The Anesthesia Patient Safety Foundation (APSF) held a multidisciplinary invitational conference to discuss information and gather opinions about the possible causes of and potential preventive strategies for postoperative visual loss (POVL). The American Society of Anesthesiologists (ASA) Postoperative Visual Loss Registry was studied, the results presented, and the literature reviewed.
Strokes or hypoxic-ischemic central nervous system (CNS) events are well-known complications of cardiac surgery. Complete or partial loss of vision after surgery involving cardiac bypass has, in the past, been grouped with other CNS injuries. Since the 1990s, however, there has been an increase in the number of cases of complete or partial vision loss associated with other surgeries, such as prone back surgery, extreme head-down pelvic surgery, and orthopedic surgeries.1
Unlike the strokes associated with cardiac surgery, most of the more recently reported cases of POVL have not been associated with embolic phenomena or global CNS injuries. The cases involve rather specific ischemia and edema of the optic nerves. The number of these cases may be increasing—which, in 1999, caused the ASA to initiate a voluntary reporting registry of POVL cases. That registry studied 80 reported cases of POVL and compared them to 315 adult case control subjects selected from 17 different institutions.2
The probable cause of POVL in many cases has been identified as edema within and around the optic nerve posterior to the retina. This edema can cause an ischemic type of nerve injury that results in loss of vision. This type of vision loss has nothing to do with pressure on the globe of the eye—which can cause blindness based on retinal artery occlusion or retinal vein obstruction. Posterior optic nerve edema can be caused by the prone and the extreme head-down position. Cases of POVL are now being reported for robotic laparoscopic pelvic surgery, which can require long periods in the extreme head-down position while the abdomen is pressurized.
The recommendations of the APSF conference were published in the Winter 2013 APSF Newsletter.3 The APSF website makes available a 10-minute video with recommendations for informed consent for patients at high risk of visual loss (www.apsf.org/resources/povl-consent). The ASA has issued a practice advisory, identifying higher-risk patients and suggesting possible strategies to reduce the likelihood of POVL.4
Although POVL can occur with any anesthesia and surgery, study of the ASA POVL Registry has identified the following independent risk factors:
- Anesthesia duration (odds ratio, 1.39/hr)
- Use of Wilson frame (odds ratio, 4.3)
- Obesity (odds ratio, 2.83)
- Male sex (odds ratio, 2.53)
- Blood loss greater than 1 liter (odds ratio, 1.34/liter)
- Replacement of blood loss with crystalloid only
Preliminary considerations for the prevention of POVL, based on what we know so far, include the following:
- When possible, keep the patient’s head at or slightly above the heart, especially during prone cases.
- Consider staging lengthy complex spine surgery in higher-risk patients.
- Consider replacing blood loss with colloids, such as albumin or hetastarch, to avoid using large amounts of crystalloid, which can produce excess edema fluid.
- Avoid induced hypotension for high-risk patients.
- During robotic surgery requiring severe head-down position, consider a 15- or 20-minute “time out” for head-up positioning if the surgery is going to last more than four hours.
The APSF video recommends that POVL be included in the surgical and anesthetic consent processes for higher-risk patients.5