Articles: anesthetics.
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Anesthetic technique in surgery for pheochromocytoma presents well recognized difficulties. Major complications (hypertensive crises, rhythm disturbances, collapse, pulmonary edema and hypoglycemia) can often be avoided by a good preoperative examination and full per-operative monitoring. The choice of drugs during anesthesia and per-operative resuscitation are discussed in this article together with particular situations such as pheochromocytoma in pregnancy or the per-operative discovery of a previously unrecognized pheochromocytoma.
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Batrachotoxin (BTX)-activated Na+ channels from rabbit skeletal muscle were incorporated into planar lipid bilayers. These channels appear to open most of the time at voltages greater than -60 mV. Local anesthetics, including QX-314, bupivacaine, and cocaine when applied internally, induce different durations of channel closures and can be characterized as "fast" (mean closed duration less than 10 ms at +50 mV), "intermediate" (approximately 80 ms), and "slow" (approximately 400 ms) blockers, respectively. ⋯ Both the cocaine association and dissociation rate constants are altered when external Na+ ion concentrations are raised. We conclude that (a) one cocaine molecule closes one BTX-activated Na+ channel in an all-or-none manner, (b) the binding affinity of cocaine is voltage sensitive, (c) this cocaine binding site can be reached by a hydrophilic pathway through internal surface and by a hydrophobic pathway through bilayer membrane, and (d) that this binding site interacts indirectly with the Na+ ions. A direct interaction between the receptor and Na+ ions seems minimal.