Risk of surgical site infection and efficacy of antibiotic prophylaxis: a cohort study of appendectomy patients in Thailand

Table 3 Association between surgical site infections and duration, timing, and antibiotic prophylaxis agent, adjusted for age, sex, ASA score, and duration of operation

Predictor variable	N	Infection	Rate*	Relative risk
				Crude	95% CI	Adjusted**	95% CI
Duration of antibiotic prophylaxis
None	167	5	3.0	1.00	Reference	1.00	Reference
1 day	1159	12	1.0	0.34	0.12–0.97	0.30	0.10–0.88
>1 day	813	9	1.1	0.36	0.12–1.09	0.32	0.10–0.98
Time of first antibiotic dose administration
None	167	5	3.0	1.00	Reference	1.00	Reference
>1 hour preoperatively	1004	8	0.8	0.26	0.08–0.81	0.22	0.07–0.70
≤ 1 hour preoperatively or interoperation	814	9	1.1	0.36	0.12–1.09	0.33	0.11–1.02
Postoperatively	154	4	2.6	0.86	0.23–3.28	0.78	0.20–3.00
Antibiotic agent
None	167	5	3.0	1.00	Reference	1.00	Reference
Single dose combination metronidazole and gentamicin	766	8	1.0	0.34	0.11–1.06	0.28	0.09–0.90
Combination metronidazole and gentamicin within 1 day	130	1	0.8	0.25	0.03–2.18	0.22	0.03–1.98
Combination metronidazole and gentamicin > 1 day	370	4	1.1	0.35	0.09–1.34	0.29	0.08–1.12
Others***	706	8	1.1	0.37	0.12–1.15	0.37	0.12–1.15

* Rate = infections/100 operations
** Adjusted for age, sex, ASA score, and duration of operation
*** Others: Penicillin, amoxicillin, amoxicillin/clavulanate, ampicillin, cloxacillin, cefazolin, cephalexin, cefotaxime, ceftriaxone, ceftazidime, cefdinir, cefoxitin, ofloxacin, norfloxacin, cotrimoxazole, chloramphenical, fosfomycin, clindamycin, and amikacin.

ISSN: 1471-2334