Surgical sepsis at a district general hospital

ffournal of Hospital Infection (1985) 6, 140-146

S u r g i c a l s e p s i s at a district g e n e r a l h o s p i t a l N . R. H u R o n , E. S. Kiff,* a n d T. D. B r o g a n

Stepping Hill Hospital, Stockport, Cheshire S K 2 7fie and * University Hospital of South Manchester, Manchester M 2 0 8 L R Accepted for publication 24 September 1984 Summary: A retrospective survey of 15,199 surgical wounds occurring over

a 5-year period was carried out at a District General Hospital. Of 9495 'clean' operations, 4"5% became infected in contrast with 15.8% of 5704 'cleancontaminated' operations, an overall wound infection rate of 8'8%. There was a downward trend in the proportion of severe wound infections in 'cleancontaminated' operations which may be related to the increasing expenditure on antibiotics.

Introduction

Elective s u r g e r y b e c a m e a realistic p o s s i b i l i t y o n l y w i t h t h e a d v e n t of a n t i s e p t i c a n d t h e n aseptic t e c h n i q u e s a n d the h e a l i n g of w o u n d s w i t h o u t c o m p l i c a t i o n has r e m a i n e d o n e o f its f u n d a m e n t a l o b j e c t i v e s . W o u n d i n f e c t i o n is still a h a z a r d of s u r g e r y a n d a well r e c o g n i z e d cause o f m o r b i d i t y a n d p r o l o n g e d h o s p i t a l stay. A l t e m e i e r (1963) s t a t e d t h a t ' t h e d e v e l o p m e n t o f i n f e c t i o n i n i n c i s i o n a l w o u n d s c o n t i n u e s to b e o n e of t h e m o s t s e r i o u s c o m p l i c a t i o n s t h a t c a n o c c u r in s u r g i c a l p a t i e n t s ' . S u r g i c a l sepsis is t h e r e f o r e b o t h u n d e s i r a b l e for t h e p a t i e n t a n d f i n a n c i a l l y d e t r i m e n t a l to a H e a l t h S e r v i c e ( P u b l i c H e a l t h L a b o r a t o r y S e r v i c e , 1960; F a r b e r & W e n z e l , 1980; R e n v a l l , N i i n i k o s k i & Alto, 1980; C o l e s et al., 1982). H o w e v e r , v a r i o u s m e t h o d s o f s u r v e i l l a n c e h a v e b e e n s h o w n to result in the l o w e r i n g o f t h e rate o f w o o n d i n f e c t i o n ( C u l b e r t s o n et aL, 1961; Brachman et al., 1980). T h i s c o m m u n i c a t i o n e x a m i n e s tile i n c i d e n c e , n a t u r e a n d s e v e r i t y o f w o u n d i n f e c t i o n f o l l o w i n g s o m e 15,000 o p e r a t i o n s p e r f o r m e d o v e r a 5 - y e a r p e r i o d in a U K d i s t r i c t g e n e r a l h o s p i t a l . I t also i l l u s t r a t e s h o w the results o f s u c h a s u r v e y c a n b e u s e d as a y a r d - s t i c k in t h e s u r v e i l l a n c e o f s u r g i c a l w o u n d infection.

Methods S u r v e i l l a n c e o f w o u n d i n f e c t i o n is c a r r i e d o u t in t h i s h o s p i t a l b y t h e f o l l o w i n g m e t h o d . I n t h e p o s t o p e r a t i v e p h a s e , s u r g i c a l w o u n d s s u s p e c t e d to *Correspondence to: M r E. S. Kiff, University Hospital of South Manchester, Nell Lane, West Didsbu~3', Manchester M20 8LR. 0195-6701/85/020I 40 + 07 103,00

~) 1985 T h e Hospital Infect/on Society

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be infected are e x a m i n e d bacteriologically by r u b b i n g d r y or salinem o i s t e n e d cotton sw abs along tile suspicious area or b y d i p p i n g a dry s w a b into exudate or p u r u l e n t discharge. Swabs are c u l t u r e d u n d e r both aerobic a n d anaerobic c o n d i t i o n s and s t a n d a r d m e t h o d s are use d for the isolation, identification and sensitivities of m i c r o - o r g a n i s m s . T h e results are r e t u r n e d to the wards with an a d d i t i o n a l f o r m r e que sti n g the w a r d sister to assess the w o u n d according to a f our - sta ge g r a d i n g s y s t e m ( T a b l e I). T h i s a s s e s s m e n t f o r m is r e t u r n e d to the laboratory and the o p e r a t i on is allocated to one of two categories called respectively ,clean' a n d Table I. Description of the criteria used in the four.stage grading of wound infections ,,,

