Posterior ischemic optic neuropathy [Neurosurgery Wiki]

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====== Posterior ischemic optic neuropathy ======

Posterior [[ischemic optic neuropathy]] (PION): may follow surgery (surgical PION).
((Hayreh SohanSingh. Ischemic optic neuropathy. Prog Retin Eye Res. 2009; 28:34–62)).

Usually in the setting of shock, rarely following spine surgery in the prone position 

===== Risk factors =====
 

● surgery in the [[prone position]] (can cause periorbital edema, and rarely, direct pressure on
the orbit)

● lack of tight glycemic control

● use of [[Trendelenburg position]].

● [[Hemodilution]] or overuse of [[crystalloid]] vs. [[colloid]] (blood) fluid replacement

● prolonged [[hypotension]]

● cellular [[hypoxia]]

● decreased renal perfusion

● male gender: odds ratio (OR) = 2.53

● obesity: by clinical assessment or BMI ≥ 30 OR = 2.83

● use of Wilson's frame: OR = 4.30

● length of anesthesia: OR = 1.39 per hour

● EBL: OR = 1.34 per liter

● use of colloid as a percentage of nonblood replacement: less certain (small difference).
OR = 0.67 per 5% colloid
((Postoperative Visual Loss Study Group. Risk factors associated with ischemic optic neuropathy after spinal fusion surgery. Anesthesiology. 2012; 116: 15–24)).