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The effect of whole body disinfection on intraoperative wound contamination
Journal
of Hospital
Infection
(1991)
18, 145-148
SHORT
REPORT
The effect of whole body disinfection intraoperative wound contamination D. J. Byrne, Departments
G. Phillips
*, A. Napier
and A. Cuschieri
of Surgery and *Microbiology, Ninewells Hospital School, Dundee DDl 9SY, Scotland Accepted for publication
on
9 April
and Medical
1991
Summary:
As part of a large whole body disinfection (WBD) trial two small sub-groups of patients who showered preoperatively with either a 4% chlorhexidine (CHX; N= 29) or placebo (N= 27) detergent were studied to assess intraoperative wound contamination. The groups were well matched for age, sex and length of surgery. A membrane filter contact technique was used for bacterial recovery from the wounds after the initial skin incision and before wound closure. The membrane filters were incubated aerobically on blood agar plates with a CHX neutralizer for 48 h at 37°C and colonies were counted. The results show a significant difference between the bacterial counts at the start and end of surgery in the CHX and placebo groups. There was no difference in bacterial counts at the start of surgery between the CHX and placebo groups. There was a significant difference in the bacterial counts at the end of surgery between the CHX and placebo groups. These results indicate that preoperative WBD with CHX reduces intraoperative wound contamination but the effect of this on postoperative wound sepsis rates awaits the results of a large WBD trial. Keywords:
Antiseptics;
chlorhexidine;
surgical
wound
infection
Introduction
The value of preoperative whole body disinfection (WBD) in reducing postoperative wound sepsis is unproven.‘p2 As part of a large trial looking at WBD and postoperative wound infection rates a small cohort of patients (N= 56) was further examined to ascertain if the level of intraoperative wound contamination differed between those patients who had undergone preoperative WBD and those who had not. Materials
Two
groups
Correspondence
of patients to: Derek
~3195~6701,91,‘0h0115+0~
and methods
were studied
J. Byrne
$03 00 0
145
(Table
I) who
were having
groin
146
D. J. Byrne Table
I. Patient
et al. characteristics Group
Number Median age in years (range) Male/female Median length of operation (range-min)
A
29 53 (19-73) 21/s 25 (l&45)
Group
B
54 $84) 20 (12-55)
hernia surgery or sapheno-femoral ligation. The groups were well-matched for age, sex and length of operation. Group A had three showers with a 4% chlorhexidine (CHX) detergent solution (‘Hibiscrub’, ICI Pharmaceuticals, Macclesfield) and Group B had three showers with a placebo detergent. The allocation was on a random blind basis. For each shower, approximately 50 ml of detergent was used which was lathered up using a sterile plastic sponge, a separate sponge being used for each shower. A standard set of washing instructions was given to each patient which instructed them to wash from the head downwards (including the hair), rinse, repeat the wash and dry themselves thoroughly with a freshly laundered towel. Clean clothes were worn after showering. The membrane filter contact technique was used in bacterial recovery from the wounds. This technique has been well described elsewhere.3 The 5 l.rrn membrane filter (Millipore Corp., Bedford, Mass., USA) is a disc with a surface area of 17.36 cm’. When the membrane filter is put into contact with a moist surface the bacteria are absorbed into the filter and trapped in its interstitial spaces. Bacterial adherence to the membrane filter surface through electrostatic forces may also be important. The 5 pm membrane filter recovered significantly more bacteria from artificially contaminated surfaces than did Rodac plates, velvet pads, velveteen pads or smaller-pore-size membrane filters.3 In sampling contaminated tissue surfaces, the bacterial recovery of the 5 pm membrane filter was similar to that of the quantitative dilutions of tissue biopsies.3 On opening the skin and subcutaneous fat bacteriological sampling of the wound was performed using 5 pm membrane filters which were placed in contact with the wound for 5 s3 and then transferred onto blood agar plates (contact side upwards) containing a chlorhexidine neutralizer (0.3% azolectin and 2% polysorbate SO). These plates were incubated aerobically at 37°C for 48 h. Colony counts were then performed and expressed in colony forming units per membrane (cfu/m). At the end of the operation, just before skin closure, another bacteriological sample of the wound was taken in the same manner as above. Results were expressed in cfu/m as median values and range of values. Statistical analysis to compare groups was performed using the Mann Whitney U-test.
Wound Table
II.
