A prospective study of hospital-acquired infection in 2330 cardiovascular surgery patients

ffournal ofHospital Infection (1985) 6, 333-341 SHORT REPORT

A p r o s p e c t i v e s t u d y o f h o s p i t a l - a c q u i r e d i n f e c t i o n in 2330 c a r d i o v a s c u l a r s u r g e r y p a t i e n t s A. Buu Hoi and H. Richet

Labora'toi~e Central de Bactdriologie, H6pital Broussais, 96 rue Didot, 75014 Paris, France Laboratoire Central de Microbiologie, HSpital HStel-Dieu, 1 Place du Parvis Notre Dame, 75181 Paris, Cedex 04, France Accepted for publication 26 November 1984 S u m m a r y : Between M a r c h 1982 and M a y 1983, 2330 patients undergoing cardiovascular surgery w e r e prospectively s u r v e y e d for hospital-acquired infections. D u r i n g the first m o n t h of the study the overall incidence of infection was 8-2%, t h e incidence of postoperative wound infection was 3-8%, urinary tract infection 3-2%, lower respiratory tract infection 1"2% and bacteraemia 0.6%. In M a y 1983 the overall incidence was 3"2% and incidence of wound, urinary tract and lower respiratory infections were :1.3%, 0"6% a n d 1.3% respectively. U r i n a r y tract infection was reduced by substituting a d o s e d drainage system for open drainage. A peak of postoperative w o u n d i n f e c t i o n was observed in N o v e m b e r 1982 and was related to changes in the functioning of the d e p a r t m e n t resulting in inadequate pre-operative preparation. T w o outbreaks of pseudobacteraemia occurred related to the arterial line stopcock and to heparin used for biochemistry tests. Antimicrobial prophylaxis was not modified during the study. However, wound infection rates dropped from 4% to 1-3%. In conclusion, this surveillance p r o g r a m m e was associated with a significant reduction in hospital-acquired infection.

Introduction

Since t h e r e is little data in F r a n c e on h o s p i t a l - a c q u i r e d i n f e c t i o n s (t-IAIs), a p r o g r a m m e for s u r v e i l l a n c e o f i n f e c t i o n was c a r r i e d o u t in the c a r d i o v a c u l a r s u r g e r y d e p a r t m e n t of t h e B r o u s s a i s H o s p i t a l (Paris, F r a n c e ) . T h e o b j e c t i v e s d f this p r o g r a m m e were: (i) t h e d e t e r m i n a t i o n o f i n f e c t i o n rates, (ii) t h e early d e t e c t i o n o f o u t b r e a k s , (iii) t h e i d e n t i f i c a t i o n o f e n d e m i c i n f e c t i o n s , a n d (iv) the a s s e s s m e n t o f t h e efficiency o f a n t i b i o t i c p r o p h y l a x i s .

Material and methods

T h i s s t u d y was p e r f o r m e d f r o m M a r c h 1982 to M a y 1983. T h e c a r d i o v a s cular s u r g e r y d e p a r t m e n t is a 110 b e d u n i t w i t h a 15 b e d i n t e n s i v e s u r g i c a l 0195--6701/85/030333+09 $03.00/0

(~ 1985 The Hospital lnfectlon Society

333

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care unit ( I C U ) . T h e patients were admitted e i t h e r as emergencies or electively 2 days before surgery. F r o m the operating theatre they were transferred to the I C U where they were nursed for the immediate p o s t o p e r ative period, a typical stay was 48 h or until they no longer required respiratory ventilation or monitoring. Surveillance method

T h e surveillance was carried out by a nurse epiderniologist who visited the wards daily, checking the patient's charts and the nursing reports, as w e l l as discussing patient problems with the staff. Daily microbiological data was given t o the nurse by the laboratory. Each case of fever or diagnosis of infection was recorded ° n a special form. T h e following data were collected: age, sex, dates of ad.mission, operation and discharge, n u m b e r of the room(s), underlying disease, diagnostic and operative procedures, antibiotic treatment and infection (date of onset, site, causative organism, if isolated, and antibiotic susceptibility). T h e nurse followed up each patient with suspected or proven H A I until discharge. Infections occurring after discharge were not specifically surveyed except if the patient came back to the Broussais Hospital. Hospital-acquired infections were defined according to the C D C definitions (Centers for Disease Control, !974) and operation wounds were classified according to the American College of Surgeons Classification (Ahemeier, 1976). T h e data was analyzed monthly. Incidence rates were determined for the following: postoperative w o u n d infections, lower respiratory tracts infections, urinary tract infections and bacteraemia.

Results

D u r i n g the 15 months survey, 2330 operations were performed as follows: valvular surgery, 46%; coronary bypass, 28%; congenital malformation surgery, 11%; vascular surgery, 15%. D u r i n g this period the antibiotic prophylaxis used was cefazolin (30 mg kg -I) given 12 h before the operation and every 8 h after surgery for 2q a8 h. Results o f the first m o n t h of surveillance are shown in T a b l e I. T h e Table I. Hospital-acquired infections in March 1982 No.

No. of patients No. of infected patients No. of infections Postoperative wound infections Urinary,tract infections Lower respirator/tract infections Baeteraemia

158 13 14 6 5 2

(%) (8.2) (3-8) (3.16) (1-26) (0.6)

Hospital-scquired infection in cardiovascular patients

335

overall i n c i d e n c e of H A I d u r i n g this t i m e was 8"22%. P o s t o p e r a t i v e w o u n d infections r e p r e s e n t e d 39% of the total w i t h an i n c i d e n c e of 3-8% a n d an i n c i d e n c e of m e d i a s t i n i t i s of 1"26%. T h e ne xt m o s t c o m m o n i n f e c t i o n was u r i n a r y tract i n f e c t i o n w i t h an i n c i d e n c e of 3"2% .and the i n c i d e n c e of b a c t e r a e m i a was 0-6%. F i g u r e s 1-5 show the c h a n g e s in the infection rate d u r i n g the 15 m o n t h s of the survey. F i g u r e 1 r e p r e s e n t s the variation in the overall i n c i d e n c e of infection. T h e overall rate of H A I s for the 15 m o n t h s survey was 5"16%. T h e i n c i d e n c e rates varied d u r i n g the s t u d y b e t w e e n 2-3% and 8"2%. T h e peaks o b s e r v e d in S e p t e m b e r a nd N o v e m b e r 1982 were related to an increase in postoperative w o u n d infection.

Postoperative wound infections A l m o s t all surgical p r o c e d u r e s p e r f o r m e d were clean operations. T a b l e II shows m o r e specifically the postoperative w o u n d inf e c tion ( P O W I ) rates a c c o r d i n g to the type of operation. Infections were m a i n l y associated with c o r o n a r y bypass and v a l v u l a r surgery. F i g u r e 2 shows the P O W I rate. T h e overall i n c i d e n c e of all P O W I s ( i n c l u d i n g mediastinitis) for the 2330 operations was 2 ' 7 7 % . M e d i a s t i n i t i s alone h a d an incidence of 0:8%. D u r i n g the first m o n t h of the survey, the i n c i d e n c e of P O W I s a p p r o a c h e d 4 % . T h e rate varied b e t w e e n 1"8% and I0'

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4~% d u r i n g the M a r c h - O c t o b e r period of 1982. T h e highest rate was observed in N o v e m b e r 1982. T h i s m o n t h was characterized by a change in the organization of the d e p a r t m e n t with new staff and a t e m p o r a r y reduction of nurses. D u r i n g this time pre-operative skin cleansing was indequate: patients were no longer showered and s c r u b b e d with p o v i d o n e - i o d i n e the day before operation. D u e to this, a pre-operative pr e pa r a tion g u i d e l i n e was established which was discussed with the surgeons and nurses. T h e final protocol for pre-operative care included a shower with p o v i d o n e - i o d i n e the day before operation and the hair was clipped j u s t before operation. However, shaving of the operative site was p e r f o r m e d the e ve ning before the operation. T h e incidenc e of P O W I s r e m a i n e d u n d e r 1.5% with these methods. Bacteria isolated from m e d i a s t i n i t i s are listed in T a b l e I I i . Staphylococcus epidermidis was considered a significant pathogen in m e d i a s tinitis when the same strain was isolated in p u r e culture from pre-operative samples from the s t e r n u m , me dia stina l pus and in addition s o m e t i m e s in blood cultures. T a b l e I I I . Bacteria isolated from mediastinitis

Number of isolates (%) Staphylococcus aureus Staphylococcus epidermidis Enterococci Proteus spp.

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F i g u r e 5. I n c i d e n c e o f b a c t e r a e m i a a n d p s e u d o b a c t e r a e m i a . i n c l u d e d in h o s p i t a l - a c q u i r e d i n f e c t i o n r a t e s .

Pseudobacteraemia

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Urinary tract infections T h e urinary tract infections ( U T I s ) are summarized in Figure 3. At the beginning of the surv.ey, patients u n d e r w e n t indwelling ureth'ral catheterization. An urethral catheter was inserted by a nurse before operation. T h e duration of catheterization was related to the duration of the stay in the I C U , normally 48 h (24 h-7 days). Urine specimens were not collected for culture until U T I s y m p t o m s were present. D u r i n g the first 3 months the incidence of U T I s varied between 2-8 and 4.25% and bacteraemia occurred in 25% of the U T I s . Investigatie.n of the m a n a g e m e n t of the drainage system showed that the bags were disconnected for e m p t y i n g and for the collection of urine for analysis. A closed drainage system was introduced in July 1982, no U T ! was observed in August. A peak of U T I s was n o t e d i n J a n u a r y 1982 because patients were not systemically catheterized in the operation room unless catheterization was needed during the postoperative period, S o m e patients presented with urinary retention and u n d e r w e n t e m e r g e n c y d r a i n a g e with

Hospital-acquired infection in cardiovascular patients

339

poor asepsis. T h i s strategy was later changed and the incidence of U T I s remained u n d e r 1%. T a b l e IV shows the bacteriological isolates from the U T I s .

