JOURNAL CLUB JOURNAL CLUB
Response to Journal Club: The Impact of Body Mass Index on Hospital Stay and Complications After Spinal Fusion Jamal McClendon Jr, MD Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois Correspondence: Jamal McClendon Jr, MD, Department of Neurological Surgery, Northwestern Memorial Hospital, 676 N. St. Clair, Suite 2210, Chicago, IL 60611. E-mail: [email protected] Copyright © 2014 by the Congress of Neurological Surgeons.
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e would like to thank Dr Payne and colleagues for their critical review of our article. Dr Payne and colleagues provided an excellent Journal Club submission. My coauthors and I appreciate the analysis provided in this Journal Club regarding our experience looking at body mass index (BMI) as a predictive factor for hospital stay and complications. Obesity and increased BMI are major healthcare issues and common risk factors for surgical complications based on medical comorbidities. Thus, we sought to evaluate BMI as an independent predictor of hospital stay and complications. The Journal Club authors have raised several important points and helpful suggestions. Our study was designed to investigate a subset of spine patients (those receiving fusion of $5 levels) to determine associations between BMI categories and adverse patient outcomes. The 2 outcome measures we were interested in were hospitalization stay and complications at 1 year. In our multivariate analysis, we treated BMI differently on the basis of our bivariate analysis. The study was not powered to categorize BMI into all 5 categories because some effects of weight would be lost with this scheme of categorization. When BMI was placed as a continuous variable in the regression analysis, it was not significant. The reason is that there was a hyperbolic relationship with hospitalization stay. Underweight and overweight patients had longer surgeries and longer intensive care unit stays on bivariate analysis, so they were categorized together in the multivariate linear regression for hospital stay as BMI category (ideal vs not ideal). Furthermore, underweight individuals had the highest troponin elevation. We felt that these variables have relevance to hospital stay. However, being underweight did not affect complication rates at 1 year. Our bivariate analysis showed significant increases in complications in the obese and morbidly obese. Because bivariate analysis demonstrated BMI
602 | VOLUME 75 | NUMBER 5 | NOVEMBER 2014
.30 kg/m2 as significant, it showed significance in logistic regression when categorized this way. Bivariate analysis (t tests, analysis of variance, Kruskal-Wallis, x2, Pearson correlation) was performed on all individual variables and outcomes. Kruskal-Wallis examined nonparametric variables. We thank Dr Payne and colleagues for the comment on ordinal data. We should have reported it as central tendency and dispersion in our tables. We built our multivariate models using a priori knowledge and bivariate analysis results, not on automatic stepwise inclusion or exclusion criteria. We agree with the Journal Club authors that this study carries inherent limitations, many of which are a result of being a retrospective study. In addition, we included both surgeries for individuals who underwent staged surgeries so as not to miss a potential complication. However, as mentioned by the Journal Club authors, there is no way to decipher a systematic difference between this population and those who underwent single operations. Thus, this creates another bias to the study. We also had a number of patients who did not seek 2-year followup, as mentioned by the Journal Club authors. Even though our primary focus was on 1-year complications, we wanted to include the number of individuals with 2-year follow-up to be transparent. This article provides further appreciation of the challenges the spinal surgeon faces when dealing with an obese patient in need of a fusion of $5 levels. This article establishes a basis for improvement in presurgical condition with operative intervention despite weight, if deemed appropriate, and provides insight into the importance of preoperative discussion and potential planning for postoperative care. Prospective studies in the future should focus on more weight loss strategies in this patient population. Disclosure The author has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
Response to Journal Club: The Impact of Body Mass Index on Hospital Stay and Complications After Spinal Fusion Jamal McClendon Jr, MD Department of Neurological Surgery, Northwestern Memorial Hospital, Chicago, Illinois Correspondence: Jamal McClendon Jr, MD, Department of Neurological Surgery, Northwestern Memorial Hospital, 676 N. St. Clair, Suite 2210, Chicago, IL 60611. E-mail: [email protected] Copyright © 2014 by the Congress of Neurological Surgeons.
W
e would like to thank Dr Payne and colleagues for their critical review of our article. Dr Payne and colleagues provided an excellent Journal Club submission. My coauthors and I appreciate the analysis provided in this Journal Club regarding our experience looking at body mass index (BMI) as a predictive factor for hospital stay and complications. Obesity and increased BMI are major healthcare issues and common risk factors for surgical complications based on medical comorbidities. Thus, we sought to evaluate BMI as an independent predictor of hospital stay and complications. The Journal Club authors have raised several important points and helpful suggestions. Our study was designed to investigate a subset of spine patients (those receiving fusion of $5 levels) to determine associations between BMI categories and adverse patient outcomes. The 2 outcome measures we were interested in were hospitalization stay and complications at 1 year. In our multivariate analysis, we treated BMI differently on the basis of our bivariate analysis. The study was not powered to categorize BMI into all 5 categories because some effects of weight would be lost with this scheme of categorization. When BMI was placed as a continuous variable in the regression analysis, it was not significant. The reason is that there was a hyperbolic relationship with hospitalization stay. Underweight and overweight patients had longer surgeries and longer intensive care unit stays on bivariate analysis, so they were categorized together in the multivariate linear regression for hospital stay as BMI category (ideal vs not ideal). Furthermore, underweight individuals had the highest troponin elevation. We felt that these variables have relevance to hospital stay. However, being underweight did not affect complication rates at 1 year. Our bivariate analysis showed significant increases in complications in the obese and morbidly obese. Because bivariate analysis demonstrated BMI
602 | VOLUME 75 | NUMBER 5 | NOVEMBER 2014
.30 kg/m2 as significant, it showed significance in logistic regression when categorized this way. Bivariate analysis (t tests, analysis of variance, Kruskal-Wallis, x2, Pearson correlation) was performed on all individual variables and outcomes. Kruskal-Wallis examined nonparametric variables. We thank Dr Payne and colleagues for the comment on ordinal data. We should have reported it as central tendency and dispersion in our tables. We built our multivariate models using a priori knowledge and bivariate analysis results, not on automatic stepwise inclusion or exclusion criteria. We agree with the Journal Club authors that this study carries inherent limitations, many of which are a result of being a retrospective study. In addition, we included both surgeries for individuals who underwent staged surgeries so as not to miss a potential complication. However, as mentioned by the Journal Club authors, there is no way to decipher a systematic difference between this population and those who underwent single operations. Thus, this creates another bias to the study. We also had a number of patients who did not seek 2-year followup, as mentioned by the Journal Club authors. Even though our primary focus was on 1-year complications, we wanted to include the number of individuals with 2-year follow-up to be transparent. This article provides further appreciation of the challenges the spinal surgeon faces when dealing with an obese patient in need of a fusion of $5 levels. This article establishes a basis for improvement in presurgical condition with operative intervention despite weight, if deemed appropriate, and provides insight into the importance of preoperative discussion and potential planning for postoperative care. Prospective studies in the future should focus on more weight loss strategies in this patient population. Disclosure The author has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
www.neurosurgery-online.com
Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited
