Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1992
Influence of volume on the spread of local anesthetic-methylene blue solution after injection for intercostal block.
The purpose of this study was to evaluate the influence of the volume of methylene blue-local anesthetic on the spread of the injectate along the costal pleura. Twenty patients undergoing elective thoracotomy were studied. Twelve patients received intercostal nerve injection with 10 mL of 0.5% bupivacaine with methylene blue (10-mL group), and eight patients received 5 mL of 0.5% bupivacaine with methylene blue (5-mL group). ⋯ In the 10-mL group, eight patients had bupivacaine-methylene blue spread to two intercostal spaces, three patients to three intercostal spaces, and one patient to four intercostal spaces. In the 5-mL group, seven patients had bupivacaine methylene blue spread confined to one intercostal space and one patient to two intercostal spaces. We conclude that a potential anatomic space exists between the costal pleura and the internal intercostal muscle and that the spread of local anesthetic after intercostal nerve block injection is volume dependent.
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Anesthesia and analgesia · Sep 1992
Interscalene brachial plexus block for shoulder surgery: a proximal paresthesia is effective.
This study was designed to determine whether the location of paresthesias is related to the success of interscalene blocks in providing anesthesia for shoulder surgery. Interscalene blocks were performed in 45 patients presenting for elective shoulder surgery. Interscalene injections of 33-55 mL of 1.5% mepivacaine with epinephrine were performed after the first elicited paresthesia to the shoulder, arm, forearm, or hand. ⋯ The time-course of onset of motor block as evaluated at the shoulder and elbow was not different between patients with shoulder paresthesias and those with more distal paresthesias. Handgrip strength was quantitatively evaluated with a dynamometer, and both paresthesia groups showed similar decrements in hand strength except at the end of the measurement period, when patients with distal paresthesias had a significantly weaker handgrip than patients with shoulder paresthesias. We recommend that paresthesias to the shoulder be accepted in performing interscalene blocks for patients undergoing shoulder surgery.
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Anesthesia and analgesia · Sep 1992
Sevoflurane is biotransformed by guinea pig liver slices but causes minimal cytotoxicity.
Guinea pig liver slices were used to evaluate the biotransformation and hepatotoxic potential of sevoflurane. Precision-cut liver slices (250-300 microns thick) were incubated in sealed roller vials in buffer at 37 degrees C under 95% O2. Sevoflurane was added to produce 0.9 or 2.1 mM medium concentrations. ⋯ Sevoflurane (2.1 mM) and isoflurane (2.3 mM) had no effect on slice K+ content, but both anesthetics depressed protein synthesis. The biotransformation of sevoflurane was maximal at 95% O2, with threefold more F- produced from sevoflurane than isoflurane. Sevoflurane appears to have a minimal effect on the guinea pig liver slices, which is consistent with in vivo studies in which minimal or no hepatotoxicity has been observed.
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Anesthesia and analgesia · Sep 1992
Comparative StudyBlood flow and tissue oxygen pressures of liver and pancreas in rats: effects of volatile anesthetics and of hemorrhage.
The object of this investigation was to compare the effects of volatile anesthetics and of hemorrhage at comparable arterial blood pressures on splanchnic blood flow (radioactive microspheres) and tissue oxygenation of the liver and pancreas (surface PO2 [PSO2] electrodes). In contrast to earlier studies, we did not use identical minimum alveolar anesthetic concentration multiples as a reference to compare volatile anesthetics; rather, we used the splanchnic perfusion pressure. Under general anesthesia (intravenous chloralose) and controlled ventilation, 12 Sprague-Dawley rats underwent laparotomy to allow access to abdominal organs. ⋯ Thus, volatile anesthetics preserved pancreatic but not hepatic blood flow and tissue oxygenation in this rat model. Despite comparable effects on perfusion, the PSO2 of the liver and pancreas was the least during hemorrhagic hypotension compared to that with the anesthetics. Because the volative anesthetic-induced hypotension has such a different effect on splanchnic tissue oxygenation compared with hemorrhagic-induced hypotension, the authors conclude that the method of inducing hypotension may have different effects on oxygenation of various tissues.