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Preoperative Antibiotics and Mortality in the Elderly

Silber, Jeffrey H. MD, PhD*†‡§; Rosenbaum, Paul R. PhD; Trudeau, Martha E. MPA, RN; Chen, Wei MS; Zhang, Xuemei MS*; Lorch, Scott A. MD, MSCE*†§; Kelz, Rachel Rapaport MD, MSCE**; Mosher, Rachel E. BA*; Even-Shoshan, Orit MS

doi: 10.1097/01.sla.0000167850.49819.ea
Original Articles
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Objective and Background: It is generally thought that the use of preoperative antibiotics reduces the risk of postoperative infection, yet few studies have described the association between preoperative antibiotics and the risk of dying. The objective of this study was to determine whether preoperative antibiotics are associated with a reduced risk of death.

Methods: We performed a multivariate matched, population-based, case-control study of death following surgery on 1362 Pennsylvania Medicare patients between 65 and 85 years of age undergoing general and orthopedic surgery. Cases (681 deaths within 60 days from hospital admission) were randomly selected throughout Pennsylvania using claims from 1995 and 1996. Models were developed to scan Medicare claims, looking for controls who did not die and who were the closest matches to the previously selected cases based on preoperative characteristics. Cases and their controls were identified, and charts were abstracted to define antibiotic use and obtain baseline severity adjustment data.

Results: For general surgery, the odds of dying within 60 days were less than half in those treated with preoperative antibiotics within 2 hours of incision as compared with those without such treatment: (odds ratio = 0.44; 95% confidence interval, 0.32–0.60), P < 0.0001). For orthopedic surgery, no significant mortality reduction was observed (OR = 0.85; 95% confidence interval, 0.54–1.32; P < 0.464).

Interpretation: Preoperative antibiotics are associated with a substantially lower 60-day mortality rate in elderly patients undergoing general surgery. In patients who appear to be comparable, the risk of death was half as large among those who received preoperative antibiotics.

Using Pennsylvania Medicare claims and chart review, 681 randomly selected patients who died after surgery were matched to 681 control patients with similar preoperative risk. The odds of dying were less than half in those treated with preoperative antibiotics within 2 hours of incision as compared with those without such treatment.

From the *Center for Outcomes Research, Children's Hospital of Philadelphia; Departments of †Pediatrics and ‡Anesthesia, University of Pennsylvania School of Medicine; §Leonard Davis Institute of Health Economics; ∥Department of Statistics, Wharton School, University of Pennsylvania; ¶VA Center for Health Equity Research and Promotion; **Department of Surgery, Hospital of the University of Pennsylvania and University of Pennsylvania School of Medicine, Philadelphia, PA.

Supported primarily by the Agency for Healthcare Research and Quality (AHRQ) (grant no. HS-R01-9460). Dr. Rosenbaum was also supported in part by a grant from the National Science Foundation (NSF). The AHRQ and the NSF had no involvement in conducting this research.

Reprints: Jeffrey H. Silber, MD, PhD, Center for Outcomes Research, Children's Hospital of Philadelphia, 3535 Market Street, Suite 1029, Philadelphia, PA 19104. E-mail: silberj@wharton.upenn.edu.

© 2005 Lippincott Williams & Wilkins, Inc.