Correspondence  |   November 2018
Surrogates or Outcomes: What Should We Measure?
Author Notes
  • Warren Alpert Medical School, Brown University, Providence, Rhode Island.
  • (Accepted for publication July 30, 2018.)
    (Accepted for publication July 30, 2018.)×
Article Information
Correspondence   |   November 2018
Surrogates or Outcomes: What Should We Measure?
Anesthesiology 11 2018, Vol.129, 1048. doi:10.1097/ALN.0000000000002418
Anesthesiology 11 2018, Vol.129, 1048. doi:10.1097/ALN.0000000000002418
I read with great interest the article by Girsberger and colleagues in a recent issue of Anesthesiology.1  The authors investigated 36 patients and concluded that postvoid residuals were significantly lower using ropivacaine compared with bupivacaine for thoracic epidural analgesia reflecting less impairment of detrusor function with ropivacaine. The authors should be congratulated for performing a well-designed randomized trial on an important topic in perioperative medicine. One may argue that by using ropivacaine for thoracic epidurals, the risk of urinary tract infection may be reduced with important consequences for patients and healthcare systems.2,3 
Although the authors performed a well-conducted study, some concerns require clarification to further establish the clinical importance of the study. The authors identified a significant mean difference (95% CI) in postvoid residuals between groups of −175 ml (−295 ml to −40 ml). I wondered why the authors did not measure or report the need for postoperative bladder catheterization, given that this has been more directly related to poor outcomes. It is possible that a large proportion of patients had small postresidual differences and did not require bladder catheterization.4  In addition, I could not determine whether the intraoperative management of these patients was standardized for anesthetics and analgesic agents, given that many of these agents (e.g., opioids, volatile anesthetics) can potentially alter the primary outcome.5,6