Anesthesiology

Refractive surgery

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What the Anesthesiologist Should Know before the Operative Procedure

Laser refractive surgery is increasingly popular as a mode of permanent vision correction. The goal of the surgery is to modify the shape of the cornea and thus correct myopia, hyperopia, astigmatism and/or presbyopia. A relatively new technique, it has developed rapidly over the past 35 years and continues to undergo constant development and modification.

The most commonly performed refractive procedures are laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and laser epithelial keratomileusis (LASEK).

Refractive surgery is always elective. It is a low risk procedure with no major physiologic derangements, fluid shifts, or blood loss.

The procedure is often carried out in an outpatient center, and, in many cases, need not involve an anesthesiologist. However, the potential for complications is always present and should never be ignored. The anesthesiologist may be called for a more complex or uncooperative patient, or if a complication has occurred.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Refractive surgery is always an elective procedure and never performed on an urgent basis. There is essentially no risk of delay to obtain additional information, where appropriate.

  1. Emergent- n/a

  2. Urgent- n/a

  3. Elective- surgery is always purely elective, and can be delayed as needed in order to ensure the patient is an appropriate candidate.

2. Preoperative evaluation

Patients presenting for most ophthalmologic surgeries tend to be very young, very old, or have extensive comorbidities. Refractive surgery stands in contrast to this. Due to its purely elective nature and rather strict exclusion criteria, patients tend not to be of extremes of age, and are generally quite healthy.

In order to be a candidate for refractive surgery, patients generally must meet the following criteria:

  • --Stable refraction of at least one year's duration

  • --Age 18 years or older (as younger patients may not have stable refractions)

  • --Absence of ocular contraindications including keratoconus, herpetic keratitis, corneal dystrophy, cataract, glaucoma or other pathology of the cornea or anterior segment

  • --Absence of the following medical conditions, which can interfere with wound healing:

    1. Diabetes mellitus, especially if associated with absent corneal sensation

    2. History of keloid formation

    3. Autoimmune diseases including rheumatoid arthritis, systemic lupus and erythematosus, polyarteritis nodosa

    4. Immunocompromised

  • --Not pregnant or lactating (which can cause changes in corneal hydration and refraction)

  • --Not taking oral steroids, accutane, amiodarone or hormone replacement therapy

Although a thorough medical history should always be obtained, routine medical testing prior to the procedure has not been shown to improve outcomes in other ophthalmological surgeries. As always, the anesthesiologist must bear in mind the patient's comorbidities if a general anesthetic is required or if one must convert to a general anesthetic. Induction drugs and doses may need to be adjusted on patients with a cardiac history, or those who are dehydrated or frail.

  1. Medically unstable conditions warranting further evaluation include: Although routine medical testing is not indicated, a medically unstable patient should not undergo elective surgery.

  2. Delaying surgery may be indicated if: there is significant acute change in the health of the patient .

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system

i. Perioperative evaluation

  1. Acute/unstable conditions: despite the exceedingly low cardiovascular risk associated with refractive surgery, patients with unstable cardiovascular conditions of any type should not undergo elective procedures.

  2. Baseline coronary artery disease or cardiac dysfunction - Patients with stable cardiovascular conditions can generally be candidates for refractive surgery, with the pre-operative interview confirming the stability of these conditions.

ii, Perioperative risk reduction

No specific cardiovascular risk given the low risk nature of the procedure. If hypertension is exacerbated during the procedure, beta blockers, hydralazine, or other antihypertensives may need to be administered in order to keep the blood pressure within a normal range.

c. Pulmonary

  1. COPD:

    • Perioperative evaluation: Not indicated

    • Perioperative risk reduction: It may be best to avoid general anesthesia in patients with poor pulmonary reserve

  1. Reactive airway disease (Asthma)

    • Perioperative evaluation: Not indicated

    • Perioperative risk reduction: Likely best to avoid general anesthesia

d. Renal-GI:

