:Acta . . N-durochlrurglca
Acta Neurochir (Wien) (1992) 119:80-84
9 Springer-Verlag 1992 Printed in Austria
Risk Factors in Postoperative Neurosurgieal Infection A Prospective Study R. Patir, A. K. Mahapatra, and A. K. Banerji Department of Neurosurgery, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India
Summary Four hundred and seventy patients who had undergone neurosurgical operations were studied prospectively. After defining postoperative infection so that is included all the infective complications irrespective of location oecuring after surgery, the overall infection rate was 17%. The infection rate in 413 cases without pre-existing infection was 15%. Wound infection was recorded in 5% and meningitis in 6%: Risk factors which lead to a significant increase in the incidence of postoperative infection were found to be altered sensorium, multiple operations, pre-existing infection, emergency surgery, duration of surgery more than 4 hours, urinary catheterisation, cerebrospinal fluid leak, and ventilatory support. Keywords: Prospective study; postoperative infection; risk fac-
tors.
Introduction T h e d e v e l o p m e n t o f asepsis w i t h e m p h a s i s o n the prevention of bacterial c o n t a m i n a t i o n by skin disinfection, efficient sterilisation, the w e a r i n g o f sterile p r o tective c l o t h i n g a n d i m p r o v e d t h e a t r e v e n t i l a t i o n , h a s m a d e a s i g n i f i c a n t i m p a c t o n the i n f e c t i o n rate. T h e o n l y r e c e n t a d v a n c e is the use o f p r o p h y l a c t i c a n t i b i o t i c s 8,11, ~3,14, as, 18. It seems r e a s o n a b l e to reserve the use o f p r o p h y l a c t i c a n t i b i o t i c s o n l y for t h o s e p a t i e n t s h a v i n g a h i g h e r risk o f d e v e l o p i n g p o s t o p e r a t i v e
infection following a neurosurgical procedure. The aim o f this s t u d y was to i d e n t i f y the risk f a c t o r s i n f l u e n c i n g the i n c i d e n c e o f i n f e c t i o n .
Materials and Methods Four hundred and eighty four patients who had undergone a neurosurgical operation during a two year period were randomly selected and prospectively studied. After excluding 14 patients who had died within 48 hours of the operation, there were 470 patients who remained in the study. Of these 420 had an elective operation and the remaining 50 an emergency operation. This patient material was analysed for the incidence of infection and the possible importance of 20 risk factors. All patients received pre-operative crystalline penicillin at a dose of one mega-unit intramuscularly six hourly starting 24 hours before surgery. Those who were sensitive to penicillin received gentamycin 80 mg twice daily intramuscularly or cephalexin 500 mg six hourly orally. The last dose was given intravenously at the time of induction of anaesthesia. Intra-operatively, a repeat dose was given when the operation lasted more than 6 hours. Antibiotics were continued postoperatively in the following situations: (a) placement of foreign material, (b) surgery lasting longer than 4 hours, (c) entry into the digestive tract, (d) re-operations, (e) presence of pre-existing infection, (f) suspected contamination during surgery, (g) emergency operations, and (h) patients more than 60 years of age. In the latter part of the study the incidence of infective complications rose to unacceptable levels with 4 wound infections and one
Table 1. Risk Factors Studied in 470 Patients Preoperative parameters
Age, altered sensorium, pre-operative hospital stay, pre-existing infection, long term pre-operative steroids, diabetes, haemoglobin
Intra-operative parameters
Routine or emergency surgery, site of operation, multiple or single, duration of surgery, blood transfusion, shunt surgery, transphenoidal operations, use of microscope CUSA and/or LASER, urinary catheterisation
Postoperative parameters
Cerebrospinal fluid leak, ventilatory support, peri-operative steroids
R. Patir et al.: Risk Factors in Postoperative Neurosurgical Infection Table 2.
Infection
Total no. of infections
Duration of postoperative hospital stay
Wound Meningitis Urinary tract Chest Brain abscess Cellulitis Osteomyelitis Bedsore
21 (5%) 28 (6%) 20 (4%) 22 (5%) 2 1 1 1
20 days 24 18 12 22 13 39 40
Total no.
96*
81 case of meningitis in less than 2 weeks, all culturing staphylococcus aureus. After consulting the microbiologist, in 23 patients, the prophylactic antibiotic was therefore changed to cefotaxime at a dose of 1 gm twice daily intramuscularly for 24 hours prior to surgery and one intravenously at the time o f induction of anaesthesia. Cefotaxime was continued in the high risk group for three days postoperatively. The criteria for defining postoperative infection were: Infection at the operative site, cerebrospinal fluid (CSF) leucocytosis with meningism and/or a positive culture, chest infection diagnosed clinically or on X-ray chest, positive urine culture, brain abscess, osteomyelitis, and bedsores. Twenty factors were identified to define their role on the incidence of infection (Table 1). The data ~vas analysed for statistical significance using the Chi square test. Observations Postoperative
* 96 sites of infection in the 82 cases with infection.
