Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of 0.5% ropivacaine and 0.5% bupivacaine for epidural anesthesia in patients undergoing lower-extremity surgery.
Ropivacaine is an amide local anesthetic structurally related to, but appearing less cardiotoxic, than bupivacaine. The authors' investigation was designed in a randomized, double-blind fashion to compare the clinical effectiveness of ropivacaine and bupivacaine in patients undergoing lower-extremity surgery. Forty-five patients were randomized to receive 20 ml of 0.5% ropivacaine or bupivacaine. ⋯ Cardiovascular changes, incidence of tourniquet pain, and the amounts of supplemental medications necessary were also similar between groups. The authors found 0.5% ropivacaine and bupivacaine to be clinically similar in both sensory- and motor-blocking characteristics, with the exception that bupivacaine produced a blockade of slightly longer duration. Because ropivacaine is reported to be less cardiotoxic than bupivacaine in animal studies, the similarity of clinical epidural anesthesia may make ropivacaine the preferred agent.
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Randomized Controlled Trial Comparative Study Clinical Trial
A double-blind assessment of segmental sensory changes with epidural fentanyl versus epidural saline in patients undergoing extracorporeal shock-wave lithotripsy.
Segmental changes to pin prick and cold stimuli were tested in a double-blind manner in pain-free patients scheduled for extracorporeal shockwave lithotripsy (ESWL). Fifty patients were randomly allocated to receive either epidural fentanyl (100 micrograms in 10 ml normal saline) or 10 ml epidural normal saline. In a further 25 patients an epidural catheter was inserted but no solution injected. ⋯ There were no significant differences between fentanyl and normal saline groups in the number of patients reporting sensory changes to pin prick, rate of onset of these changes, or segmental level. For cold stimuli, more patients in the fentanyl group than in the normal saline group reported a change (16 vs. 8; P = 0.02) but the segmental level was similar. The effect of normal saline as a diluent in epidurally administered opioids may be of clinical importance.
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Randomized Controlled Trial Clinical Trial
Continuous epidural infusion of 0.0625% bupivacaine-0.0002% fentanyl during the second stage of labor.
A randomized, double-blind, placebo-controlled study was performed to evaluate the analgesic efficacy and influence of continuing an epidural infusion of 0.0625% bupivacaine-0.0002% fentanyl during the second stage of labor in nulliparous women. When the cervix was fully dilated, coded study solution was substituted for the known bupivacaine-fentanyl solution. The study solution for 29 patients was 0.0625% bupivacaine-0.0002% fentanyl; 34 patients received saline placebo. ⋯ Among the women who delivered vaginally, eleven of 28 (39%) women in the bupivacaine-fentanyl group, versus five of 34 (15%) in the saline-placebo group, had surgical perineal anesthesia for vaginal delivery (P less than .05). Six of 28 (21%) women in the bupivacaine-fentanyl group, and five of 34 (15%) in the saline-placebo group, underwent instrumental vaginal delivery (P = NS). The median duration of the second stage of labor was 53 min (range = 5-283) in the bupivacaine-fentanyl group, and 63 min (range = 16-181) in the saline-placebo group (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
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Impulse block by LA occurs through the inhibition of voltage-gated Na+ channels. Both protonated and neutral LAs can inhibit Na+ channels though interference with the conformational changes that underly the activation process (the sequence of events that occurs as channels progress from the closed resting state to the open conducting state). The occlusion of open channels contributes little to the overall inhibition. ⋯ If one accounts for the membrane-concentrating effects of LA hydrophobicity that are expressed as membrane: buffer partition coefficients equal to 10(2)-10(4), then the apparent LA affinities are low. The equilibrium dissociation constants calculated on the basis of free drug in the membrane are 1-10 mM, with a correspondingly weak binding to the inhibitory LA site. The stereospecificity of LA action is also relatively nonselective, suggesting a loose fit between ligand and binding site.(ABSTRACT TRUNCATED AT 400 WORDS)
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Randomized Controlled Trial Clinical Trial
Labor analgesia with epidural bupivacaine plus fentanyl: enhancement with epinephrine and inhibition with 2-chloroprocaine.
Epidural injection of drug combinations may decrease toxicity by decreasing the dose of each component, but may also result in detrimental drug interactions. In this study interactions among bupivaciane, fentanyl, epinephrine, 2-chloroprocaine, and lidocaine for epidural analgesia during labor were examined. In part 1 of the study, healthy parturients received in a random manner either 10 ml of 0.25% bupivacaine with 5 micrograms/ml fentanyl (n = 50), or 10 ml of this combination with 3.33 micrograms/ml freshly added epinephrine (n = 50). ⋯ The lidocaine test dose group had a greater duration of analgesia than the 2-chloroprocaine test dose group (median duration of 164 vs. 91 min, P less than 0.05). The authors conclude that the addition of epinephrine 3.33 micrograms/ml significantly increases the duration of analgesia obtained from 0.25% bupivacaine with 5 micrograms/ml fentanyl. However, prior injection of 2-chloroprocaine, but not lidocaine, significantly decreases the duration of analgesia achieved with this BFE mixture.