Pediatric Ophthalmic Surgery



Pediatric Ophthalmic Surgery


D. M. Alcorn MD1

Natalia F. Callaway MD1

Darius M. Moshfeghi MD1

Julie Williamson DO, FAAP2


1SURGEONS

2ANESTHESIOLOGIST




STRABISMUS SURGERY


SURGICAL CONSIDERATIONS

Description: Surgical correction of strabismus is a common procedure in ophthalmic practice, as strabismus occurs in 3-5% of the general population. Strabismus surgery is the most common pediatric eye surgery performed. The goal of this procedure is to correct the ocular misalignment caused by this condition. This can be achieved by several methods: (a) weakening the muscles (either by recession, marginal myotomy, or inserting a spacer); (b) strengthening the muscles, by shortening their length (resection), moving the muscle’s insertion toward the limbus (advancement), or tightening the muscle’s fibers (plication or tuck); or (c) by transposing the muscles. Surgery can be performed on any of the four recti muscles (medial rectus, lateral rectus, superior rectus, and/or lateral rectus muscle) or the two oblique muscles (superior oblique and inferior oblique).

There are many indications for strabismus surgery. These include maintaining and restoring binocular vision, improvement in diplopia, improvement of anomalous eye movements, locating and/or transposition surgery for lost muscle, improvement in asthenopic symptoms, improvement in anomalous/altered head posture, dampening of nystagmus, and improvement in psychosocial function.

Often, forced duction testing (FDT) is performed during surgery to determine if there is evidence of limited ductions. This helps to differentiate a paretic muscle vs. a restriction that may limit motility. The eyes should be immobile during FDT as well as during surgery. If succinylcholine has been used, at least 20 min should pass before performing duction testing because succinylcholine causes contraction of extraocular muscles. Alternatively, a different muscle relaxant may be used.

Eye position under GA is well documented: the eyes will become more divergent, and this tendency is increased in misaligned eyes; therefore, exotropic eyes appear more outwardly deviated, and esotropic (inward deviation) eyes actually appear straighter (less esotropic). Hence, it is important that the surgeon have solid measurements preoperatively.

The surgery usually is performed through one of two possible approaches. The limbal incision is made at the junction of the cornea and the conjunctiva, with radial relaxing incisions in the quadrants on either side of the muscle. The other is a fornix or cul-de-sac incision, which is made ˜4-8 mm from the limbus in the quadrant adjacent to the muscle on which to operate. This approach is subposterior to tenon’s capsule. Comfort and cosmesis immediately postop are superior with the fornix incision.

Variant procedure or approaches: In very cooperative older children, an adjustable suture technique may be used. Unlike fixed sutures, the adjustable suture technique allows modification of the position of the muscle. An adjustable suture involves temporarily positioning the muscle, but not finally tying it down until the patient is awake and has been remeasured. After the patient is free of the effects of anesthesia, measurements are retaken, and the muscle is placed in its optimum position, to properly align the eyes, and then securely tied down. This adjustment may be performed the same day of surgery or the following day. Adjustable strabismus surgery ideally reduces the frequency of reoperations by eliminating undesirable early postop undercorrections or overcorrections and increases the rate of surgical success.

Although GA is most commonly used, strabismus surgery may be done using a retrobulbar, peribulbar, subtenon, or subconjunctival block, or even topical anesthesia. Both topical and peribulbar anesthesia have the advantage of providing good akinesia and anesthesia but without the risks associated with a retrobulbar injection (e.g., hemorrhage, optic nerve damage, ocular perforation). When using topical anesthesia, this may be augmented by the use of minimal sedation and/or antianxiety medications.

Usual preop diagnosis: Strabismus



▪ SUMMARY OF PROCEDURE






































Position

Supine (turned 180°)


Incision

Limbal or fornix


Antibiotics

Topical and/or conjunctival by surgeon


Unique considerations

Avoid neuromuscular blockade for forced duction test. Succinylcholine will compromise forced duction test for 15-20 min after administration. A stable deep plane of anesthesia will keep eyes from moving or being disconjugate. Incidence of PONV is 45-85% without prophylaxis. Topical tetracaine may ↓ postop pain. Oculocardiac reflex may cause ↓↓ HR. Hypercarbia, light anesthesia, and remifentanil may increase incidence of OCR.