(17%).
Table 3. Risk Factors o f Significance Risk factors
Site of infection* Wound Meninges Urine Chest
Total no. of cases
Total no. of cases with infection
Sensorium - normal - abnormal
11 11 (p < 0.001)
392 78
59 23
0.01
No. of operations single multiple
10 11 (p < 0.01)
361 109
51 31
0.001
46 413
14 68
0.01
-
-
Pre-existing infection present absent -
-
Nature of operation - routine - emergency
15 7 (p < 0.001)
420 50
66 16
0.001
Duration of surgery - < 4 hours - > 4 hours
9 11 (p < 0.01)
351 119
52 30
0.01
33
0.001"*
Urinary catheter absent 0 - present 20 (p < 0.001) -
CSF leak - absent - present Ventilation absent presnt -
-
185 285
11 22 435 10 6 (p < o.ool) (p < O.Ol) 10 12 (p < 0.001)
398 72
* For clarity, only those individual infections which are significantly higher are included. ** Total number of wound infections and meningitis only.
Amongst
infection was encountered
i n 82 c a s e s
t h e 413 c a s e s w i t h n o p r e - e x i s t i n g
82
R. Patir et al.: Risk Factors in Postoperative Neurosurgical Infection
infection there were 63 infections (15%). Infection was noted at a single site in 71 cases and the remaining 11 cases had infection at multiple sites. The average postoperative hospital stay o f patients who developed an infection was 17 days while it was 9 days in those patients w h o had an uneventful postoperative period (Table 2). R i s k Factors
T w e n t y risk factors were analysed (Table 1) and g r o u p e d into (a) factors o f significance, (b) factors o f possible importance, and (c) factors w i t h o u t suggestion o f increased risk. Table 4
Risk factors
Haemoglobin < 9 gm% - > 9gm% Blood transfusion - no - yes Shunt - no - yes Long term steroids preoperatively - no - yes Age < 60 years > 60 years Diabetes - absent - present Transphenoidal - culture positive - culture negative Steroids pre and/or postoperatively no - yes Microscope - no - yes CUSA and/or LASER no - yes Preoperative hospital stay - < one week - > one week
Total no. of cases
Total no. of cases with infection
Odds ratio
24 446
75
1.7-fold not sig.
242 228
32 50
1.7-fold not sig.
396 74
62 20
1.7-fold not sig.
369 71
68 14
2-fold not sig.
408 62
72 10
447 23
78 4
14 28
0 2
85 385
14 68
226 244
40 42
68 402
15 67
315 155
57 25
7
(a) Factors o f significance: an altered sensorium, emergency surgery, and elective ventilation significantly increased the risk o f p u l m o n a r y infection (p < 0.001) while a C S F leak predisposed to b o t h w o u n d infection (t3 < 0 . 0 0 1 ) a n d meningitis (p < 0.01). U r i n a r y catheterisation increased the risk o f urinary tract infection (p < 0.001) Multiplicity o f operation, pre-existing infection even when purely extracranial and surgery lasting longer than 4 hours was associated with an increased incidence o f infection (p < 0.01) (Table 3). (b) Factors o f possible importance: there was a 1.7fold higher incidence o f infection when any one o f the following were present: blood transfusion, shunt surgery and h a e m o g l o b i n less than 9 g m % (Table 4). Steroids given over prolonged periods pre-operatively was associated with a 2-fold higher incidence o f postoperative infection. Patients w h o had a suboccipital cranie c t o m y had the highest rate o f infection with 26% (Table 5). (c) Factors without increased risk o f infection. Age above 60 years, presence o f diabetes, use o f peri-operative steroids, use o f microscope, C U S A a n d / o r L A S E R , a positive nasal culture in transphenoidal operations and d u r a t i o n o f pre-operative hospital stay (Table 5).
Antibiotic Prophylaxis
O f the 447 patients w h o received crystalline penicilin, cephalexin, gentamycin, or an appropritate antibiotic depending on the sensitivity profile, 77 (17%) developed infection. Twenty three patients received prophylactic cefotaxime and o f them 4 developed meningitis (17%) and two developed w o u n d infection (8%), maing for an overall infection rate o f 25%.
Table 5
Site of surgery
Total no. of cases
No. of infections
Supratentorial Shunt alone Spinal Infratentorial Peripheral nerve Transphenoidal Cranioplasty Others
230 19 72 72 15 47 2 13
46 (20%) 2 (1 I%) 7 (10%) 19 (26%) 1 (7%) 5 (11%) 2 (15%)
R, Patir
etal.:
T a b l e 6.
