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A prospective study of nosocomial infections in cardiac surgery pots in China
A prospective study of rwsocern,W infections in cardiac surgery pa&&nts in China Li Liu-yi, MS Wang Shuqun, MD Beijing, People’s Republic of China
A prospective survey of postoperative nosocomial infections (NI) in cardiac surgery was carried out in a cardiovascular specialty hospital in Beijing, China. During the period from December 1986 to December 1987, 1208 cardiovascular surgery patients were surveyed for NI. The overall incidence of NI was found to be 7.5%. The incidence of lower respiratory tract and wound infections were 4.5% and 2.9%, respectively. These two kinds of infection accounted for 78.1% of the total infections. After effective control measures were taken at the end of the first 6 months (December 1986 to May 1987) of the study, the incidence fell from 10.6% to 5.1% in the next 7-month period (June to December 1987). The pathogens causing NI were mostly gram-negative bacteria, and they were mainly opportunistic. The contribution of fungal infection was significant in the hospitals. The ma.jority of the pathogenic isolates were highly resistant to the antibiotics commonly used in the hospital. (AM J INFECT CONTROL 1990;18:365-70)
Postoperative nosocomial infection (NI) after cardiac surgery is a serious problem for surgical patients, because they have more complications and undergo a long operation time and a large number of invasive procedures. In addition, once NI occurs, the illness will be critical and even risky to the patient’s life. Therefore the study of NI in cardiac surgery is vital to understand the problem and to reduce its incidence. In a prospective study of NI in cardiovascular surgery (CVS) patients conducted by Buu Hoi and Richet,’ it was reported that the postoperative infection rate was 8.2% and that the most common NI was wound infection (WI), followed by urinary tract infection, lower respiratory tract infection (LRTI), and bacteremia. Pathogens causing NI were mainly gramnegative bacterias2 However, there are few data in China on the incidence of NI in CVS patients. A prospective survey on hospital-acquired inFrom the Institute of Epidemiology Academy of Preventive Medicine.
and
Reprint requests: Wang Shu-qun, MD, miology, 3 Yabao Rd., Chaoyang District, ple’s Republic of China. 17146119657
Microbiology,
Chinese
Department of EpideBeijing, 100020, Peo-
fections was carried out in a cardiac surgery hospital for the purpose of determining the infection rate, identifying the epidemiologic features and finding common pathogens, and determining the antibiotic resistance patterns of these pathogens. METHODS
This study was performed from{ December 1986 to December 1987 in a CVS specialty hospital. There were three cardiac surgery departments with a total of 150 beds and an intensive care unit with six pediatric beds andlnine adult beds. Each week, 30 to 40 surgical operations were performed, 98% of them were elective. After their operations the patients were brought to the intensive care unit and cared for by special nurses until the patients’ conditions were improved. The surveillance was carried out by visiting all the patients after CVS once every 2 to 3 days; by checking the patients’ charts, the muses’ reports, and microbiologic reports; and by discussing the patients’ problems with the staff until the patients were discharged. Infections occurring after discharge were not surveyed unless a patient came back to this hospital. In-
American INFECTION
Li and Wang
Journal of CONTROL
16 control
measurea
4 2 0 MC l888
.
I
I
I
.
I
I
I
I
I
I
I
JAN 1987
FEB
MAR
APR
MAY
JUNE
JULY
Affi
SEPT
OCT
NOV
MC
d
Fig. 1.
RESULTS
Table 1. Incidence by infection site before and after control measures taken No. (%) of NI Before*
All NI LRTI WI SBE Septicemia Other TOTAL
$8E, Subacute ‘N = 517. tN = 691.
bacterial
55 (10.6) 38 (7.4)
20 (3.9) 2 2 8 70
(0.4) (0.4) (1.5) (13.5)
AftWt 35 16 15 2 2
(5.1) (2.3) (2.2) (0.3) (0.3)
endocarditis.
