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Editorial Views  |   October 2006
Postoperative Visual Loss: Experts, Data, and Practice
Author Notes
  • Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.
Article Information
Editorial Views / Central and Peripheral Nervous Systems / Neurosurgical Anesthesia / Ophthalmologic Anesthesia
Editorial Views   |   October 2006
Postoperative Visual Loss: Experts, Data, and Practice
Anesthesiology 10 2006, Vol.105, 641-642. doi:
Anesthesiology 10 2006, Vol.105, 641-642. doi:
PLEASE allow me to paraphrase recent plaintiffs’ experts in cases related to postoperative visual loss (POVL) in patients who had undergone spine surgery while positioned prone.
The anesthesiologist clearly caused this patient’s vision loss by letting the mean arterial blood pressure drop below 60 mmHg for more than 5 min.
This patient is now blind because the anesthesiologist let the patient’s hematocrit level decrease to less than 24% during the case.
The person providing the patient’s anesthesia failed to avoid prolonged pressure on the eye, leading to the patient’s ischemic optic neuropathy and blindness.
No one wants any patient to experience a catastrophic perioperative event such as permanent blindness. However, these statements (and others similar to them) are devastating to the anesthesiologists who have provided apparent good care to patients undergoing spine procedures, only to find that their patients have awakened with near complete loss of vision in one or both eyes.
What is wrong with these statements? First, these plaintiff “experts” are making statements for which there are no supporting data. Second, good anesthesiologists experience loss of confidence and, in some cases, shattered practices while these legal actions are being resolved. Last, these statements detract attention and effort from the development of studies to determine the etiologies of, and possible preventive measures for, perioperative blindness. Our patients deserve better.
Postoperative visual loss is a real problem in patients undergoing cardiac and spine surgical procedures. POVL occurs more frequently in cardiac surgical patients. There seem to be multiple etiologies for POVL in cardiac surgical patients (e.g.  , embolic, thrombotic, oncotic, and ischemic reasons), several of which may be related to the surgical procedures and operative techniques themselves.1 These patients have numerous visual pathologic consequences, including central retinal artery occlusion and ischemic optic neuropathy (ION). Because there are many factors that may contribute to the development of POVL in cardiac surgical patients, it is a difficult problem to study.
In contrast, POVL in patients undergoing spine surgery entices us with the potential to discern etiologic factors in a group of patients who have less variation in visual pathology and outcomes. Dr. Lee et al.  2 report these findings this month in their review of the first 6 yr of cases submitted to the American Society of Anesthesiologists Postoperative Visual Loss Registry. This registry was established in 1999 after anesthesiologists and others voiced concern that the frequency of POVL seemed to be increasing, particularly in patients undergoing spine surgery. In their comprehensive report of 93 cases of POVL in patients undergoing spine surgery, the authors note that 89% of the patients developed ION, with the other 11% of patients experiencing central retinal artery occlusion. Most patients with central retinal artery occlusion had evidence of ocular trauma and unilateral visual loss, suggesting that in some instances, positioning or other potentially controllable factors may have played a role. Many of the patients with ION had bilateral visual loss, suggesting that one or more systemic factors, including inherent patient-specific factors, may have been present. In the patients with ION, the highest-risk group included patients who had anesthetics lasting more than 6 h and estimated blood loss of greater than 1 l. The authors were unable to find any factor under the direct control of anesthesiologists that led to a high frequency of ION. Specifically, patients who developed ION had intraoperative mean arterial blood pressures and hematocrits that ranged widely, with patients at each extreme of these parameters developing ION.
What is the typical natural history of ION in spine surgery patients? After awakening, the patients often note an inability to see, citing that they can only perceive gray shadows (usually in response to objects in motion). An ophthalmologic examination may show an edematous optic disc if the ischemia is associated with the anterior portion of the optic nerve, but more often there are no acute funduscopic findings. The papillary light reflex may be reduced or absent, but this finding, too, often is difficult to discern. Imaging of the visual pathways by magnetic resonance or computed tomography is usually fruitless but may be worthwhile to confirm the absence of other pathologic changes (e.g.  , cerebral infarction or hemorrhage). As demonstrated by Dr. Lee et al.  , vision rarely is improved over time from the initial impaired postoperative status.
A recently published American Society of Anesthesiologists Practice Advisory3 provided several important findings:
The use of deliberate hypotensive techniques during spine surgery has not been shown to be associated with the development of perioperative visual loss.
At this time, there is no apparent transfusion threshold that would eliminate the risk of perioperative visual loss related to anemia.
These findings seem to be confirmed by data from the current article and negate the veracity of the first two statements above that are paraphrased from plaintiffs’ experts. The current article also reports that none of the 83 spine surgery patients who developed ION had periorbital or ocular findings suggestive of intraoperative trauma or externally applied pressure, thus negating the third statement paraphrased above.
Unfortunately, the current article does not advance our understanding of potential etiologic factors that cause ION in spine surgery patients except for the confirmation that the highest-risk patients are those who undergo anesthetics greater than 6 h in duration and who experience intraoperative blood loss of more than 1 l. How can we best use this information? First, we should consider informing patients in this high-risk group that there is a small, unpredictable risk of POVL. Second, we should collaborate with our surgical colleagues to consider staging spine procedures in these high-risk patients in an effort to reduce prolonged, bloody procedures in patients who are positioned prone. This latter suggestion has been endorsed by the North American Neuro-Ophthalmology Society and supported by the North American Spine Society.
Opportunities at the bench side to study POVL are severely limited by the lack of animal models that have eye and visual pathway characteristics and anatomy similar to that of humans. Newer or improved imaging modalities (i.e.  , positron emission tomography) may offer the ability to better distinguish between ION occurring in the anterior or posterior optic nerve, but it is unclear whether imaging techniques can provide the information needed to make a positive impact on the frequency of ION. In the meantime, we must rely on multi-institutional case–control and difficult-to-perform prospective studies of this rare but catastrophic event to determine potential risk factors and practice changes that may lead to reductions in its frequency.
In summary, Dr. Lee et al.  , along with the American Society of Anesthesiologists, should be congratulated for providing data that at least help us to identify patients undergoing spine surgery who fall into a high-risk group for POVL. Ironically, their data also tell us what we do not yet know about POVL. The current article provides important information that, if examined responsibly by plaintiffs’“experts,” should reduce the frequency of unsubstantiated claims and promote a more informed and fair resolution of legal actions.
Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.
References
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; 93:1410–6Nuttall, GA Garrity, JA Dearani, JA Abel, MD Schroeder, DR Mullany, CJ
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; 105:652–9Lee, LA Roth, S Posner, KL Cheney, FW Caplan, RA Newman, NJ Domino, KB
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; 104:1319–28American Society of Anesthesiologists Task Force on Perioperative Blindness,