Bacteriology
Risk Factors in Postoperative
Organisms
Wound
Meningitis
Urine
Neurosurgical
Infection
Abscess
Chest
Total 11
Staphylococcus
4
5
-
I
1
E. coli
-
2
6
1
-
9
Klebsiella
2
1
8
-
1
12
Proteus
-
-
3
-
1
4
Pseudomonas
2
1
2
-
-
5
Enterobacter
-
-
1
-
-
1
Bacteriology
Out of the 13 cases where a pus culture was sent from the wound, 6 had a positive culture. Two had 2 organisms and the remaining had a single organism cultured. The commonest organism was staphylococcus aureus. Out of the 28 cases of meningitis, only 9 cases had a positive culture, and of these 5 were due to staphylococcus aureus and the remaining 3 were due to gram negative organisms. Klebsiella and E. coli were the commonest organisms encountered in urinary tract infection (Table 6). Discussion Reports in the recent literature have documented postoperative wound infection between 0% and 10% 6, 8, 11, 14, 15, 16, 17, 20, 21, 23 though the usual infection rate encountered is between 1% and 2% 13. The wide variation in the defination of infection 11' 17, 21, 23 makes comparison between vaious studies impractical. While most studies have defined postoperative infection as the presence of wound infection or meningitis, we have included all the infective complications such as chest infection, urinary tract infection etc. within the definition of postoperative infection. We felt that this approach was more realistic considering that besides wound infection and meningitis, other infections occur in a significant number of patients in the postoperative period and become relevant in the management. Altered sensorium 7' 9,17,24, and CSF leak 2' 2o has been uniformly found to be a high risk factor for postoperative infection in various studies as well as in the present study. While there have been some reports of an increase in infection following multiple operations 2"23, 24, others have found no such correlation 2~ 21. The increased risk of postoperative infection following multiple operations was found to be highly significant in the present study.
83
Mollman and Haines 2~in a case controlled study of 9202 patients found that a concurrent non-central nervous system infection increased the risk of developing a postoperative infection 6-fold. He strongly recommended the control of any infection before subjecting a patient to an operation. The conclusion in the present study is the same. While Wright 24 found no correlation of postoperative infection with the duration o f surgery, however, many other studies 4, 5, 10, 17 reported a higher incidence of infection with prolonged operations. The present study finds a similar correlation with a significantly higher risk of infection in operations lasting longer than 4 hours. Grimmond et aL 12 reported catheter related urinary tract infection in neurosurgical cases as 33 % in females and 13% in males. During the same time, the figures from the urology service were 6% and 15% in females and males respectively. He suggested that the lower rates of infection was related to a shorter duration of catheterisation and a greater care and concern for catheters shown by that particular service. The bacteriuria that follows the use of indwelling catheters is due to the continuous entry of bacteria into the bladder and counts of 100,000 or more per ml of urine rises from 50% at 24 hours to 9 8 - 100% after 4 days 16. All the urinary tract infections in this study were catheter related and occurred in 7% of the catheterised patients. Maiztegui et al. 18 found that 65% of the gram negative sepficaemias had their origin in the urinary tract. In this study only 2 patients had a similar organism cultured from the wound. However, this does not refute the findings of Maiztegui et al.18, as the positive culture rate has been low in this study. The relatively low rate of positive cultures is possibly related to the use of antibiotic prophylaxis. A corollary to this of considerable clinical importance is the high index of suspicion required to diagnose meningitis. This partly explains as to why meningitis has been the commonest infection in this study at 6% while a culture positive meningitis was recorded in 2% cases.
Mahapatra et al. 17 found a significantly higher incidence of infection in patients who were either anaemic or clinically malnourished. A similar trend was seen in this study when the haemoglobin was < 9 g m % , though this was not significant. Several studies as well as the present one show a higher infection rate following a craniotomy 18' 23 or a C S F shunt surgery 1' 22, 16
84
C o n t r a r y to the in a g r e e m e n t with no c o r r e l a t i o n o f Diabetes 24, use o f
R. Patir et al.: Risk Factors in Postoperative Neurosurgieal Infection findings o f M a h a p a t r a et al. 17 a n d W r i g h t 24, the p r e s e n t s t u d y f o u n d p o s t o p e r a t i v e infection with age. eorticosteroids 17" 20, 21, 24 a n d the
microscope 2~ h a v e been r e p o r t e d to have no b e a r i n g o n p o s t o p e r a t i v e infection rate. T h e 2-fold higher incidence o f p o s t o p e r a t i v e infection with long t e r m preo p e r a t i v e steroids is p a r t l y e x p l a i n e d b y the i n h e r e n t l y p o o r e r n e u r o l o g i c a l status in this g r o u p o f patients. M o l l m a n a n d H a i n e s 2~ o b s e r v e d t h a t entry into the paranasal air sinuses i n c r e a s e d the infection rate. T h e u s u a l r o u t i n e is to have a sterile n a s a l c u l t u r e before p r o c e e d i n g f o r a n o p e r a t i o n . This s t u d y shows no difference in the infection rate w h e t h e r a culture was p o sitive o r n o t a n d in fact the two cases o f meningitis o c c u r r e d in cases where the n a s a l culture was sterile. H o w e v e r , the n u m b e r s are t o o few to c o m e to a n y definite conclusion. T h e pre-operative hospital stay was f o u n d to have no r e l a t i o n to the infection rate. M a h a p a t r a etal. a7 f o u n d a n i n c r e a s e d incidence o f infection with a p r o l o n g e d p r e - o p e r a t i v e h o s p i t a l stay in clean cases. T h e results o f this study are p o s s i b l y e x p l a i n e d b y the l a r g e r n u m b e r o f cases w h o r e q u i r e d a n emergeny operation and, therefore, were o p e r a t e d u p o n i m m e d i a t e l y on a d m i s s i o n .