vestigated data were recorded on a special form for each CVS patient. The patient’s name and sex, date of admission, operation, and discharge (or death), underlying diseases, operation procedures, complications, risk factors, invasive procedures, and infection (date of onset; site; pathogens, if isolated; and antibiotic susceptibility) were collected. The Centers for Disease Control’s definitions for NI were used in determining the presence of these infections3
During the 13-month period, 1229 patients were surveyed. Among them, 1208 cases were analyzed to determine the presence of NI; 90 patients were found to have NI. The rate of infection was 7.5%. Incidence Monthly incidence. Incidence rates by months varied from 2.6% in January 1988 to 14.9% in April 1987 (Fig. 1). Incidence rate for the first 6 months was higher than for the second 7 months; it fell from 10.6% to 5.1% after the initiation of effective control measures at the end of the first 6 months of the study (Table 1). The descending infection rate curve was due to the decrease in WI and especially in LRTI. Incidence by age and sex. As shown in Table 2, the incidence rates of infection in the age groups were greatly different. The lo-year-old age group had the lowest incidence (2.8%). There were no significant differences by gender. Incidence by type of operation and infection site.
Operations were classified into five types, according to the kind and the complexity. The incidence varied with the different types of op-
Volume18 Number6 December1990
Nosocomial
infections
in cardiac
surgery
in China
367
Table 2. Incidence by age and sex Male
Age group
No. of operations
(Ye o5lo20304050-
95 272 82 51 34 37
TOTAL
Female
No. (%) of patients with NI 11 16 3 5 5 4
(11.6) (5.9) (3.7) (9.8) (14.7) (10.8)
No. of OperatiOnS
79 216 133 74 66 34 14 616
erations (Table 3). The highest was 20.0% for correction of the tetralogy of Fallot (TF) (including trilogy and pentalogy of Fallot). The lower respiratory tract was the most common site of infection, with a rate of 4.5%, followed by infection of wound sites, with an incidence rate of 2.9% (Table 3). These two sites accounted for 78.1% of the total distribution of NI. Septicemia and subacute bacterial endocarditis commonly developed after complicated operations, such as TF correction and prosthetic valve replacement. Patients with prosthetic valve replacement and TF correction procedures were more likely to acquire multisite infections. Potential
risk factors
Table 4 shows that the duration of tracheotomy ductus was the highest risk factor for NI (odds ratio, 62.8) followed by the duration of trachea catheterization (odds ratio, 9.4). Length of surgical procedure, complications, the duration of thoracic closed draining, pericardiotomy and closed draining, mediastinotomy and closed draining, and duration of hospital stay before surgical procedures were also associated with an increased risk of NI. Case fatality
rate
The case fatality rates of CVS patients with or without infection were compared with those with or without complications (Table 5). The case fatality rate was 17.8% in patients with NI and 0.4% in patients without infections. It is important to point out that the contribution of
Total
No. (%) of patients with NI 12 15 3 4 4 5
No. of operations
(15.2) (6.9) (2.3) (5.4) (6.1) (14.7)
174 488 215 125 100 71
No. (%) of patient0 with NI 23 31 6 9 9 9
(13.2) (6.4) (2.8) (7.2) (9.0) (12.7)
NI to the case fatality rate was influenced whether the patients had a complication. Preventive nosocomial
and control infections
meawwes
by
against
Maay risk factors were found through surveillance during the first 6 months of the study. The following major control measures were instituted in June 1987: An improvement in the care and management of the ICU was made, resulting in all patients getting better service. Aims were made at preventing and controlling NI emphasized isolating infected patients, improving the environmental hygiene, and asking physicians to follow the rules for proper use of antibiotics. An educational program was conducted for hospital personnel on the topic of NI control. The focus of the program was to control LRTI and WI. The preoperative preparation and postoperative nursing of the patients focused on care of the lower respiratory tract. Postoperatively, there was an emphasis on turning patients from side to side, timely suctioning of respiratory sections, and aerosol aspiration. Aseptic technique was required for all sue tioning procedures. The microbiologic laboratory played a supporting role. All microbiologic results and antibiotic resistance test results were reported to the physicians. Handwashing was strongly recommended because it was shown that the hands of doctors and nurses were seriously contaminative. Be-
388
American Journal INFECTIONCONTROL
Li and Wang
Table 3. Incidence of infection by site and type of surgical
of
procedure infection
Operation
---No. performfad
Type
Tetralogy of Fallot* Prosthetic valve replacement Closure of patent ductus arteriosus Atrial or ventricular septal defect Other
T&lo
WI
UTI
SSE
NI 6)
NI W
NI W
NI (%)
Septicemia NI (%I
Other
Total
NI (%I
NI W
125 158
15 (12.0) 10 (6.3)
9 (7.2) 9 (5.7)
2 (1.6) 0 (0)
2 (1.6) 2 (1.3)
2 (1.6) 2 (1.3)
3 (2.4) 2 (1.3)
33 (26.4) 25 (15.8)
199
8 (4.0)
3 (1.5)
0 (0)
0 (0)
0 (0)
1 (0.5)
12 (6.0)
545
17 (3.1)
9 (1.7)
1 (0.2)
0 (0)
1 (0.2)
4 (0.7)
32 (5.9)
181 1,208
TOTAL
*Includes
LRTI
trilogy
and pentalogy-of
Fallot.
