Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1998
Medial canthus single-injection episcleral (sub-tenon anesthesia): computed tomography imaging.
Single-injection medial canthus periocular anesthesia is a promising regional anesthesia technique for ophthalmic surgery. The purpose of this computed tomography (CT) study was to confirm that this technique is an episcleral injection and to explain why it provides a good akinesia of the globe. Four fresh nonpreserved cadavers (eight eyes) were injected with fractioned various volumes of a contrast media using a previously described technique. For each injection and each eye, CT scans were performed in three planes of the space, and the site and spread of the injection was observed. We confirm that single-injection medial canthus periocular anesthesia is, in fact, an episcleral anesthesia, which explains the good sensory block of the globe. When larger volumes are injected, the contrast media spreads to the lids and extraocular muscle sheaths. We believe that this may explain why this technique provides good sensory and motor block of the globe and eyelids. This technique is a promising alternative to both retro- and peribulbar anesthesia. ⋯ We describe medial canthus single-injection periocular anesthesia by a computed tomography injection study in eight human cadaver eyes. It was confirmed to be an episcleral injection. Akinesia of the eyeball is provided by spreading of the local anesthetic solution from the episcleral space to the rectus muscle sheaths.
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Anesthesia and analgesia · Jun 1998
0.45% saline and 5% dextrose in water, but not 0.9% saline or 5% dextrose in 0.9% saline, worsen brain edema two hours after closed head trauma in rats.
In this study, we examined the effect of four i.v. fluids (250 mL/kg) on blood glucose and osmolality and brain tissue specific gravity after closed head trauma (CHT) in rats. CHT was delivered at Time 0; blood was sampled at 60 min; fluid infusion began at 75 min and ended at 105 min. Blood was again sampled at 105 and 120 min, and brain tissue specific gravity was determined at 120 min. Five groups (one control and four fluid-treated groups) received CHT, and five other groups (one control and four fluid-treated) did not (n = 9 in each group). 0.45% saline (1/2 NS) and 5% dextrose in water (D5W) accentuated the decrease of brain tissue specific gravity (1.0366 +/- 0.0025 and 1.0368 +/- 0.0028, respectively; mean +/- SD) caused by CHT (1.0395 +/- 0.0036), but 5% dextrose in 0.9% saline (D5NS) and 0.9% saline (NS) did not (1.0431 +/- 0.0042 and 1.0389 +/- 0.0049, respectively). In addition, 1/2 NS decreased blood osmolality (248 +/- 6 mOsm/L), D5W increased blood glucose (1095 +/- 173 mg/dL), D5NS increased blood osmolality (350 +/- 5 mOsm/L) and glucose (1695 +/- 76 mg/dL), and NS caused no significant change. We conclude that administering hypoosmolar i.v. fluids after CHT causes a significant worsening of cerebral edema 2 h after CHT. ⋯ We previously reported worse neurological outcome and/or mortality after closed head trauma in rats when 5% dextrose in water or 0.45% saline was given i.v. compared with 0.9% saline or 5% dextrose in 0.9% saline. The present results and our previous findings indicate that worsening of outcome after closed head trauma in rats may be caused more by edema formation than by hyperglycemia.