There are several risks associated with multilevel surgery on the lumbar spine. One risk that patients should be aware of is postoperative vision loss (POVL).
The most common cause of POVL is a decrease in blood and oxygen levels to the optic nerve, called ischemic optic neuropathy. It is the duty of the anesthesiologist to maintain adequate blood circulation and oxygenation during surgery. When an anesthesiologist uses poor technique, blood circulation and oxygenation is not adequately maintained and the anesthesiologist is in breech of his duty. This breech can result in POVL. Unfortunately, this risk is not routinely communicated to patients before surgery.
Many factors can cause POVL. But, there are three big factors that must be looked at in every case of POVL caused by ischemic optic neuropathy.
- Hematocrit and hemodilution
- Increased blood and tissue pressure
- Patient positioning
Hematocrit is the percentage of red blood cells in the bloodstream. It is used to determine how much oxygen the blood is capable of holding. The normal level of hematocrit in the bloodstream is fifty percent. When a patient losses a significant amount of blood, hematocrit is lowered, which means the blood’s oxygen carrying capability is lowered, and bodily tissues are put at a high-risk of damage. Further, surgeons use non-blood fluids to maintain blood pressure during long surgical procedures because of significant blood loss. This is called hemodilution, which also decreases hematocrit and in turn places bodily tissues including the optic nerve at a high-risk damage.
Another major factor that can contribute to POVL is increased blood and tissue pressure. This occurs when tissues are swollen in confined spaces, such as the spinal canal, and reduces the blood’s ability to get oxygen to the optic nerves. The lack of oxygen to the optic nerves can cause permanent blindness.
Finally, patient positioning during spinal surgery may also contribute to POVL. Often, surgeons will keep a patient’s head lower than the patient’s heart for easier access to the surgical site. When this is combined with diluted blood the results can be catastrophic. Injury to the optic nerves and permanent blindness may result from this combination.
Long spinal surgeries have become more commonplace as medical technologies have advanced in recent years. But just because these surgeries are more common does not mean they do not come with substantial risks. Before undergoing spinal surgery, or any surgery for that matter, it is important to discuss all the risks of that particular procedure with your doctor. If POVL is a possibility, your doctor must inform you of that risk, and you must consent before that surgery can take place.