  • Perioperative evaluation: not indicated

  • Perioperative risk reduction: no specific recommendations

e. Neurologic:

  1. Acute issues: Surgery should be delayed for acute neurologic issues

  2. Chronic disease: No specific recommendations

f. Endocrine:

Diabetics are particularly poor candidates for refractive surgery. In addition to retinal ischemia and edema, they may have poor epithelial adhesion, thus increasing the risk of erosion. Despite this, there is recent evidence to suggest that diabetics who have intact corneal sensation still have satisfactory results with refractive surgery. Blood sugar fluctuations can also cause unpredictable refractive changes. Specific surgeons may have varying willingness to perform refractive surgery on diabetic patients. From an anesthetic standpoint, perioperative glucose checks should be performed and treated as appropriate.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

As mentioned above, patients with autoimmune disorders or immunocompromised are often poor candidates for refractive surgery, given the potential for interference in wound healing.

4. What are the patient's medications and how should they be managed in the perioperative period?

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

  1. Patients tend to be relatively healthy, and are often on few or no medications.

i. What should be recommended with regard to continuation of medications taken chronically?

  1. Cardiac - should generally be continued through surgery. This includes antihypertensives, antiarrhythmics, and cholesterol lowering medications.

  2. Pulmonary - should be continued

  3. Renal - should be continued

  4. Neurologic - should be continued

  5. Anti-platelet - should generally be held, but must be considered on a case-by-case basis

  6. Psychiatric - should be continued

j. How To modify care for patients with known allergies -

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

The OR should be prepared with latex-free products

l. Does the patient have any antibiotic allergies- - Common antibiotic allergies and alternative antibiotics]

If the patient has an allergy to fluoroquinolone antibiotics, one can consider tobramycin drops. Alternatives to these include tetracycline or erythromycin.

m. Does the patient have a history of allergy to anesthesia?

  1. Malignant hyperthermia:

    1. Documented- avoid all trigger agents such as succinylcholine and inhalational agents:

      1. Proposed general anesthetic plan: It may be ideal to opt for a topical or regional anesthetic, with or without sedation. If general anesthesia is absolutely necessary, a propofol infusion could be considered.

      2. Insure MH cart available:

        [- MH protocol]

    2. Family history or risk factors for MH: should be treated as though they have a personal documented case of malignant hyperthermia

  2. Local anesthetics/ muscle relaxants: A patient with a true/documented local anesthetic allergy could be a candidate for use of a local anesthetic of a different class.

5. What laboratory tests should be obtained and has everything been reviewed?

It is generally not necessary to obtain baseline lab values prior to surgery.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

The decision on what type of anesthetic to perform is multifactorial, including the surgeon's preference, the patient's preference, and the ability of the patient to be cooperative. The vast majority of refractive surgery procedures can be performed with topical anesthetic only, as the procedure is not significantly painful or stimulating. A pre-operative anxiolytic is often added.

a. Regional anesthesia - Can be considered in a cooperative patient if topical anesthetic is deemed inadequate

  1. Neuraxial is not an option for refractive surgery

    1. Benefits - n/a

    2. Drawbacks - n/a

  2. Issues - n/a

  3. Peripheral Nerve Blocks are generally not required, but should a block be needed, the patient will likely require a small amount of propofol (20 - 50mg) or remifentanyl (20 - 50mcg).

    1. Benefits - 1. Provides excellent analgesia, 2. Patient can remain awake for the procedure

    2. Drawbacks - 1. Inability to fixate the eye centered on the visual axis, 2. Chemosis preventing the proper placement of the suction ring, 3. Risk of retrobulbar hemorrhage, 4. Risk of intravascular injection or anaphylaxis from local anesthetic, 5. Patient discomfort during the injection

    3. Issues

b. General Anesthesia is generally not required for refractive surgery, but could be considered for an uncooperative patient. Although pediatric patients undergo refractive surgery only on rare occasions, general anesthesia may need to be considered in that population.