,

Grade 1 2

3 4

,,

,,,

,,

,

,i

i

t,,,i

,,

,,,

,,i

,,

,,,,,

!,,,i

Criteria for clinical assessment Incision shows greater than expected marginal erythema: oozing slight or nil. Serous or sero-sanguinous exudate from an incision that shows erythema but no separation of edges: or, pustule close to a suture. Patient may not have a pyrexia. Frankly purulent discharge from less than half the incision with or without separation of the edges. Patient may have a pyrexia. Purulent discharge from most of the incision with or without separation or dehiscence. Patient will usually have a pyrexia.

' c l e a n - c o n t a m i n a t e d ' ; operations involving p r o c e d u r e s s u c h as drainage o f abscesses are d e e m e d to be ' se ptic ' and are not i n c l u d e d in t h e analysis. ' C l e a n - c o n t a m i n a t e d ' operations are those in w h i c h the large or small bowel or an infected or p o t e n t i a l l y infected space is e n t e r e d in a ny way; an e x a m p l e of s u c h an operation w o u l d be an a p p e n d i c e c t o m y . F u r t h e r swabs are sent w h e n w o u n d s deteriorate a n d t h e i r receipt at the l a b o r a t o r y br ings a bou t a r e q u e st for regrading. H i t h e r t o , data was filed m a n u a l l y b u t the details are n o w recorded on the ' f l o p p y disc' of a m i c r o - c o m p u t e r . A r e t r o s p e c t i v e s u r v e y w a s carried out b y t w o of us ( N R H a nd E S K ) e x a m i n i n g t h e records of all operations p e r f o r m e d d u r i n g the period 1 J a n u a r y 1977-31 D e c e m b e r 1981; surgical a n d gynaecological operations were i n c l u d e d if a n incision was made. ' S e p t i c ' p r o c e d u r e s were n o t i n c l u d e d and the o p e r a t i o n s w e r e a l l o c a t e d t o the 'c le a n' and 'cleanc o n t a m i n a t e d '~ categories • def ine d above. It was a s s u m e d t h a t every p o s t o p e r a t i v e w o u n d s w a b r e c e i v e d by t h e l a b o r a t o r y was t a k e n f r o m an infected w o u n d since each year a small b u t v a r i a b l e proportions(average 15%) o f assessment f o r m s were not r e tur ne d to t h e l a b o r a t o r y / T h e yearly overall p e r c e n t a g e of i n f e c t e d w o u n d s w a s t h e r e f o r e calculated f r o m l t h e total n u m b e r of postoperative w o u n d swabs, a n d the a n n u a l percentages of the: two c a t e g o r i e s of• o p e r a t i o n d e e m e d t o b e m i n o r ~ w o u n d infections (grades 1 and 2 ) a n d severe w o u n d infections (grades 3 a n d 4) were a djuste d b y s i m p l e proportion. T h e c a l c u l a t i o n w a s b a s e d on t h e a s s u m p t i o n that;the d i s t r i b u t i o n o f the categories o f operation a n d gr a de s o f t h e : 1 5 % o f w o u n d

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N . R . H u R o n e t M.

infections not assessed w a s closely similar to that of t h e population which was graded. Statistical analyses were carried out mostly by the Z 2 test for independent samples and the method +of calculation was that described by Siegel (1956). Results

Included in the survey were 15,199 operations; the overall percentage of infected w o u n d s during the 5-year period w a s 8"8:k0"67 and the year-toyear variation was not significant (Z2=6"17; 0 - 1 < P < 0 " 2 ) . T h e annual variation in the proportion of wound infections belonging to grades 1, 2, 3 and 4 is illustrated i n Figure 1; the year-to-year differences, which suggest an increase in the proportion of relativeIy minor w o u n d infections (grades 1 and 2 ) a n d a corresponding decrease in severe w o u n d infections (grades 3 and 4), were highly significant (Z 2 = 34"27; P < 0"001). 1977

1979

1978

1980

1981

Figure 1. Annual variation in the proportion of wound infections belonging to grades of severity I, 2,3 and 4. Grade 1 ~ ; Grade 2 ~ ; Grade 3 ~;:Grade 4 I .