4. Risk factors for postoperative
Risk factor
Preoperative study 1 O-20 days >20 days Length of surgery (hr) Complications Duration of trachea catheterization (53 days) Duration of tracheotomy ductus (22 days) Duration of mediastinotomy and closed drainage (23 days) Duration of pericardiotomy and closed drainage (23 days) Duration of thoracic closed drainage (53 days)
nosocomial
No. of Procedures
376 329 135 115 53
infections
in patients
No. of NI (%)
28 41 24 26 20
No. of prmures
who had cardiac
surgery
No. of NI (%)
ratio
503 503 1073 1093 1155
21 21 66 64 70
16
13 (81.3)
1192
77 (6.5)
62.8
co.01
72
15 (20.8)
1136
75 (6.6)
3.7
co.01
74
16 (21.6)
1134
74 (6.5)
4.0
co.01
1'4
4 (28.6)
1194
86 (7.2)
5.2
co.01
Pathofjens Thirty-seven microbiologic isolates were obtained from the 90 patients with NI. Table 6 shows that the isolates were mostly identified as gram-negative bacteria, accounting for 56.8%. We found that fungi were important pathogens (29.7%). All pathogens were mainly opportunistic, such as Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa (Table 6).
1.9 3.3 3.3 4.7 9.4
p value
(7.5) (12.5) (17.8) (22.6) (37.7)
fore examining patients, the doctors and nurses were asked to wash their hands in running water with soap. With these measures, the incidence decreased, as previously reported, to 5.1%.
(4.2) (4.2) (6.2) (5.9) (6.0)
Odds
co.05 co.01 co.01 co.01 co.01
The majority of isolates were highly resistant to the antibiotics commonly used in hospitals; of 16 P. aeruginosa isolates tested, 13 (8 1%) were resistant to gentamicin, 16 (100%) were resistant to erythromycin, and 12 (75%) were resistant to chloramphenicol. P. aeruginosa isolates were 100% sensitive to amikacin and polymyxin B. DISCUSblOW
Our study showed that the overall incidence of NI in CVS was 13.5% before preventive measures were instituted. It was higher than that reported by Buu Hoi and Richet’ (8.2%), although the Centers for Disease Control’s definitions were used for determining NI in both
Volume 18 Number December 1990
6
Nosocomial
Table 5. Case fatality rates of cardiovascular according
to presence
or absence
surgery of complications
patients
With complication No. of patients With NI Without NI
26 89
TOTAL
No. of deaths
(%)
No. of patients
9 (34.6) 3 (3.4) 12 (10.4)
115
Table 6. Pathogens
Without
isolated
64 1029 1093
from cardiovascular
surgery
infections
in cardiac
by status of nosocomial
surgery
369
No. of deaths
(%)
infections
complication
TOW
No. of deaths
(%)
No. of patients
7 (10.9)
patients
in China
90 1118 1208
with nosocomial
16 (17.8)
infections
Site of NI Pathogen
Staphylococcus aureus Staphylococcus epidermidis Pseudomonas aeruginosa Escherichia co/i Candida sp. Other
fungi
TOTAL
LRTI
0 0 11 2 1 _1 15
WI
SBE
0
1 0 0 0 1 2 4
2 2 3 2 0 9
Septicemia 0 2 1 0 1 1 5
Other
Total
0 0 2 0 2 P 4
1 4 16 5 7 2 37
Mstributlon
(%)
2.7 10.8 3.2 13.5 18.9 10.8 99.9*
SEE, Subacute bacterial endocarditis. ‘Total does not equal 100.0 due to rounding.