References 1. Albright L, Riegel DH (1977) Management of hydrocephalus secondary to posterior fossa tumors. J Neurosurg 26:41-45 2. Balch RE (1967) Wound infection complicating neurosurgical procedures. J Neurosurg 26:41-45 3. Blomstedt GC (1985) Infection in neurosurgery. A retrospective study of 1143 patients and 1517 operations. Acta Neurochir (Wien) 78:81-90 4. Brachman PS, Dan BB, Haley RH, Haron TN, Garner JS, Alert JR (1980) Nosocomial surgical infection. Surg Clin North Am 60:14-24 5. Cairns H (1939) Bacterial infection during intracranial operations. Lancet 1:1193-1198 6. Cushing H (1931) Experience with cerebellar astrocytomas. A critical review of seventy-six cases. Surg Obstet 52:129~04 7. De Jong RN, Currier RD, Sugar O (1982) Infection. Year book of neurology and neurosurgery 24:343-349 8. Dempsey R, Rapp RP, Young B, Johnston S, Tibbs P (1988) Prophylactic paranteral antibiotics in clean neurosurgical procedures: a review. J Neurosurg 69:52-56
9. Eichkoff TE (1980) Pulmonary infection in surgical services. Surg Clin North Am 60:158 160 10. Forbes GB (1961) Staphylococcal infection of operation wounds with special reference to topical antibiotic prophylaxis. Lancet 1:505-508 11. Geraghty J, Feely M (1984) Antibiotic prophylaxis in neurosurgery. A randomised controlled trial. J Neurosurg 60: 724726 12. Grimmond TR, Sinclair G, Marshall VR (1981) Catheter associated urinary tract infections. In: Watts JM et al (eds) Infection in neurosurgery. Churchill Livingstone, Edinburgh, London, pp 389-398 13. Haines SJ (1985) Prophylactic antibiotics. In: Wilkins RH, Rengachary SS (eds) Neurosurgery, Vol I. McGraw-Hill, New York, pp 448-452 14. Haines SJ, Goodman ML (1982) Antibiotic prophylaxis of postoperative neurosurgical wound infection. J Neurosurg 56: 103110 15. Horwitz NH, Curtin JA (1975) Prophylactic antibiotics and wound infection following laminectomy for lumbar disc disease. A retrospective study. J Neurosurg 43:727-731 16. Klastersky J, Kahan-Coppens L, Brihaye J (1979) Infections in neurosurgery. In: Krayenbtihl et al (eds) Advances and technical standards in neurosurgery, Vol 6. Springer, Wien New York 17. Mahapatra AK, Banerji AK, Bhatia R, Tandon PN (1989) Prevalence of infection among neurosurgical patients - a prospective study of 507 operated patients. Neurology India 37: 229-237 18. Maiztegui JI, Biegeleisen JN, Cherry WB, Kass EH (1965) Bacterimia due to gram-negative rods: a clinical, bacteriologic, serologic and immunofluorescent study. NE Med 272:222-229 19. Mallis LI (1979) Prevention of neurosurgical infection by intraoperative antibiotics. Neurosurgery 5:339-343 20. Mollman HD, Haines SJ (1986) Risk factors of postoperative neurosurgical wound infection. A case control study. J Neurosurg 64:902-906 21. Quadery LA, Medlery AV, Miles J (1977) Factors affecting the incidence of infection in neurosurgery. Acta Neurochir (Wien) 39:141 22. Raimondi AJ, Tomita T (1981) Brain tumors in children: advantages and disadvantages of different modalities. Concepts in paediatric neurosurgery 1:1-28 23. Tenney JH, Vlahov D, Salcman M e t a l (1985) Wide variations in risk of wound infection following clean neurosurgery, indications for perioperative antibiotic prophylaxis. J Neurosurg 62: 243-247 24. Wright RL (1966) A survey of possible etiologic agents in postoperative craniotomy infections. J Neurosurg 25:125-132 Correspondence and Reprints: Dr. A. K. Mahapatra, Assistant Professor, Department of Neurosurgery, Neuroseiences Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
Acta Neurochir (Wien) (1992) 119:80-84
9 Springer-Verlag 1992 Printed in Austria
Risk Factors in Postoperative Neurosurgieal Infection A Prospective Study R. Patir, A. K. Mahapatra, and A. K. Banerji Department of Neurosurgery, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India
Summary Four hundred and seventy patients who had undergone neurosurgical operations were studied prospectively. After defining postoperative infection so that is included all the infective complications irrespective of location oecuring after surgery, the overall infection rate was 17%. The infection rate in 413 cases without pre-existing infection was 15%. Wound infection was recorded in 5% and meningitis in 6%: Risk factors which lead to a significant increase in the incidence of postoperative infection were found to be altered sensorium, multiple operations, pre-existing infection, emergency surgery, duration of surgery more than 4 hours, urinary catheterisation, cerebrospinal fluid leak, and ventilatory support. Keywords: Prospective study; postoperative infection; risk fac-
tors.