Little variation, however, was found from year-to-year in the percentages of wounds yielding Staphylococcus aureus a n d Gram-negative organisms. ~ a l y s i s of the data s h o w e d that t h e r e was no significant differences between the distribution: each quarter of w o u n d s yielding Staph. aureus (17-23%); coliforms (including Escherichia cell, Klebsiella spp. a n d similar Enterobacteriaceae) ( 4 1 - 4 8 % ) a n d P r o t ~ s andPseudomonas s p p : (! 5-23 %); this •last mixed :group were m o s t l y Pr~ mirabilis,and Ps. ++aeruginosa, t h e pseudomonads accounting for o n l y 1 7 % o f the group.+ T h e slight upward dlstrtbutIo was analysed •(Z2 = 1 0 : 7 2 ; 0"02 < P ~ 0 - 0 5 ) ; m o s t of the organisms.~:were enterbcocci and only ~1 4 patients: yielded ~Str. pyogenes dbring tI4i~~5,year peri0d::The total n u m b e r of patients (82) with bacteroides °

"

"

n

shows that this kZ: --,1 Z ~O, U ' U L ~ P < U'UZ). -

+

,

.

+

+

~

+

•

Surgical sepsis

143

severe wound infections (grades 3 and 4) did not show marked variation from year to year (Figure 2). Statistical analysis showed that the variation was not significant (X2=0.84; 0 " 9 < P < 0 " 9 5 ) . O n e third of a l l infected wounds in this category did not yield pathogens; of the r e m a i n d e r . approximately 60% yielded Staph. aureus or Streptococcus spp. alone or mixed with Gram-negative bacilli; and in the other 40%, Gram-negative bacilli were the only pathogens isolated.

20.0 ~ '13

1977

1978

1979

l

._¢

1980 C-T

1981 C'T

QJ

E 0

15-0

.2 o

10.0

0

5"0 C

1845 1263

1865 1151

1740 1046

1963 1181

2082 1065

Annual totol of operations in each cateqory

Figure 2. Year to year variation in the percentages of 'clean' and 'clean-contaminated' operations that were infected. M i n o r w o u n d infections (grades 1 and 2) N; severe w o u n d infections ( g r a d e s 3 and 4) m; C = operation category designated 'clean'; C - T = operation category designated 'clean-contaminated'.

Of the 5704 operations designated 'clean-contaminated', 15"8% became infected; only 12% of all w o u n d s in this category failed to yield pathogens and. of t h e remainder, almost 4 0 % yielded Staph. aureus or: Streptococcus spp. w i t h o r w i t h o u t G r a m , n e g a t i v e bacilli, and in over 60%, G r a m ' negative bacilli were the only pathogens isolated. In contrast with the 'clean' categorY, the relative proportion of minor wound infeCtiOns (grades 1 a n d 2) s h o w e d a n u p w a r d trend oVer t h e 5.year : p e r i o d ( F i g u r e 2 ) ; statistical analysis : c o n f i r m e d t h a t t h e trend was h i g h l y significant: : (g2= 23,5; P < 0.001), D u r i n g the year following the survey, a further increase in the proportion of minor Wound infections: oCcurred;operations graded:l :a n d 2 accounted f0ialmost~:tl~ree.quarters: (74%):of: the 282: mfections ~in clean Woundsi:~d f o r T 0 % of the 191 infeCtions!ini~i0unds of 'clean.contammated'operatmns.

144

N . II. H u l t o n e t a L

H o w e v e r , t h e first q u a r t e r of the year s h o w e d a m a r k e d increase in the p e r c e n t a ge of w o u n d s y i e l d i n g S t a p h . a u r e u s ( T a b l e II), to a level a l m o s t three s t a n d a r d deviations above the m e a n percentage o b t a i n e d in the s u r v e y (204-5-2%). N o n e of the othe r q u a r t e r l y figures differed f r o m the c o r r e s p o n d i n g s u r v e y averages by as m u c h as two s t a n d a r d deviations. O v e r 80% of the w o u n d s infected with S t a p h . a u r e u s were m i n o r (grades 1 a nd 2) and a l m o s t 60% of the operations w e r e de signa te d ' c l e a n - c o n t a m i n a t e d ' . T h e p h a g e types of the staphylococci were either diverse or the o r g a n i s m s were n o n - t y p a b l e . Table I I. Quarterly variation in the percentages of wounds yielding staplzvlococci, streptococci and Gram-negative organisms during the year following the survey (1982) as compared with the corresponding mean percentages obtained during the 5-year survey Percentage of infected wounds yielding pathogens 5-year s u r v e y

Quarter of 1982 Organism

Ist

2nd

3rd

4th

Mean sD

Staphylococcus aureus Streptococcus spp.

