Safety of Indocyanine Green as a Vital Stain

The Rayne Institute, St. Thomas’ Hospital, London, United Kingdom. TimLJackson@hotmail.comTo the Editor:— Indocyanine green (ICG) has been identified as a potential alternative to epinephrine as a means of detecting inadvertent intravascular injection of local anesthetic during epidural anesthesia. Dietz and Jaffe 1have shown apparent neurotoxicity with this agent and cautioned against its use. They noted that neurotoxicity had not been reported previously. However, there are a series of reports of possible retinal neurotoxicity that may support the authors’ claim. ICG is commonly used as an intraoperative vital stain to identify and remove the internal limiting membrane during macular surgery. 2Concerns have been expressed regarding its safety. 3Some experimental reports have shown ICG mediated neororetinal 4and retinal pigment epithelial cell damage. 5There are also clinical studies showing functional visual loss after ICG-assisted macular surgery. 6ICG is usually mixed in distilled water and then saline, resulting in a hypoosmolar solution. Some reports suggest that it is the combined exposure to low osmolarity and ICG that produces cell damage. 7Authors have suggested alternative means of preparing ICG, and other agents, such as infracyanine green and trypan blue, have been advocated. 8Other vital stains, such as sodium fluorescein, are widely available and well tested. Many of these and other related articles may be of interest to readers concerned about the safety of ICG.The Rayne Institute, St. Thomas’ Hospital, London, United Kingdom. TimLJackson@hotmail.com