  1. Benefits - 1. Not reliant on patient's cooperation during procedure, and can ensure that they remain still

  2. Drawbacks 1. Potential for increased extraocular pressure during intubation and emergence, 2. Oculocardiac reflex more common (see below), 3. Leakage of anesthetic gases have potential to cause laser malfunction, 4. Subjecting patient to typical risks of general anesthetic including cardiac and pulmonary concerns.

  3. Other issues - If not contraindicated, a laryngeal mask airway is often the best technique for general anesthesia in the setting of refractive surgery. Given the short duration of the case, it would be reasonable to consider a mask anesthetic. However, the mask will likely need to be displaced to allow positioning of the suction ring by the surgeon. This increases the risk of leaking anesthetic gases, which have the potential to cause laser malfunction. Nitrous oxide is of particular concern.

  4. Airway concerns - Given the bed positioning, location of the surgical field, and draping, the anesthesiologist may have limited access to the airway. Extra care should be taken to secure the endotracheal tube or LMA, once placed.

c. Monitored Anesthesia Care

  1. Benefits - can provide anxiolytic for the nervous patient without subjection to general anesthesia

  2. Drawbacks - disinhibition may make it difficult for the patient to follow direction/remain still for the procedure

  3. Other Issues - a small dose of a benzodiazepine is usually sufficient.

6. What is the author's preferred method of anesthesia technique and why?

The optimal anesthetic for this procedure is topical application of local anesthetic to the eye, which provides adequate analgesia with minimal risk and recovery time. This can be supplemented with small doses of a benzodiazepine prior to surgery, in order to provide anxiolysis yet still facilitate patient cooperation and interaction.

  1. What prophylactic antibiotics should be administered? - Fluoroquinolone eyedrops are administered prior to the procedure. Prophylactic systemic antibiotics are not indicated.

  2. What do I need to know about the surgical technique to optimize my anesthetic care? - The procedures tend to be very brief, and the anesthesiologist should keep that in mind when considering medication dosages. LASIK, by far the most common of the refractive surgeries, involves the use of a microkeratome to raise a corneal flap roughly the size of a contact lens. It is then reflected at its hinge. At this point the patient is asked to fixate on a light and the excimer laser is used to ablate part of the corneal stroma and the flap is replaced. No sutures are needed to stabilize the cap.

  3. What can I do intraoperatively to assist the surgeon and optimize patient care? It is imperative that the patient remain still during the surgery, and the anesthesiologist should strive to facilitate this in order to assist the surgeon.

  4. What are the most common intraoperative complications and how can they be avoided/treated? Intraoperative complications are rare. One should be aware that during creation of the flap during LASIK, the microkeratome may create a thin or incomplete flap, potentially forcing the surgeon to abort the procedure and allow the cornea to heal before another attempt at refractive surgery.

  1. Cardiac complications- Although very rare in refractive surgery, any anesthesiologist involved in managing ophthalmic surgery should be knowledgeable about the oculocardiac reflex (OCR). Caused by traction on the extraocular muscles or pressure on the globe, its most common manifestation is bradycardia, and often resultant hypotension. Arrhythmias including bigeminy, ectopy, nodal rhythms, AV block or asystole. The afferent pathway of the OCR is via the ophthalmic division of the trigeminal nerve, and the efferent pathway is through the vagus nerve. Because of the vagus innervation of the abdominal viscera, the reflex may be accompanied by nausea. Treatment, if necessary, should include cessation of the inciting stimulus. When severe, treatment with anticholinergics (glycopyrrolate or atropine) is indicated. If an effective local blockade is done, it can ablate the reflex by blocking the afferent nerve pathway. If a nerve block is performed, there is risk of central spread of the local anesthetic, which, if severe, can lead to dysrhythmias and ultimately cardiovascular collapse. It is imperative that there be appropriate resuscitation equipment available should this occur.

