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The ultrasonic localization of retrobulbar needles during retrobulbar block
A A Birch1, M Evans, E Redembo
1Department of Anesthesiology, Oregon Health Sciences University, Casey Eye Institute, Portland 97201-3098, USA.
Purpose:
The tips of retrobulbar needles were visualized during retrobulbar block using ultrasound. The purpose of this study is to see how often the needle tip was located 5 mm behind the hind surface of the globe.
Methods:
Twenty-five patients ranging in age from 22 to 84 years were studied after written informed consent was obtained. An ultrasonic photograph was taken before needle placement, with the needle in the proper position, and after local anesthetic had been injected.
Results:
In none of the 25 patients studied was the needle tip at the 5-mm mark behind the eye. Placement ranged from 0.2 to 3.3 mm behind the globe. In 14 to 25 placements, the needle shaft was seen actually to indent the globe. The optic nerve was seen to be at least 9 mm from the needle tip in 6 of 25 patients.
Conclusion:
This study demonstrates that retrobulbar needle tips are closer to the globe than thought previously. A false sense of security may occur when performing retrobulbar blocks using only anatomic landmarks.