General Principles

• 1.
  

  General anesthesia is almost always required because children do not tolerate sedation and local analgesia for eye surgery.

  
  
• 2.
  

  Intraocular surgery and surgery of the nasolacrimal duct and eyelids require a bloodless field. Although induced hypotension is seldom indicated for these operations, all measures should be taken to ensure that the anesthetic does not increase bleeding. Smooth, general anesthesia—with optimal airway, good positioning of the child, and quiet emergence without coughing or straining—is important.

  
  
• 3.
  

  The oculocardiac reflex (OCR) is powerful in children but is readily blocked by intravenous atropine (0.01 to 0.02 mg/kg) at induction of anesthesia. Do not rely on atropine given intramuscularly or on local anesthetic (retrobulbar) blocks to prevent this reflex. Monitor the heart rate carefully during manipulation of the eyes and extraocular muscles. In the rare event that atropine is contraindicated, remember that the oculocardiac reflex is more likely to be triggered by a sudden pull than by a gradually applied progressive traction on the extraocular muscles. The reflex usually fatigues rapidly; that is, a second pull does not elicit the same powerful effect.

  
  
• 4.
  

  Some children may be taking medications that have significant side effects ( Table 9-1 ).

  
  
  
  

  TABLE 9-1

  
  

  Ophthalmic Eye Drops That May Cause Systemic Side Effects

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Ophthalmic Medication	Indication	Side Effects
  Echothiophate iodide (phospholine iodide), (long-acting plasma cholinesterase inhibitor)	Glaucoma, esotropia	Nausea, vomiting, abdominal pain, prolonged apnea after administration of succinylcholine
  Timolol maleate topical (ß-blocking agent)	Glaucoma	Bradycardia refractory to atropine, bronchospasm, Exacerbation of the disease in asthmatics
  Acetazolamide (Diamox) (Carbonic anhydrase inhibitor)	Glaucoma	Metabolic acidosis, and depletion of sodium, potassium, and water. It may also rarely trigger anaphylaxis, Stevens-Johnson syndrome, and bone marrow depression.
  Dorzolamine (Carbonic anhydrase inhibitor)	Glaucoma	Bradycardia

   
  
  
  
  
• 5.
  

  Medications that are applied to the conjunctivas or injected into the eye during surgery may have important systemic effects or significant implications ( Table 9-2 ).

  
  
  
  

  TABLE 9-2

  
  

  Ophthalmic Medications That May Have Significant Effects During Anesthesia

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Medication	Potential Adverse Effects and Implications
  Epinephrine, phenylephrine	Hypertension and arrhythmias (especially dangerous during halothane anesthesia). Epinephrine eye drops are specifically contraindicated in children with tetralogy of Fallot because they may precipitate a cyanotic “tet” spell. Phenylephrine drops cause fewer problems, especially if the concentration is limited to 2.5%; but if instilled on a hyperemic conjunctiva, they may cause severe hypertension. Monitor the heart rate and blood pressure carefully after drug instillation. Ensure that you know what is being instilled: 10% phenylephrine drops should not be used in children; cardiac arrest may occur.
  Cyclopentolate (Cyclogyl)	Ataxia, disorientation, psychosis, and convulsions, especially if a 2% solution is used. A 0.5% solution should be used for infants, and a 1% solution for children
  Tropicamide (Mydriacyl)	Behavior disturbance, psychotic reactions, and rarely, vasomotor collapse.
  Scopolamine eye drops	Excitation, disorientation, possible psychosis; may be treated with physostigmine 0.01 mg/kg IV.
  Pilocarpine	Hypertension, tachycardia, bronchospasm, nausea, vomiting, and diarrhea.
  Intraocular injection of acetylcholine	Increased secretions, salivation, bronchospasm, and bradycardia. Treat with IV atropine (to produce miosis after lens extraction).
  Sulfur hexafluoride gas or air injection to globe (to assist in retinal reattachment surgery)	Discontinue N 2 O 20 minutes beforehand to prevent an increase in intraocular pressure (IOP) followed by an even more dangerous decrease in IOP as the N 2 O is withdrawn; this could damage the retinal reattachment

   
  
  
  
  
• 6.
  

  The effects of anesthetic drugs and techniques on IOP must be remembered:

  
  
  
  
  • a.
    

