Does Lidocaine Gel Modify the Risk of Infection?
The use of lidocaine gel for anesthesia before intravitreal injection is widespread.
However, we do not know if the use of lidocaine gel influences the risk of developing post-injection endophthalmitis, nor do we understand the mechanism by which it may promote infection.
A study by Lad et al included 8,802 injections and its results suggested that the risk of endophthalmitis was not influenced by the use of anesthetic gel before povidone iodine (PI).1
However, a large retrospective analysis of 154,198 intravitreal injections reported that the use of anesthetic gel (2% lidocaine [Xylocaine] or 0.5% tetracaine hydrochloride [Tetravisc]) increased the rate of endophthalmitis 4 to 10-fold after adjusting for other covariates (use of eyelid speculum, use of gloves, injection site and specific anti-VEGF agent).2
Notably, the studies did not take into account the sequence of application of povidone-iodine gel and lidocaine.
Related: Snapshot: Management of Endogenous Endophthalmitis in Patients
We want to know if there is anything inherent in lidocaine gel that promotes endophthalmitis or if it protects against PI. PI is the only step that has been consistently shown to prevent endophthalmitis.
We only use corneal tissue to resemble the in vivo growth of bacteria with the application of lidocaine and / or PI.
Five isolates of bacteria from previous cases of eyes with endophthalmitis were tested: Streptococcus, Staphylococcus epidermidis, Streptococcus viridans, Enterococcus cash, and Staphylococcus aureus.
Corneal edges were used to test the interactions of 3.5% lidocaine gel (Akten) and 5% PI. A 0.01 ml sample of each bacterial isolate (approximately 1000 CFU) was used to inoculate each corneal margin.
For each bacterial isolate, 5 corneal edges were prepared after initial bacterial inoculation of the corneal edge: bacteria alone, lidocaine gel only, PI only, PI then lidocaine, and lidocaine then PI.
Related: Preventing post-cataract endophthalmitis
A contact time of 5 minutes was allowed before the inoculated rim was placed in 10 ml of growth broth medium.
Lidocaine gel was not bactericidal for all 5 pathogens. In fact, the lidocaine gel appeared to be protective against the known bactericidal activity of 5% PI, as demonstrated by the sequential application of the lidocaine gel followed by PI.
Application of 5% PI alone was bactericidal for all pathogens as expected. Interestingly, when the lidocaine gel was applied after the PI, the PI was ineffective in removing Enterococcus. This finding was confirmed by repetition.
Related: Research: Similar endophthalmitis rates for brand name generic topical antibiotics
Lidocaine gel may promote endophthalmitis by acting as a physical barrier and protecting bacteria from exposure to PIs while preparing for the intravitreal injection.
Notably, the destructive properties of PI were effective when applied before the lidocaine gel for all bacteria except Enterococcus.
For Enterococcus, the gel itself can serve as a growth medium and / or can dilute the PI.
Although increased bactericidal activity against S. aureus and Mycobacterium can be caused by diluting PI up to 0.1%, which is believed to weaken the binding of iodine to the carrier polymer and increase “free” iodine, we hypothesize that the gel of lidocaine itself can prevent the release of iodine as theorized in Berkelman et al.3
In addition, previous in vitro studies of oral biofilms have shown that local anesthetics such as lidocaine gel have significant bactericidal properties; however, lidocaine was an ineffective 2.5% disinfectant in gel form, which is consistent with our results when 3.5% lidocaine gel was applied.4
Related: Tool Offers Rapid Cooling For Intravitreal Injections
When choosing to use lidocaine gel before intravitreal injection, application of PI before lidocaine gel is the best sequence to prevent endophthalmitis. Avoiding the use of lidocaine gel is probably the safest option.
About the Author
Jamie Odden, MD, MPH
e: [email protected]
Odden, an ophthalmology resident at the University of Pittsburgh Medical Center in Pennsylvania, has no financial disclosure related to this content.
1. Lad EM, Maltenfort MG, Leng T. Effect of lidocaine gel anesthesia on endophthalmitis rates after intravitreal injection. Ophthalmic surgery laser imaging. 2012; 43 (2): 115-120. doi: 10.3928 / 15428877-20120119-01
2. Stem MS, Rao P, Lee IJ, et al. Predictors of endophthalmitis after intravitreal injection: a multivariate analysis based on injection protocol and povidone iodine assay. Ophthalmol Retina. 2019; 3 (1): 3-7. doi: 10.1016 / j.oret.2018.09.013
3. Berkelman RL, Holland BW, Anderson RL. Increased bactericidal activity of dilute preparations of povidone-iodine solutions. J Clin Microbiol. 1982; 15 (4): 635-639. doi: 10.1128 / jcm.15.4.635-639.1982
4. Gocmen JS, Buyukkocak U, Caglayan O, Aksoy A. Antibacterial effects in vitro of topical local anesthetics. J Dermatolog Treat. 2008; 19 (6): 351-353. doi: 10.1080 / 09546630802050498