A marked hypertensive response is often seen when the Mayfield skull-pin device is applied to stabilize the head of the anesthetized patient for neurosurgery. In a prospective, blinded and randomized trial, 10 patients received an infiltration block of 0.5% mepivacaine with epinephrine 5 micrograms/ml (3 ml at each pin site) 1 min before the Mayfield holder was applied. Ten patients received normal saline and served as controls. All patients were under general anesthesia induced with sodium pentothal, fentanyl and pancuronium, and maintained with isoflurane in nitrous oxide/oxygen and increments of fentanyl. In the control group, there were significant increases in mean arterial pressure (mean increase 43%, P less than 0.001) and heart rate (15%, P less than 0.01) at 0.5, 1 and 2 min after application. In the mepivacaine group, no significant changes occurred. Infiltration of local anesthetic with epinephrine can thus safely protect against potentially dangerous increases in arterial pressure when the Mayfield holder is used.
A quantitative and qualitative study of the superior laryngeal nerve (SLN) and its branches was performed on the intact nerve and after experimental denervation procedures. The distribution patterns of the myelinated fibers of the intact internal (SLNI) and external (SLNE) branches in the rat were unimodal with a fiber diameter range of 0.5-12 microns and with peaks at 2-4 microns. Numerous unmyelinated fibers, ranging in diameter from 0.1-2.3 microns, were evenly distributed all over the nerve. The SLNI contained no degenerated myelinated fibers after intracranial vagotomy, but about 25% of the unmyelinated fibers showed degenerative features. In the SLNE 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers were degenerated after the same procedure. Extracranial vagotomy caused degeneration of nearly all fibers in the SLNI and SLNE. Single unmyelinated fibers appeared normal after this procedure. Occasional myelinated and a few unmyelinated fibers were degenerated after excision of the superior cervical ganglion. It is inferred from the results that a majority of the myelinated fibers in the SLN (96-99%) are sensory, with the cell bodies in the extracranial vagal ganglia. The SLNE was also found to be predominantly sensory, as only 2-10% of the myelinated fibers and about 25% of the unmyelinated fibers had their cell bodies in the brainstem. Single myelinated and a few unmyelinated fibers in both the SLNI and SLNE had their origin in the superior cervical ganglion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.