    Atropine (by any route) causes only a very slight increase in IOP. Its use as a premedicant is not contraindicated in children with glaucoma.

    
    
  • b.
    

    All potent inhalation anesthetic agents, intravenous agents (i.e., propofol, thiopental) and nondepolarizing relaxants decrease IOP; effect may be dose related.

    
    
  • c.
    

    Intravenous succinylcholine may cause a transient increase in IOP that is not reliably prevented by pretreatment with a nondepolarizing relaxant drug. The increase in IOP occurs within 30 seconds after administration but abates quickly, returning to normal within 6 minutes. Succinylcholine is usually avoided in children undergoing intraocular surgery. The increase in IOP may be less in those in whom the IOP is already increased (i.e., glaucoma), but it seems prudent to omit succinylcholine in such children, especially if IOP is to be measured. The use of succinylcholine in children with penetrating eye trauma has been controversial. Although it was originally contraindicated, it has been shown to be safe in at least one very large series. Indeed, when given after thiopental in a rapid sequence induction, succinylcholine does not increase in IOP. However, with the intermediate duration, relatively rapid-acting nondepolarizing relaxants (i.e., rocuronium), there are alternatives to succinylcholine for RSI in children with penetrating eye injury.

    
    
  • d.
    

    Ketamine, originally thought to increase IOP, probably has little effect.

    
    
  • e.
    

    Diuretic drugs decrease IOP, and chronic diuretic therapy may reduce the increase in IOP after succinylcholine administration.

    
    
  • f.
    

    Pressure on the globe from a facemask increases IOP, avoid compressing the eyes; use of a contoured mask (i.e., Rendell-Baker-Soucek mask) in small children makes it easier to do this. Laryngoscopy and endotracheal intubation may increase IOP; this effect can be modified by the administration of lidocaine 1 mg/kg IV, preferably 3 minutes before intubation. The insertion of a LMA causes a smaller increase in IOP than tracheal intubation, and its removal may be associated with less coughing and straining. Therefore, the LMA may be useful for children undergoing elective eye surgery.

    
    
  • g.
    

    Coughing, bucking, crying, and straining all markedly increase IOP. Smooth extubation with reduced risk of coughing can be effected by prior administration of lidocaine 1 to 2 mg IV, a small dose of propofol (1 mg/kg) immediately before removal of the tracheal tube, or by deep extubation (contraindicated in the presence of a full stomach).

    
    
  • h.
    

    Hypercapnia increases IOP, and hypocapnia decreases it.

  
  
  
  
• 7.
  

  Succinylcholine causes contracture of the extraocular smooth muscles and interferes with forced duction testing that is performed within 15 minutes after its administration.

  
  
• 8.
  

  The depth of anesthesia for ophthalmology surgery must be sufficient to ensure that the eyes are immobile and fixed centrally; during light anesthesia the eyes often “roll up” cephalad. Ketamine is generally unsatisfactory for ophthalmic surgery because of the associated nystagmus.

  
  
• 9.
  

  Postoperative pain may be troublesome after eye operations, but nonsteroidal antiinflammatory drugs such as rectal acetaminophen (35 to 45 mg/kg administered postinduction) may be sufficient after minor surgery. Immediately after intraocular surgery or trauma repair a retrobulbar block placed during anesthesia may be very effective. Topical analgesics (i.e., tetracaine ophthalmic drops) may significantly reduce postoperative discomfort.

  
  
• 10.
  

  Postoperative nausea and vomiting are common. It may be reduced by the use of propofol as the primary anesthetic, and it may be further reduced by the intraoperative administration of intravenous ondansetron (0.1 mg/kg), dexamethasone (0.0625 to 0.15 mg/kg), dimenhydrinate (0.5 mg/kg), or metoclopramide (0.15 mg/kg). Avoid dimenhydrinate which produces sedation if adjustable sutures are being used.

  
  
• 11.
  

  Be very cautious when using facemask anesthesia for surgery of the eyelids and similar operations (e.g., chalazion excision). Do not use high concentrations of oxygen, which might leak around the mask when the surgeon uses cautery; serious facial burns may occur if the drapes catch fire. An air or helium/oxygen mixture is preferred. Avoid N ₂ O.