Chalazion removal.

Delivered quantities of 20% benzocaine spray (Hurricaine; Beutlich L.P. Pharmaceuticals, Waukegan, IL) are estimated by counting the number of sprays or the spraying time. Because Hurricaine spray supplies a continuous (albeit nonmetered) stream of benzocaine, neither method addresses delivered dose. We hypothesized that dose per time is a function of canister content and orientation. Thirty full canisters of Hurricaine were placed into three equal orientations (upright, inverted, or horizontal). Extrapolating from a full canister, four different estimates of benzocaine residual volume were determined before spraying out the contents (80%, 60%, 40%, and 20% full). Each canister was then sprayed for 10-s intervals, and the quantity delivered was calculated and compared statistically. Upright canisters 100% full emitted more benzocaine than canisters with residual volume 20% full (190 +/- 10 vs 172 +/- 10 mg/s). Inverted canisters emitted significantly less benzocaine from 100% full to residual volume 20% full (188 +/- 14 vs 70 +/- 10 mg/s). Oriented horizontally, two full canisters emitted <76 mg/s benzocaine, contrasted with the remaining eight in that group (186 +/- 20 mg/s). We conclude that the benzocaine (Hurricaine) sprayed in milligrams per second depends on canister content and orientation. When residual volumes diminish, there is a reduction in spraying volume per time. This diminution occurs progressively from larger to smaller residual volumes with canisters oriented horizontally, inverted, or upright. Arbitrary documentation of spraying time bears no relationship to dose delivered. Perhaps affixing an atomization device to a graduated syringe filled with benzocaine will help increase accuracy and precision in dosing.

Anesthesia, Local↗

PubMed2001

Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections.

BACKGROUND: Peribulbar and retrobulbar anesthesia have long been opposed on the basis of the existence of an intermuscular membrane, which is supposed to separate the intraconal from the extraconal spaces in a water-tight fashion. A local anesthetic injected outside the cone should spread through this septum to reach the nerves to be blocked. The existence of this septum is questioned. The aim of this study was to compare the spread of a colored latex dye injected intraconally or extraconally to simulate both retrobulbar and peribulbar anesthesia. METHODS: The authors used 10 heads from human cadavers. For each head, one eye was injected intraconally, and the other eye was injected extraconally. The heads were then frozen and sectioned into thin slices following various planes. They were then photographed and observed. RESULTS: There was no evidence of the existence of an intermuscular septum separating the intraconal and extraconal spaces. Those two spaces appeared to be part of a common spreading space, the corpus adiposum of the orbit. CONCLUSIONS: These results are in accord with the fact that clinical studies were not able to clearly demonstrate that retrobulbar anesthesia is more efficient than peribulbar anesthesia. On the basis of a similar clinical efficacy of the two techniques as a result of similar spreading of the local anesthetic injected, and a potentially higher risk of introducing the needle into the muscular cone, the authors recommend replacing retrobulbar anesthesia with peribulbar anesthesia.

Anesthesia, Local↗