Methods

RCT.
Power calculation: yes.
Follow‐up period: 6 weeks after discharge.

Participants

3733 patients undergoing elective or potentially contaminated surgery.
Exclusion criteria: patients undergoing day surgery, emergency surgery, re‐operation or contaminated surgery and those unable to comply with the washing procedure, or with a known allergy to chlorhexidine or having more than the standard prophylactic antibiotic regimen.
Baseline comparability: age, sex, type of surgery, ASEPSIS score.

Interventions

All patients showered 3 times (on admission, the night before surgery and the morning of surgery) using 50 ml of either:
Group 1: 4% chlorhexidine, or
Group 2: a placebo.
Written instructions were provided to all participants.

Outcomes

Primary outcome:
Wound infection was defined as discharge of pus from a wound for inpatients or outpatients, or an ASEPSIS score greater than 10.
Group 1: 256/1754 (14.6%);
Group 2: 272/1735 (15.7%).
Secondary outcomes:
Death, allergic reactions, cost.

Notes

Data were extracted from 3 papers reporting results from 1 study (see Lynch 1992 & Byrne 1994). There were minor discrepancies in numbers reported between the 3 studies. The version reported is the definitive study (personal correspondence with author). The abstract stated there were 1753 patients in the placebo group but this should have been 1735

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Randomisation was performed in blocks of 6. Randomisation in each group of 6 was by computer‐generated random numbers.

Allocation concealment (selection bias)

Low risk

Personal communication with author. Allocation in sealed envelopes.

Blinding (performance bias and detection bias)
Investigator and participant

Low risk

2 bottles of either 4% chlorhexidine detergent solution or a physically‐identical placebo detergent were given to the patient. Neither the investigators nor the patient were aware of the allocation.
Outcome blinding was not specifically mentioned, however, it seems likely that those assessing infection status would have been unaware of the allocation.

Blinding (performance bias and detection bias)
Outcome assessor

Low risk

Outcome assessment blinded

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Of 3733 patients randomised, 244 (6.5%) were excluded from the outcome analysis. The majority of these, 219 (5.9%) were because the operation was cancelled after randomisation. 4 patients in the chlorhexidine group and 9 patients in the control group were excluded for protocol violations. However, as these numbers are extremely small (0.4% of those randomised), it is unlikely that results were compromised.

Selective reporting (reporting bias)

Low risk

The study reported on all of the stated outcomes.

Other bias

Low risk

The trial was supported by ICI Pharmaceuticals. However, as results did not support the use of chlorhexidine, it is unlikely that results were compromised.

Methods

RCT.
Power calculation: no.
Follow‐up period: until hospital discharge.

Participants

66 patients undergoing vascular reconstruction surgery.
Exclusion: none reported.
Baseline comparability: stated that groups were similar, no data.

Interventions

All patients had 2 baths.
Group 1: painted entire body with undiluted 4% chlorhexidine followed by rinsing in the bath. Precise instructions given;
Group 2: non‐medicated soap used. No specific instructions provided.

Outcomes

Primary outcome:
Wound infection was defined as discharge of pus from a wound; 1 patient with severe cellulitis was also included.
Group 1: 8/31 (26%);
Group 2: 4/35, (11.4%).
Secondary outcome:
Death.

Notes

Different washing information provided to participants in each group.

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Not described. Investigator contacted ‐ no further information available.

Allocation concealment (selection bias)

Unclear risk

Not described. Investigator contacted ‐ no further information available.

Blinding (performance bias and detection bias)
Investigator and participant

High risk

Both the investigator and the participant were aware of the allocation.
Postoperatively wounds were reviewed blind until patients left hospital.

Blinding (performance bias and detection bias)
Outcome assessor

Low risk

Outcome assessment blinded.

Incomplete outcome data (attrition bias)
All outcomes

Low risk

Results were available for all those enrolled. No drop outs or exclusions were described.

Selective reporting (reporting bias)

Low risk

The study reported on wound infection. A number of post hoc analyses were also conducted.

Other bias

High risk

Baseline data tables were not provided but the author stated that "clinical details of the two groups were similar".
Different washing information provided to participants in each group.
Hibiscrub (chlorhexidine) was provided by ICI. However, as results favoured the use of soap, it is unlikely that the involvement of the pharmaceutical company influenced results.

Methods

Cluster RCT.
Power calculation: no.
Follow‐up period: until hospital discharge.

Participants

2015 patients undergoing routine surgery.
Exclusion: those receiving antibiotics or with an existing infection.
Baseline comparability: age, sex, preoperative skin preparation, wound classification, proportion who washed their hair.

