Abstract
Purpose: :
To determine whether application of subconjunctival 2% lidocaine for anesthesia reduces rates of endophthalmitis after intravitreal injection.
Methods: :
We performed in vitro experiments to confirm the antibacterial properties of commercially available 2% lidocaine with 0.1% methylparaben (Hospira, Inc., Lake Forest, IL) against causative organisms of endophthalmitis. Isolates of Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus viridans from patients with endophthalmitis were incubated in trypticase soy broth with either 2% lidocaine/0.1%methylparaben or equal volume distilled water (control). Aliquots (100 µl) were plated on Mueller-Hinton (S. aureus and S. epidermidis) or blood agar plates (S. viridans) at 0, 10, 30, 120, and 240 minutes and colonies were counted after 24 hours.We performed a retrospective chart review from January 2005 to February 2011 at the Vanderbilt University, Nashville, TN, the Nashville Veteran’s Administration Hospital, and Emory University, Atlanta, GA to determine the rate of intravitreal injection-related endophthalmitis with or without the pre-application of subconjunctival 2% lidocaine/0.1% methylparaben (lidocaine) for anesthesia. Total number of intravitreal injections was determined by procedure code and endophthalmitis cases were identified using ICD-9 codes. Endophthalmitis cases were only included if they occurred within 7 days after an injection and either had a positive culture or hypopyon. All suspected cases related to triamcinolone without a positive culture were excluded. Intravitreal injections were then categorized by providers who strictly adhered to always using or never using subconjunctival lidocaine.
Results: :
In vitro, 2% lidocaine/0.1% methylparaben demonstrated rapid bactericidal effects against all 3 organisms. After 10 minutes of exposure, there was approximately a 90% (P < 0.01), 95% (P < 0.001), and 92% (P < 0.001) reduction in colony forming units (CFU) when compared to time 0 for S. aureus, S. epidermidis, and S. viridans respectively. Complete elimination of CFU occurred at subsequent time points for each organism in contrast to logarithmic increase for control plates. There were a total of 8 cases (7 culture positive) of post-injection endophthalmitis out of 7969 (0.1%) intravitreal injections performed without the use of subconjunctival lidocaine. In contrast, there were 0 cases out of 7224 injections performed with subconjunctival lidocaine (P = 0.02).
Conclusions: :
Application of subconjunctival 2% lidocaine for anesthesia may reduce the incidence of post-injection endophthalmitis.
Keywords: endophthalmitis • injection • antibiotics/antifungals/antiparasitics