Correspondence  |   January 2019
In Reply
Author Notes
  • Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois (S.S.). sshahul1@dacc.uchicago.edu
  • (Accepted for publication October 2, 2018.)
    (Accepted for publication October 2, 2018.)×
Article Information
Correspondence
Correspondence   |   January 2019
In Reply
Anesthesiology 1 2019, Vol.130, 174-175. doi:10.1097/ALN.0000000000002498
Anesthesiology 1 2019, Vol.130, 174-175. doi:10.1097/ALN.0000000000002498
We thank Dr. Pivalizza for his insightful observations on our article.1  We agree that our work does not demonstrate a causal relationship between a history of opioid use and postsurgical readmission, and that our title mistakenly suggests that possibility. Because this study was observational, we expected many covariates to be differentially distributed between opioid abuse or dependence and non-opioid abuse or dependence groups. This relationship was indeed evident from table 2,1  where 29 out of 32 covariates had significant P values. However, we did not choose adjustment covariates based upon P values. We chose covariates a priori because of the possibility that they might confound the association between opioid abuse or dependence or that they were known surrogate markers for the severity of a patient’s postoperative condition (e.g., transfusion).2