The Americal Society of Anesthesiologists Postoperative Visual Loss Registry

1. The Americal Society of Anesthesiologists Postoperative Visual Loss Registry Analysis of 93 spine surgery cases with postoperative visual loss Anesthesiology 2006; 105:652-9 R2 김용일

2. Postoperative visual loss (POVL) • Relatively uncommon but devastating complication • 0.2-4.5% in spine & cardiac surgery • Ophthalmologic lesions • Ischemic optic neuropathy (ION) • Not consistent with an etiology of globe compression • associated atherosclerotic risk factors • Adverse effects of antihypertensive medications • Sildenafil • Multi-institutional database • Very low number of POVL case • ASA POVL Registry • Established in 1999

3. Materials and Methods

4. Study populations • POVL occurring within 7 days after nonocular surgery • 93 cases associated with spine surgery

5. Patient and perioperative characteristics • Information collected • Patient demographics • Medical Hx : riskfactors for vascular disease, current medications, surgical history • Obesity, HTN, coronary artery disease, MI, CVA, DM, hypercholesterolemia, tobacco Hx • Intraoperative information • Procedure description, number of levels, type of headrest & surgical frame, position, frequency of eye checks • Duration of anesthetic, surgery, prone positioning • Type of anesthetic, drugs, fluids, estimated blood loss, type of blood products, preoperative & lowest Hb/Hct, urine output • Use of deliberate hypotension, specific hypotensive agents • Intraoperative blood pressure • Presence of hypothermia (<35℃) • Intraoperative events • Cardiiogenic shock, cardiac arrest, seizures, direct trauma to the eye

6. Ophthalmologic examination characteristics and diagnostic criteria • Ophthalmologic examination • Type of visual deficit, time when visual symptoms were first noted, funduscopic examination, ophthalmologic diagnosis • Classification of specific lesion • Central retinal artery occlusion (CRAO) • Pale ischemic retina with pathognomonic cherry-red spot at macula • And relative afferent pupillary defect or reduced pupillary light reflex • Anterior ischemic optic neuropathy (AION) • Edematous disc with or without peripapillary flame-shaped hemorrhages • And relative afferent pupillary defect or reduced pupillary light reflex • Posterior ischemic optic neuropathy (PION) • Normal early funduscopic examination • With relative afferent pupillary defect or absent pupillary light reflex • Any treatment and prognosis for recovery of vision was noted • Inclusion criteria • Any POVL case associated with spine surgery from ASA POVL Registry • Diagnosis of CRAO, AION, PION, or unspecified ION

7. Results 93 cases of POVL associated with spine surgery As of June 2005

8. No statistically significant differences between AION and PION • Demographics, coexisting diseases, surgical characteristics, anesthetic management • Uncertainty whether AION and PION are different disease states with separate etiologies  all AION, PION, and unspecified ION were combined under ION

9. Demographics and coexisting diseases No patient had a preoperative history of glaucoma

10. Description of operations and positioning

11. Description of operations and positioning (2) All were positioned prone for a portion of procedure Except two anterior spine procedure Eye checks were documented by anesthesiologist in 51%

12. Anesthetic management Mean anesthetic duration 9.8 ± 3.1 h • General anesthesia • Combination of volatile and narcotic (89%) • Isoflurane (59%), sevoflurane (14%), desflurane (22%), nitrous oxide (29%) • TIVA with propofol and narcotic (2%) • Unknown general anesthetic agents (8%) Median EBL 2.0 L

13. Anesthetic management (2) Colloid (hydroxydthyl starch or albumin) used in 30% Nadir Hct of 30% or greater in 17% of cases Urine output was less than 0.5ml/kg/h In 24% of cases

14. Anesthetic management (3) Labetalol or esmolol (n=10) Volatile agents (n=5) Phenylephrine administered in 27% Hypothermia in 10%

15. Ophthalmologic findings Complete blindness with loss of light perception 64 of 138 affected eyes (47 Pts) Median onset time of reporting Postoperatively 15 h

16. Spine surgery cases with CRAO Not significantly different Horseshoe headrests in 3 cases Foam pads in 2 cases Miscellaneous headrests in 5 cases Not significantly different Eye checks in 6 cases

17. Discussion

18. Limitation of this study • POVL is low-incidence complication  prospective data collection was impractical • Incidence of any POVL cannot be ascertained • Reporting bias, error from retrospective data collection • Increase in POVL in spine surgery may be related to • Increased awareness of the problem • Increased rates of spinal fusion operations

19. Etiology of ION • Etiology of ION remains unknown • Male patients is 72% • 48% male : 52% female in spinal fusion procedures • National inpatient sample data for 1999 • Influence of sex on ulnar nerve injuries : 70% male • Previous study of ulnar neuropathy • Anatomical differences & hormonal differences • Protective effect of estrogen on cerebral ischemia • Experimental animal models

20. Etiology of ION (2) • Age • Older patients may be more vulnerable • Young age did not immune to this complication • “Normal” anatomical or physiologic variation in optic nerve blood supply  may place more at risk than others • Preoperative identification of high risk group  not currently possible

21. Etiology of ION (3) • Mayfield pins used in 16 pts • With eyes free of pressure  ION occurs in absence of pressure on globe • Lack of retinal ischemia in ION • ION in both eyes in the majority  more consistent with a systemic etiology • 10 Pts of CRAO (result from globe compression)  all had unilateral disease  usually with ipsilateral periocular trauma

22. Etiology of ION (4) • Blood pressure management varied widely • Autoregulation of cerebral blood flow has been well demonstrated • Not clear whether optic nerve also has autoregulation • No difference in lowest BP between visual loss and no visual loss • Case-control study by Myers et al. • Anemia • Cannot be discerned by this study • ION occurs in the absence of anemia

23. Etiology of ION (5) • Estimated blood loss (EBL) and anesthetic duration EBL of 1,000ml or greater in 82% Anesthetic duration of 6 h or longer in 94% • Not yet enough information to confirm a relation

24. Etiology of ION (6) • Prone position in 72% • Hypothesis • Venous pressure within optic nerve may increased during prone  Perhaps due to venous engorgement • Intraocular pressure increased in prone position • Artery on posterior optic nerve are small end-vessel from surrounding pia •  blood flow in posterior optic nerve may be susceptible to increased venous pressure • Case reports of ION after radical neck operation with bilateralinternal jugular vein ligation • Increased venous and intracranial pressure • Hypothesis “compartment syndrome of the optic nerve” • Increased venous pressure and interstitial fluid accumulation • Within relatively nondistensible space • Semirigid lamina cribrosa at optic nerve head • Bony optic canal  recommended head-up position and colloid-based fluid resuscitation • Its role in prevention of ION remains undetermined

25. Etiology of ION (7) • ION almost always occurred • Without any accompanying evidence of vascular injury in other critical organs • Such as heart or brain • Optic nerve vasculature may be uniquely vulnerable tohemodynamic perturbations in prone position in some patients

26. Summary • More than two thirds of ASA POVL Registry • Related to spine surgery in prone position • 89% : ION • Relatively healthy Pts • Wide range of nadir Hct & BP management  multifactorial etiology • EBL > 1,000ml or anesthetic duration > 6 hr  96% • For lengthy spine surgery in prone position  risk of visual loss should be considered