Surgical time

20-90 min, dependent on procedure and number of involved muscles. Some surgeons use preop antibiotic eye drops (day of surgery, at time of surgery) or use of topical 5% povidone iodine solution in conjunctival fornices with surgical prep. Timing of antibiotic administration may add to surgical time.


EBL

Minimal


Mortality

Rare


Morbidity

Failure to achieve ocular alignment


Infection


Hemorrhage


Anterior segment ischemia


Dissatisfaction with cosmetic result


Postop care

PACU with discharge home within hours. Typically eye patches not required but varies by surgical preference. Some children may need “no-nos” or arm restraints. High incidence of emergence delirium. Topical tetrocaine, one drop at beginning of case, and one drop at end has been shown to ↓ postop pain.


Postop issues: All patients respond differently to the strabismus surgery. Some may be drowsy or have PONV. Pain is usually mild and responds to acetaminophen. Many physicians avoid NSAIDs due to potential bleeding. Children may be frightened to open their eyes, but generally this improves within a few days.


Pain score

2-4 (moderate)





▪ PATIENT POPULATION CHARACTERISTICS























Age range

Children


Male:Female

1:1


Incidence

3-5% of general population


Etiology

Generally idiopathic; muscle palsies may be associated with trauma, inflammation, tumors, and/ or ischemia; restrictive strabismus may occur with thyroid disease (Graves’ disease), fibrosis syndromes, or to a scleral buckle or mass.


Associated conditions

↑ incidence in premature infants, small-for-gestational-age infants, those with a positive family history of strabismus, craniosynostosis syndromes, or associated craniofacial syndromes (Apert, Crouzon, Pfeiffer, etc.), trisomy 21, fetal alcohol syndrome, CNS disease affecting ocular muscles or nerves. No longer considered an independent risk factor for malignant hyperthermia.



ANESTHETIC CONSIDERATIONS


PREOPERATIVE

Strabismus is the most frequent ophthalmic condition in children requiring surgical repair. Most children will be healthy, but the association of strabismus with cerebral palsy, prematurity, and craniofacial and neurological disorders requires careful preop evaluation. Unlike adult eye surgeries that often are performed using retrobulbar or peribulbar blocks, in children GETA is required to achieve successful operative conditions. For the anesthesiologist there are three key perioperative problems associated with strabismus surgery: the oculocardiac reflex (OCR), an extremely high incidence of PONV in the untreated patient (45-85%), and a high incidence of emergence delirium (10-80%). At one time, it was believed that children undergoing strabismus surgery were at increased risk for malignant hyperthermia.
Although this has been shown to be inaccurate, many neuromuscular syndromes are associated with musculoskeletal abnormalities including strabismus and ptosis. A thorough family history of anesthetic problems must be obtained. The surgeon may plan to execute a forced duction test (FDT) in which the eye is grasped at the limbus causing a slight proptosis and moved into each field of gaze to determine if the strabismus is the result of paresis or restrictive extraocular muscles. Succinylcholine compromises the test by causing tonic contractions of the extraocular muscles for 15-20 min after administration, so it is avoided when possible. Neuromuscular blockade will also confuse the results of the FDT.

Anesthetic technique: GETA, LMA






































Induction

Following standard pediatric induction (see p. D-1) the anesthesiologist should have available a vagolytic agent (atropine or glycopyrrolate 0.01-0.02 mg/kg) to attenuate the OCR. Sevoflurane maintenance is associated with diminished OCR compared to propofol and remifentanil. FDT may be performed prior to the administration of NMB. Rocuronium (0.6 mg/kg) may be used to facilitate endotracheal intubation. An oral RAE tube or flexible LMA secured to the mandible will keep the airway away from the surgical field.


