Postoperative Blindness after Spine Surgery in the Prone PositionRichard NgJune 21, 2011

A Bad Day at the Office… 15 y/o M with scoliotic

deformity after ASIA A C5 level injury at age 4

PSIF from T2 – Pelvis Patient positioned prone, head

held by pins in halo EBL 4000cc, 8 hour operation Extubated POD5: bilateral complete blindness Neurology & ophthamology

consults -> posterior optic ischemic neuropathy

At 6 months, return of light perception & shapes < 3ft

Samdani et al. Vision Loss After Spinal Fusion for Scoliosis in a Child With Spinal Cord Injury. J Spinal Cord Med. Nov 2009;32(5):591–594

A rare complication…

What are the causes of postoperative vision loss (POVL) after spine surgery in the prone position?

How do we prevent it?

Incidence POVL in non-ophthalmic surgery:

0.056%: “eye injury” over 60,965 cases from 1988-1992 (Roth et al., Anesth., 1996)

0.0008%: vision loss >30 days in 410,189 non-cardiac pts from 1986-1998 at Mayo Clinic (Warner et al., Anesth Analg, 2001)

Estimated 0.07% for cardiac surgery, <1/10000 (0.001%) for appendectomy (Shen et al. Anesth Analg, 2009)

Incidence POVL in spine surgery:

0.094%: 4,728,815 cases of laminectomy/discectomy/spinal fusion in US NIS database from 1993-2002 (Patil et al. Spine, 2008) Highest incidence was scoliosis at 0.28%

0.03%: spinal fusion in 465,345 discharges from 1996-2005 US NIS database (Shen et al. Anesth Analg, 2009)

Smaller series ranging from 0.09% to 0.2%

Pathophysiology Cortical Blindness

Infarction of visual pathways in brain Normal pupillary reflex, normal fundoscopy

Retinal Artery Occlusion (central vs branch) External compression or emboli CRAO: Afferent pupil defect, retinal edema,

“cherry red spot”

Ischemic Optic Neuropathy (ION) Anterior versus Posterior Afferent pupil defect, optic disc edema,

subsequent atrophy

Cortical Blindness Stroke of visual pathways

Incidence: 0.014% (1.4 / 10000) in spinal fusion More common than in cardiac surgeries! (Shen et al.)

Much more common in patients < 18 (4.3/10000) versus patients > 18 (0.12-0.25/10000)

Patil et al. showed that non-CRAO, non-ION visual loss 5.8 times more prevalent in age <18 vs 18-44.

Limited literature related to spine surgery Thought to be caused by embolism or sustained

profound hypotension resulting in infarction (Williams, Anesthesiology Clin N Am, 2002)

Retinal Vascular Occlusion Central Retinal Artery

Occlusion ? Due to external compression

due to positioning Increased IOP -> occlusion of

retinal artery Case of CRAO with OptiGard

goggles Branch Retinal Artery

Occlusion Microemboli thru right to left

shunt Central Retinal Vein Occlusion

Roth et al. Visual Loss in a Prone-Positioned Spine Surgery Patient with the Head on a Foam Headrest and Goggles Covering the Eyes: An Old Complication with a New Mechanism, Anesth Analg, 2007Katz and Karlin, Visual Field Defect After Posterior Spine Fusion, Spine, 2005.

Retinal Vascular Occlusion Incidence:

Retinal vascular occlusion: 0.6/10000 in spinal fusion (Shen et al)

CRAO: 0.001% (0.1 / 10000) (Patil et al.) All cases of CRAO reported in ASA Postoperative Vision

Loss Registry were unilateral (Lee et al., Anesth, 2006)

Multiple case reports relating to horseshoe headrests

A small turn in the patient’s head may result in pressure to the globe

Hollenhorst et al. Unilateral blindness occurring during anesthesia for neurosurgical operations. AMA Arch Ophthalmol 1954Grossman and Ward. Central Retinal Artery Occlusion After Scoliosis Surgery with a Horseshoe Headrest. Spine, 1993.Bekar et al. Unilateral Blindness due to Patient Positioning During Cervical Syringomyelia Surgery: Unilateral Blindness After Prone Position. J Neuro Anesth, 1996.

