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Homer Chiang, Sophie Kim, Jeong-Hyeon Sohn; Penetration of Povidone-Iodine Solution and Swabsticks Through Lidocaine Gel. Invest. Ophthalmol. Vis. Sci. 2020;61(7):316.
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The use of topical lidocaine gel was recently reported as a potential independent risk factor in the development of post-intravitreal injection endophthalmitis. This study aimed to determine the penetration of povidone-iodine (PVI) through lidocaine gel using various applications of 5% and 10% PVI, cotton-tip applicators (CTA) and swabsticks. We hypothesized that the viscous lidocaine gel represents a barrier to PVI penetration, but that PVI swabsticks may be able to overcome this barrier.
6-millimeter diameter discs were punched from cellulose filter paper. In the control group, 50 microliters of 5% PVI solution was applied to the discs. Four variable groups were treated with (1) 3.5% lidocaine gel plus 50 microliters of 5% PVI solution, (2) gel plus 10% PVI swabstick, (3) gel plus 5% PVI soaked CTA, and (4) gel plus 10% PVI soaked CTA. Excess gel and PVI were removed with cellulose sponges. The discs were submerged in 500 microliters of distilled water and agitated to allow PVI to elute out, then removed. Absorbance was measured with a SpectraCount microplate photometer. Data was analyzed using 2-sample 2-sided z-tests with alpha=0.05.
Thirty-six discs were read for each group. Using the no gel group as control, significantly less PVI was recovered in the gel + solution (p<0.0001), gel + 5% CTA (p<0.0001), and gel + 10% CTA (p=0.0002) groups. There was no significant difference in PVI recovery between the control and gel + 10% swab groups (p=0.065).
Use of 10% PVI swabs after application of lidocaine gel resulted in comparable PVI recovery with 5% PVI solution without lidocaine gel, while 5% solution with lidocaine gel resulted in undetectable PVI concentrations. Eluted PVI from applications of 5% and 10% PVI soaked cotton-tipped applicators after gel was applied also resulted in significantly less PVI recovered. These results suggest that lidocaine gel may prohibit penetration of PVI to the underlying target tissue, but this limitation may be overcome by using 10% PVI swabsticks. Further investigation with prospective randomized controlled trials are needed to elucidate the relationship between post-injection endophthalmitis and method of PVI application.
This is a 2020 ARVO Annual Meeting abstract.
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