In a rare but devastating complication that has long confounded surgeons, anesthesia providers and ophthalmologists, some healthy patients undergoing spinal fusion surgery suffer unexpected post-operative blindness. Writing in this month's issue of the journal Anesthesiology, researchers have identified patients at risk of and practices that contribute to this rare complication.
The vision defects, caused by ischemic optic neuropathy (ION), range from blurred vision to complete blindness, usually without significant recovery. The study's authors say obese male patients are at greater risk of suffering the complication. They also point to the use of a surgical frame that places the patient's head lower than the heart, which may exacerbate venous congestion and ultimately limit oxygen delivery to the optic nerve. Significant blood loss and subsequent fluid replacement also expose patients to the physiologic causes of ION, say the researchers.
Preventative strategies are the only viable option to reduce the complication's effects, for which treatment options have yet to be identified, notes the study. They include modifying table frame selection and patient positioning to keep the head at or above the heart during surgery; minimizing anesthesia duration; using colloids as well as crystalloids to maintain intravascular volume; and placing patients in positions that help reduce intra-abdominal pressure and venous congestion.
This is the largest study to date on blindness following spinal surgery, says lead author Lorri A. Lee, MD, an anesthesiologist from the University of Washington in Seattle. "Our identification of the major risk factors hopefully means that some can be modified in certain situations, with the potential to decrease the risk of blindness after major back surgery."
"Rare events are nearly impossible to study," says Mayo Clinic anesthesiologist Mark A. Warner, MD, in an accompanying editorial. "Until now, there have been no data to support speculation on etiologies of ION in spine fusion patients."
Daniel Cook
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