Determination of the Effective Volume of 0.125% Bupivacaine-fentanyl 5mcg/mL in Labour Epidurals
Condition: Pain
Study type: Interventional

Summary: 
      Different medications can be used as analgesics in labor epidurals. Bupivacaine is one of the
      most commonly used drugs for that purpose. The efficacy of a certain medication injected
      epidurally depends on the dose that is given. A certain dose can be administered in different
      concentrations, which will consequently mean different volumes. Studies have been done to
      determine volumes for different concentrations of bupivacaine. However, those studies fall
      short in the sense that this information cannot be readily applicable in clinical practice,
      as we don't use bupivacaine plain. The combination of bupivacaine and fentanyl or sufentanil
      is common practice, as it is well established that the opioids will reduce the concentration
      of local anesthetic required to produce optimal effect with the least side effects.

      This study is being planned to determine and compare the EV90 of the bupivacaine
      0.125%-fentanyl mixture for initiation of labor epidural analgesia, following the
      administration of the 2 different test doses (3cc of lidocaine 2% or 3cc of the bupivacaine
      0.125%-fentanyl mixture) used in our Department.
    

Detailed description: 
      Epidural administration of local anesthetics during labor produces analgesia, sympathetic
      block and motor block. The characteristics of the block depend on the volume and
      concentration of the local anesthetic that is used as well as the use of adjuncts(in our
      case: Fentanyl). Although many researchers have investigated the efficacy of different drugs
      at different concentrations, the volumes used have been arbitrary. There is limited data
      regarding the minimum volume that is necessary for a successful anesthetic for a given
      concentration of bupivacaine.

      This study is conducted as a prospective, randomized, up-down sequential allocation trial.
      The aim is to determine the minimum volume of 0.125% bupivacaine in combination with 5mcgr/ml
      fentanyl that will provide effective analgesia for 90% of parturients in the first stage of
      labor. The verbal numeric rating scale (VNRS) is used to rate the pain felt over the first 20
      minutes, where 0 is no pain and 10 is the worst pain imaginable. After 20 minutes, if the
      VNRS was greater than 1, the volume of the bupivacaine/fentanyl mixture was considered
      inadequate and additional volume of the mixture will be given.

      After the randomised test dose of either 3cc lidocaine 2% or 3cc of the bupivacaine/fentanyl
      mixture is given, the loading volume of the bupivacaine/fentanyl mixture will be given. The
      volume of the bupivacaine/fentanyl mixture for the first patient was chosen at 10 ml (This is
      the volume with which is generally started in standard practice), and the dose for each
      subsequent patient depends on the outcome of the previous injection. Doses will be increased
      or decreased in increments of 2 ml. If the previous response was ineffective, the next
      patient will receive 2 ml more than the last patient. If the response of the previous patient
      is effective, the biased coin up-and-down allocation design, which is used to cluster doses
      around EV90, will be applied to determine if the dose remains the same or decreases.

      40 patients will be included in each group within the study. The target volume, EV90, which
      is defined as the volume at which adequate response would occur in 90% of patients, will be
      estimated for each of the two test dose groups using Dixon and Mood method. The 95%
      confidence interval of EV90s will be estimated and based in comparing the EV90 between two
      groups. Isotonic Regression method will also be conducted to assess the EV90s. The side
      effects will also be summarized by the volume levels descriptively.
    

Intervention name(s): Bupivacaine-fentanyl; Lidocaine
Intervention type(s): Drug; Drug
Intervention description(s): 0.125% bupivacaine-fentanyl 5mcg/mL; 2% lidocaine
Other intervention name(s): Marcaine
Intervention MeSH terms: Lidocaine; Fentanyl; Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Epidural; Labor Analgesia; Bupivacaine; Minimum effective volume