title: Increasing body mass index predicts increasing difficulty, failure rate, and time to discovery of failure of epidural anesthesia in laboring patients.
abstract: OBJECTIVE
  Obese parturients both greatly benefit from neuraxial techniques, and may represent a technical challenge to obstetric anesthesiologists. Several studies address the topic of obesity and neuraxial analgesia in general, but few offer well described definitions or rates of "difficulty" and "failure" of labor epidural analgesia. Providing those definitions, we hypothesized that increasing body mass index (BMI) is associated with negative outcomes in both categories and increased time needed for epidural placement.
  
  
  METHODS
  Single center retrospective chart review.
  
  
  METHODS
  Labor and Delivery Unit of an inner city academic teaching hospital.
  
  
  METHODS
  2485 parturients, ASA status 2 to 4, receiving labor epidural analgesia for anticipated vaginal delivery.
  
  
  METHODS
  None.
  
  
  METHODS
  We reviewed quality assurance and anesthesia records over a 12-month period. "Failure" was defined as either inadequate analgesia or a positive test dose, requiring replacement, and/or when the anesthesia record stated they failed. "Difficulty" was defined as six or more needle redirections or a note indicating difficulty in the anesthesia record.
  
  
  RESULTS
  Overall epidural failure and difficulty rates were 4.3% and 3.0%, respectively. Patients with a BMI of 30kg/m2or higher had a higher chance of both failure and difficulty with two and almost three fold increases, respectively. Regression analysis indicated that failure was best predicted by BMI and less provider training while difficulty was best predicted by BMI. Additionally, increased BMI was associated with increased time of discovery of epidural catheter failure.
  
  
  CONCLUSIONS
  Obesity is associated with increasing technical difficulty and failure of neuraxial analgesia for labor. Practitioners should consider allotting extra time for obese parturients in order to manage potential problems.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, 9200 W Wisconsin Ave, Milwaukee, WI 53226, USA. Electronic address: akula@mcw.edu.
authors.forename: Ayse O
authors.initials: AO
authors.lastname: Kula
authors.affiliation: Tennessee Valley Healthcare System VA Medical Center, 1310 24(th) Avenue South, Nashville, TN 37212, United States; Department of Anesthesiology, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN 37232-2520, United States; Department of Pharmacology, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN 37232-2520, United States.
authors.forename: Matthias L
authors.initials: ML
authors.lastname: Riess
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, 9200 W Wisconsin Ave, Milwaukee, WI 53226, USA.
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: Ellinas
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural / Q000009:adverse effects* / Q000295:instrumentation; D016362:Analgesia, Obstetrical / Q000009:adverse effects* / Q000295:instrumentation; D000767:Anesthesia, Epidural / Q000009:adverse effects* / Q000295:instrumentation; D000773:Anesthesia, Obstetrical / Q000009:adverse effects* / Q000295:instrumentation; D015992:Body Mass Index; D057785:Catheters; D036861:Delivery, Obstetric / Q000009:adverse effects*; D005260:Female; D006801:Humans; D009765:Obesity / Q000503:physiopathology*; D059408:Pain Management / Q000009:adverse effects; D011247:Pregnancy; D011248:Pregnancy Complications / Q000503:physiopathology*; D012189:Retrospective Studies; D013997:Time Factors; D017211:Treatment Failure; D016896:Treatment Outcome
keywords: BMI; Cesarean section; Dural puncture; Inadequate analgesia; Labor epidural; Morbid obesity; Neuraxial; Quality assurance