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Howard D. Palte, Steven Gayer, Esdras Arrieta-Quintero, Izuru Nose, Elizabete Lee, Sander Dubovy, Jean-Marie Parel; A Rabbit Model Comparative Evaluation of Two Ultrasound Devices for Thermal and Structural Injury. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1734.
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The aim of this study was to compare thermal and mechanical changes produced by an ophthalmic rated ultrasound machine versus a non-rated device commonly used by anesthesiologists for peripheral nerve blocks in OR suites.
The study protocol was approved by the University of Miami Institutional Animal Care and Use Review Board Committee and conforms to the ARVO Statement for Use of Animals in Ophthalmic and Vision Research. This is a dual phase comparative rabbit-model investigation. In Phase 1, thermocouples were surgically implanted in the anterior chamber, lens, vitreous, and peri-orbital skin. Thermal changes were recorded during 10 minute ultrasound exposure to FDA orbital and non-orbital rated devices. Ophthalmic pathologists determined anatomic impact using light microscopy and histopathology. In an analogous manner, Phase 2 eyes were exposed to 10 minutes ultrasound using either device and examined for 3 days via light microscopy and then histology. A control group was exposed to a 10 minute application from a dormant transducer of each machine, and assessed similarly.
A greater rate of temperature appreciation and higher final temperature occurred in all eyes with use of the non-orbital rated device. In both groups intraocular temperatures approached the subcutaneous value. Minor tissue injury was detected only in eyes which had undergone surgical thermocouple implantation. Histopathology did not identify structural or thermal cellular injury in eyes from either group.
Under conditions of prolonged exposure we compared a FDA-approved ophthalmic ultrasound transducer with a non-rated ultrasonic probe for ocular damage. Both phases of the study did not show evidence of ultrasound-induced macro-or microscopic thermal or structural injury. These outcomes suggest that certain non-rated devices commonly found in operating room suites may be safe for ophthalmic regional anesthesia. The tangible benefits of anesthesiologists using available OR equipment for ocular anesthesia may include faster turnover times, reduced block-related complications and enhanced patient safety.
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