Timing of prophylactic antibiotics in abdominal surgery: trial of a pre-operative versus an intra-operative first dose
T Bates1, G Siller, B C Crathern
1William Harvey Hospital, Ashford, Kent, UK.
Insights
Starting prophylactic antibiotics before abdominal surgery did not reduce wound infections. However, pre-operative antibiotic administration was linked to a higher incidence of deep sepsis, suggesting intra-operative timing may be preferable for high-risk patients.
Area of Science:
- Surgical Infections
- Clinical Pharmacology
- Evidence-Based Medicine
Background:
- Prophylactic antibiotics are standard in abdominal surgery, typically given pre-operatively.
- The optimal timing for antibiotic administration, especially in cases with existing infection like appendicitis, remains debated.
- Pre-operative versus intra-operative antibiotic initiation requires comparative analysis.
Purpose of the Study:
- To compare the efficacy and safety of pre-operative versus intra-operative prophylactic antibiotic administration in high-risk abdominal surgeries.
- To evaluate the impact of antibiotic timing on wound infection and deep sepsis rates.
- To assess the influence of patient factors, such as obesity, on postoperative infection outcomes.
Main Methods:
- A randomized, double-blind study involving 700 patients undergoing emergency and elective high-risk abdominal operations.
- Comparison of two antibiotic regimens: pre-operative (Group P) versus intra-operative (Group T) initiation.
- Intravenous administration of metronidazole (500 mg) plus cephazolin (1 g) for three doses.
Main Results:
- Wound infection rates were similar between Group P (16.7%) and Group T (15.4%), including in appendicitis cases.
- Significantly higher rates of non-fatal deep sepsis were observed in Group P (nine cases) compared to Group T (two cases).
- Obese patients (BMI ≥ 26) experienced twice the rate of postoperative infection compared to non-obese patients (BMI < 24).
Conclusions:
- Initiating prophylactic antibiotics pre-operatively does not offer an advantage in reducing wound infections in high-risk abdominal surgery, even with appendicitis.
- Pre-operative antibiotic administration is associated with an increased risk of deep sepsis.
- Obesity is a significant risk factor for increased postoperative infection rates, highlighting the need for tailored strategies.
Abstract:
When prophylactic antibiotics are used in abdominal surgery it is customary to give the first dose before the operation. Whilst intra-operative antibiotics may be effective in elective surgery, there may be an advantage to starting pre-operatively when there is already an infective focus such as appendicitis. Antibiotics started pre-operatively (group P) have been compared with antibiotics started after initial abdominal exploration (group T). Three intravenous doses of 500 mg metronidazole plus 1 g cephazolin were given in a randomized, double-blind study of 700 emergency and elective high-risk abdominal operations. Antibiotic plasma concentrations at the end of the operation were significantly lower in group P but lay well within the therapeutic range. Wound infection rates, which included minor and delayed infections, were similar in both groups (group P, 57 of 342, 16.7 per cent; group T, 55 of 358, 15.4 per cent; 95 per cent confidence intervals for the difference being -4.1 to +6.7 per cent. In appendicitis, wound infection rates were 12.1 and 13.9 per cent for groups P and T respectively. However, non-fatal deep sepsis was more common in group P (nine cases) than in group T (two cases) (chi 2 = 4.9, P less than 0.05). Postoperative infection was twice as common in obese patients whose body mass index (BMI) was greater than or equal to 26 (39 of 132, 30 per cent) than in thin patients whose BMI was less than 24 (41 of 288, 14 per cent; chi 2 = 13.8, P less than 0.001). This study failed to show any advantage to starting antibiotics pre-operatively, even in appendicitis.
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