Ischemic Optic Neuropathy Anterior ION

Anterior = in the eye (optic disc)

Perfusion pressure affected by MAP and IOP

Posterior ION Posterior = optic nerve

in orbit behind globe (retrobulbar)

Less blood flow than in anterior portion, less autoregulation

Ischemic Optic Neuropathy Incidence:

Patil et al.: ION incidence of 0.006% over all spine cases, 0.02% in spinal fusion scoliosis surgeries.

Chang et al. (John Hopkins): ION incidence of 0.028% in 14,000 patients

Most cases are PION and are frequently bilateral (>50% in Lee et al.)

Patil et al. used risk-adjusted multivariate analysis to identify Hypotension (OR 10.1), Peripheral Vascular Disease (OR 6.3) Anemia (OR 5.9), and Blood Transfusion (OR 4.3) as strongest risk factors for ION in 271 patients

“Hypotension” and “Anemia” not specific to intraoperative hypotension or anemia

Prone Positioning Prone positioning has been shown to increase

intraocular pressure (IOP) in anesthetized patients (Cheng et al, Anesth, 2001) 20 patients without eye disease had spine surgery

prone IOP followed with Tono-pen

Supine: 13 ± 1 mmHg Prone: 27 ± 2 mmHg Prone at end of case (average 320 min): 40 ± 2 mmHg Supine at end of case: 31 ± 2 mmHg

Unclear how much intraoperative fluids / edema contributed to increase in IOP over duration of surgery

Literature Case Series:

Cheng et al. Neurosurg, 2000: Survey sent out, 24 patients reported. 2 cases CRAO despite head held in pins 12/24 patients had hematocrit > 30%, and 5/24 had EBL<500cc

American Society of Anesthesiologists Postoperative Visual Loss Registry: 93 spine cases 1999-2005, (Lee et. al., Anesthesiology, 2006) 89% of cases were ION (60% PION), 11% of cases CRAO No clear association with anesthetic agent, hypotension,

hematocrit 94% of cases > 6 hours

Literature Case-Control Series:

Myers et al. Spine, 1997: 37 cases of POVL after spine surgery through survey and review of recent cases. Matched to control group for age, type of surgery, number of

levels, instrumentation Relative to control group, affected group had increased

blood loss and longer surgery No difference in hematocrit or blood pressure

Holy et al. Anesth, 2009: 17 cases of ION after any surgery, 1998-2005 Each case matched to two controls for age and surgery. 4/17

were spine surgeries. No statistically significant correlation with EBL, intraop

hypotension, hematocrit, surgical time, hypothermia, vasopressors

Literature Literature Reviews:

Roth et al, Perioperative visual loss: what do we know, what can we do?, Brit J Anesth, 2009. “In summary, much is unknown about the pathogenesis of perioperative ION”

Gill et al, Postoperative visual loss associated with spine surgery, Eur Spine J, 2006. 7 studies, 102 cases “The etiology of postoperative visual loss is probably multifactorial, however,

patients with a large amount of blood loss producing hypotension and anemia along with prolonged operative times may be causing a greater risk in developing visual disturbances.”

Lee et al, Postoperative Ischemic Optic Neuropathy, Spine, 2010. 19 studies The overall strength of evidence to identify predictors of postoperative ischemic

optic neuropathy is “Very Low,” that is, any estimate of effect is very uncertain. The overall strength of evidence for current recommended preventative measures is also “Very Low,”

Summary Causes:

Direct pressure to eye Multifactorial

Prone positioning ?Prolonged operation ?Blood loss ?Hypotension ?Fluid Replacement

PreventionRecommendations of ASA Task Force on

Perioperative Blindness (2006) Consider informing patients of risk of

perioperative visual loss. Use colloids along with crystalloids to maintain

euvolemia. Position the head at the level of heart or higher,

and in a neutral position, when possible. Consider staging prolonged procedures in high-

risk patients.

And… appropriate positioning and frequent eye checks in the prone position may CRAO and other direct eye injuries from globe compression