35 14 28 8 4

15 18 42 25 4

20 15 45 21 4

20 22 32 28 5

20 4- 5"2 184- 7-0 44 4- 8.4 20=t=6"9 6 4- 4-7

Co|ifo.rms

Proteus spp. +Pseudomonas spp. Bacteroides spp.

Discussion

D i s t r i c t general hospitals carry out ' r o u t i n e ' s u r g e r y in the s h a p e of w a i t i n g list case~-and e m e r g e n c y operations. O u r investigation is an a na lysis of surgical sepsis over a period of 5 years in a typical district h o s p i t a l s e r v i n g a p o p u l a t i o n of a p p r o x i m a t e l y 300,000 people. O u r results ha ve b e e n d e r i v e d f r o m the surveillance of over 15,000 operations; very few sur ve ys of c o m p a r a b l e size have been m a d e a n d m o s t of these have b e e n carried out in N o r t h A m e r i c a ( C r u s e & Foord, 1973; C r u s e & F o o r d , 1980; F a r b e r & W e n z e l , 1980) and have s o m e t i m e s covered m o r e t h a n one hospital. A n overall wound, infection rate of 8"8% was f o u n d a n d this d i d not va r y f r o m year-to-year. T h u s , it was c o m p a r a b l e with the figures d e r i v e d a q u a r t e r of a c e n t u r y ago f r o m a large sur ve y of a n u m b e r of c e ntr e s a n d reported to0the P u b l i c H e a l t h L a b o r a t o r y Service (1960) a n d s i m i l a r to those of other large s u r v e y s since that t i m e ( Cr use & F o o r d , 1973; W e n z e l , H u n t i n g & O s t e r m a n , 1977; Cr use & Foor d, 1980; F a r b e r & W e n z e l , 1980). Anal~csis of t h e data s h o w e d that the r e was a significant u p w a r d t r e n d in the p r o p o r t i o n of r e l a t i v e l y m i n o r w o u n d i n f e c t i o n s and a c o r r e s p o n d i n g decrease , i n t h e p e r c e n t a g e of seyerely infected w o u n d s . A s i m p l i f i e d m o d i f i c a t i o n of the classification o f A l t e m e i e r (I 963) was u s e d to place the operations into categories that we defined as ' c l e a n ' a n d ' c l e a n -