studies. The sites of NI were found to be mainly LRTI, followed by WI. However, Butt Hoi and Richet reported that the sites of NI were mainly wounds followed by LRTI. The rate of LRTI was higher than what they reported. This is due to bed crowding, poor ventilation, and poor respiratory tract nursing. The rate of urinary tract infection was lower than that reported by Buu Hoi and Richet. It may be that the asymptomatic bacteriuria was not included, because urine cultures after surgical procedures were done only in the patient with symptoms of urinary tract infection, and because the duration of catheterization was usually 1 or 2 days. Numerous variables were significantly associated with risk of postoperative infections in patients who had CVS, such as age, length of surgical procedure, and type of operation. Similar results were reported in other studies.4’ 5 This study showed that length of hospital stay before surgical operation, complications after operation, duration of trachea catheterization, tracheotomy ducts, and all kinds of closed drainages were associated with the incidence of NI. In addition, other factors that may be relative to NI should be surveyed, such as patients’
health status, antibiotic prophylaxis, rates by surgeons, rates by operating room numbers, and number of operations. The incidence of postoperative NI in CVS was 10.5% before control measures were taken and dropped to 5.1% after the measures were taken. Clerk et al.6 has also reported a similar decrease in NI incidence after effective control measures were carried out; that is, the incidence of WI decreased from 6.6% to 3.3% and that of subacute bacterial endocarditis from 5.6% to 1.4% after similar measures were taken. These findings mean that once NI was given special attention, the necessary studies were done, and effective measures were taken, at least 50% of NI could be prevented, as documented in this patient population. As shown in Fig. 1, the rate of NI in February and April was lower than that in the other months in the first 6 months. This is due mainly to the decrease of LRTI. Only 37 isolates from 90 patients with NI were obtained; perhaps because several of antibiotics were used or because NI was caused by virus or anaerobic bacteria, for which we did not test. Endogenous infections are often caused by
American
370
Li and Wang
taking large doses of antibiotics, resulting in flora imbalance.’ Therefore controlling the abuse of antibiotics, especially of large doses of broad-spectrum antibiotics used for prophylaxis, seemed important for preventing endogenous NI. We are greatly indebted to Professors Zhu Shiao-dong, Dr. Yu Xun-xiang, Gao Yang, Yang Fang-i-en, and Liu Qi-ming, Fu-wai Hospital, for their help in collecting data and also thank Ms. Li Qiu-li and Dr. Wang Jian-ming of the Chinese Academy of Preventive Medicine, for their help in using the computer and in doing statistical analysis.
References 1. Buu Hoi A, Richet H. A prospective study of hospitalacquired infection in 2330 cardiovascular surgery patients. J Hosp Infect 1985;6:331-41.
INFECTION
Journal
of
CONTROL
2. Engleman RM, Chase RM Jr, Boyd AD, Reed GE. Lethal postoperative infections following cardiac surgery: review of four years’ experience. Circulation 1973;48(suppl 3):31-6. 3. Centers for Disease Control. National nosocomial infection study definitions manual. Atlanta: Centers for Disease Control, 1975. 4. Simchen E, Shapiro M. Michel J, Sacks T. Multivariate analysis of determinants of postoperative wound infection: a possible basis for intervention. Rev Infect Dis 1981;3:678-82. 5. Simchen E, Stein H, Sacks TG, Shapiro M, Michel J. Multivariate analysis of determinants of postoperative wound infections in orthopaedic patients. J Hosp Infect 1984;5:137-46. 6. Clerk RE, Amos WC, Higgins V, Bemberg KF, Weldom CS. Infection control in cardiac surgery. Surgery 1976;79:89-96. 7. Flynn DM, Weinstein RA, Nathan C, Gaston MA, Kabins SA. Patients’ endogenous flora as the source of “nosocomial” Entembacter in cardiac surgery. J Infect Dis 1987;156:363-9.