Introduction T h e d e v e l o p m e n t o f asepsis w i t h e m p h a s i s o n the prevention of bacterial c o n t a m i n a t i o n by skin disinfection, efficient sterilisation, the w e a r i n g o f sterile p r o tective c l o t h i n g a n d i m p r o v e d t h e a t r e v e n t i l a t i o n , h a s m a d e a s i g n i f i c a n t i m p a c t o n the i n f e c t i o n rate. T h e o n l y r e c e n t a d v a n c e is the use o f p r o p h y l a c t i c a n t i b i o t i c s 8,11, ~3,14, as, 18. It seems r e a s o n a b l e to reserve the use o f p r o p h y l a c t i c a n t i b i o t i c s o n l y for t h o s e p a t i e n t s h a v i n g a h i g h e r risk o f d e v e l o p i n g p o s t o p e r a t i v e
infection following a neurosurgical procedure. The aim o f this s t u d y was to i d e n t i f y the risk f a c t o r s i n f l u e n c i n g the i n c i d e n c e o f i n f e c t i o n .
Materials and Methods Four hundred and eighty four patients who had undergone a neurosurgical operation during a two year period were randomly selected and prospectively studied. After excluding 14 patients who had died within 48 hours of the operation, there were 470 patients who remained in the study. Of these 420 had an elective operation and the remaining 50 an emergency operation. This patient material was analysed for the incidence of infection and the possible importance of 20 risk factors. All patients received pre-operative crystalline penicillin at a dose of one mega-unit intramuscularly six hourly starting 24 hours before surgery. Those who were sensitive to penicillin received gentamycin 80 mg twice daily intramuscularly or cephalexin 500 mg six hourly orally. The last dose was given intravenously at the time of induction of anaesthesia. Intra-operatively, a repeat dose was given when the operation lasted more than 6 hours. Antibiotics were continued postoperatively in the following situations: (a) placement of foreign material, (b) surgery lasting longer than 4 hours, (c) entry into the digestive tract, (d) re-operations, (e) presence of pre-existing infection, (f) suspected contamination during surgery, (g) emergency operations, and (h) patients more than 60 years of age. In the latter part of the study the incidence of infective complications rose to unacceptable levels with 4 wound infections and one
Table 1. Risk Factors Studied in 470 Patients Preoperative parameters
Age, altered sensorium, pre-operative hospital stay, pre-existing infection, long term pre-operative steroids, diabetes, haemoglobin
Intra-operative parameters
Routine or emergency surgery, site of operation, multiple or single, duration of surgery, blood transfusion, shunt surgery, transphenoidal operations, use of microscope CUSA and/or LASER, urinary catheterisation
Postoperative parameters
Cerebrospinal fluid leak, ventilatory support, peri-operative steroids
R. Patir et al.: Risk Factors in Postoperative Neurosurgical Infection Table 2.
Infection
Total no. of infections
Duration of postoperative hospital stay
Wound Meningitis Urinary tract Chest Brain abscess Cellulitis Osteomyelitis Bedsore
21 (5%) 28 (6%) 20 (4%) 22 (5%) 2 1 1 1
20 days 24 18 12 22 13 39 40
Total no.
96*
81 case of meningitis in less than 2 weeks, all culturing staphylococcus aureus. After consulting the microbiologist, in 23 patients, the prophylactic antibiotic was therefore changed to cefotaxime at a dose of 1 gm twice daily intramuscularly for 24 hours prior to surgery and one intravenously at the time o f induction of anaesthesia. Cefotaxime was continued in the high risk group for three days postoperatively. The criteria for defining postoperative infection were: Infection at the operative site, cerebrospinal fluid (CSF) leucocytosis with meningism and/or a positive culture, chest infection diagnosed clinically or on X-ray chest, positive urine culture, brain abscess, osteomyelitis, and bedsores. Twenty factors were identified to define their role on the incidence of infection (Table 1). The data ~vas analysed for statistical significance using the Chi square test. Observations Postoperative
* 96 sites of infection in the 82 cases with infection.