Surgical sepsis

145

c o n t a m i n a t e d ' . T h e first category.corresponds to the A l t e m e i e r definition of a 'clean' o p e r a t i o n b u t the o t h e r category i n c l u d e d operations that A l t e m e i e r classified as ' c l e a n - c o n t a m i n a t e d ' and ' c o n t a m i n a t e d ' . W e e x c l u d e d septic p r o c e d u r e s that A l t e m e i e r designated as ' d i r t y ' . T h e advantage of o u r m e t h o d of classification is the ready allocation of operative p r o c e d u r e s to one of two b r o a d categories, and it had ~he f u r t h e r advantage of simplifying the task of retrospectively analysing over 15,000 operations. It was found that the p r o p o r t i o n of severe w o u n d infections did not vary from y e a r - t o - y e a r in 'clean' operations; in contrast, a significant d o w n w a r d t r e n d in the relative p r o p o r t i o n of severe w o u n d infections was noted in the category of operations designated as ' c l e a n - c o n t a m i n a t e d ' . A high p r o p o r t i o n ( 6 3 % ) of the pathogens in ' c l e a n - c o n t a m i n a t e d ' operations a p p e a r e d to be exclusively G r a m - n e g a t i v e bacilli, a n d this g r o u p of o r g a n i s m s has been shown to be capable of initiating infection (Quick & Brogan, 1968). Since our survey began, there, has been an increasing t e n d e n c y to use the n e w e r ~-lactam antibiotics, such as cefuroxime a n d ticarcillin, and amin0glycosides in c o m b i n a t i o n with m e t r o n i d a z o l e in surgical patients. T h i s is reflected in the 23"5% per a n n u m increase in e x p e n d i t u r e on antimicrobial drugs in o u r district o v e r the same period and it is therefore possible that pre-operative p r o p h y l a x i s and postoperative t h e r a p y with antibiotics was responsible for the changes in w o u n d sepsis observed. N o y e a r - t o - y e a r differences were noted in the percentages of infected w o u n d s that yielded ,Staph. aureus or G r a m - n e g a t i v e bacilli; in contrast, a small, b u t significant, annual increase occurred in the p r o p o r t i o n of septic w o u n d s infected with Streptococcus spp. and it is possible that this could reflect the increased usage of so-called second generation cephalosporins which have little effect against enterococci. T h e c o n s t a n c y of t h e incidence of staphylococcal infections, which a m o u n t e d overall to only 1.8% of all operations, was a valuable finding in that it helped to identify a significant increase in staphylococcal sepsis which o c c u r r e d in one q u a r t e r d u r i n g the year following the survey. O f the organisms isolated from infected w o u n d s 6 0 % were G r a m - n e g a t i v e bacilli, a p r o p o r t i o n similar to that f o u n d over 15 years ago by Quick & Brogan (1968). J u s t over o n e - q u a r t e r of these were Proteus spp. b u t p s e u d o m o n a d s accounted for only 5 % of the total. A n a e r o b i c organisms such as Bacteroides spp. were isolated f r o m only 6 % of all infected wounds; it is t e m p t i n g to speculate that the small b u t significant decline in this t y p e of infection over the 5 years s u r v e y e d was due to the increasing use of metronidazole, both prophylactically a n d therapeutically, b y some of the surgical firms. A change in t h e p a t t e r n of surgical sepsis was noted b y one o f us o v e r 15 years ago (Quick & Brogan, 1968) and p r e s e n t d a y p o s t o p e r a t i v e infection in a district general hospital, a s depicted b y o u r survey, does not differ qualitatively f r o m that observed then, However, the t r e n d d u r i n g the 5-year period of o u r s u r v e y suggested a quantitative decline in clinically severe

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sepsis, mostly associated with Gram-negative bacilli. This could be due in part to the increasing availability of antibiotics active against this type of pathogen. Surveillance is t h e keynote of control of infection and demands the acquisition and efficient retrieval of data for analysis. The system we describe, which is now programmed to a computer, makes possible effective surveillance without the services of a specialized nursing officer. References Ahemeier, W. A. (1963). Prevention of postoperative infections: operating theater practice. In 'Infection in Hospitals' (Williams R. E. O. & Shooter, R. A., Eds), pp. 207-220. Blackwell Scientific Publications, Oxford. Brachman, P. S., Dan, B. B., Haley, R. W., Hooton, T. M., Garner, J. S. & Alien, J. R. (1980). Nosocomial surgical infections; incidence and cost. Surgical Clinics of North America 60,' 15-25. Coles, B., van Heerden, J. A., Keys, T. F. & Haldorson, A. (1982). Incidence of wound infection for common general surgical procedures. Surgery, Gynaecology and Obstetrics 154, 557-560. Cruse, P. J. E. & Foord, R. (1973). A five year prospective study of 23,649 surgical wounds. Archives of Surgery 107, 206-210. Cruse, P. J. E. & Foord, R. (1980). The epidemiology of wound infection (a 10 year prospective study of 62,939 wounds). Surgical Ch'nics of North America 60, 27-40. Culbertson, W. R., Altemeier, W. A., Gonzales, L. L. & Hill, E. O. (I961). Studies on the epidemiology of postoperative infection of clean operative wounds. Annals qf Surgery 154, 599-610. Farber, B. F. & Wenzel, R. P. (1980). Postoperative wound infection rates: results of postoperative statewide surveillance. American jTournal of Surgery 140, 343-350. Public Health Laboratory Service (1960). Incidence of surgical wound infection in England and Wales. Lancet 2, 659-663. Quick, C. A. & Brogan, T. D. (1968). Gram-negative rods and surgical wound infection. Lancet 1, 1163-1167. Renvall, S., Niinikoski, J. & Aho, A. J. (1980). Wound infections in abdominal surgery./lcta Chirurgia Scandinavia 146, 25-30. Siegel, S. (1956). The case of k unrelated samples. In 'Non-parametric statistics for the behavioural sciences' pp. 175-179. McGraw-Hill Book Company, New York, Toronto, London. Wenzel, R. P., Hunting, K. J. & Osterman, C. A. (1977). Postoperative wound infection rates. Surgery, Gynaecology and Obstetrics 144, 749-752.