Post-anesthetic cortical blindness in cats

Written on February 11, 2013 by Mark Troxel, DVM, DACVIM (Neurology) Hospital: Massachuesetts Veterinary Referral Hospital

I thought I would share this abstract with all of you. It is very disconcerting, to say the least, to think that we veterinary professionals may be inadvertently harming our patients. I frequently am asked to evaluate patients, especially cats, that are acutely blind and/or showing other neurological signs after a “routine” procedure, such as a dental cleaning. We often try to blame the anesthesia protocol/monitoring, apnea, or hypotension as the cause, but a recent study suggests that the use of spring-held mouth gags may predispose cats to post-anesthetic neurological complications. Although not proven in this study, the authors theorize that “it is possible that the use of a spring-held mouth gag reduces blood flow to the brain through the maxillary artery by stretching of the vasculature and/or adjacent muscles with resulting vascular compromise.” This clearly isn’t the only reason since mouth gags were not used in 4/20 cats in the study, but decreasing the use of mouth gags during procedures is definitely something we should consider.

Post-anesthetic cortical blindness in cats: Twenty cases.
Vet J. August 2012;193(2):367-73.
J Stiles1; A B Weil; R A Packer; G C Lantz
1Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA.

Article Abstract

The medical records of 20 cats with post-anesthetic cortical blindness were reviewed. Information collected included signalment and health status, reason for anesthesia, anesthetic protocols and adverse events, post-anesthetic visual and neurological abnormalities, clinical outcome, and risk factors. The vascular anatomy of the cat brain was reviewed by cadaver dissections. Thirteen cats were anaesthetised for dentistry, four for endoscopy, two for neutering procedures and one for urethral obstruction. A mouth gag was used in 16/20 cats. Three cats had had cardiac arrest, whereas in the remaining 17 cases, no specific cause of blindness was identified. Seventeen cats (85%) had neurological deficits in addition to blindness. Fourteen of 20 cats (70%) had documented recovery of vision, whereas four (20%) remained blind. Two cats (10%) were lost to follow up while still blind. Ten of 17 cats (59%) with neurological deficits had full recovery from neurological disease, two (12%) had mild persistent deficits and one (6%) was euthanased as it failed to recover. Four cats (23%) without documented resolution of neurological signs were lost to follow up. Mouth gags were identified as a potential risk factor for cerebral ischemia and blindness in cats.