Anesthesiology
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The authors sought to characterize the pharmacologic characteristic and site of action of gabapentin (Neurontin) in a model of thermal hyperalgesia induced by intrathecal substance P administration. ⋯ The structure-activity relationship and the stereospecificity noted after intrathecal delivery suggest that gabapentin and S(+)-3-isobutyl-gamma aminobutyric acid act at a common spinal locus to modulate selectively a facilitated state of nociceptive processing.
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It has been proposed that the measure of noxious stimulus-induced Fos (the protein product of the immediate early gene c-fos) expression in the spinal cord dorsal horn of laboratory animals may provide an estimate of the potential of specific treatments to produce preemptive analgesia. The present study examined this hypothesis by comparing the effects of intrathecal lidocaine given before and after hindpaw formalin injection on persistent nociceptive responses and Fos expression in spinal cord dorsal horn of rats. ⋯ The finding that persistent nociceptive behaviors and Fos expression were suppressed by intrathecal lidocaine pretreatment suggests that nociception in the second phase of the formalin test depends on increases in central hyperexcitability generated during the first phase. On the other hand, the finding that the intrathecal injection of lidocaine after formalin treatment reduced Fos expression but not nociceptive responses indicates an uncoupling of the behavioral and Fos protein responses to formalin and suggests that changes in Fos expression may not be a good predictor of the ability of agents to produce preemptive analgesia.
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A cerebral oximeter measures oxygen saturation of brain tissue noninvasively by near infrared spectroscopy. The accuracy of a commercially available oximeter was tested in healthy volunteers by precisely controlling end-tidal oxygen (P[ET]O2) and carbon dioxide (P[ET]CO2) tensions to alter global cerebral oxygen saturation. ⋯ During isocapnic hypoxia in healthy persons, cerebral oxygenation as estimated by near infrared spectroscopy precisely tracks changes in measured S(jv)O2 within individuals, but the relation exhibits a wide range of slopes and intercepts. Therefore the clinical utility of the device is limited to situations in which tracking trends in cerebral oxygenation would be acceptable.
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Recent evidence suggests that the duration of the nociceptive block may be an important factor in determining the effect of the block on injury-induced hyperalgesia after block resolution. The authors examined whether a tonicaine nerve block lasting for 12 to 16 h could prevent late inflammatory hyperalgesia. ⋯ A prolonged nerve block (12-16 h) can prevent the development of long-lasting (3-5 days) inflammatory hyperalgesia. Prevention of late hyperalgesia can be provided not only by the preinjury block but also by the postinjury block administered when hyperalgesia is already well established.
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Respiratory failure secondary to cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors previously found that the increase in intrapulmonary shunt was well correlated with the amount of atelectasis. They tested the hypothesis that post-CPB atelectasis can be prevented by a vital capacity maneuver (VCM) performed before termination of the bypass. ⋯ In this pig model, postcardiopulmonary bypass atelectasis was effectively prevented by a VCM.