title: Influence of obesity on surgical regional anesthesia in the ambulatory setting: an analysis of 9,038 blocks.
abstract: BACKGROUND
  Regional anesthesia is increasing in popularity for ambulatory surgical procedures. Concomitantly, the prevalence of obesity in the United States population is increasing. The objective of the present investigation was to assess the impact of body mass index (BMI) on patient outcomes after ambulatory regional anesthesia.
  
  
  METHODS
  This study was based on prospectively collected data including 9,038 blocks performed on 6,920 patients in a single ambulatory surgery center. Patients were categorized into three groups according to their BMI (<25 kg/m2, 25-29 kg/m2, > or =30 kg/m2). Block efficacy, rate of acute complications, postoperative pain (at rest and with movement), postoperative nausea and vomiting, rate of unscheduled hospital admissions, and overall patient satisfaction were assessed. Linear and logistic multivariable analyses were used to obtain the risk-adjusted effect of BMI on these outcomes.
  
  
  RESULTS
  Of all patients 34.8% had a BMI <25 kg/m2, 34.0% were overweight (BMI 25-29 kg/m2), and 31.3% were obese (BMI > or = 30 kg/m2). Patients with BMI > or =30 kg/m2 were 1.62 times more likely to have a failed block (P = 0.04). The unadjusted rate of acute complications was higher in obese patients (P = 0.001). However, when compared with patients with a normal BMI, postoperative pain at rest, unanticipated admissions, and overall satisfaction were similar in overweight and obese patients.
  
  
  CONCLUSIONS
  The present investigation shows that obesity is associated with higher block failure and complication rates in surgical regional anesthesia in the ambulatory setting. Nonetheless, the rate of successful blocks and overall satisfaction remained high in patients with increased BMI. Therefore, overweight and obese patients should not be excluded from regional anesthesia procedures in the ambulatory setting.
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA. niels006@mc.duke.edu
authors.forename: Karen C
authors.initials: KC
authors.lastname: Nielsen
authors.forename: Ulrich
authors.initials: U
authors.lastname: Guller
authors.forename: Susan M
authors.initials: SM
authors.lastname: Steele
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Klein
authors.forename: Roy A
authors.initials: RA
authors.lastname: Greengrass
authors.forename: Ricardo
authors.initials: R
authors.lastname: Pietrobon
mesh_terms: D000328:Adult; D000368:Aged; D000556:Ambulatory Surgical Procedures / Q000009:adverse effects; D000765:Anesthesia, Conduction / Q000009:adverse effects; D015992:Body Mass Index; D004558:Electric Stimulation; D023381:Endpoint Determination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects; D009765:Obesity / Q000150:complications*; D010147:Pain Measurement; D011446:Prospective Studies; D018570:Risk Assessment; D017211:Treatment Failure