(17%).
Table 3. Risk Factors o f Significance Risk factors
Site of infection* Wound Meninges Urine Chest
Total no. of cases
Total no. of cases with infection
Sensorium - normal - abnormal
11 11 (p < 0.001)
392 78
59 23
0.01
No. of operations single multiple
10 11 (p < 0.01)
361 109
51 31
0.001
46 413
14 68
0.01
-
-
Pre-existing infection present absent -
-
Nature of operation - routine - emergency
15 7 (p < 0.001)
420 50
66 16
0.001
Duration of surgery - < 4 hours - > 4 hours
9 11 (p < 0.01)
351 119
52 30
0.01
33
0.001"*
Urinary catheter absent 0 - present 20 (p < 0.001) -
CSF leak - absent - present Ventilation absent presnt -
-
185 285
11 22 435 10 6 (p < o.ool) (p < O.Ol) 10 12 (p < 0.001)
398 72
* For clarity, only those individual infections which are significantly higher are included. ** Total number of wound infections and meningitis only.
Amongst
infection was encountered
i n 82 c a s e s
t h e 413 c a s e s w i t h n o p r e - e x i s t i n g
82
R. Patir et al.: Risk Factors in Postoperative Neurosurgical Infection
infection there were 63 infections (15%). Infection was noted at a single site in 71 cases and the remaining 11 cases had infection at multiple sites. The average postoperative hospital stay o f patients who developed an infection was 17 days while it was 9 days in those patients w h o had an uneventful postoperative period (Table 2). R i s k Factors
T w e n t y risk factors were analysed (Table 1) and g r o u p e d into (a) factors o f significance, (b) factors o f possible importance, and (c) factors w i t h o u t suggestion o f increased risk. Table 4
Risk factors
Haemoglobin < 9 gm% - > 9gm% Blood transfusion - no - yes Shunt - no - yes Long term steroids preoperatively - no - yes Age < 60 years > 60 years Diabetes - absent - present Transphenoidal - culture positive - culture negative Steroids pre and/or postoperatively no - yes Microscope - no - yes CUSA and/or LASER no - yes Preoperative hospital stay - < one week - > one week
Total no. of cases
Total no. of cases with infection
Odds ratio
24 446
75
1.7-fold not sig.
242 228
32 50
1.7-fold not sig.
396 74
62 20
1.7-fold not sig.
369 71
68 14
2-fold not sig.
408 62
72 10
447 23
78 4
14 28
0 2
85 385
14 68
226 244
40 42
68 402
15 67
315 155
57 25
7
(a) Factors o f significance: an altered sensorium, emergency surgery, and elective ventilation significantly increased the risk o f p u l m o n a r y infection (p < 0.001) while a C S F leak predisposed to b o t h w o u n d infection (t3 < 0 . 0 0 1 ) a n d meningitis (p < 0.01). U r i n a r y catheterisation increased the risk o f urinary tract infection (p < 0.001) Multiplicity o f operation, pre-existing infection even when purely extracranial and surgery lasting longer than 4 hours was associated with an increased incidence o f infection (p < 0.01) (Table 3). (b) Factors o f possible importance: there was a 1.7fold higher incidence o f infection when any one o f the following were present: blood transfusion, shunt surgery and h a e m o g l o b i n less than 9 g m % (Table 4). Steroids given over prolonged periods pre-operatively was associated with a 2-fold higher incidence o f postoperative infection. Patients w h o had a suboccipital cranie c t o m y had the highest rate o f infection with 26% (Table 5). (c) Factors without increased risk o f infection. Age above 60 years, presence o f diabetes, use o f peri-operative steroids, use o f microscope, C U S A a n d / o r L A S E R , a positive nasal culture in transphenoidal operations and d u r a t i o n o f pre-operative hospital stay (Table 5).
Antibiotic Prophylaxis
O f the 447 patients w h o received crystalline penicilin, cephalexin, gentamycin, or an appropritate antibiotic depending on the sensitivity profile, 77 (17%) developed infection. Twenty three patients received prophylactic cefotaxime and o f them 4 developed meningitis (17%) and two developed w o u n d infection (8%), maing for an overall infection rate o f 25%.
Table 5
Site of surgery
Total no. of cases
No. of infections
Supratentorial Shunt alone Spinal Infratentorial Peripheral nerve Transphenoidal Cranioplasty Others
230 19 72 72 15 47 2 13
46 (20%) 2 (1 I%) 7 (10%) 19 (26%) 1 (7%) 5 (11%) 2 (15%)
R, Patir
etal.:
T a b l e 6.
