Anesthesiology
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Randomized Controlled Trial Clinical Trial
Epidural anesthesia increases apparent leg temperature and decreases the shivering threshold.
Lower core temperatures than usual are required to trigger shivering during epidural and spinal anesthesia, but the etiology of this impairment remains unknown. In this investigation, we propose and test a specific mechanism by which a peripheral action of regional anesthesia might alter centrally mediated thermoregulatory responses. Conduction anesthesia blocks all thermal sensations; however, cold signals are disproportionately affected because at typical leg temperatures mostly cold receptors fire tonically. It thus seems likely that epidural and spinal anesthesia increase the leg temperature perceived by the thermoregulatory system. Because skin temperature reportedly contributes 5-20% to thermoregulatory control, increased apparent (as distinguished from actual) leg temperature would produce a complimentary decrease in the core temperature triggering thermoregulatory shivering. Accordingly, we tested the hypothesis that abnormal tolerance for hypothermia during epidural anesthesia coincides with an increase in apparent leg temperature. We defined apparent temperature as the leg-skin temperature required to induce a reduction in the shivering threshold comparable to that produced by epidural anesthesia. ⋯ Because leg-skin contributed approximately 11% to the shivering threshold, it is unlikely that the entire skin surface contributes at much less than 20%. These data suggest that the shivering threshold during epidural anesthesia is reduced by a specific mechanism, namely that conduction block significantly increases apparent (as distinguished from actual) leg temperature.
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Randomized Controlled Trial Clinical Trial
Deliberate mild intraoperative hypothermia for craniotomy.
Despite enthusiasm for the use of mild hypothermia during neurosurgical procedures, this therapy has not been evaluated systematically. This study examined the feasibility and safety of deliberate mild hypothermia and rewarming. ⋯ Although deliberate mild hypothermia is easily achieved intraoperatively, complete rewarming may be difficult to attain during craniotomy with current methods. In addition to the need for determining whether deliberate mild hypothermia confers cerebral protection in humans, the potential risks of the therapy need to be further characterized.
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Randomized Controlled Trial Clinical Trial
Thermoregulatory thresholds during epidural and spinal anesthesia.
There are significant physiologic differences between spinal and epidural anesthesia. Consequently, these two types of regional anesthesia may influence thermoregulatory processing differently. Accordingly, in volunteers and in patients, we tested the null hypothesis that the core-temperature thresholds triggering thermoregulatory sweating, vasoconstriction, and shivering are similar during epidural and spinal anesthesia. ⋯ Comparable sweating, vasoconstriction, and shivering thresholds during epidural and spinal anesthesia suggest that thermoregulatory processing is similar during each type of regional anesthesia. However, thermoregulatory control was impaired during regional anesthesia, as indicated by the significantly enlarged inter-threshold and sweating-to-shivering ranges.
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Clinical Trial Controlled Clinical Trial
Long-duration, low-flow sevoflurane anesthesia using two carbon dioxide absorbents. Quantification of degradation products in the circuit.
Sevoflurane reacts with soda lime, generating degradation products. The concentrations of sevoflurane degradation products in a low-flow circuit have been reported for anesthesia times of less than 5 h. In this study, sevoflurane degradation products generated during low-flow anesthesia exceeding 10 h were examined. ⋯ The degradation products detected were at low concentrations in long-duration, low-flow anesthesia with sevoflurane. Baralyme produced higher concentrations of degradation products than soda lime.
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Randomized Controlled Trial Comparative Study Clinical Trial
A prospective, randomized, double-blind comparison of epidural and intravenous sufentanil infusions.
The site of action (spinal vs. central) of epidurally administered lipid-soluble opioids has been the subject of controversy. We compared the efficacy, plasma concentration and side effects of epidural and intravenously administered sufentanil for postoperative pain relief. ⋯ Many clinical similarities were found when epidural and intravenous sufentanil infusions were compared. The higher incidence of excessive sedation in the patients receiving intravenous sufentanil could not be explained on the basis of plasma sufentanil concentrations alone. This study indicates that little clinical difference exists between epidural and intravenous administration of sufentanil.