The data were collected by review of ward charts and are compared with those of earlier reports. Particularly high rates of infection were found after surgery for perforative appendicitis, colorectal resection, radical neck dissection and leg amputations. These rates should serve as a baseline for future comparisons. The potential value of centralized infection reporting is discussed. Acknowledgment: We gratefully acknowledge the kind assistance and review of the manuscript by William R. Sandusky, MD. References 1. Dixon R. Effects of infections on hospital care. Ann Intern Msd 1978;89:749-53. 2. Green JW, Wenzel RP. Postoperative wound infection: a controlled study of the increased duration of hospital stay and direct cost of hospitalization. Ann Surg 1977; 1852868. 3. Cruise P. Surgical wound sepsis. Can Med Assoc J 1970; 102:251-8. 4. Wenzel RP, Dsterman CA, Hunting KJ. Gwaltney JM Jr. Hospital-acquired Infections. I. Surveillance in a university hospital. Am J Epidemloi 1978;103:251-80. 5. Wenzei RP, Dsterman CA, Townsend TR, st al. The deveiopment of a statewide program for surveillance and reporting of hospital acquired infections. J Infect Dls 1979;140: 741-5. 8. Rarker WF, Longmire W, Altemeier WA, et al. Postoperative wound infections: ths jnfluence of ultraviolet radiation of the operating room and of various other factors. Ann Surg 1984;180&ppl 2:l. 7. Paskln D. A prospective study of wound infections. Am Surg 1989;35:827-9. 8. Cruise PJ, Foord R. A five ypar prospective study of 23,849 surgical wounds. Areh Surg 1973;107:208-10. 9. Karl RC, Mertz JJ, Veith FJ, Mnesn P. Prcphylactk antimiaobtal drugs in surgery. N Engl J bled 1988;275:305-8. 10. Polk H. The value of a nurse epldemioiogist in the control of surgical infection. Surg Clln North Am 1975;55: 1277-82. 11. Wenzel RP, Huntlng KJ. Dsterman CA. Postoperative wound infection rates. Surg Gynecol Obstet 1977; 144:749-52. 12. Cruise PJ. IncMence of wound infections on the surgical services. Surg Clin North Am 1975;55:1289-75. 13. incidence of wound infection in England and Wales. Lancet 1980;2:859-83. 14. Sweet R, Ledgsr W. Pusmsml infectkms morbkiii. Am J Dbstet Gynecol1973;117:1093-100. 15. Cruise P. Infection surveillance: identifying the problems and the high risk patient. South Med J 1977;70: Suppl 14-7.
lha Amarlcan Journal of Surgery