Anesthesiology

Glaucoma surgery

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What the Anesthesiologist Should Know before the Operative Procedure

Glaucoma (Greek: "opacity of the crystalline lens") is a condition in which there is elevated intraocular pressure (IOP) which may eventually compress blood flow to the optic nerve, leading to eventual blindness. It is the second most common cause of blindness in the United States. It is often treated with IOP lowering medications, but when these fail, surgery is often necessary. Trabeculectomy is the most common surgery for this disorder, followed by placement of a glaucoma drainage implant when this fails. Like with most ophthalmalogic surgeries, trabeculectomy is often very brief in duration (<60 minutes), and done under monitored anesthesia care (MAC) with local or topical anesthesia, where as drain placement is often performed under general anesthesia.

Glaucoma in general has two forms.

  • Open angle glaucoma (most common type), chronic, slowing progressing form in which there is gradual vision loss. Due to difficulty in drainage of aqueous humor through the trabecular network in the eye. Represents majority of glaucoma cases in the United States.

  • Closed angle glaucoma (much more rare), represents an acute event in individuals who already have a narrow angle between the iris and cornea where aqueous humor drains through. There is acute closure when the iris comes into contact with the cornea, causing immediate outflow obstruction. This is characterized by a sudden onset of ocular pain, acutely increased IOP, visual disturbances (e.g., seeing halos) and vision loss.

Important general considerations

  • Patient populations are often elderly and may have several coexisting comorbid conditions, including, hypertension, diabetes, and cardiovascular disease. Pediatric populations may also have several coexisting genetic and/or congenital anomalies.

  • Given the short duration of these surgeries, any existing comorbid conditions among this patient population may require only small and brief interventions.

  • These are very delicate surgeries; care must be taken to increases in IOP (e.g., avoid certain medications, prevent coughing/bucking, nausea/vomiting, Valsalva maneuvers). Otherwise disastrous results may occur including expulsion of the intraocular contents and resulting blindness.

  • Must take into special consideration medications taken by the patient for their glaucoma and their possible reactions with certain anesthetic drugs.

1. What is the urgency of the surgery?

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

In patients with open angle glaucoma, this is often a slowly progressive condition, which is often managed medically at first prior to surgical intervention. Emergent surgery is often unnecessary.

However, in patients with acute closed angleglaucoma, this is a sudden event and is an ophthalmologic emergency, as patients may develop blindness if not treated promptly.

Emergent:Often related to acute angle closure in the setting of an acutely swollen lens or trauma, presenting with acute visual disturbances, ocular pain, and elevated IOP. May not have adequate time for further optimization of underlying medical conditions, and the procedure must be performed to avoid permanent blindness. Preoperative assessment should include a focused H&P to assess and manage any underlying medical conditions (even if uncontrolled/optimized conditions exist).

Urgent:Also often related to acute angle closure. May not have adequate time, as in emergent surgeries, for further optimization of underlying medical conditions, and the procedure must be performed to avoid permanent blindness.

Elective:The majority of glaucoma surgeries are elective outpatient procedures. As with most outpatient procedures, patients should have a adequate preoperative evaluation of their underlying medical conditions to assess the need for further medical optimization prior to surgery (see below).

2. Preoperative evaluation

As with most ocular procedures, patient populations undergoing glaucoma surgery are often elderly and may have several coexisting comorbid condtions, including:

  • Coronary artery disease

  • Congestive heart failure

  • Diabetes

  • Valvular heart disease (e.g., aortic stenosis)

  • Heart arrhythmias (e.g., atrial fibrillation)

  • History of cerebrovascular accident

  • History of deep vein thrombosis

  • Hypertension

  • Chronic obstructive pulmonary disease (COPD)

  • Reflux/hiatal hernia

  • Osteoarthritis

  • Renal insufficiency/failure

There are some data to suggest that routine preoperative evaluation, including laboratory tests, of patients undergoing eye surgery may not be necessary, as morbidity and mortality following these surgeries are the same regardless of surgery. However, most practitioners would likely order further testing in any potentially unstable medical conditions.

