We thank Melloni1 for his positive appreciation of the guidelines of the European Society of Anaesthesiology on the preoperative evaluation of the adult patient undergoing noncardiac surgery.2 As specifically stated in the guidelines, these recommendations are based on the best available evidence from published reports in the literature.2 For the current guidelines, this best available evidence was obtained from a MEDLINE and EMBASE search for the period 2000 to June 2010. Best available evidence may change over time, among others because new studies provide new information and insights. For these reasons, guidelines and recommendations need regular updating.
Our current recommendations on obesity are as follows.2 First, preoperative assessment of obese patients includes at least clinical evaluation, Berlin or STOP questionnaire, ECG, polysomnography and/or oximetry (grade of recommendation: D). Second, laboratory examination is indicated in obese patients in order to detect pathological glucose/HbA1C concentrations and anaemia (grade of recommendation: D). Third, neck circumferences of at least 43 cm as well as a high Mallampati score are predictors for a difficult intubation in obese patients (grade of recommendation: D). Fourth, use of CPAP perioperatively may reduce hypoxic events in obese patients (grade of recommendation: D).
The comments of Melloni do not refer to these recommendations but to the summary of the available evidence where we reported on a retrospective study in 332 patients from a single centre.3 As correctly analysed by Melloni, this study suffers from a number of methodological flaws; therefore, this contribution was graded with a level of evidence 2-. This grading refers to case–control or cohort studies with a high risk of confounding or bias and a significant risk that the relationship was not causal.
Recently, a study by Yadla et al.4 has also addressed the question of a relation between obesity and the incidence of complications after spine surgery. This study involved a prospective assessment of perioperative spine surgery complications in a cohort of 87 consecutive patients undergoing elective surgery for degenerative thoracolumbar disorder. The authors identified type of surgery, hypertension and age as risk factors for postoperative complications, whereas the presence of obesity was not associated with complications. Although of interest, this study also suffers from major methodological limitations. Certainly for an outcome study, the very limited number of patients included is a major concern. The authors failed to provide a sample size calculation and/or a report of the power of the study. In addition, a selection of patients was applied with the aim of eliminating potential confounding factors such as co-morbidity and urgency of the intervention. These factors demonstrate that this particular study carries an important risk of bias and would also be qualified as a report with a level of evidence 2-. In other words, even with these additional, more recent data, the potential relation between obesity and postoperative morbidity remains to be definitively established. It is obvious that well performed studies on the topic are urgently needed.
Of note, a very recent contribution by Kalanithi et al.5 has shown that morbid obesity increased cost and complication rates in spinal arthrodesis. In this study, a retrospective cross-sectional analysis of all spine fusions in California over a time period of 5 years was performed. A total of 84 607 admissions were found, 1455 of whom were morbidly obese. In the latter patients, a two-fold higher complication rate (13.6 vs. 6.9%) was observed. These were cardiac, pulmonary and renal complications as well as wound infections and others. On multivariate analysis, morbid obesity was the most significant predictor for complications in the groups with anterior cervical as well as lumbar fusion. Although the study also has its limitations (such as a retrospective study design and measurement of in-hospital events only), these data indicate that in a large cohort of patients, obesity has a negative impact on perioperative morbidity and challenge the finding of Yadla et al.4 and the comments of Melloni.1
In conclusion, we thank Melloni for his comments. The production and writing of guidelines on clinical practice strategies is a dynamic process, which also necessitates the input of practitioners involved in the daily preoperative evaluation and assessment of surgical patients. This input is of utmost importance, not only for providing new data and evidence but also for commenting on how guidelines are applicable in daily practice. As such, this reply is also a new call for the anaesthesiological, surgical and medical community inside and outside Europe to comment on the different issues addressed in the guidelines. Only then, evidence-based medicine, and in this particular case recommendations on the preoperative evaluation of the adult patient undergoing noncardiac surgery, can evolve and improve.
1. Melloni C. Obesity is not a risk factor for patients undergoing spinal surgery. Eur J Anaesthesiol
2. De Hert S, Imberger G, Carlisle J, et al. Preoperative evaluation of the adult patient undergoing noncardiac surgery: guidelines from the European Society of Anaesthesiology. Eur J Anaesthesiol
3. Patel N, Bagan B, Vadera S, et al. Obesity and spine surgery: relation to perioperative complications. J Neurosurg Spine
4. Yadla S, Malone J, Campbell PG, et al. Obesity and spine surgery: reassessment based on a prospective evaluation of perioperative complications in elective degenerative thoracolumbar procedures. Spine J
5. Kalanithi PS, Arrigo R, Boakye M. Morbid obesity increases cost and complication rates in spinal arthrodesis. Spine
(Phila Pa 1976) 2011. [Epub ahead of print]