A prospective survey of postoperative nosocomial infections (NI) in cardiac surgery was carried out in a cardiovascular specialty hospital in Beijing, China. During the period from December 1986 to December 1987, 1208 cardiovascular surgery patients were surveyed for NI. The overall incidence of NI was found to be 7.5%. The incidence of lower respiratory tract and wound infections were 4.5% and 2.9%, respectively. These two kinds of infection accounted for 78.1% of the total infections. After effective control measures were taken at the end of the first 6 months (December 1986 to May 1987) of the study, the incidence fell from 10.6% to 5.1% in the next 7-month period (June to December 1987). The pathogens causing NI were mostly gram-negative bacteria, and they were mainly opportunistic. The contribution of fungal infection was significant in the hospitals. The ma.jority of the pathogenic isolates were highly resistant to the antibiotics commonly used in the hospital. (AM J INFECT CONTROL 1990;18:365-70)
Postoperative nosocomial infection (NI) after cardiac surgery is a serious problem for surgical patients, because they have more complications and undergo a long operation time and a large number of invasive procedures. In addition, once NI occurs, the illness will be critical and even risky to the patient’s life. Therefore the study of NI in cardiac surgery is vital to understand the problem and to reduce its incidence. In a prospective study of NI in cardiovascular surgery (CVS) patients conducted by Buu Hoi and Richet,’ it was reported that the postoperative infection rate was 8.2% and that the most common NI was wound infection (WI), followed by urinary tract infection, lower respiratory tract infection (LRTI), and bacteremia. Pathogens causing NI were mainly gramnegative bacterias2 However, there are few data in China on the incidence of NI in CVS patients. A prospective survey on hospital-acquired inFrom the Institute of Epidemiology Academy of Preventive Medicine.
and
Reprint requests: Wang Shu-qun, MD, miology, 3 Yabao Rd., Chaoyang District, ple’s Republic of China. 17146119657
Microbiology,
Chinese
Department of EpideBeijing, 100020, Peo-
fections was carried out in a cardiac surgery hospital for the purpose of determining the infection rate, identifying the epidemiologic features and finding common pathogens, and determining the antibiotic resistance patterns of these pathogens. METHODS
This study was performed from{ December 1986 to December 1987 in a CVS specialty hospital. There were three cardiac surgery departments with a total of 150 beds and an intensive care unit with six pediatric beds andlnine adult beds. Each week, 30 to 40 surgical operations were performed, 98% of them were elective. After their operations the patients were brought to the intensive care unit and cared for by special nurses until the patients’ conditions were improved. The surveillance was carried out by visiting all the patients after CVS once every 2 to 3 days; by checking the patients’ charts, the muses’ reports, and microbiologic reports; and by discussing the patients’ problems with the staff until the patients were discharged. Infections occurring after discharge were not surveyed unless a patient came back to this hospital. In-
American INFECTION
Li and Wang
Journal of CONTROL
16 control
measurea
4 2 0 MC l888
.
I
I
I
.
I
I
I
I
I
I
I
JAN 1987
FEB
MAR
APR
MAY
JUNE
JULY
Affi
SEPT
OCT
NOV
MC
d
Fig. 1.
RESULTS
Table 1. Incidence by infection site before and after control measures taken No. (%) of NI Before*
All NI LRTI WI SBE Septicemia Other TOTAL
$8E, Subacute ‘N = 517. tN = 691.
bacterial
55 (10.6) 38 (7.4)
20 (3.9) 2 2 8 70
(0.4) (0.4) (1.5) (13.5)
AftWt 35 16 15 2 2
(5.1) (2.3) (2.2) (0.3) (0.3)
endocarditis.
