title: An analysis of the need for anesthetic interventions with differing concentrations of labor epidural bupivacaine: an observational study.
abstract: BACKGROUND
  Labor epidural analgesia techniques using lower concentrations of bupivacaine are designed to maintain pain control with fewer side effects such as hypotension and motor block. However, the increase in sensation may allow breakthrough pain resulting in the need for additional interventions. We examined the number of interventions, both for analgesia and for treatment of side effects, required when using three concentrations of bupivacaine.
  
  
  METHODS
  Retrospective observational investigation examining 4493 women who received epidural analgesia during two periods. In the first period, higher concentrations of bupivacaine were used (0.125% and 0.0625%, both with fentanyl 2 microg/mL). In the second period, a very low concentration was used (0.04% plus fentanyl 1.7 microg/mL and epinephrine 1.7 microg/mL). Outcomes were compared using univariate tests, and multivariate Poisson regression was used to identify independent factors influencing interventions.
  
  
  RESULTS
  The frequencies of interventions were similar for women receiving bupivacaine concentrations of 0.04% (1.4+/-2.0) and 0.125% (1.5+/-2.0), while women receiving the 0.0625% solution required more interventions (1.8+/-2.3; P<0.001). Women who received 0.04% or 0.0625% bupivacaine required more treatment of breakthrough pain (P<0.002), while those receiving 0.125% bupivacaine required more treatment for hypotension and motor block (P<0.05). Multivariate Poisson regression showed that duration of treatment, maternal age and body mass index were independent factors for the number of interventions.
  
  
  CONCLUSIONS
  Neither the total interventions nor intervention rate per hour varied significantly with the concentrations of bupivacaine used in this study. Lower concentrations produced fewer side effects including hypotension, while the higher concentration resulted in less breakthrough pain.
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA. phess@bidmc.harvard.edu
authors.forename: P E
authors.initials: PE
authors.lastname: Hess
authors.forename: S D
authors.initials: SD
authors.lastname: Pratt
authors.forename: N E
authors.initials: NE
authors.lastname: Oriol
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural / Q000009:adverse effects / Q000379:methods*; D016362:Analgesia, Obstetrical / Q000009:adverse effects / Q000379:methods*; D016058:Analgesia, Patient-Controlled; D019162:Anesthetics, Combined / Q000008:administration & dosage* / Q000737:chemistry; D002045:Bupivacaine / Q000008:administration & dosage* / Q000737:chemistry; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage; D006801:Humans; D007022:Hypotension / Q000139:chemically induced / Q000628:therapy; D007743:Labor, Obstetric; D011247:Pregnancy; D012044:Regression Analysis; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D019162:Anesthetics, Combined; D005283:Fentanyl; D002045:Bupivacaine