Anesthesiology
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Biodegradable microspheres are a useful method of drug delivery because they are both injectable and biodegradable, eliminating the need for surgical implantation or removal. Previous work has characterized implantable preparations of local anesthetics in polymer pellets for prolonged regional anesthesia. In this article, the authors characterize injectable suspensions of bupivacaine-polymer microspheres and examine whether they can produce prolonged blockade of the sciatic nerve in rats. ⋯ Prolonged percutaneous blockade of peripheral nerves is feasible. The recovery from blockade is complete, and plasma bupivacaine levels are far below the range associated with systemic toxicity. The mechanisms underlying the dexamethasone block-prolonging effect are under investigation.
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Barbiturates have previously been demonstrated to reduce focal cerebral ischemic brain damage. However, the dose of drug required to elicit maximal neuroprotection has not been defined. The authors' hypothesized that doses of pentobarbital substantially lower than those required to cause electroencephalographic burst suppression would result in maximal magnitudes of reduction of cerebral infarct volume. ⋯ Sodium pentobarbital administered at either dose (active electroencephalogram or burst suppression) resulted in an approximately equal to 25% reduction of cerebral infarct size, indicating that burst suppression is not required to elicit maximal neuroprotective efficacy.
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Jugular venous hemoglobin desaturation during the rewarming phase of cardiopulmonary bypass is associated with adverse neuropsychologic outcome and may indicate a pathologic mismatch between cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2). In some studies, rapid rewarming from hypothermic cardiopulmonary bypass results in greater jugular venous hemoglobin desaturation. The authors wished to determine if rewarming rate influences the temperature dependence of CBF and CMRO2. ⋯ Cerebral venous hemoglobin desaturation with rapid rewarming is caused by an increase in CMRO2 that is temporarily greater than the increase in CBF. This mismatch may indicate a transient abnormality in flow-metabolism coupling, or the effect of temperature gradients on oxygen transfer from hemoglobin to brain.
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In upper abdominal or chest surgery, the segmental approach to thoracic epidural space has the advantage of reducing the total dose of local anesthetic needed. This approach, however, is associated with greater risk of neurologic damage or dural puncture. The aim of this study was to assess the success and the degree of difficulty in advancing a 19-G catheter from the lumbar epidural space to the thoracic level in patients aged 0-96 months. ⋯ The 19-G catheter is inappropriate for use in reaching the thoracic epidural space by the lumbar approach. Easy entrance of a catheter is not a reliable sign of having reached the desired level.
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The chemical breakdown of isoflurane, enflurane, or desflurane in dried carbon dioxide absorbents may produce carbon monoxide. Some mass spectrometers can give false indications of enflurane during anesthetic breakdown. ⋯ Trifluoromethane causes the inappropriate indication of enflurane by mass spectrometry, and indicates isoflurane and desflurane breakdown. Because the ratio of carbon monoxide to trifluoromethane varies with conditions, this technique cannot be used to quantitatively determine the amount of carbon monoxide to which a patient is exposed. If any warning of anesthetic breakdown results from this technique then remedial steps should be taken immediately to stop patient exposure to carbon monoxide. No warning can be provided for the breakdown of enflurane by this technique.