vestigated data were recorded on a special form for each CVS patient. The patient’s name and sex, date of admission, operation, and discharge (or death), underlying diseases, operation procedures, complications, risk factors, invasive procedures, and infection (date of onset; site; pathogens, if isolated; and antibiotic susceptibility) were collected. The Centers for Disease Control’s definitions for NI were used in determining the presence of these infections3
During the 13-month period, 1229 patients were surveyed. Among them, 1208 cases were analyzed to determine the presence of NI; 90 patients were found to have NI. The rate of infection was 7.5%. Incidence Monthly incidence. Incidence rates by months varied from 2.6% in January 1988 to 14.9% in April 1987 (Fig. 1). Incidence rate for the first 6 months was higher than for the second 7 months; it fell from 10.6% to 5.1% after the initiation of effective control measures at the end of the first 6 months of the study (Table 1). The descending infection rate curve was due to the decrease in WI and especially in LRTI. Incidence by age and sex. As shown in Table 2, the incidence rates of infection in the age groups were greatly different. The lo-year-old age group had the lowest incidence (2.8%). There were no significant differences by gender. Incidence by type of operation and infection site.
Operations were classified into five types, according to the kind and the complexity. The incidence varied with the different types of op-
Volume18 Number6 December1990
Nosocomial
infections
in cardiac
surgery
in China
367
Table 2. Incidence by age and sex Male
Age group
No. of operations
(Ye o5lo20304050-
95 272 82 51 34 37
TOTAL
Female
No. (%) of patients with NI 11 16 3 5 5 4
(11.6) (5.9) (3.7) (9.8) (14.7) (10.8)
No. of OperatiOnS
79 216 133 74 66 34 14 616
erations (Table 3). The highest was 20.0% for correction of the tetralogy of Fallot (TF) (including trilogy and pentalogy of Fallot). The lower respiratory tract was the most common site of infection, with a rate of 4.5%, followed by infection of wound sites, with an incidence rate of 2.9% (Table 3). These two sites accounted for 78.1% of the total distribution of NI. Septicemia and subacute bacterial endocarditis commonly developed after complicated operations, such as TF correction and prosthetic valve replacement. Patients with prosthetic valve replacement and TF correction procedures were more likely to acquire multisite infections. Potential
risk factors
Table 4 shows that the duration of tracheotomy ductus was the highest risk factor for NI (odds ratio, 62.8) followed by the duration of trachea catheterization (odds ratio, 9.4). Length of surgical procedure, complications, the duration of thoracic closed draining, pericardiotomy and closed draining, mediastinotomy and closed draining, and duration of hospital stay before surgical procedures were also associated with an increased risk of NI. Case fatality
rate
The case fatality rates of CVS patients with or without infection were compared with those with or without complications (Table 5). The case fatality rate was 17.8% in patients with NI and 0.4% in patients without infections. It is important to point out that the contribution of
Total
No. (%) of patients with NI 12 15 3 4 4 5
No. of operations
(15.2) (6.9) (2.3) (5.4) (6.1) (14.7)
174 488 215 125 100 71
No. (%) of patient0 with NI 23 31 6 9 9 9
(13.2) (6.4) (2.8) (7.2) (9.0) (12.7)
NI to the case fatality rate was influenced whether the patients had a complication. Preventive nosocomial
and control infections
meawwes
by
against
Maay risk factors were found through surveillance during the first 6 months of the study. The following major control measures were instituted in June 1987: An improvement in the care and management of the ICU was made, resulting in all patients getting better service. Aims were made at preventing and controlling NI emphasized isolating infected patients, improving the environmental hygiene, and asking physicians to follow the rules for proper use of antibiotics. An educational program was conducted for hospital personnel on the topic of NI control. The focus of the program was to control LRTI and WI. The preoperative preparation and postoperative nursing of the patients focused on care of the lower respiratory tract. Postoperatively, there was an emphasis on turning patients from side to side, timely suctioning of respiratory sections, and aerosol aspiration. Aseptic technique was required for all sue tioning procedures. The microbiologic laboratory played a supporting role. All microbiologic results and antibiotic resistance test results were reported to the physicians. Handwashing was strongly recommended because it was shown that the hands of doctors and nurses were seriously contaminative. Be-
388
American Journal INFECTIONCONTROL
Li and Wang
Table 3. Incidence of infection by site and type of surgical
of
procedure infection
Operation
---No. performfad
Type
Tetralogy of Fallot* Prosthetic valve replacement Closure of patent ductus arteriosus Atrial or ventricular septal defect Other
T&lo
WI
UTI
SSE
NI 6)
NI W
NI W
NI (%)
Septicemia NI (%I
Other
Total
NI (%I
NI W
125 158
15 (12.0) 10 (6.3)
9 (7.2) 9 (5.7)
2 (1.6) 0 (0)
2 (1.6) 2 (1.3)
2 (1.6) 2 (1.3)
3 (2.4) 2 (1.3)
33 (26.4) 25 (15.8)
199
8 (4.0)
3 (1.5)
0 (0)
0 (0)
0 (0)
1 (0.5)
12 (6.0)
545
17 (3.1)
9 (1.7)
1 (0.2)
0 (0)
1 (0.2)
4 (0.7)
32 (5.9)
181 1,208
TOTAL
*Includes
LRTI
trilogy
and pentalogy-of
Fallot.
4. Risk factors for postoperative
Risk factor
Preoperative study 1 O-20 days >20 days Length of surgery (hr) Complications Duration of trachea catheterization (53 days) Duration of tracheotomy ductus (22 days) Duration of mediastinotomy and closed drainage (23 days) Duration of pericardiotomy and closed drainage (23 days) Duration of thoracic closed drainage (53 days)
nosocomial
No. of Procedures
376 329 135 115 53
infections
in patients
No. of NI (%)
28 41 24 26 20
No. of prmures
who had cardiac
surgery
No. of NI (%)
ratio
503 503 1073 1093 1155
21 21 66 64 70
16
13 (81.3)
1192
77 (6.5)
62.8
co.01
72
15 (20.8)
1136
75 (6.6)
3.7
co.01
74
16 (21.6)
1134
74 (6.5)
4.0
co.01
1'4
4 (28.6)
1194
86 (7.2)
5.2
co.01
Pathofjens Thirty-seven microbiologic isolates were obtained from the 90 patients with NI. Table 6 shows that the isolates were mostly identified as gram-negative bacteria, accounting for 56.8%. We found that fungi were important pathogens (29.7%). All pathogens were mainly opportunistic, such as Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa (Table 6).
1.9 3.3 3.3 4.7 9.4
p value
(7.5) (12.5) (17.8) (22.6) (37.7)
fore examining patients, the doctors and nurses were asked to wash their hands in running water with soap. With these measures, the incidence decreased, as previously reported, to 5.1%.
(4.2) (4.2) (6.2) (5.9) (6.0)
Odds
co.05 co.01 co.01 co.01 co.01
The majority of isolates were highly resistant to the antibiotics commonly used in hospitals; of 16 P. aeruginosa isolates tested, 13 (8 1%) were resistant to gentamicin, 16 (100%) were resistant to erythromycin, and 12 (75%) were resistant to chloramphenicol. P. aeruginosa isolates were 100% sensitive to amikacin and polymyxin B. DISCUSblOW
Our study showed that the overall incidence of NI in CVS was 13.5% before preventive measures were instituted. It was higher than that reported by Buu Hoi and Richet’ (8.2%), although the Centers for Disease Control’s definitions were used for determining NI in both
Volume 18 Number December 1990
6
Nosocomial
Table 5. Case fatality rates of cardiovascular according
to presence
or absence
surgery of complications
patients
With complication No. of patients With NI Without NI
26 89
TOTAL
No. of deaths
(%)
No. of patients
9 (34.6) 3 (3.4) 12 (10.4)
115
Table 6. Pathogens
Without
isolated
64 1029 1093
from cardiovascular
surgery
infections
in cardiac
by status of nosocomial
surgery
369
No. of deaths
(%)
infections
complication
TOW
No. of deaths
(%)
No. of patients
7 (10.9)
patients
in China
90 1118 1208
with nosocomial
16 (17.8)
infections
Site of NI Pathogen
Staphylococcus aureus Staphylococcus epidermidis Pseudomonas aeruginosa Escherichia co/i Candida sp. Other
fungi
TOTAL
LRTI
0 0 11 2 1 _1 15
WI
SBE
0
1 0 0 0 1 2 4
2 2 3 2 0 9
Septicemia 0 2 1 0 1 1 5
Other
Total
0 0 2 0 2 P 4
1 4 16 5 7 2 37
Mstributlon
(%)
2.7 10.8 3.2 13.5 18.9 10.8 99.9*
SEE, Subacute bacterial endocarditis. ‘Total does not equal 100.0 due to rounding.