Bacteriology
Risk Factors in Postoperative
Organisms
Wound
Meningitis
Urine
Neurosurgical
Infection
Abscess
Chest
Total 11
Staphylococcus
4
5
-
I
1
E. coli
-
2
6
1
-
9
Klebsiella
2
1
8
-
1
12
Proteus
-
-
3
-
1
4
Pseudomonas
2
1
2
-
-
5
Enterobacter
-
-
1
-
-
1
Bacteriology
Out of the 13 cases where a pus culture was sent from the wound, 6 had a positive culture. Two had 2 organisms and the remaining had a single organism cultured. The commonest organism was staphylococcus aureus. Out of the 28 cases of meningitis, only 9 cases had a positive culture, and of these 5 were due to staphylococcus aureus and the remaining 3 were due to gram negative organisms. Klebsiella and E. coli were the commonest organisms encountered in urinary tract infection (Table 6). Discussion Reports in the recent literature have documented postoperative wound infection between 0% and 10% 6, 8, 11, 14, 15, 16, 17, 20, 21, 23 though the usual infection rate encountered is between 1% and 2% 13. The wide variation in the defination of infection 11' 17, 21, 23 makes comparison between vaious studies impractical. While most studies have defined postoperative infection as the presence of wound infection or meningitis, we have included all the infective complications such as chest infection, urinary tract infection etc. within the definition of postoperative infection. We felt that this approach was more realistic considering that besides wound infection and meningitis, other infections occur in a significant number of patients in the postoperative period and become relevant in the management. Altered sensorium 7' 9,17,24, and CSF leak 2' 2o has been uniformly found to be a high risk factor for postoperative infection in various studies as well as in the present study. While there have been some reports of an increase in infection following multiple operations 2"23, 24, others have found no such correlation 2~ 21. The increased risk of postoperative infection following multiple operations was found to be highly significant in the present study.
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Mollman and Haines 2~in a case controlled study of 9202 patients found that a concurrent non-central nervous system infection increased the risk of developing a postoperative infection 6-fold. He strongly recommended the control of any infection before subjecting a patient to an operation. The conclusion in the present study is the same. While Wright 24 found no correlation of postoperative infection with the duration o f surgery, however, many other studies 4, 5, 10, 17 reported a higher incidence of infection with prolonged operations. The present study finds a similar correlation with a significantly higher risk of infection in operations lasting longer than 4 hours. Grimmond et aL 12 reported catheter related urinary tract infection in neurosurgical cases as 33 % in females and 13% in males. During the same time, the figures from the urology service were 6% and 15% in females and males respectively. He suggested that the lower rates of infection was related to a shorter duration of catheterisation and a greater care and concern for catheters shown by that particular service. The bacteriuria that follows the use of indwelling catheters is due to the continuous entry of bacteria into the bladder and counts of 100,000 or more per ml of urine rises from 50% at 24 hours to 9 8 - 100% after 4 days 16. All the urinary tract infections in this study were catheter related and occurred in 7% of the catheterised patients. Maiztegui et al. 18 found that 65% of the gram negative sepficaemias had their origin in the urinary tract. In this study only 2 patients had a similar organism cultured from the wound. However, this does not refute the findings of Maiztegui et al.18, as the positive culture rate has been low in this study. The relatively low rate of positive cultures is possibly related to the use of antibiotic prophylaxis. A corollary to this of considerable clinical importance is the high index of suspicion required to diagnose meningitis. This partly explains as to why meningitis has been the commonest infection in this study at 6% while a culture positive meningitis was recorded in 2% cases.
Mahapatra et al. 17 found a significantly higher incidence of infection in patients who were either anaemic or clinically malnourished. A similar trend was seen in this study when the haemoglobin was < 9 g m % , though this was not significant. Several studies as well as the present one show a higher infection rate following a craniotomy 18' 23 or a C S F shunt surgery 1' 22, 16
84
C o n t r a r y to the in a g r e e m e n t with no c o r r e l a t i o n o f Diabetes 24, use o f
R. Patir et al.: Risk Factors in Postoperative Neurosurgieal Infection findings o f M a h a p a t r a et al. 17 a n d W r i g h t 24, the p r e s e n t s t u d y f o u n d p o s t o p e r a t i v e infection with age. eorticosteroids 17" 20, 21, 24 a n d the
microscope 2~ h a v e been r e p o r t e d to have no b e a r i n g o n p o s t o p e r a t i v e infection rate. T h e 2-fold higher incidence o f p o s t o p e r a t i v e infection with long t e r m preo p e r a t i v e steroids is p a r t l y e x p l a i n e d b y the i n h e r e n t l y p o o r e r n e u r o l o g i c a l status in this g r o u p o f patients. M o l l m a n a n d H a i n e s 2~ o b s e r v e d t h a t entry into the paranasal air sinuses i n c r e a s e d the infection rate. T h e u s u a l r o u t i n e is to have a sterile n a s a l c u l t u r e before p r o c e e d i n g f o r a n o p e r a t i o n . This s t u d y shows no difference in the infection rate w h e t h e r a culture was p o sitive o r n o t a n d in fact the two cases o f meningitis o c c u r r e d in cases where the n a s a l culture was sterile. H o w e v e r , the n u m b e r s are t o o few to c o m e to a n y definite conclusion. T h e pre-operative hospital stay was f o u n d to have no r e l a t i o n to the infection rate. M a h a p a t r a etal. a7 f o u n d a n i n c r e a s e d incidence o f infection with a p r o l o n g e d p r e - o p e r a t i v e h o s p i t a l stay in clean cases. T h e results o f this study are p o s s i b l y e x p l a i n e d b y the l a r g e r n u m b e r o f cases w h o r e q u i r e d a n emergeny operation and, therefore, were o p e r a t e d u p o n i m m e d i a t e l y on a d m i s s i o n .
