Anesthesiology
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Comparative Study
Effects of sevoflurane and propofol on the nociceptive withdrawal reflex and on the H reflex.
The predominant target of anesthetics to suppress movement responses to noxious stimuli is located in the spinal cord. Although volatile anesthetics appear to produce immobility by actions on the ventral rather than the dorsal horn, the site of action of propofol remains unclear. ⋯ Probably because of the polysynaptic relay, the attenuation of the withdrawal reflex exceeds the attenuation of the H reflex. Sevoflurane produces a larger inhibitory effect on the H reflex than propofol, which confirms that the ventral horn is a more important target for volatile anesthetics, whereas effects of propofol on this site of action are rather limited. Our findings indirectly suggest for propofol a relatively stronger effect within the dorsal horn.
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Comparative Study
An estimation of the minimum effective anesthetic volume of 2% lidocaine in ultrasound-guided axillary brachial plexus block.
Ultrasound guidance facilitates precise needle and injectate placement, increasing axillary block success rates, reducing onset times, and permitting local anesthetic dose reduction. The minimum effective volume of local anesthetic in ultrasound-guided axillary brachial plexus block is unknown. The authors performed a study to estimate the minimum effective anesthetic volume of 2% lidocaine with 1:200,000 epinephrine (2% LidoEpi) in ultrasound-guided axillary brachial plexus block. ⋯ Successful ultrasound-guided axillary brachial plexus block may be performed with 1 ml per nerve of 2% LidoEpi.
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Comparative Study
Evolution of changes in upper airway collapsibility during slow induction of anesthesia with propofol.
Upper airway collapsibility is known to increase under anesthesia. This study assessed how this increase in collapsibility evolves during slow Propofol induction and how it relates to anesthesia-induced changes in upper airway muscle activity and conscious state. ⋯ Slow stepwise induction of Propofol anesthesia is associated with an alinear increase in upper airway collapsibility. Disproportionate decreases in genioglossus electromyogram activity and increases in pharyngeal critical closing pressure were observed proximate to loss of consciousness, suggesting that particular vulnerability exists after transition from conscious to unconscious sedation. Such changes may have parallels with upper airway behavior at sleep onset.
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Comparative Study
Noninvasive temperature monitoring in postanesthesia care units.
Initial postoperative core temperature is a physician and hospital performance measure. However, the extent to which core temperature changes during emergence from anesthesia and transport from the operating room to the postanesthesia care unit (PACU) remains unknown. Similarly, the accuracy of many noninvasive temperature-monitoring methods used in the PACU has yet to be quantified. This study, therefore, quantified the change in core temperature occurring during emergence and transport and evaluated the accuracy and precision of eight noninvasive thermometers in the PACU. ⋯ Invasive temperature monitoring available intraoperatively is more accurate than any generally available postoperative methods. Physician performance measures should therefore not be based exclusively on postoperative temperatures. Among the generally available postoperative monitoring methods, electronic oral thermometry appears to be the best.
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Comparative Study
Coapplication of lidocaine and the permanently charged sodium channel blocker QX-314 produces a long-lasting nociceptive blockade in rodents.
Nociceptive-selective local anesthesia is produced by entry of the permanently charged lidocaine-derivative QX-314 into nociceptors when coadministered with capsaicin, a transient receptor potential vanilloid 1 (TRPV1) channel agonist. However, the pain evoked by capsaicin before establishment of the QX-314-mediated block would limit clinical utility. Because TRPV1 channels are also activated by lidocaine, the authors tested whether lidocaine can substitute for capsaicin to introduce QX-314 into nociceptors through TRPV1 channels and produce selective analgesia. ⋯ Coapplication of lidocaine and its quaternary derivative QX-314 produces a long-lasting, predominantly nociceptor-selective block, likely by facilitating QX-314 entry through TRPV1 channels. Delivery of QX-314 into nociceptors by using lidocaine instead of capsaicin produces sustained regional analgesia without nocifensive behavior.