We sought to determine the contemporary frequency of seizures, and the associated cardiovascular changes, resulting from local anesthetic-induced seizures in all patients undergoing brachial plexus, epidural, and caudal regional anesthetics. We investigated the following variables: development and treatment of seizure or cardiac arrest during the regional anesthetic, type of anesthetic (including local anesthetic used), gender, age, ASA physical status class and type of operation (elective or emergent). In addition, each patient who experienced a seizure underwent retrospective review of the acute event to determine the arterial blood pressure and heart rate changes accompanying the seizure, as well as details of the regional block technique. There was a significant difference between the rate of seizure development between epidural, brachia, and caudal anesthetics, with caudal > brachial > epidural. A significant difference was also noted in the rate of seizure development within types of brachial block, with supraclavicular and interscalene > axillary. No adverse cardiovascular, pulmonary or nervous system events were associated with any of the seizures, including the 16 patients who received bupivacaine blocks. The frequency of local anesthetic-induced seizures stratified by block type has a wide range, and cardiovascular collapse after bupivacaine-associated seizure has a low incidence.

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SUMMARY. The results of a petrofabric study on recrystallization of quartz in nature are presented and compared with recent experimental work. The orientations of newly recrystallized quartz grains are shown to be dependent on the orientation of host grains from or in which they grew. The results are compatible with the experiments of Hobbs 0968). The orientation of new grains appears to be unrelated to stress.Tr~E experimental work of Hobbs 0968) on the recrystallization of single crystals of quartz showed that the orientation of newly recrystallized grains was controlled fundamentally by the orientation of the host grain from or in which they grew. This observation contradicts previous theory (Kamb, I959, I96I ; Brace, ~96o), experiment (Griggs et aL, I96o), and field studies (Sylvester and Christie, I968), which suggested that the orientation of newly recrystallized grains and any resulting preferred orientation was controlled by stress. These studies largely ignored the long recognized phenomenon of host-controlled recrystallization in metals (Barrett and Massalski, ~966).In order to verify that a host control operates in the orientation of newly recrystallized quartz grains in nature and hence contributes to the development of natural preferred orientations, a study of quartz recrystaHization was undertaken on a suite of retrograde rocks from the Broken Hill area of western New South Wales, Australia. These rocks occur in and near retrograde schist-zones, described in detail by Vernon 0969), Hobbs et aL 0968), and Vernon and Ransom (I97O), which are narrow (from a few millimetres to over Ioom in width), conjugate, planar zones (similar to mylonite zones) transecting the high-grade metamorphic rocks of the region and locally reducing the grade of metamorphism from granulite to amphibolite facies. The specimens studied were collected from a quarry in Eyre Street, Broken Hill, where there outcrops 9

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