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BACKGROUND: A correlation between deep anesthesia (defined as time with Bispectral Index (BIS) 80 yr (HR 2.93 1.79-4.79), and preexisting malignancy associated with less favorable prognosis (HR 9.30 6.60-13.1).When the initial multivariate regression was repeated using preexisting malignancy status among the co-variates in the model, the previously significant relation between 1, and 2-yr mortality and T(BIS <45) did not reach statistical significance. CONCLUSION: Using a similar set of co-variates as in previous work, we confirmed the statistical relation between 1-yr mortality and T(BIS <45), and we extended this observation to 2-yr mortality. However, this relation is sensitive to the selection of co-variates in the statistical model, and a randomized study is required to demonstrate that there really is a causal impact from and T(BIS <45) on postoperative mortality and, if it does, the effect is probably very weak in comparison with co-morbidity as assessed by ASA physical score, the preexisting malignancy status at surgery and age.
Lindholm et al. (Wed,) studied this question.