Bacterial (range)
Results
of intraoperative bacterial units per membrane
counts
Group
Start of surgery End of surgery *PC 0.05;
**Pi
contamination wound
counts in colony forming
(cjulm)
A
12* ((t250) 26* (2-448) 0.01 Mann-Whitney
147
Group
B
16** ((f284) lOl** (o-1080)
P value (A vs B) NS < 0.05
LT.test
Results There was no significant difference between the bacterial counts at the start of surgery in the CHX and placebo groups (Table II). There was a significant difference between the colony counts at the start and end of surgery in both the CHX and placebo groups (Table II). The colony count at the end of surgery was lower in the CHX group than in the placebo group and this difference was significant at the 5% level (Table II). There were two wound infections in each group. Discussion One of the theoretical arguments for preoperative WBD is that by reducing the patients’ skin bacterial counts preoperatively, less intraoperative wound contamination would result which, hopefully, would be translated into lower wound infection rates. So far no properly constructed trial has tackled the problem of preoperative WBD and wound sepsis and so the matter of reduced postoperative wound infection rates is unresolved. It has previously been shown that there is a highly significant correlation between the densities of bacteria during operation and subsequent wound sepsis.4 A previous study has shown lower intraoperative wound contamination rates with a chlorhexidine shower and scrub compared to povidoneiodine and medicated soap.’ Our results show that there appears to be a distinct reduction in intraoperative wound contamination in the group that had preoperative WBD compared to those patients who showered preoperatively with placebo detergent. The wound cultures taken immediately after incising the skin did not show any difference between the two groups. The numbers were too small to make any comment on the wound infection rate of two in each group. Whether this reduction in wound contamination results in lower wound infection rates awaits the results of a large WBD trial. References 1. Hayek LJ, Emerson JM, Gardner AMN. A placebo-controlled preoperative baths or showers with chlorhexidine detergent infection rates. J Hasp Infect 1987; 10: 165-l 72.
trial of the effect of two on postoperative wound
148
D. J. Byrne
et al.
2. European Working Party on Control of Hospital Infection. A comparison of the effects of preoperative whole-body bathing with detergent alone and with detergent containing chlorhexidine gluconate on the frequency of wound infection after clean surgery. J Hosp Infect 1988; 11: 31c-320. 3. Craythorn JM, Barbour AG, Matsen JM, Britt MR, Garibaldi RA. Membrane filter contact technique for bacteriological sampling of moist surfaces. J Clin Microbial 1980;
12: 250-255. 4. Raahave D, Friis-Moller A, Bjerre-Jepsen K, Thiis-Knudsen J, Rasmussen LB. The infective dose of aerobic and anaerobic bacteria in postoperative wound sepsis. Arch Surg 1986; 121: 924-929. 5. Garibaldi RA. Prevention of intraoperative wound contamination with chlorhexidine shower and scrub. J Hasp Infect 1988; 11 (Suppl. B): 5-9.
of Hospital
Infection
(1991)
18, 145-148
SHORT
REPORT
The effect of whole body disinfection intraoperative wound contamination D. J. Byrne, Departments
G. Phillips
*, A. Napier
and A. Cuschieri
of Surgery and *Microbiology, Ninewells Hospital School, Dundee DDl 9SY, Scotland Accepted for publication
on
9 April
and Medical
1991
Summary:
As part of a large whole body disinfection (WBD) trial two small sub-groups of patients who showered preoperatively with either a 4% chlorhexidine (CHX; N= 29) or placebo (N= 27) detergent were studied to assess intraoperative wound contamination. The groups were well matched for age, sex and length of surgery. A membrane filter contact technique was used for bacterial recovery from the wounds after the initial skin incision and before wound closure. The membrane filters were incubated aerobically on blood agar plates with a CHX neutralizer for 48 h at 37°C and colonies were counted. The results show a significant difference between the bacterial counts at the start and end of surgery in the CHX and placebo groups. There was no difference in bacterial counts at the start of surgery between the CHX and placebo groups. There was a significant difference in the bacterial counts at the end of surgery between the CHX and placebo groups. These results indicate that preoperative WBD with CHX reduces intraoperative wound contamination but the effect of this on postoperative wound sepsis rates awaits the results of a large WBD trial. Keywords:
Antiseptics;
chlorhexidine;
surgical
wound
infection
Introduction
The value of preoperative whole body disinfection (WBD) in reducing postoperative wound sepsis is unproven.‘p2 As part of a large trial looking at WBD and postoperative wound infection rates a small cohort of patients (N= 56) was further examined to ascertain if the level of intraoperative wound contamination differed between those patients who had undergone preoperative WBD and those who had not. Materials
Two
groups
Correspondence
of patients to: Derek
~3195~6701,91,‘0h0115+0~
and methods
were studied
J. Byrne
$03 00 0
145
(Table
I) who
were having
groin
146
D. J. Byrne Table
I. Patient
et al. characteristics Group
Number Median age in years (range) Male/female Median length of operation (range-min)
A
29 53 (19-73) 21/s 25 (l&45)
Group
B
54 $84) 20 (12-55)