studies. The sites of NI were found to be mainly LRTI, followed by WI. However, Butt Hoi and Richet reported that the sites of NI were mainly wounds followed by LRTI. The rate of LRTI was higher than what they reported. This is due to bed crowding, poor ventilation, and poor respiratory tract nursing. The rate of urinary tract infection was lower than that reported by Buu Hoi and Richet. It may be that the asymptomatic bacteriuria was not included, because urine cultures after surgical procedures were done only in the patient with symptoms of urinary tract infection, and because the duration of catheterization was usually 1 or 2 days. Numerous variables were significantly associated with risk of postoperative infections in patients who had CVS, such as age, length of surgical procedure, and type of operation. Similar results were reported in other studies.4’ 5 This study showed that length of hospital stay before surgical operation, complications after operation, duration of trachea catheterization, tracheotomy ducts, and all kinds of closed drainages were associated with the incidence of NI. In addition, other factors that may be relative to NI should be surveyed, such as patients’
health status, antibiotic prophylaxis, rates by surgeons, rates by operating room numbers, and number of operations. The incidence of postoperative NI in CVS was 10.5% before control measures were taken and dropped to 5.1% after the measures were taken. Clerk et al.6 has also reported a similar decrease in NI incidence after effective control measures were carried out; that is, the incidence of WI decreased from 6.6% to 3.3% and that of subacute bacterial endocarditis from 5.6% to 1.4% after similar measures were taken. These findings mean that once NI was given special attention, the necessary studies were done, and effective measures were taken, at least 50% of NI could be prevented, as documented in this patient population. As shown in Fig. 1, the rate of NI in February and April was lower than that in the other months in the first 6 months. This is due mainly to the decrease of LRTI. Only 37 isolates from 90 patients with NI were obtained; perhaps because several of antibiotics were used or because NI was caused by virus or anaerobic bacteria, for which we did not test. Endogenous infections are often caused by
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taking large doses of antibiotics, resulting in flora imbalance.’ Therefore controlling the abuse of antibiotics, especially of large doses of broad-spectrum antibiotics used for prophylaxis, seemed important for preventing endogenous NI. We are greatly indebted to Professors Zhu Shiao-dong, Dr. Yu Xun-xiang, Gao Yang, Yang Fang-i-en, and Liu Qi-ming, Fu-wai Hospital, for their help in collecting data and also thank Ms. Li Qiu-li and Dr. Wang Jian-ming of the Chinese Academy of Preventive Medicine, for their help in using the computer and in doing statistical analysis.
References 1. Buu Hoi A, Richet H. A prospective study of hospitalacquired infection in 2330 cardiovascular surgery patients. J Hosp Infect 1985;6:331-41.
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2. Engleman RM, Chase RM Jr, Boyd AD, Reed GE. Lethal postoperative infections following cardiac surgery: review of four years’ experience. Circulation 1973;48(suppl 3):31-6. 3. Centers for Disease Control. National nosocomial infection study definitions manual. Atlanta: Centers for Disease Control, 1975. 4. Simchen E, Shapiro M. Michel J, Sacks T. Multivariate analysis of determinants of postoperative wound infection: a possible basis for intervention. Rev Infect Dis 1981;3:678-82. 5. Simchen E, Stein H, Sacks TG, Shapiro M, Michel J. Multivariate analysis of determinants of postoperative wound infections in orthopaedic patients. J Hosp Infect 1984;5:137-46. 6. Clerk RE, Amos WC, Higgins V, Bemberg KF, Weldom CS. Infection control in cardiac surgery. Surgery 1976;79:89-96. 7. Flynn DM, Weinstein RA, Nathan C, Gaston MA, Kabins SA. Patients’ endogenous flora as the source of “nosocomial” Entembacter in cardiac surgery. J Infect Dis 1987;156:363-9.