SURGICAL INFECTIONS Volume 00, Number 00, 2010 ª Mary Ann Liebert, Inc. DOI: 10.1089=sur.2009.9931
Response to ‘‘Power in the Study of Mortality and Necrotizing Soft Tissue Infections’’ Greg Beilman and Jeff Chipman
(number of debridements was one fewer in the non-HBO group, p ¼ 0.03). When we performed multivariable logistic regression evaluating the effects of various outcome variables on mortality, HBO use was not a significant factor in outcome. The two variables retained in the model were hypotension (odds ratio, 11) and immunosuppression (odds ratio, 28). We therefore conclude that in this study HBO did not result in improved outcome. We agree with the respondents that a prospective, randomized, multi-center trial that is powered appropriately to demonstrate a difference is necessary to define the role of HBO in treatment of NSTIs. In the absence of such a study, our work suggests that there is no benefit to use of HBO therapy for treatment of this condition. For now, the mainstays of therapy for NSTI remain rapid, complete, and repeated surgical debridement, thorough ICU care, and appropriate antibiotic treatment.
To the Editor: We appreciate the comments of Doctors Westgard and Adkinson with regard to our referenced study [1]. With respect to the assertion that the two groups were different, there is no question that patients admitted to two different hospitals will have potential differences biasing the results. For example, in our study, patients admitted to the University of Minnesota were more likely to have received a previous organ transplant (p ¼ 0.03) and possibly immunosuppressed (p ¼ 0.14), conditions that would be expected to increase mortality from this serious illness, whereas patients admitted to Hennepin County Medical Center (HCMC) had higher white blood cell counts (WBC) (p ¼ 0.01) and possibly higher admission glucose (p ¼ 0.06) and body mass index (BMI; p ¼ 0.07), conditions that have all been associated with higher risk. Differences such as these are likely to exist in any retrospective analysis. We did not include patients from HCMC who did not receive hyperbaric oxygen (HBO) in our analysis because we were not able to identify these patients with the medical record system available to us. We utilized an intention-to-treat analysis and therefore did not include full treatment with hyperbaric oxygen as a variable. We appreciate the respondents’ comments regarding other studies of HBO therapy in necrotizing soft tissue infections (NSTIs). They note, and we agree (and note in our discussion), that this literature suffers overall from a lack of power with respect to sample size. This is likely for at least two reasons: (1) NSTIs are an uncommon disease; and (2) for a variety of reasons, centers that have access to HBO therapy use HBO therapy. With respect to the assertion that patients in this study showed a trend toward improved mortality, we disagree. There was no significant benefit toward survival between the groups in our analysis (p ¼ 0.48); indeed the only outcome variable suggesting benefit favored the non-HBO group
Author Disclosure Statement No competing financial interests exist. Reference 1. George ME, Reuth N, Skarda DE, et al. Hyperbaric oxygen does not improve outcomes in patients with necrotizing soft tissue infections. Surg Infect 2009;10:21–28.
Address correspondence to: Dr. Greg Beilman Department of Surgery, Box 11 University of Minnesota 420 Delaware St., NE Minneapolis, MN 55455 E-mail: [email protected]
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Response to ‘‘Power in the Study of Mortality and Necrotizing Soft Tissue Infections’’ Greg Beilman and Jeff Chipman
(number of debridements was one fewer in the non-HBO group, p ¼ 0.03). When we performed multivariable logistic regression evaluating the effects of various outcome variables on mortality, HBO use was not a significant factor in outcome. The two variables retained in the model were hypotension (odds ratio, 11) and immunosuppression (odds ratio, 28). We therefore conclude that in this study HBO did not result in improved outcome. We agree with the respondents that a prospective, randomized, multi-center trial that is powered appropriately to demonstrate a difference is necessary to define the role of HBO in treatment of NSTIs. In the absence of such a study, our work suggests that there is no benefit to use of HBO therapy for treatment of this condition. For now, the mainstays of therapy for NSTI remain rapid, complete, and repeated surgical debridement, thorough ICU care, and appropriate antibiotic treatment.
To the Editor: We appreciate the comments of Doctors Westgard and Adkinson with regard to our referenced study [1]. With respect to the assertion that the two groups were different, there is no question that patients admitted to two different hospitals will have potential differences biasing the results. For example, in our study, patients admitted to the University of Minnesota were more likely to have received a previous organ transplant (p ¼ 0.03) and possibly immunosuppressed (p ¼ 0.14), conditions that would be expected to increase mortality from this serious illness, whereas patients admitted to Hennepin County Medical Center (HCMC) had higher white blood cell counts (WBC) (p ¼ 0.01) and possibly higher admission glucose (p ¼ 0.06) and body mass index (BMI; p ¼ 0.07), conditions that have all been associated with higher risk. Differences such as these are likely to exist in any retrospective analysis. We did not include patients from HCMC who did not receive hyperbaric oxygen (HBO) in our analysis because we were not able to identify these patients with the medical record system available to us. We utilized an intention-to-treat analysis and therefore did not include full treatment with hyperbaric oxygen as a variable. We appreciate the respondents’ comments regarding other studies of HBO therapy in necrotizing soft tissue infections (NSTIs). They note, and we agree (and note in our discussion), that this literature suffers overall from a lack of power with respect to sample size. This is likely for at least two reasons: (1) NSTIs are an uncommon disease; and (2) for a variety of reasons, centers that have access to HBO therapy use HBO therapy. With respect to the assertion that patients in this study showed a trend toward improved mortality, we disagree. There was no significant benefit toward survival between the groups in our analysis (p ¼ 0.48); indeed the only outcome variable suggesting benefit favored the non-HBO group
Author Disclosure Statement No competing financial interests exist. Reference 1. George ME, Reuth N, Skarda DE, et al. Hyperbaric oxygen does not improve outcomes in patients with necrotizing soft tissue infections. Surg Infect 2009;10:21–28.
Address correspondence to: Dr. Greg Beilman Department of Surgery, Box 11 University of Minnesota 420 Delaware St., NE Minneapolis, MN 55455 E-mail: [email protected]
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