Letters to the Editor ND:YAG LASER CAPSULOTOMY UNDER GENERAL ANESTHESIA IN THE SITTING POSITION To the Editor: We read with great interest the recent article by Longmuir and colleagues1 in which they describe an interesting technique for Nd:YAG laser capsulotomy in a seated position under general anesthesia, also mentioned elsewhere.2,3 The authors concede this is a technically challenging procedure “requiring additional anesthesia and nursing staff to help position the patient.”1 We propose a simple and safer alternative that maintains the patient in a supine position, thus avoiding problems associated with positioning and cerebral blood flow. The anesthetized patient is at risk of orthostatic hypotension when being transferred from the supine to the sitting position. This decrease in blood pressure may persist throughout the procedure due to a decrease in venous return combined with anesthesia-induced vasodilation and decreased myocardial contractility. This decrease in blood pressure, combined with the hydrostatic gradient from the heart to the brain, results in a decrease in cerebral perfusion. There are documented cases of cerebral ischemia in adult patients undergoing shoulder surgery in the sitting position.4 These complications can be partially attributed to the decrease in cerebral perfusion pressure in the sitting position. Maintenance of cerebral perfusion is critical for neurodevelopment. The importance of avoiding hypotension during anesthesia in order to protect the developing brain is gathering much attention in the pediatric anesthesiology community.5 To ensure an adequate cerebral perfusion pressure in an anesthetised patient in the sitting position, the mean arterial pressure (MAP) can be measured at the level of the circle of Willis via an arterial line. However, invasive blood pressure monitoring is undesirable during such a short procedure as a laser capsulotomy. A less exact alternative would be to extrapolate the cerebral perfusion pressure from a blood pressure cuff measurement. For every 1 cm in vertical distance from the blood pressure cuff to the external auditory meatus, the MAP at the circle of Willis decreases by 0.77 mm Hg compared to the value measured by the cuff.6 When placing patients in the seated position, attention must be given to the arms, hips and knees to avoid stretch injuries to the brachial plexus and to the sciatic nerves.7 Also care must be taken to avoid cervical flexion in patients with cervical instability (such as Trisomy 21). The endotracheal tube needs to be carefully fixed to avoid accidental extubation. We have developed a safer and simpler approach that we have used for the past 3 years by maintaining the supine position and only turning the head laterally while the patient is under general anesthesia. Using the Nd:YAG laser (NIDEK YC-1800) without the chinrest and positioning the patient’s head on a narrow headrest, we have achieved excellent visualization and stability for various procedures

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FIG 1. Child under general anesthesia, in a supine position, ready to have a Nd:YAG laser capsulotomy performed.

including capsulotomy in children (Figure 1). We recommend this technique as an alternative to the one reported by Longmuir colleagues.1 Aaron Winter, MSc Kathryn DeKoven, MD, FRCPC Rosanne Superstein, MD, FRCSC Patrick Hamel, MD, FRCSC Department of Ophthalmology, Centre Hospitalier Universitaire Sainte-Justine, University of Montreal, Montreal, Quebec, Canada

References 1. Longmuir S, Titler S, Johnson T, Kitzmann A. Nd:YAG laser capsulotomy under general anesthesia in the sitting position. JAAPOS 2013;17:417-19. 2. Stager DR Jr., Wang X, Weakley DR Jr., Felius J. The effectiveness of Nd:YAG laser capsulotomy for the treatment of posterior capsule opacification in children with acrylic intraocular lenses. JAAPOS 2006;10: 159-63. 3. Cinal A, Demirok A, Yasar T, Yazicioglu A, Yener HI, Kilic¸ A. Nd:YAG laser posterior capsulotomy after pediatric and adult cataract surgery. Ann Ophthalmol 2007;39:321-6. 4. Pohl A, Cullen DJ. Cerebral ischemia during shoulder surgery in the upright position: a case series. J Clin Anesth 2005;17:463-9. 5. Weiss M, Bissonnette B, Engelhardt T, Soriano S. Anesthetists rather than anesthetics are the threat to baby brains. Pediatr Anesth 2013;23: 881-2. 6. Sia S. Hypotensive technique and sitting position in shoulder surgery. Anesth Analg 2003;97:1198. 7. Warner MA. Patient positioning and related injuries. In: Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC, eds. Clinical Anesthesia. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2009. 809-11. http://dx.doi.org/10.1016/j.jaapos.2013.10.021 J AAPOS 2014;18:208. Copyright Ó 2014 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/$36.00

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