References 1. Albright L, Riegel DH (1977) Management of hydrocephalus secondary to posterior fossa tumors. J Neurosurg 26:41-45 2. Balch RE (1967) Wound infection complicating neurosurgical procedures. J Neurosurg 26:41-45 3. Blomstedt GC (1985) Infection in neurosurgery. A retrospective study of 1143 patients and 1517 operations. Acta Neurochir (Wien) 78:81-90 4. Brachman PS, Dan BB, Haley RH, Haron TN, Garner JS, Alert JR (1980) Nosocomial surgical infection. Surg Clin North Am 60:14-24 5. Cairns H (1939) Bacterial infection during intracranial operations. Lancet 1:1193-1198 6. Cushing H (1931) Experience with cerebellar astrocytomas. A critical review of seventy-six cases. Surg Obstet 52:129~04 7. De Jong RN, Currier RD, Sugar O (1982) Infection. Year book of neurology and neurosurgery 24:343-349 8. Dempsey R, Rapp RP, Young B, Johnston S, Tibbs P (1988) Prophylactic paranteral antibiotics in clean neurosurgical procedures: a review. J Neurosurg 69:52-56
9. Eichkoff TE (1980) Pulmonary infection in surgical services. Surg Clin North Am 60:158 160 10. Forbes GB (1961) Staphylococcal infection of operation wounds with special reference to topical antibiotic prophylaxis. Lancet 1:505-508 11. Geraghty J, Feely M (1984) Antibiotic prophylaxis in neurosurgery. A randomised controlled trial. J Neurosurg 60: 724726 12. Grimmond TR, Sinclair G, Marshall VR (1981) Catheter associated urinary tract infections. In: Watts JM et al (eds) Infection in neurosurgery. Churchill Livingstone, Edinburgh, London, pp 389-398 13. Haines SJ (1985) Prophylactic antibiotics. In: Wilkins RH, Rengachary SS (eds) Neurosurgery, Vol I. McGraw-Hill, New York, pp 448-452 14. Haines SJ, Goodman ML (1982) Antibiotic prophylaxis of postoperative neurosurgical wound infection. J Neurosurg 56: 103110 15. Horwitz NH, Curtin JA (1975) Prophylactic antibiotics and wound infection following laminectomy for lumbar disc disease. A retrospective study. J Neurosurg 43:727-731 16. Klastersky J, Kahan-Coppens L, Brihaye J (1979) Infections in neurosurgery. In: Krayenbtihl et al (eds) Advances and technical standards in neurosurgery, Vol 6. Springer, Wien New York 17. Mahapatra AK, Banerji AK, Bhatia R, Tandon PN (1989) Prevalence of infection among neurosurgical patients - a prospective study of 507 operated patients. Neurology India 37: 229-237 18. Maiztegui JI, Biegeleisen JN, Cherry WB, Kass EH (1965) Bacterimia due to gram-negative rods: a clinical, bacteriologic, serologic and immunofluorescent study. NE Med 272:222-229 19. Mallis LI (1979) Prevention of neurosurgical infection by intraoperative antibiotics. Neurosurgery 5:339-343 20. Mollman HD, Haines SJ (1986) Risk factors of postoperative neurosurgical wound infection. A case control study. J Neurosurg 64:902-906 21. Quadery LA, Medlery AV, Miles J (1977) Factors affecting the incidence of infection in neurosurgery. Acta Neurochir (Wien) 39:141 22. Raimondi AJ, Tomita T (1981) Brain tumors in children: advantages and disadvantages of different modalities. Concepts in paediatric neurosurgery 1:1-28 23. Tenney JH, Vlahov D, Salcman M e t a l (1985) Wide variations in risk of wound infection following clean neurosurgery, indications for perioperative antibiotic prophylaxis. J Neurosurg 62: 243-247 24. Wright RL (1966) A survey of possible etiologic agents in postoperative craniotomy infections. J Neurosurg 25:125-132 Correspondence and Reprints: Dr. A. K. Mahapatra, Assistant Professor, Department of Neurosurgery, Neuroseiences Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
