Dissections
INTERVENTIONAL 22 April 2009
Evidence-based Medicine for Surgeons
Antibiotic prophylaxis at urinary catheter removal prevents urinary tract infections Authors: Pfefferkorn U, Lea S, Moldenhauer J, et al Journal: Annals of Surgery 2009; 249:573–575 Centre: Department of Surgery, St Claraspital, Basel, Switzerland
BACKGROUND
Catheter-associated urinary tract infections are the most common healthcare-associated (nosocomial) infections seen in surgical practice. Even though the prevalence of bacteruria increases by 3-10% per day of catheterization, it is currently accepted that indwelling urinary catheters should not be covered by antibiotics during their period of usage. However, the role and value of prophylactic antibiotic administration at the time of catheter removal is controversial.
RESEARCH QUESTION Population Patients undergoing elective abdominal surgery at a single centre with planned perioperative urethral catheterization Indicator variable Three doses of sulfamethoxazole catheter removal.
trimethoprimat urinary
Outcome variable Primary: occurrence of urinary tract infection after catheter removal. Secondary: occurrence of asymptomatic bacteruria. Comparison
Authors' claim(s): “...we suggest the use of antibiotic prophylaxis at urinary catheter removal to prevent a common, in most cases inconvenient but potentially harmful, complication.”
IN
SUMMARY Primary and secondary endpoints: results
With prophylaxis (103)
No prophylaxis (102)
5 (4.9%)
22 (21.6%)
Significant bacteruria after catheter removal (p < 0.001)
17 (16.5%)
42 (41.2%)
Significant bacteruria before catheter removal (p = 0.66)
39 (37.7%)
35 (34.3%)
Symptomatic UTI after catheter removal (p <0.001)
The absolute risk reduction for the occurrence of a urinary tract infection was 16.7% (CI: 7.8%–22.1%). The number needed to treat (NNT)was 6 (CI: 4.5–12.8). Six patients have to be treated with antibiotic at catheter removal to prevent one infection.
No antibiotic prophylaxis.
THE
BOTTOM LINE
This is a gem of a study that appears to have done everything right. The research question is precise and sharply focused. The study design and statistical analysis leaves little room for objections. Shortcomings of the study are listed and addressed squarely. The issues at hand are common and important. This study needs to be incorporated into our clinical practices.
EBM-O-METER Evidence level
Overall rating
Bias levels
Double blind RCT
Sampling
Randomized controlled trial (RCT) Prospective cohort study - not randomized Case controlled study
Trash Life's too short for this
Swiss cheese Full of holes
Safe Holds water
Newsworthy “Just do it”
Case series - retrospective
Comparison Measurement
l | Novel l | Feasible l Ethical l | Resource saving l
Interesting
The devil is in the details (more on the paper) ...
© Dr Arjun Rajagopalan
SAMPLING Sample type Simple random Stratified random Cluster Consecutive
Inclusion criteria Patients undergoing elective abdominal surgery with planned perioperative urethral catheterization
Convenience Judgmental
Exclusion criteria
Final score card
Received antibiotic coverage > 48 hours during catheterization Received antibiotics after catheter removal Patients not completing all tests
Study
Controls
Target
?
?
Accessible
?
?
Intended
119
119
Drop outs
16
17
103
102
Study
= Reasonable | ? = Arguable | = Questionable To detect a 10% difference with a significance level of 0.05 and statistical power of 80%, 220 patients were required. Sampling bias: The drop out rate of 14% is high, but the drop outs were similar in characteristics in either arm. The study is a single centre experience limited to patients undergoing abdominal surgery (predominantly colorectal).
COMPARISON Randomized
Case-control
Non-random
Historical
None
Controls - details Allocation details
At admission patients were consecutively randomized into 2 groups. One group received 960 mg trimethoprim-sulfamethoxazole orally once the night before, and twice on the day of catheter removal. Ciprofloxacin 250 mg was used as a replacement in patients with known allergy to trimethoprim-sulfamethoxazole. Patients in the other group did not receive any prophylaxis. Urinary cultures were obtained the day before and 3 days after catheter removal.
Comparability
The two groups were similar in demographic characteristics and co-morbidties. The urinary catheters were left in place for 7 +/- 1.7 days in the group with prophylaxis and for 6.5 +/1.7 days in the group without prophylaxis, (p = 0.68). There were no significant differences between the groups of patients who were excluded from the study after randomization.
Disparity
No significant differences in the overall population or drop outs.
Comparison bias: No detectable flaws.
MEASUREMENT Measurement error Blinding
N
Scoring
?
Protocols
Y
Training
Device suited to task
Observer error Gold std.
Device error Repetition
Device used
1.Symptom assessment: before discharge, patients were seen by a study-blind specialist in urology to assess subjective symptoms before and after catheter removal.
Y
N
Y
Y
-
-
Y
2.Significant urinary tract infection: patients with positive urine culture (>105 microorganisms per cm3) and at least one of the following signs or symptoms with no other recognized cause: fever (>38°C), urgency, frequency, dysuria, or suprapubic tenderness.
Y
N
Y
-
Y
-
-
3.Asymptomatic bacteriuria, which was diagnosed in patients with positive urinary culture but none of the earlier mentioned signs or symptoms.
Y
N
Y
-
y
-
-
Measurement bias: Nothing to complain about. © Dr Arjun Rajagopalan