Interventions

All patients had either a shower or bath on the day before and morning of their operation.
Group 1: chlorhexidine 4%. Instruction card for washing provided.
Group 2: placebo. Instruction card for washing provided (5 months into the study, the placebo was found to have antimicrobial properties and was changed).
Group 3: bar soap. No washing instructions provided.

Outcomes

Primary outcome:
Wound infection was defined as either discharge of pus from a wound, or erythema, or swelling considered to be greater than expected.
Group 1: 62/689 (9.0%);
Group 2: 83/700 (11.7%);
Group 3: 80/626 (12.8%).

Notes

Data were extracted from 2 papers reporting results from 1 study (Hayek 1988).

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Unclear risk

Not described.

Allocation concealment (selection bias)

Unclear risk

Not described.

Blinding (performance bias and detection bias)
Investigator and participant

High risk

3 arms to the study. "None of the ward staff or those assessing the wounds were aware of whether placebo or active compound was being used as these were issued in identical coded sachets, though no form of double blind was possible for the bar soap group".

Blinding (performance bias and detection bias)
Outcome assessor

Low risk

Outcome assessment blinded.

Incomplete outcome data (attrition bias)
All outcomes

Unclear risk

It appears from the text that results were available from all patients who entered the study. However, as patients were followed up for 6 weeks postoperatively; it seems unusual that none were lost to follow‐up.

Selective reporting (reporting bias)

Low risk

All data reported.

Other bias

High risk

No baseline data presented. The authors state that "The three groups are comparable except for one interesting facet; only 14% washed their hair with bar soap against 28% with either of the liquids.
Specific washing instructions were provided to the chlorhexidine and placebo groups but not to the bar soap group.
5 months into the study, the placebo was found to have antimicrobial properties and was changed.
It is unclear how this large study was funded. No competing interests were declared.

Methods

RCT.
Power calculation: no.
Follow‐up period: 1 week after discharge.

Participants

94 patients undergoing vasectomy.
Exclusion: none stated.
Baseline comparability: none stated.

Interventions

Group 1: 1 preoperative shower with chlorhexidine 4%,
Group 2: 1 shower with normal soap.
Group 3: no shower.

Outcomes

Primary outcome:
Wound infection was defined as discharging either purulent or serous fluid.
Group 1: 12/32 (37.5%);
Group 2: 10/30 (33.3%);
Group 3: 9/32 (28.1%).

Notes

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Personal correspondence with study authors confirmed that trialists used computer‐generated random numbers.

Allocation concealment (selection bias)

Unclear risk

Method not described.

Blinding (performance bias and detection bias)
Investigator and participant

High risk

Blinding of the intervention was not possible.

Blinding (performance bias and detection bias)
Outcome assessor

Unclear risk

It is unclear if outcome assessment was blinded.

Incomplete outcome data (attrition bias)
All outcomes

Low risk

All but 1 enrolled patient were assessed 7 days postoperatively; 83 returned to the ward, 10 were contacted at home and 1 was lost to follow‐up (it is unclear which group this patient was in); results were presented for the total number enrolled.

Selective reporting (reporting bias)

Low risk

All data reported.

Other bias

Low risk

No baseline data presented.
No competing interests declared.

Methods

Cluster RCT.
Power calculation: no.
Follow‐up period: 3 weeks after discharge.

Participants

2953 patients undergoing elective clean surgery.
Exclusion: patients with a temperature of 37.5^oC on the day of or day before surgery, infection remote from operation site, antibiotics given within 7 days prior to surgery for infection, incarcerated inguinal hernia, radical mastectomy.
Baseline comparability: age, sex, type of surgery, antibiotic prophylaxis, hair washed, hair removal method, wound drainage.

Interventions

All patients had 2 showers;1 the day before surgery and 1 on the day of surgery.
Group 1: used 50 ml of chlorhexidine 4% for each shower;
Group 2: placebo.
Special application instructions were provided to all participants.

Outcomes

Primary outcome:
Wound infection was defined in the report as "inflammation of the surgical wound with discharge of pus, spontaneous and/or after surgical intervention that occurs during hospitalisation or during routine follow‐up"
Group 1: 37/1413 (2.6%);
Group 2: 33/1400 (2.4%).

Notes

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Randomisation was carried out for each surgical unit by means of computer‐generated patient trial numbers.

Allocation concealment (selection bias)

Low risk

Bottles of solution were contained in boxes of 10, each holding 5 chlorhexidine and 5 placebo in random sequence. Unless the code was broken, it was impossible to know which preparation the patient had used.

