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*Division of Critical Care Anesthesiology and Department of Anesthesiology & Pain Management, Cook County Hospital; Department of Anesthesiology, Rush-Presbyterian-St. Luke’s Medical Center; and §Division of Surgical Critical Care, Cook County Hospital, and Department of Surgery, University of Illinois College of Medicine at Chicago, Chicago, Illinois
Address correspondence and reprint requests to Arjang Khorasani, MD, Department of Anesthesiology & Pain Management, Cook County Hospital, 1835 W. Harrison St., Chicago, IL 60612. Address e-mail to arjangk{at}SPHK.com
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.
Implications: There is substantial variability in dose of benzocaine administered by nonmetered Hurricaine® spray. Canister orientation and residual volume of anesthetic significantly affect output of benzocaine and are clinically uncontrollable. Methemoglobinemia may occur even after the manufacturer’s suggested spraying guidelines. We saw no correlation between dose and spraying time or number of sprays.
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  T. J. Moore, C. S. Walsh, and M. R. Cohen Reported Adverse Event Cases of Methemoglobinemia Associated With Benzocaine Products Arch Intern Med, June 14, 2004; 164(11): 1192 - 1196. [Abstract] [Full Text] [PDF]
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