The risk of blindness caused by spinal fusion has dropped almost three-fold since the late 1990s in the USA, according to the largest study of the topic to date.
Results of the research were published online in Anesthesiology.
“While there are significant complications that can result from spinal fusion surgery, it seems that blindness, a catastrophic and devastating complication, is one that has become far rarer in recent years,” said Steven Roth, professor of anesthesiology at the University of Illinois at Chicago College of Medicine, and senior author on the paper.
Nearly 480,000 spinal fusions are performed in the USA each year, with an incidence of blindness placed between one-in-1000 and one-in-10,000. Because most studies on the operation have been very small, it has been difficult to devise guidelines for patients and surgeons in decision-making. With the steep jump in numbers of people undergoing spinal fusion in the last 20 years, Roth said, spinal surgeons and anaethetists have become even more concerned about the risk for blindness. “We wanted to know if rates of blindness as a result of these surgeries were stable, increasing or decreasing over time,” he said.
Using data from the Nationwide Inpatient Sample, Roth and colleagues estimated the number of spinal fusions and cases of blindness caused by the surgery between 1998 and 2012. They looked for procedure codes for spinal fusion surgery and diagnosis codes for ischaemic optic neuropathy occurring during or directly after the surgery. Ischaemic optic neuropathy causes blindness by damaging the optic nerve.
They estimated that 2,511,073 spinal fusions were performed, resulting in 257 instances of ischaemic optic neuropathy, or 1.02 per 10,000 surgeries; however, over the time period studied, the risk decreased 2.7 fold, or 60 per cent. The researchers noted that significantly increased risk for ischaemic optic neuropathy during spinal fusion surgery came with age (over 50), gender (male), receiving a blood transfusion during the procedure and obesity. Roth attributes the decline in risk to the increasing use of minimally invasive surgical techniques.
“The characteristics of the patients undergoing spine fusion haven’t changed all that much over the years, although the population has aged,” he said. “So the variables that must be contributing to the decline in blindness caused by spine fusion surgery are most likely the result of changes made in how the surgery is performed.”
Roth believes that changes in anaesthesia practice may also be driving the decrease in risk of blindness. Many anaesthetists now set a stricter limit for how low they will allow blood pressure to drop during surgery, he said, which may help reduce the risk for ischaemic optic neuropathy.
Source: University of Illinois at Chicago
Reference: Rubin, D.S., et al/ (2016) Perioperative visual loss in spine fusion surgery: ischemic optic neuropathy in the United States from 1998 to 2012 in the Nationwide Inpatient Sample. Anesthesiology. doi: 10.1097/ALN.0000000000001211