Anesthesiology
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The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of glutamate receptor mediates fast excitatory neurotransmission in the central nervous system. Many general anesthetics inhibit AMPA receptors in vitro; however, it is not certain if this inhibition contributes to the behavioral properties of these drugs. AMPA receptors lacking the GluR2 subunit are resistant to blockade by barbiturates in vitro. Paradoxically, GluR2 null mutant (-/-) mice are more sensitive to barbiturate-induced loss of the righting reflex (LORR) compared with wild-type (+/+) littermates. To determine if interactions between anesthetics and AMPA receptors account for the increased sensitivity of (-/-) mice, the effects of volatile anesthetics that do not directly inhibit AMPA receptors were examined. ⋯ Direct blockade of AMPA receptors did not account for the increased sensitivity to volatile anesthetics in GluR2 null mutant mice for HPWL or LORR. Thus, the deficiency of GluR2-containing AMPA receptors increases the sensitivity of neuronal circuitry mediating these end points, but not MAC. GluR2-containing receptors do not contribute appreciably to MAC in this mouse model. These results illustrate the difficulties in attributing behavioral responses to drug-receptor interactions in genetically engineered animals.
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Randomized Controlled Trial Clinical Trial
Analgesic effect of low-dose intrathecal morphine after spinal fusion in children.
This study was designed to assess the postoperative analgesic effect of low-dose intrathecal morphine after scoliosis surgery in children. ⋯ These data demonstrate that low-dose intrathecal morphine supplemented by PCA morphine provides better analgesia than PCA morphine alone after spinal fusion in children. The doses of 2 and 5 microg/kg seem to have similar effectiveness and side-effect profiles, whereas a reduction of intraoperative bleeding was observed in patients who received 5 microg/kg but not 2 microg/kg intrathecal morphine.
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An accepted concept in septic shock is that preload adaptation by acute left ventricular dilatation, when occurring spontaneously or with the aid of volume loading, permits maintenance of an adequate cardiac output, leading to final recovery. From a physiologic point of view, this concept appears debatable because a normal pericardium exerts a restraining action on a normal heart. ⋯ The transesophageal echocardiography study was unable to confirm the reality of the concept of early preload adaptation by left ventricular dilatation in septic shock. Conversely, because left ventricular volume always remained in a normal range after correcting hypovolemia, systolic function was the unique determinant of stroke index in septic shock.
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Randomized Controlled Trial Clinical Trial
Reduced need for vasopressors in patients receiving aprotinin during orthotopic liver transplantation.
Graft reperfusion in orthotopic liver transplantation is often associated with significant hemodynamic changes, including decreased systemic vascular resistance and arterial blood pressure. Vasopressive drugs are often required to maintain adequate perfusion pressure during the early postreperfusion period. The exact mechanism of this postreperfusion syndrome is unknown, but release of bradykinin, a potent vasodilatator, via the kallikrein system may play a role. Aprotinin is a broad-spectrum inhibitor of serine proteases such as kallikrein and therefore may ameliorate the postreperfusion syndrome and reduce the need for vasopressors. ⋯ Prophylactic use of aprotinin ameliorates the postreperfusion syndrome in orthotopic liver transplantation, as reflected by a significant reduction in vasopressor requirements.
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Randomized Controlled Trial Comparative Study Clinical Trial
Airway anesthesia alone does not explain attenuation of histamine-induced bronchospasm by local anesthetics: a comparison of lidocaine, ropivacaine, and dyclonine.
Lidocaine inhalation attenuates histamine-induced bronchospasm while evoking airway anesthesia. Because this occurs at plasma concentrations much lower than those required for intravenous lidocaine to attenuate bronchial reactivity, this effect is likely related to topical airway anesthesia and presumably independent of the specific local anesthetic used. Therefore, the authors tested the effect of dyclonine, lidocaine, and ropivacaine inhalation on histamine-induced bronchospasm in 15 volunteers with bronchial hyperreactivity. ⋯ Both lidocaine and the new amide local anesthetic ropivacaine significantly attenuate histamine-induced bronchospasm. In contrast, dyclonine, despite its longer lasting and more intense local anesthesia, does not alter histamine-evoked bronchoconstriction and irritates the airways. Thus, airway anesthesia alone does not necessarily attenuate bronchial hyperreactivity. Other properties of inhaled local anesthetics may be responsible for attenuation of bronchial hyperreactivity.