Clinical Updates

By Michael C. Brody, M.D.

Perioperative Visual Loss
Common causes
Task force recommendations
Conclusion

Perioperative Visual Loss

The American Society of Anesthesiologists (ASA) established the Postoperative Visual Loss (POVL) Registry in 1999 because of increasing reports of perioperative visual deficits. Debate has ensued that questions whether the incidence of the problem is actually increasing or if increased awareness has resulted in more frequent recognition and reporting. Although uncommon, POVL is devastating for the patient who awakens with visual deficits not present before surgery.

The incidence of POVL for all non-ophthalmic surgeries is between 0.002 percent and 0.013 percent.^4,3 The reported incidence of POVL is much higher among patients undergoing spine surgery and cardiac surgery.² The incidence of visual impairment after spine surgery has been reported between 0.11 percent and 0.36 percent.^6,4

Common causes

The most common diagnosis associated with blindness after spine surgery is ischemic optic neuropathy; central retinal artery occlusion has also been described. Posterior ischemic optic neuropathy is most often associated with spine procedures, while anterior ischemic optic neuropathy tends to be more prevalent with cardiopulmonary bypass procedures.

The incidence of visual impairment after cardiopulmonary bypass procedures has been reported between 0.06 percent and .33 percent.^7,4 Other causes of perioperative blindness include intracranial pathology anywhere along the visual pathways, including occipital infarction.⁵

Identifying discernible factors associated with perioperative blindness would allow for preoperative risk stratification and guide clinical management strategies. Owing to the infrequent nature of the problem and the paucity of well-designed clinical studies, linking risk factors to causation has been enigmatic. Frequently reported co-morbidities associated with perioperative blindness include age, gender, peripheral vascular disease, hypertension, diabetes, smoking, hypercholesterolemia, anemia, obesity, blood loss, crystalloid transfusion, use of vasopressors, hypotension, increased venous pressures and elevated ocular pressure.

Nonetheless, perioperative blindness has been reported in young and old, ASA I and II patients, patients positioned supine and prone, and patients undergoing a variety of surgical procedures.^8,2

Task force recommendations

The ASA appointed a 12-member task force in 2005 who subsequently issued a “practice advisory” for POVL associated with spine surgery.¹ The task force identified the highest risk patients as those anticipated to undergo a prolonged procedure in the prone position (greater than 6.5 hours) and to have substantial blood loss (greater than 44.7 percent of estimated blood volume).

The task force suggests that physicians consider informing these high-risk patients of the small, unpredictable risk of POVL. They also recommend that high-risk patients should be positioned so their heads are level with or higher than the level of the heart, and that their heads should be maintained in a neutral, head forward position.

Staged spine procedures should be considered for high-risk patients. To maintain intravascular volume during blood loss colloids should be used along with crystalloid solutions. They also suggest that there is no transfusion threshold that would eliminate the risk of POVL related to anemia, and that the use of deliberate hypotension techniques during spine surgery has not been shown to be associated with POVL.

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Conclusion

It appears the causes of POVL are multifactorial. Individual variations in blood supply to the eye and more frequent procedures that are complex and prolonged may help explain some of the cases of POVL.

The mission of the ASA is "to raise and maintain the standards of the medical practice of anesthesiology and improve the care of the patient." One opportunity to fulfill this mission is for us to anonymously provide case reports of POVL to the Postoperative Visual Loss Registry on standardized forms available at www.asaclosedclaims.org.

The hope is that detailed information will lead to a better understanding of the common features active in POVL along with the development of more effective prognostic and therapeutic care strategies.

References:

1. American Society of Anesthesiologists Task Force on Perioperative Blindness. Practice Advisory for Perioperative Visual Loss Associated with Spine Surgery. A Report by the American Society of Anesthesiologists Task Force on Perioperative Blindness. Anesthesiology 2006; 104:1319-1328.
2. Shen Y, Drum M, Roth S. The Prevalence of Perioperative Visual Loss in the United States: A 10-Year Study from 1996 to 2005 of Spinal, Orthopedic, Cardiac, and General Surgery. Anesthesia & Analgesia 2009; 109:1534-1545.
3. Holy SE, Tsai JH, McAllister RK, Smith KH. Perioperative Ischemic Optic Neuropathy: A Case Control Analysis of 126,666 Surgical Procedures at a Single Institution. Anesthesiology 2009; 110:246-253.
4. Newman, NJ: Perioperative Visual Loss After Nonocular Surgeries. American Journal of Opthalmology 2008; 145:604-610.
5. Williams, EL: Postoperative blindness. Anesthesiology Clinics of North America 2002; 20:605-622.
6. Kalyani SD, Miller NR, Dong LM, Baumgartner WA, Alejo DE, Gilbert TB. Incidence of and Risk Factors for Perioperative Optic Neuropathy After Cardiac Surgery. Annuals of Thoracic Surgery 2004; 78:34-37.
7. Nuttall GA, Garrity JA, Dearani JA, Abel MD, Schroeder DR, Mullany CJ. Risk Factors for Ischemic Optic Neuropathy After Cardiopulmonary Bypass: A Matched Case/Control Study Anesth Analg 2001;93:1410-1416.
8. Lee LA, Roth S, Posner KL, Cheney FW, Caplan RA, Newman NJ, Domino KB. The American Society of Anesthesiologists Postoperative Visual Loss Registry: Analysis of 93 Spine Surgery Cases with Postoperative Visual Loss. Anesthesiology. 2006 Oct;105(4):652-659.

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