Blinding (performance bias and detection bias)
Investigator and participant

Low risk

Neither patients nor investigators were aware of group allocation.

Blinding (performance bias and detection bias)
Outcome assessor

Low risk

Outcome assessment was by routine surveillance methods employed by individual hospitals (infection control nurse or surgeon). They were unaware of group allocation.

Incomplete outcome data (attrition bias)
All outcomes

Low risk

140 (4.7%) patients were withdrawn after randomisation either because the patient was not operated on (62 patients), had had 1 bath only (26), operation not stated 'clean' (14) or had a current infection (38). The withdrawals were evenly distributed between the chlorhexidine and placebo groups.

Selective reporting (reporting bias)

Low risk

All data reported.

Other bias

Low risk

ICI supplied the bathing materials. However, as results favoured the placebo group, this is unlikely to have affected results.

Methods

RCT.
Power calculation: no.
Follow‐up period: 30 days.

Participants

Adult patients, scheduled for plastic surgery at a University‐affiliated hospital in Brazil.

Exclusions: hypersensitivity to chlorhexidine, presence of skin lesions, antibiotic use at time of surgery, diabetes, heavy smoking, immunosuppression.

Interventions

Group 1: shower with liquid‐based detergent containing 4% chlorhexidine;
Group 2: shower with the same liquid‐based detergent, without chlorhexidine;
Group 3: no preoperative showering instructions were given.
Patients in Groups 1 and 2 were asked to rinse thoroughly, lather with the antiseptic, rinse, lather and rinse again.

Outcomes

Primary outcome:
Surgical site infection (defined using Centers for Disease Control criteria for wound infection and wound classification)
Group 1: 1/50 (2%);
Group 2: 1/50 (2%);
Group 3: 0/50 (0%).

Secondary outcome:
Adverse reactions: no adverse reactions were reported.

Notes

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Computer‐generated.

Allocation concealment (selection bias)

Unclear risk

Not described.

Blinding (performance bias and detection bias)
Investigator and participant

Low risk

Surgeons and patients were all blinded to the allocation group.

Blinding (performance bias and detection bias)
Outcome assessor

Low risk

Outcome assessors and microbiologists were all blinded to the allocation group.

Incomplete outcome data (attrition bias)
All outcomes

Low risk

All patients were followed for the nominated 30 days.

Selective reporting (reporting bias)

Low risk

Expected outcomes were reported.

Other bias

Low risk

The placebo solution was provided by Rioquimica Industria Farmaceutica, the manufacturer of the intervention product. However, as results in different groups were similar, this is unlikely to have affected results.

Methods

RCT.
Power calculation: no.
Follow‐up period: until hospital discharge.

Participants

1530 patients undergoing elective surgery of the biliary tract, inguinal hernia and breast cancer.
Exclusion: none stated.
Baseline comparability: age, duration of surgery > 2 hours, steroids, diabetes, malignancy (other than breast cancer), type of surgery.

Interventions

Group 1: patients washed their entire body with chlorhexidine on the day before surgery using 2 consecutive applications followed by rinsing under the shower;
Group 2: washed only that part of the body to be submitted to surgery with chlorhexidine soap;
Group 3: No chlorhexidine wash.

Outcomes

Primary outcome:
Wound infection was defined as a definite collection of pus emptying itself spontaneously or after incision:
Group 1: 9/541 (1.7%);
Group 2: 23/552 (4.2%);
Group 3: 20/437 (4.6).

Notes

This study was conducted over a 7 year period from 1978 to 1984.
It was unclear from the text whether patients allocated to the 'no chlorhexidine wash' group had any preoperative shower. 3 patients died and were not included in the analysis.
Strength of wash solution was not stated.

Risk of bias

Bias

Authors' judgement

Support for judgement

Random sequence generation (selection bias)

Low risk

Personal correspondence with study authors confirmed that they used a randomisation list.

Allocation concealment (selection bias)

Low risk

Patients were randomly allocated to 1 of 3 wards in which different preoperative preparation schedules were used. The author states that "The randomisation was done by the Chief surgeon in such a way that he did not know the identity of the patients allocated to each ward."

Blinding (performance bias and detection bias)
Investigator and participant

High risk

Blinding would have been impossible because of the allocation method.

Blinding (performance bias and detection bias)
Outcome assessor

High risk

Outcome assessment was not blinded (personal correspondence with study authors).

Incomplete outcome data (attrition bias)
All outcomes

Low risk

3 patients died in the few days following surgery, these were not identified by group.

Selective reporting (reporting bias)

Low risk

All data reported.

Other bias

Unclear risk

Baseline risk factors were similar across groups.
No competing interests declared.