Medically unstable conditions warranting further evaluation may include:

  • History of coronary artery disease

  • History of congestive heart failure

  • History of uncontrolled diabetes

  • History of recent cerebrovascular accident

  • History of poor exercise tolerance (<4 METs [metabolic equivalent])

Delaying surgery may be indicated if:

  • Setting of new-onset chest pain, unstable angina, recent myocardial infarction (MI), and/or stent placement

  • Setting of uncompensated congestive heart failure

  • Setting of a hypertensive crisis

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

Since most ophthalmologic surgeries are brief in duration, and done under topical or local anesthesia, comorbid diseases generally require only small interventions. However, as with any other procedure, a thorough evaluation must take place.

Perioperative evaluation

A thorough pre-operative history and physical, along with appropriate laboratory studies are imperative to assess the status of any underlying co-morbidities, as well as any medications the patient is taking.

Perioperative risk reduction strategies

Depending on the disease and the severity, consultation with a patient's primary care physician or cardiologist for further evaluation and treatment (in the setting of unstable angina, congestive heart failure [CHF], uncontrolled hypertension [HTN], cardiac dysrhythmias, diabetes) is warranted, as most glaucoma surgery is elective. This allows the anesthesiologist the day of surgery to better manage any comorbid diseases. Also it should be noted that the majority of patients undergoing these procedures are awake, and assessment by the anesthesia provider of how they are feeling can further guide management.

b. Cardiovascular system

Acute/unstable conditions: Uncompensated CHF, unstable angina, history of recent MI, history of recent stroke, uncontrolled HTN.

Goals of assessment and management: maintain homeostasis given patients underlying disease status near their baseline as possible without exacerbating their underlying conditions.

CHF

Assessment should include symptoms and underlying disease, including exercise tolerance, ability to lie flat, type of heart failure (systolic versus diastolic dysfunction), and any echocardiogram data outlining ejection fraction and any wall motion abnormalities.

Intraoperative management should include vigilance of fluid management and assessment of patient ability/comfort when lying flat for the procedure.

Coronary artery disease

Should be optimized prior to the procedure, including any interventions such as a cardiac catheterization, stent placement, and/or coronary artery bypass grafting, as with most elective procedures.

Intraoperative management should include maintaining the patient's normal heart rate and blood pressure, as well as continuing any perioperative beta-blockers, as well as attenuating any sympathetic response with an adequate perioperative regional block and/or pain control. Rate control and blood pressure control may be necessary with beta-blockers and/or hydralazine and other antihypertensive agents.

HTN

Assessment of preoperative blood pressure baseline is necessary, as well as evaluation of any chronic antihypertensive medications.

Maintaining a patient's normal blood pressure is the goal. Perioperative hypertension can be managed accordingly. Beta-blockers, hydralazine, or other medications may need to be administered.

c. Pulmonary

COPD

Assessment of the patient's history (including smoking and any other chronic lung conditions), as well as respiratory status preoperatively, specifically any home baseline oxygen requirement and controller medications is essential. Pulmonary function tests, while useful for determining the severity of a patient's condition, are often unnecessary.

Reactive airway disease (asthma)

Assessment of patient's underlying disease state, including symptoms, triggers, controller medications, recent steroid use, and frequency of albuterol use, should done as part of any routine perioperative evaluation.

Perioperative management should include easy access to inhaled beta-agonist medications and should be free to be utilized before and after the procedure, to prevent bronchospasm and coughing, as this will elevated IOP.

d. Renal-GI:

Gastroesophageal reflux/hiatal hernia

As with most surgeries, assessment of a patient's symptoms of reflux and history of gastritis or hiatal hernia are important to evaluate for risk of reflux and possible aspiration of gastric contents.

Pretreatment with H2 blockers, proton-pump inhibitors, or oral sodium bicitrate may be warranted.

Vomiting is to be avoided in these patients as it acutely increases intraocular pressure and could result in the expulsion of the ocular contents during the procedure.

Renal insufficiency/chronic renal failure

As with most other surgeries, it is important to be mindful of a patients renal function and the use of certain renally cleared anesthetics appropriately, particularly those with renal elimination (e.g., neuromuscular blockers, midazolam, morphine).

