Preemptive Remifentanil Analgesia Modality (PRAM) using an Automated Smart-pump: A new paradigm for labor analgesia in women who do not receive neuraxial blockade.
Abstract Number: 14
Abstract Type: Original Research
Introduction: Current choices for opioid analgesia in women who cannot receive neuraxial analgesia are limited and have maternal and fetal implications. Recent evidence suggests that remifentanil offers many advantages especially as relates to fetal well being, but reports to date have not found the optimal dosing regimen. We present a potential new method that could change the way that remifentanil is administered for labor analgesia. Our new modality will predict when the next contraction will occur based on a mathematical analysis of the previous three contractions, and automatically boluses a dose of remifentanil 45 seconds prior to the time of the next anticipated contraction so that the pain relief matches the contraction.
Methods: The project has four components. First, a pilot to determine if a bolus of remifentanil administered between 45-60 seconds prior to a contraction will alleviate the pain. Second, to develop rules to electronically identify uterine contractions. Third, development of a smart algorithm, using uterine pressure data for an initial period, after which it should be capable of making real-time prediction on when the next contraction will occur. The algorithm being developed employs techniques in predictive data mining and fuzzy feedback control; it will ultimately be embedded in the fetal heart rate monitor in order to continuously and adaptively predict the next contraction in real time, as well as determine the remifentanil dose to be injected before each contraction. Fourth, a connection between the infusion device and the fetal heart rate monitor is being developed.
Results: In a small pilot, a bolus of 0.2 to 1 mcg per kg of remifentanil between 45-60 seconds before a contraction was found to relieve labor pain for contractions that last less than two minutes. The following rules have thus far been identified for identification of contractions: Rule 1: Uterine activity (UA) increases more than 15 within 5 seconds. Rule 2: UA increases more than 5 within 5 seconds, and does not decrease in the following 10 seconds. Rule 3: UA increases more than 2 within 5 seconds, increases more than 2 for the next 10 seconds, and does not decrease in the other following 10 seconds.
Discussion: The onset of analgesia following a bolus of remifentanil is approximately 30-45 seconds and lasts for approximately 3 minutes. Therefore, assuming relatively regular contractions, if a bolus of remifentanil is administered 45 seconds prior to contractions, optimal analgesia may be possible for the entire contraction. But how can one determine when a contraction will occur? We are currently refining artifact rejection and believe that a smart algorithm to predict onset of contractions is possible, and will allow for the administration of parenteral analgesia that will have maximal efficacy during contractions, little effect between contractions, and minimal impact on the fetus.