Same side-effect profile Different side-effect profileīupivacaine infusion Epidural vs IV Fentanylġ 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20īupivacaine infusion with the addition of IV vs. Plasma levels identical, analgesia depends on plasma levels epidural)Ģ0ml of bupivacaine and 60mcg IV fentanyl vs 20ml bupivacaine and 3mcg/ml fentanyl (60mcg/20ml)įentanyl dose constant in both IV and epidural groups MLAC bupivacaine and IV fentanyl 0.064% (95% CI 0.049Ġ.080)% MLAC of bupivacaine and epidural fentanyl 0.034% (95%Įpidural fentanyl increase analgesic potency of bupivacaine by 1.88 compared to IV doseĮpidural fentanyl increased occurrence of pruritusĮpidural fentanyl increased occurrence of pruritus Epidural fentanyl had higher cephalad spread of blockĪll Suggesting Primarily a Spinal Site of Actionįentanyl Site of ActionSystemic site of action Spinal site of action P = 0.0008Ropivacaine 66% as potent as bupivacaine in producing motor blockĢ0mL bolus, VAS of 10 or less (0-100) in 30 min CPC: 0.43% (95 CI 0.29-0.56) CPC with 3mcg/ml fentanyl: 0.26% (95% CI 0.2-0.32)ģmcg/ml (60mcg) of fentanyl leading to 0.17% reduction in CPC MLAC.1.65 times increase in relative potency 40% dose reductionīupivacaine andFentanyl (IV vs. Ropivacaine is 60% as potent as Bupivacaine Ropivacaine is 60% as potent as Bupivacaine No difference in motor blockade, side effectsīupivacaine vs. spontaneous labor)Ĭenter Only valid in labor epidural settingīupivacaine vs. Late labor (5cm cervical dilation)MLAC bupivacaine 0.140%ĭilation Values depend on patient population and the studyĬenter (parity, induction vs.
MLAC increases with labor progressionEarly labor (2cm cervical dilation) Possible variations in dose-response curveĮD95 would be more clinically useful A snap-shot of labor pain at that particular cervical MLAC Limitations Designed only to obtain ED50
MLAC of lidocaine was 0.37% (95% CI 0.32-0.42) (Dixon and Massey formula) MLAC- Bupivacaine/Lidocaine MLAC of bupivacaine was 0.065% (95% CI 0.045-0.085) Rejected: Unresponsive to initial or rescue dose (segmental pain, unilateral block etc) Ineffective: Unable to achieve VAPS of 10 or below but responsive to predetermined rescue dose MLACFirst Stage of Labor epidural requestCervical dilation not exceeding 5cmLumbar epidural, LOR saline (2ml)No test dose20mL bolus of solution over 5 minutesVAPS of 10 or below (0-100 range) within 60 minUp-Down sequential allocationĮffective: Achieve VAPS of 10 or below (0-100 range) Minimum Local Anesthetic Concentration (MLAC)Effective concentration in 50% of patients in 1st stage of labor (EC50)Clincial model to allow determination of relative potency of LAsAllow measurement of LA sparing effects of other drugs May contribute to maternal neurologic injury from malpositioning Why not just Local AnestheticsLocal anesthetics (LA) alone associated with Motor blockMotor Block associated with:
Increased instrumental deliverydecreased maternal satisfaction Why not just Local AnestheticsLocal anesthetics (LA) alone associated with Motor blockMotor block associated with: Why not just Local AnestheticsLocal anesthetics (LA) alone associated with Motor block Goals:Review Concept of MLACLocal anesthetic efficacyLocal anesthetic sparing effects: Pedram Aleshi MDThe Changing Practice of Anesthesia Labor Epidural:Local Anesthetics and Beyond