As these procedures of short duration, patients do not often require much in the way of intravenous (IV) fluids; however, one should be mindful of a patient's fluid status and adjust appropriately.

e. Neurologic:

This patient population may have several neurologic conditions, such has a history of stroke or transient ischemic attack, as well as cerebrovascular disease. In general, one must assess the patient's baseline neurologic status preoperatively. Due to the short duration of these anesthetics, only small interventions may be necessary, and tend to focus on keeping stable vital signs (e.g., blood pressure), stable. Due to many of these cases being performed under MAC anesthesia, it is possible to assess intraoperatively mentation and how a patient is feeling to determine need for any interventions.

Acute issues

In patients with a recent history of stroke or transient ischemic attack, an overview of the patient's current medications and symptoms are necessary in order to elicit the full functional status of a patient. As this is mostly an elective surgery, delaying until symptoms have reached a stable baseline may be necessary.

Chronic disease

In patients with a history of a stroke, spinal cord injury, and chronic weakness/paralysis and other neurologic deficits, one must be aware of these symptoms in performing the rest of the evaluation and monitoring intraoperatively. Caution must be advised when using succinylcholine in such patients, as there may be an exaggerated response and life-threatening hyperkalemia due to up-regulation of acetylcholine receptors after the first 24 hours of the insult. Intraoperatively, one must be aware of any baseline neurologic deficits for moving the patient, and padding of pressure points is essential.

f. Endocrine:

Diabetes

  • Often seen in this population of eye surgery patients

  • Overview of a patient's control and types of medications taken are essential

  • For a normally controlled diabetic, a preoperative glucose may be all that is required for evaluation

  • For the poorly controlled diabetic an intraoperative blood glucose may need to be drawn and/or treated

  • Again, as the patients are awake, patients may be able to tell how they are feeling and describe symptoms of hypoglycemia

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)

Musculoskeletal system

  • Osteoarthritis

  • - Often seen in this population of patients

  • - Careful evaluation of pain when lying flat and padding of pressure point are essential. If unable to lie flat, treatment of arthritic pain may be necessary.

Hematologic system

Assessment of bleeding/clotting disorders is necessary, and any anticoagulation or antiplatelet medications that the patient is taking, and discussion with the surgeon and possibly the patient's cardiologist or primary care provider may be necessary to assess the risk/benefit of a patient taking these medications throughout the perioperative period.

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

In general, a patient's medications must be elicited at the time of taking an H&P and the anesthesiologist must be made aware of any medications that may interview or react with certain anesthetics. Due to the extensive nature of this list, the specific medications taken in this population for their underlying glaucoma will be discussed.

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

Glaucoma medications

Timolol

  • Nonselective beta-blocking agent administered topically as drops to the eye

  • Systemic absorption:

  • - May result in bronchospasm or acute exacerbation of asthma

  • - May result in bradycardia which is resistant to atropine

  • - Worsening of congestive heart failure

  • - Possible worsening of myasthenia gravis

Betaxolol

  • Specific beta-1 blocker

  • Reported to have minimal systemic side effects compared to timolol

  • Avoid in sinus bradycardia, heart block, and CHF

Echothiophate (phospholine iodide)

  • Long-acting acetylcholinesterase inhibitor

  • Reported to prolong succinylcholine's action for up to 3-6 weeks (up to 7 in some cases) after discontinuation of drug

  • Likely will see prolonged apnea after normal dosage of succinylcholine, and in some cases, may be advisable to discontinue drug prior to surgery 3-4 weeks prior to surgery (discussion with patient's ophthalmologist is essential)

Acetazolamide

  • Carbonic anhydase inhibitor (taken systemically or topically)

  • Systemically, results in diuresis and possibly metabolic acidosis (especially in patients with chronic lung disease) or electrolyte disturbances

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

In general, as these operations are of short duration and are often performed electively and under topical/regional anesthesia, one must follow general recommendations regarding the perioperative use of a patient's medications, with care taken to note and be able to readily discuss any medication concerns with the patient's primary care physician or cardiologist prior to surgery.

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

As these surgeries do not involve very many intraoperative medications (e.g., topical antibiotics and local anesthetics), any patient allergies and their reactions (e.g., nausea versus anaphylaxis), should be documented and alternatives should be used when indicated

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

N/A

l. Does the patient have any antibiotic allergies?

Discuss with surgeon the patient's existing allergies and the use of topical antibiotics and possible alternatives depending on patient's reported reaction (e.g., nausea versus anaphylaxis).

