Study identifies six risk factors associated with blindness after spine surgery

A study published in the January 2012 issue of Anesthesiology identified six risk factors associated with blindness or partial blindness that can occur after major spine surgery: 1) male sex, 2) obesity, 3) use of a surgical frame that places the head lower than the heart, 4) length of the surgery, 5) amount of blood loss and 6) use of certain fluids that replace lost blood.

Although ischemic optic neuropathy (ION) - which involves injury to the optic nerve located directly behind the eyeball - is a rare complication (with the highest incidence reported as 1 in 1,000 spine operations), it is a devastating complication for patients and a frustrating problem for anesthesiologists, spine surgeons and ophthalmologists because it is known to unexpectedly occur in even healthy patients of all ages.

The present study is important because it could open doors for practical modifications by health care providers to lessen the chance of occurrence.

"Our research represents the largest study performed on this complication to date with very detailed data available for comparison," said lead study author Lorri A. Lee, M.D., from the University of Washington. "Our identification of the six major risk factors for ION hopefully means that some of these risk factors can be modified in certain situations, with the potential to decrease the risk of blindness after major back surgery."

Dr. Lee and her research group culled data from a large national database created by the American Society of Anesthesiologists to identify cases of blindness occurring after surgery and compared them to patients undergoing similar spine operations who did not develop blindness from 17 medical centers in North America.

In an accompanying editorial, Mark A. Warner, M.D., from the Mayo Clinic, Rochester, Minnesota, said the study is significant on a number of levels, not the least of which is because no other researchers have consolidated so many cases of this rare complication into one study. "Rare events are nearly impossible to study," said Dr. Warner.

Dr. Lee stated that an effective treatment for ION has yet to be identified, so preventative strategies are imperative.

"Our study demonstrates that obese and male patients have an increased risk of developing ION after major spinal surgery in the prone position," she said. "Avoidance of the 'Wilson frame' and minimizing anesthesia duration and blood loss may also decrease the risk. And prediction tables for ION based on this study may help inform patients, surgeons and anesthesiologists of the risks and can guide decision-making."