The effect of intravenous magnesium therapy on the duration of intrathecal fentanyl labor analgesia
International Journal of Obstetric Anesthesia , 06/29/2012
Sullivan JT et al. - Intravenous magnesium therapy at doses typically used for seizure prophylaxis in preeclampsia did not influence the duration of intrathecal fentanyl labor analgesia.Methods
- Thirty-four nulliparous parturients having labor induced for preeclampsia and receiving intravenous magnesium therapy were recruited.
- Thirty-four nulliparous patients having labor induced for elective or medical reasons were recruited as controls.
- At request for analgesia, baseline serum magnesium levels were obtained and combined spinal–epidural analgesia was initiated with intrathecal fentanyl 25µg.
- Before injection of fentanyl, a sample of cerebrospinal fluid was obtained for magnesium assay.
- An epidural catheter was sited but no additional medications were administered until the second request for analgesia.
- The primary outcome was duration of intrathecal fentanyl analgesia.
- There was no difference in the median duration of analgesia between the magnesium [79min (95% CI 76 to 82)] and control groups [69min (95% CI 56 to 82)] (difference between medians: 10min (95% CI-4 to 21min; P=0.16).
- There was neither a relationship between the serum and cerebrospinal fluid magnesium concentrations nor the cerebrospinal magnesium concentration and duration of intrathecal fentanyl analgesia.