1458. The Incidence of Surgical Site Infection after Planned Laparoscopic Inpatient vs. Ambulatory Cholecystectomy: A Matched Propensity Score Analysis
Session: Poster Abstract Session: HAI: Surgical Site Infections
Friday, October 28, 2016
Room: Poster Hall
Background: There are little data on the risk of surgical site infection (SSI) after laparoscopic cholecystectomy performed during inpatient vs. ambulatory surgery. Our objective was to determine if SSI incidence after planned laparoscopic cholecystectomy differs by performance site, accounting for underlying differences between the two populations.

Methods: We established a retrospective cohort of commercially-insured persons aged 18–64 years with laparoscopic cholecystectomy (including open conversions) per ICD-9-CM procedure or CPT-4 codes during an inpatient hospitalization or in ambulatory surgery from 12/31/2004–12/31/2010. SSIs ≤ 90 days post-surgery were identified by ICD-9-CM diagnosis codes. We used logistic regression to create the propensity score to have surgery performed as an inpatient, and compared the incidence of SSI in the matched pairs using McNemar's test. A chi-square test was used to compare the SSI incidence in the unmatched populations.

Results: The analysis included 49,440 procedures; 38,861 (78.6%) ambulatory surgery procedures and 10,579 (21.4%) inpatient procedures. The median age of patients was 45 years (range 18–64), 74.5% were female, and 1.0% of the procedures were laparoscopic to open conversions (4.4% among inpatient vs. 0.02% among ambulatory procedures). 148 (1.4%) patients had an SSI following an inpatient procedure vs. 188 (0.5%) following an ambulatory procedure (P < 0.001). After propensity score matching (8,654 pairs), the incidence of SSI remained significantly higher in the inpatient (122 [1.4%]) vs. ambulatory population (67 [0.8%]; P < 0.001). The SSI incidence remained significantly higher in the inpatient population after excluding pairs in which one or both patients had conversion to an open procedure (1.2% vs. 0.8%, P = 0.008).

Conclusion: The incidence of SSI was higher after inpatient than ambulatory laparoscopic cholecystectomy before and after propensity matching. The SSI incidence was lower in the inpatient group after removing matched pairs with open conversion, but remained significantly higher than ambulatory procedures. Although we attempted to control for confounding by indication, our results suggest that residual differences in the patient populations persist.

Katelin B. Nickel, MPH1, Anna E. Wallace, MPH2, Fang Tian, PhD, MPH2, William J. Symons, MD3, Victoria J. Fraser, MD, FIDSA, FSHEA4, David K. Warren, MD, MPH, FIDSA, FSHEA1 and Margaret a. Olsen, PhD, MPH1,5, (1)Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO, (2)HealthCore, Inc., Wilmington, DE, (3)Division of General Surgery, Washington University School of Medicine, St. Louis, MO, (4)Washington University School of Medicine, St. Louis, MO, (5)Division of Public Health Sciences, Washington University School of Medicine, St. Louis, MO


K. B. Nickel, None

A. E. Wallace, None

F. Tian, None

W. J. Symons, None

V. J. Fraser, NIH: Grant Investigator , Research grant
CDC: Grant Investigator , Research grant
The Foundation for Barnes-Jewish Hospital: Grant Investigator , Research grant
Doris Duke Charitable Foundation: Grant Investigator , Research grant
Express Scripts: Spouse is Senior Vice President and Chief Medical Officer at Express Scripts , Spouse employment

D. K. Warren, None

M. A. Olsen, Sanofi Pasteur: Consultant and Grant Investigator , Consulting fee and Research grant
Pfizer: Consultant and Scientific Advisor , Consulting fee

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