T a b l e IV. Bacteria isolated from urinary tract infections

No. of isolates from Open drainage Closed drainage system system Escherichia coli Enterobaeter cloacae Serratia s p p . Proteus mirabilis Morganella morganii Escherichia coil+ Enterobacter cloacae Proteus mirabilis + Klebsiella pneumoniae Pseudomonas aeruginosa Pseudomonas aeruginosa + Enterobacter cloacae Streptococcus faecalis Staphylococcus aureus Candida albicans Total

7 4 2 1

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Figure 4 shows the findings in lower respiratory tract irVections ( L R T I s ) . T h e overall rate of L R T I s was 0"9% which may have been underestimated due to the clinical and laboratory difficulties of defining these infections. t3acteraemia T h e results of bacteraemia surveillance are shown in Figure 5. These surgical p a t i e n t s had an indwelling arterial line with a continuous flush device for haemodynamic monitoring during the operation and during their stay in the I C U . Between M a y and August 1982, a rate of bacteraemia as high as 10% was observed. M o s t of these blood cultures were collected by a three-way stopcock from lines of patients without any s y m p t o m s of bacteraemia. T h e control blood cultures collected by venepuncture were negative. I n j ~ v e m b e r 1982 two symptomatic bacteraemic patients w e r e f o u n d to have positive blood cultures when the blood was drawn by stopcock as well a s v e n e p u n c t u r e . Since that time stopcocks have been changed after surgery and every 48 h t h e r e a f t e r . In addition stopcocks werer h a n d l e d ~with a povidone-iodine Compress. Subsequently intra,arterial~line associated bacteraemia and pseudobacteraemia disappeared. In M a r c h 1983; six patients in the cardiovascular surgery d e p a r t m e n t and

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14 in o t h e r d e p a r t m e n t s o f t h e h o s p i t a l h a d o n e o r m o r e p o s i t i v e b l o o d c u l t u r e s w i t h K l e b s i e l l a o x y t o c a . All s t r a i n s w e r e s h o w n to b e l o n g to t h e s a m e c a p s u l a r t y p e , K 6 8 a n d to t h e s a m e b i o t y p e . T h e s a m e s t r a i n w a s isolated f r o m h e p a r i n u s e d for b i o c h e m i s t r y tests a n d t h e s e s p e c i m e n s w e r e collected j u s t b e f o r e b l o o d culture.s. T h e s e p s e u d o b a c t e r a e m i a s also d i s a p p e a r e d a f t e r a d e q u a t e b l o o d collection. T a b l e V s h o w s t h e b a c t e r i a c a u s i n g pseudobacteraemia. Table V. Bacteria causing pseudobacteraemias Bacteria

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(%)

2 3 2

(4.25) (6.4) (4.25)

Single species Escherichia coli Enterobacter cloacae Morganella morganii Proteus mirabilis Serratia marcescens Acinetobacter calcoaceticus Alcaligenes spp. Pseudomonas aeruginosa Pseudomonas maltophilia Pseudomonas spp. Streptococcus faecalis

1

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Discussion

T h i s s u r v e i l l a n c e p r o g r a m m e w a s d e v e l o p e d a n d c a r r i e d o u t as an e x p e r i m e n t in o n e o f t h e s u r g e r y u n i t s o f t h e B r o u s s a i s H o s p i t a l . T h e p r o g r a m m e c o v e r e d 110 o f t h e 646 b e d s o f t h e h o s p i t a l . Before i m p l e m e n t a t i o n of this p r o g r a m m e there were no infection control activities in t h e h o s p i t a l . R e c o m m e n d a t i o n s o n h y g i e n e a n d t h e f u n c t i o n i n g of t h e o p e r a t i n g t h e a t r e a n d I C U w e r e d r a w n u p b y t h e m i c r o b i o l o g i s t . T h e r e w a s n o c o n t r o I o f t h e efficiency o f t h e s e r e c o m m e n d a t i o n s u n t i l the s u r v e i l l a n c e p r o g r a m m e was i m p l e m e n t e d , T h u s , t h e r e s u l t s of the first m o n t h s o f t h e s u r v e y can be u s e d t o d e t e r m i n e t h e c o n s e q u e n c e s of t h e s u r v e i l l a n c e p r o g r a m m e on H A I s a n d to ~compare o u r r e s u l t s w i t h t h o s e in the:iliterature, ~ T h e r a t e s a r e s i m i l a r to thOse d e s c r i b e d i n o t h e r c o u n t r i e s . S o m e o f t h e m are~higher, : a s in t h e C h a i m S h e b a M e d i c a l C e n t e r ( E g o z & M i c h a e l i , 1 9 8 1 ) w h e r e , in a c h e s t a n d h e a r t s u r g e r y d e p a r t m e n t , t h e overall rate w a s 1 7 . 6 % w i t h a P O W I r a t e o f 8 - 9 % . O u r r e s u l t s a r e s i m i l a r to t h o s e