Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2000
The addition of dilute epinephrine produces equieffectiveness of bupivacaine enantiomers for cutaneous analgesia in the rat.
We investigated the effectiveness for cutaneous analgesia of bupivacaine (Bup) stereoisomers in male rats. As a model of infiltration anesthesia, inhibition of a nocifensive reflex by subcutaneous injection of 0.6 mL of different concentrations of R-, S-, and racemic-Bup was evaluated quantitatively by the fraction of times a pinprick failed to evoke a nocifensive motor response. R-Bup was more potent in the extent of block; however, S-Bup had a longer-lasting action at smaller doses. This significant difference was apparent when R-Bup and S-Bup were administered in equipotent doses of 0.06% and 0.075%, respectively. Co-injection of epinephrine (Epi) with these equipotent doses enhanced and prolonged the blocking effects of both Bup stereoisomers, although at dilutions of 1:100,000 to 1:1,000,000 Epi itself induced partial, transient analgesia. At 1:2,000,000 dilution, Epi alone had no analgesic effect; however, when co-injected with the shorter-acting R-Bup (0. 06%), Epi prolonged its blocking effect to equal the duration of block evoked by equipotent S-Bup (0.075%). We conclude R-Bup is more potent for cutaneous analgesia and that the longer duration of block by S-Bup probably originates from vasoconstrictor activity. ⋯ Here we show that the more potent optical R-isomer of bupivacaine (Bup) can be used at a smaller dose (80%) than the S-isomer of Bup to give equal pain relief of a skin prick. Although the analgesia from R-Bup is briefer than that from equipotent S-Bup solutions, the durations become equal when a very dilute solution of the vasoconstrictor epinephrine is mixed with the R-isomer. The resulting vasoconstriction thus reduces vascular drug uptake and peak blood levels of systemic drug, reducing potential toxicity.
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Anesthesia and analgesia · Aug 2000
Case ReportsNaloxone-resistant respiratory depression and neurological eye symptoms after intrathecal morphine.
We describe a case of neurological symptoms after the intrathecal use of an opioid. These symptoms were not reversible by the use of an opioid-antagonist.
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Anesthesia and analgesia · Aug 2000
Randomized Controlled Trial Clinical TrialSmall-dose clonidine prolongs postoperative analgesia after sciatic-femoral nerve block with 0.75% ropivacaine for foot surgery.
To evaluate the effects of adding small-dose clonidine to 0.75% ropivacaine during peripheral nerve blocks, 30 ASA physical status I and II patients undergoing hallux valgus repair under combined sciatic-femoral nerve block were randomly allocated in a double-blinded fashion to receive block placement with 30 mL of either 0.75% ropivacaine alone (group Ropivacaine, n = 15) or 0.75% ropivacaine plus 1 microg/kg clonidine (group Ropivacaine-Clonidine, n = 15). Hemodynamic variables, oxygen saturation, and levels of sedation, as well as the time required to achieve surgical block and time to first analgesic request, were recorded by a blinded observer. Time to surgical blockade required 10 min in both groups. Patients in the Ropivacaine-Clonidine group were more sedated than patients in the Ropivacaine group only 10 min after block placement. No differences in oxygen saturation and hemodynamic variables, degree of pain measured at first analgesic request, and consumption of postoperative analgesics were observed between the two groups. The mean time from block placement to first request for pain medication was shorter in group Ropivacaine (13.7 h; 25th-75th percentiles: 11. 8-14.5 h) than in group Ropivacaine-Clonidine (16.8 h; 25th-75th percentiles: 13.5-17.8 h) (P = 0.038). We conclude that adding 1 microg/kg clonidine to 0.75% ropivacaine provided a 3-h delay in first request for pain medication after hallux valgus repair, with no clinically relevant side effects. ⋯ This prospective, randomized, double-blinded study demonstrated that, when providing combined sciatic-femoral nerve block for hallux valgus repair, the addition of 1 microg/kg clonidine to 0.75% ropivacaine prolongs the duration of postoperative analgesia by 3 h, with only a slight and short-lived increase in the degree of sedation and no hemodynamic adverse effects.
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Anesthesia and analgesia · Aug 2000
Randomized Controlled Trial Clinical TrialFentanyl improves analgesia but prolongs the onset of axillary brachial plexus block by peripheral mechanism.
We evaluated the effects of fentanyl added to lidocaine for axillary brachial plexus block in 66 adult patients scheduled for elective hand and forearm surgery. In this double-blinded study, all patients received 40 mL of 1.5% lidocaine with 1:200,000 epinephrine, injected into the brachial plexus sheath using the axillary perivascular technique, and they were randomized into three groups. Group 1 was given lidocaine containing 2 mL of normal saline plus 2 mL of normal saline IV. Patients in Group 2 received lidocaine containing 100 microg fentanyl plus 2 mL of normal saline IV. Group 3 patients received lidocaine containing 2 mL of normal saline plus 100 microg fentanyl IV. Sensory and motor blockade were evaluated by using a pinprick technique and by measuring the gripping force, respectively. The success rate of sensory blockade for radial and musculocutaneous nerves and the duration of the sensory blockade significantly increased in Group 2 (323 +/- 96 min) as compared with Group 1 (250 +/- 79 min). However, onset time of analgesia was prolonged in every nerve distribution by adding fentanyl to brachial plexus block. IV fentanyl had no effect on the success rate, onset, or duration of blockade. We conclude that the addition of fentanyl to lidocaine causes an improved success rate of sensory blockade but a delayed onset of analgesia, although this may be accounted for by the decreased pH caused by the fentanyl. ⋯ It is still unclear whether the addition of a peripheral opioid is useful for nerve blockade in humans. Peripheral application of fentanyl to lidocaine for axillary brachial plexus blockade in this study provided an improved success rate of sensory blockade and prolonged duration.
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Anesthesia and analgesia · Aug 2000
Randomized Controlled Trial Comparative Study Clinical TrialComparison of epidural fentanyl versus epidural sufentanil for analgesia in ambulatory patients in early labor.
Epidural sufentanil, after a lidocaine and epinephrine test dose, provides adequate analgesia and allows for ambulation during early labor. Epidural fentanyl has not been evaluated in this setting. The current study was designed to determine whether there is an analgesic difference between epidural fentanyl and epidural sufentanil in laboring patients. Forty-six laboring nulliparous women, at <5-cm cervical dilation, who requested epidural analgesia were enrolled. After a 3-mL test dose of lidocaine with epinephrine, patients were randomized to receive either sufentanil 20 microg or fentanyl 100 microg. After administration of the analgesic, pain scores and side effects were recorded for each patient at 5, 10, 15, 20, and 30 min and every 30 min thereafter, by an observer blinded to the technique used. There were no demographic differences between the two groups. Pain relief was rapid for all patients. The mean durations of analgesia were similar between the sufentanil group (138 +/- 50 min) and the fentanyl group (124 +/- 42 min). Side effects were similar between the two groups. In early laboring patients, epidural fentanyl 100 microg, after a lidocaine and epinephrine test dose, provides analgesia comparable to that of sufentanil 20 microg. ⋯ In early laboring patients, epidural fentanyl 100 microg, after a lidocaine and epinephrine test dose, provides analgesia comparable to that of sufentanil 20 microg.