The influence of posture on the effectiveness of local anesthetics of clinical dose for epidural labor analgesia.
Abstract Number: T 28
Abstract Type: Original Research
【Introduction】 Sacral nerve block (S2-S4) is necessary to control pain during second labor stage. Epidural injection of local anesthetics with supine position leads to the spread of analgesia in the cephalad direction. This may inhibit contraction of the uterus and restrict the use of local anesthetics. The optimal situation is efficient sacral nerve block without the spread of analgesia in the cephalad direction. We hypothesized that extended sitting after local anesthesia would prevent the spread of analgesia in the cephalad direction.
【Method】 Following IRB approval and informed consent, 24 parturients scheduled for epidural labor anesthesia were enrolled in this prospective study. The patients were divided into 2 groups; sitting position for 30min (Sit 30) and supine position for 30min (Sup 30) after epidural dose. An epidural catheter was inserted at L3/4. Epidural injection was performed with 0.06% levobupivacaine which contains 2μg/ml fentanyl 60min after test dose with 2% lidocaine 3ml as sitting position. We confirmed analgesic area by pin-prick test 30 min after epidural injection. Measurement was taken up to S2. A case of unilateral block was defined as a negative pin-prick test on less than 3 analgesic segments. Statistical analysis was performed using Tukey-kramer test for demographic data and Scheffe test for analgesia. P<0.05 was considered statistically significant.
【Results】Two patients in Sit 30 group and one patient in Sup 30 group were excluded as unilateral block. Demographic data was similar in each group. There was less spread of analgesia in the cephalad direction in Sit 30 compared to Sup 30. There was no significant difference in the spread of analgesia in the caudad direction among the groups. Analgesic segments of Sit 30 were significantly narrow while Sup 30 analgesic segments were significantly wide. [figiure1]
【Discussion】 Several studies suggest that posture has no significant effect on the analgesic level1,2. In our study, extended sitting after local anesthesia prevented the spread of analgesia in the cephalad direction. However, this effect was limited when sitting time was short. Changing posture from sitting to supine position may result in wider spread of analgesia.
【Conclusion】 Supine position may result in superior and wider spread of local anesthetics of clinical dose for epidural labor analgesia.
【References】 1. Br J Anaesth 1983;55(4):303-7, 2. Int J Obstet Anesth 1993;2(3):134-6