Intravenous versus Volatile Anesthesia and Cancer Outcomes: The Value of Precise Definitions and Pitfalls of Multivariate Analysis

Abstract

Letters to the Editor recommendation for replacing CO 2 absorbent that had been identified. 1 As mentioned in our other response, the threshold of 0.05% for changing CO 2 absorbent should have been 0.5% and not 0.05%. We recognize this threshold in percent to be different from 5 mm Hg, but the intention was to provide a threshold that is easy to remember. Dr Gross 1 also identified that mm Hg should be used as the units of partial pressure rather than torr. We included torr to ensure that the information was complete, as some may still use that term, although we agree it is not a recommended unit.

In Response

“…2 They raised concerns regarding the methodology of our study, arguing that the use of adjusted effect estimates derived from the multivariable Cox proportional hazards model and/or propensity-score matching might lead to a biased and potentially misleading result and that a meta-analysis of the unadjusted effect estimates should have been undertaken along with that of the adjusted ones. We agree with Dr Ackerman et al 1 that using adjusted effect estimates for a meta-analysis of observational studies is imperfect, when the variables adjusted for by the included studies vary; however, using unadjusted effect estimates for meta-analysis would be neither less biased nor be justifiable. The limitation of our meta-analyses is intrinsic to observational studies.…”

“…We thank Dr Ackerman et al 1 for their interest in our study investigating the impacts of anesthesia on the long-term oncological outcomes. 2 They raised concerns regarding the methodology of our study, arguing that the use of adjusted effect estimates derived from the multivariable Cox proportional hazards model and/or propensity-score matching might lead to a biased and potentially misleading result and that a meta-analysis of the unadjusted effect estimates should have been undertaken along with that of the adjusted ones.…”