  2. Pulmonary- There are no specific pulmonary complications associated with the surgery, but one should be aware of possible pulmonary complications associated with general anesthesia, should that be the anesthetic of choice. Central spread of local anesthetic, intravascular injection or anaphylaxis can lead to respiratory depression and apnea, and the patient may need to be rapidly intubated.

  3. Neurologic - Neurologic complications from the surgery are also unusual. If a regional technique is chosen there is a remote risk of nerve damage with the injections. Central spread of the local anesthetic can also lead to neurologic change.

a. Neurologic:

b. If the patient is intubated, are there any special criteria for extubation?

There are no specific criteria for extubation, but care should be taken to ensure smooth emergence in order to prevent changes in intraocular pressure as a result of coughing, bucking, and hypertension.

c. Postoperative management

  1. What analgesic modalities can I implement? Refractive surgery, particularly LASIK surgery, is not associated with significant post-operative pain. Pain is often managed modalities such as NSAIDS and acetaminophen. Narcotic medications are generally not needed.

  2. What level bed acuity is appropriate? Refractive surgery is performed as an outpatient procedure. In the absence of major intraoperative complications, the patient should be safe to go home following the procedure and a short recovery period.

  3. What are common postoperative complications, and ways to prevent and treat them? a. Postoperative dry eye is the most frequent complication, particularly in LASIK surgery, in which cornel nerves are severed during creation of the flap. Dry eye can significantly interfere with wound healing. In addition to surgical technique and systemic medical comorbidities that may predispose to dry eye, medications can also play a role. Commonly used medications which may induce dry eye include: clonidine, methyldopa, prazosin, propranolol, ephedrine, pseudoephedrine, metoclopramide, oral contraceptives, multiple Parkinson medications, and tricyclic antidepressants. b. Flap slippage after LASIK can occur as a result of eye rubbing or lid squeezing. c. Post-operative scaring and haze can occur, although more commonly after surface ablation that after LASIK. d. Infection is uncommon as patients remain on antibiotics for one week following surgery. e. Diffuse lamellar keratitis is a non-infectious inflammatory condition, and can be treated with intensive topical anti-inflammatory condition, and can be treated with intensive topical anti-inflammatory treatment (often already prescribed for one week following surgery). f. Halo and glare are frequent complications after refractive surgery, although these symptoms tend to dissipate over time. g. Corneal ectasia is a dreaded late-onset condition, causing bowing of the cornea anteriorly, and resulting myopia and astigmatism.

What's the Evidence?

Azar, D. Refractive Surgery. Mosby Elsevier. 2007.

Feder, R, Rapuano, C. The LASIK Handbook, A Case-Based Approach. Lippincott Williams &Wilkins. 2007.

Huang, S, Chen, H. ""Overview of Laser Refractive Surgery."". Chang Gung Medical Journal. vol. 31. 2008. pp. 237-251.

Longnecker, D, Brown, D, Newman, M, Zapol, W. Anesthesiology. McGraw Hill. 2008.

Schein, O, Katz, J. ""The Value of Routine Preoperative Medical Testing before Cataract Surgery."". New England Journal of Medicine. vol. 342. 2000. pp. 168-1-75.

Sakimoto, T, Rosenblatt, M, Azar, D. ""Laser Eye Surgery for Refractive Errors."". Lancet. vol. 367. 2006. pp. 1432-47.

Vajpayee, R, Melki, S, Sharma, N, Sullivan, L. Step By Step Lasik Surgery. Taylor & Francis. 2003.

Varvinski, A, Eltringham, R. ""Anaesthesia for Opthalmic Surgery Part 1: Regional Techniques"". Update in Anaesthesia. 1996.

Varvinski, A, Eltringham, R. ""Anaesthesia for OPthalmic Surgery Part 2: General Anesthesia."". Update in Anaesthesia. 1998.

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