Articles: analgesia.
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Acta Anaesthesiol Scand · Oct 1988
Pharmacokinetics and protein binding of bupivacaine in postoperative epidural analgesia.
We describe a method, which is both specific and rapid, for the measurement of bupivacaine concentrations in plasma using high-performance liquid chromatography. Bupivacaine plasma concentrations, pharmacokinetics and protein binding in the postoperative period were investigated in seven patients (58-77 years old) following hip surgery. Postoperative analgesia was achieved by epidural bolus injections of 25 mg bupivacaine 0.25% every 6 h. ⋯ The free fraction decreased from 5.4% preoperatively to 2.7% in the postoperative period (P less than 0.05). Changes in plasma protein binding of bupivacaine and changes in plasma levels of the acute phase reactant alpha-1-acid glycoprotein were correlated (r = 0.8, P less than 0.05). Difficulties in interpreting the elimination parameters following epidural administration are discussed, leading to the conclusion that the derivation of dosage regimens from kinetic parameters following epidural administration is not warranted.
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Pharmacol. Biochem. Behav. · Oct 1988
Tolerance to tobacco smoke- and nicotine-induced analgesia in rats.
Acute exposure of male Sprague-Dawley rats to either nicotine or tobacco smoke results in analgesia as measured by tail-flick latencies. A second treatment, 24 hr after the first, failed to produce analgesia, thereby demonstrating the rapid development of tolerance. The restraint which was a necessary part of the tobacco smoke exposure also produced analgesia, although of a more transient nature and lesser magnitude than that resulting from tobacco smoke exposure. ⋯ Additionally, long-term tobacco smoke exposure resulted in an increased tail-flick latency when the animals had been withdrawn from tobacco smoke for 24 hr, suggesting the development of tolerance. The data also suggest a differential time course for the development of tolerance and dependence. This is the first report that addresses the effect of acute and chronic tobacco smoke exposure on pain sensitivity.
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The pressures used in vivo to administer epidural doses of local anaesthetic were recorded for 16- and 18-gauge multihole catheters. Observations were made on 10 patients in labour for each catheter gauge. ⋯ For each size of catheter, with increasing pressure, flow appeared at the proximal, then the middle, and finally the distal hole. This emphasises that the effect of epidural doses can vary depending on the pressure of injection, especially if the catheter had been passed partially through the dura.