hernia surgery or sapheno-femoral ligation. The groups were well-matched for age, sex and length of operation. Group A had three showers with a 4% chlorhexidine (CHX) detergent solution (‘Hibiscrub’, ICI Pharmaceuticals, Macclesfield) and Group B had three showers with a placebo detergent. The allocation was on a random blind basis. For each shower, approximately 50 ml of detergent was used which was lathered up using a sterile plastic sponge, a separate sponge being used for each shower. A standard set of washing instructions was given to each patient which instructed them to wash from the head downwards (including the hair), rinse, repeat the wash and dry themselves thoroughly with a freshly laundered towel. Clean clothes were worn after showering. The membrane filter contact technique was used in bacterial recovery from the wounds. This technique has been well described elsewhere.3 The 5 l.rrn membrane filter (Millipore Corp., Bedford, Mass., USA) is a disc with a surface area of 17.36 cm’. When the membrane filter is put into contact with a moist surface the bacteria are absorbed into the filter and trapped in its interstitial spaces. Bacterial adherence to the membrane filter surface through electrostatic forces may also be important. The 5 pm membrane filter recovered significantly more bacteria from artificially contaminated surfaces than did Rodac plates, velvet pads, velveteen pads or smaller-pore-size membrane filters.3 In sampling contaminated tissue surfaces, the bacterial recovery of the 5 pm membrane filter was similar to that of the quantitative dilutions of tissue biopsies.3 On opening the skin and subcutaneous fat bacteriological sampling of the wound was performed using 5 pm membrane filters which were placed in contact with the wound for 5 s3 and then transferred onto blood agar plates (contact side upwards) containing a chlorhexidine neutralizer (0.3% azolectin and 2% polysorbate SO). These plates were incubated aerobically at 37°C for 48 h. Colony counts were then performed and expressed in colony forming units per membrane (cfu/m). At the end of the operation, just before skin closure, another bacteriological sample of the wound was taken in the same manner as above. Results were expressed in cfu/m as median values and range of values. Statistical analysis to compare groups was performed using the Mann Whitney U-test.
Wound Table
II.
Bacterial (range)
Results
of intraoperative bacterial units per membrane
counts
Group
Start of surgery End of surgery *PC 0.05;
**Pi
contamination wound
counts in colony forming
(cjulm)
A
12* ((t250) 26* (2-448) 0.01 Mann-Whitney
147
Group
B
16** ((f284) lOl** (o-1080)
P value (A vs B) NS < 0.05
LT.test
Results There was no significant difference between the bacterial counts at the start of surgery in the CHX and placebo groups (Table II). There was a significant difference between the colony counts at the start and end of surgery in both the CHX and placebo groups (Table II). The colony count at the end of surgery was lower in the CHX group than in the placebo group and this difference was significant at the 5% level (Table II). There were two wound infections in each group. Discussion One of the theoretical arguments for preoperative WBD is that by reducing the patients’ skin bacterial counts preoperatively, less intraoperative wound contamination would result which, hopefully, would be translated into lower wound infection rates. So far no properly constructed trial has tackled the problem of preoperative WBD and wound sepsis and so the matter of reduced postoperative wound infection rates is unresolved. It has previously been shown that there is a highly significant correlation between the densities of bacteria during operation and subsequent wound sepsis.4 A previous study has shown lower intraoperative wound contamination rates with a chlorhexidine shower and scrub compared to povidoneiodine and medicated soap.’ Our results show that there appears to be a distinct reduction in intraoperative wound contamination in the group that had preoperative WBD compared to those patients who showered preoperatively with placebo detergent. The wound cultures taken immediately after incising the skin did not show any difference between the two groups. The numbers were too small to make any comment on the wound infection rate of two in each group. Whether this reduction in wound contamination results in lower wound infection rates awaits the results of a large WBD trial. References 1. Hayek LJ, Emerson JM, Gardner AMN. A placebo-controlled preoperative baths or showers with chlorhexidine detergent infection rates. J Hasp Infect 1987; 10: 165-l 72.
trial of the effect of two on postoperative wound
148
D. J. Byrne
et al.
2. European Working Party on Control of Hospital Infection. A comparison of the effects of preoperative whole-body bathing with detergent alone and with detergent containing chlorhexidine gluconate on the frequency of wound infection after clean surgery. J Hosp Infect 1988; 11: 31c-320. 3. Craythorn JM, Barbour AG, Matsen JM, Britt MR, Garibaldi RA. Membrane filter contact technique for bacteriological sampling of moist surfaces. J Clin Microbial 1980;
12: 250-255. 4. Raahave D, Friis-Moller A, Bjerre-Jepsen K, Thiis-Knudsen J, Rasmussen LB. The infective dose of aerobic and anaerobic bacteria in postoperative wound sepsis. Arch Surg 1986; 121: 924-929. 5. Garibaldi RA. Prevention of intraoperative wound contamination with chlorhexidine shower and scrub. J Hasp Infect 1988; 11 (Suppl. B): 5-9.