Maintenance

May use inhalation anesthetic or TIVA. Avoid N2O as this is a highly emetogenic surgery. Propofol infusion (150-200 mcg/kg/min) may require NMB or augmentation with remifentanil to maintain a motionless patient (be aware that remifentanil may increase OCR). Postop analgesia should be multimodal to minimize opioids (due to high risk of PONV). Acetaminophen (30-40 mg/kg PR or 10 mg/kg iv) and a short-acting opioid (fentanyl 1-2 mcg/kg iv) should be used. Combination therapy for PONV prevention is most effective. Ondansetron (0.1 mg/kg up to 4 mg) plus dexamethasone (0.15 mg/kg up to 5 mg) is preferred. “Super” hydration with 30 mL/kg of crystalloid has also been shown to ↓ PONV. Children exhibiting OCR are more likely to have PONV.


Emergence

The surgeon may request “deep extubation.” In this case, the anesthetic (sevoflurane or TIVA) is increased until the patient has no response to airway manipulation such as suctioning but has steady spontaneous ventilation. The ETT or LMA is removed and an oral airway placed. The patient is allowed to awaken with no further stimulation, monitoring carefully for signs of laryngospasm.


Blood and fluid requirements

Peripheral iv: 22-20 g


Crystalloid to replace calculated deficit plus maintenance during care.


Hydration with 30 mL/kg has been shown to reduce PONV.


Monitoring

Standard monitors (see p. D-1). Temperature.


Positioning

Supine ± shoulder roll. Head of bed usually rotated 180° away.


Complications

Oculocardiac reflex

Traction on the extraocular muscles or the levator, or external pressure to the globe, initiates a trigeminal reflex via parasympathetic output from the vagus nerve. This may cause bradyarrhythmias, AV block, ventricular ectopy, or even asystole. May be attenuated by pretreatment with anticholinergics (see above). Tends to extinguish with repeated manipulation. Treat by removing pressure to globe or tension on the extraocular muscle and administer atropine or glycopyrrolate. Rarely may require epinephrine (1-10 mcg/kg). The oculorespiratory reflex (ORR) is a less well-understood response to trigeminal nerve stimulus that results in cessation of spontaneous ventilation and should be considered if spontaneous ventilation via LMA is the preferred technique.

Accidental extubation

May result from surgical repositioning or removal of drapes. The ETT/LMA should be firmly secured, and the anesthesiogist should be attentive in changes to positioning (e.g., moving from one eye to the other) and removal of drapes.

Emergence delirium

Dexmedetomidine (0.5-1 mcg/kg iv over 10 min) or clonidine (1-2 mcg/kg iv) decrease emergence delirium and may increase parental satisfaction. Dexmedetomidine plus ketamine (1-3 mg/kg/h) decrease emergence delirium, the OCR, pain, and need for postop analgesia in one study. The sub-Tenon block, usually performed by the surgeon, also may decrease emergence delirium.




POSTOPERATIVE















Only gold members can continue reading. Log In or Register to continue

Related posts:

Intracranial Neurosurgery Heart/Lung Transplantation Pancreatic Surgery Obstetric Surgery Hip, Pelvis, Upper Leg Surgery Pediatric Otolaryngology
Tags:
May 23, 2016 | Posted by in ANESTHESIA | Comments Off on Pediatric Ophthalmic Surgery

Full access? Get Clinical Tree

 Get Clinical Tree app for offline access

Complications

PONV

Even with prophylaxis, up to 10% experience PONV. Rescue antiemetic therapy: ondansetron 0.01 mg/kg up to 4 mg; metoclopramide 0.1 mg/kg up to 10 mg; promethazine (> 2 yr old) 0.25-1 mg/kg PO/PR/im/iv up to 25 mg).

Emergence delirium

May be decreased with use of alpha-agonists dexmedetomidine or clonidine (see above). At emergence or in the PACU, treat with opioid analgesia (fentanyl 0.2-0.5 mcg/kg iv) or propofol (1 mg/kg iv).