Antibiotic choices may vary among ophthalmologists and institutions.

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

Malignant hyperthermia

  • Documented: avoid all trigger agents such as succinylcholine and inhalational agents:

  • - Proposed general anesthetic (GA) plan: follow standard MH protocol for cleaning the anesthetic machine (removing volatile agents, changing CO2 absorbent, flushing machine with O2)

  • - Ensure MH cart available: follow standard institutional protocol for MH

  • Family history or risk factors for MH:

- As these surgeries can be done without the use of MH-triggering agents very safely and effectively, it is still prudent to follow standard MH protocol when risk factors are present.

Local anesthetics/muscle relaxants

  • In the event a rare allergy exists to the either category of local anesthetics (esters versus amides), the other category may be chosen.

  • If there is a contraindication to both local anesthetics, general anesthesia must be performed.

  • In the event a patient has an allergy to muscle relaxants and local anesthesia cannot be performed, it is advisable to use an alternative muscle relaxant, although this situation is quite rare.

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

As this procedure is done generally under local anesthesia, in general routine laboratory testing should be performed based on the findings of the history and physical, including medication list. Routine laboratory testing based on the procedure itself is often not warranted. There are also some data to suggest that the routine preoperative testing prior to cataract surgery does not reduce morbidity and mortality versus those patients that did not undergo a battery of tests.

Common laboratory normal values will be same for all procedures, with a difference by age and gender.

  • Hemoglobin levels: as indicated by H&P

  • Electrolytes: as indicated by H&P

  • Coagulation panel: as indicated by H&P (noting anticoagulation medications)

  • Imaging: generally none needed unless indicated by H&P

  • Other tests: (e.g., ECG, echocardiogram, etc): as indicated by H&P

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

Overall anesthetic goals during ophthalmalogic procedures, including glaucoma surgery

  • Safety, akinesia (movement) of globe, minimize pain and blood loss, awareness and prevention of oculocardiac reflex, prevention of increased IOP during and following administration of anesthesia

  • IOP

    • ˆ Factors increasing IOP

      • ▪ Increased arterial pressure

      • ▪ Increased venous pressure (e.g., from coughing, bucking, vomiting, or straining)

      • ▪ Hypoxia and hypercarbia (vasodilate intraocular blood vessels)

      • ▪ Ketamine

      • ▪ Succinylcholine

        • ▪ Unknown mechanism, but possibly due to contraction of intraocular muscles

        • ▪ Duration is brief (maximal increase occurs within 2-4 minutes and returns to normal in about 7 minutes)

        • ▪ If unable to tolerate this transient increase in IOP, rocuronium may be utilized for rapid-sequence induction, although this has a slightly longer onset

    • Factors lowering IOP

      • ▪ Decreased arterial and venous pressure

      • ▪ Hypocarbia (constricts choroidal blood vessels)

      • ▪ IV induction anesthetic agents (except ketamine)

      • ▪ Inhalational anesthetic agents

      • ▪ Nondepolarizing muscle relaxants

      • ▪ Reductions in aqueous or vitreous humor volume (e.g., by certain medications)

Regional anesthesia

Two blocks are most commonly used for this procedure (can be administered by either the ophthalmologist or the anesthesiologist), often performed in conjunction with mild sedation for the block (see monitored anesthesia care below).

Retrobulbar block

  • Accomplished by directing a needle angled below the globe toward the orbital apex, instilling local anesthetic deep in the orbit close to the optic nerve and muscle origins

  • Requires less local anesthetic, has a fast onset, and has a dense block

  • However, is applied closer to vital orbital structures (e.g., muscles, globe, optic nerve)

Peribulbar block

  • Accomplished by directing a needle parallel to the globe, placing local anesthetic farther from the optic nerve and apex, allowing for it to eventually penetrate the optic nerve

  • Requires larger volumes of local anesthetic and has a slower onset compared to the retrobulbar block

  • Theoretically safer as need is directed farther from vital structures in the orbit

Benefits

  • Able to perform with either topical anesthesia or mild, brief sedation during placement of the block, minimizing amount of medications needed and their potential side effects/interactions

  • Adequate anesthesia and akinesia for surgery are achieved quickly and effectively

  • Minimal change in IOP

  • Less equipment is required versus general anesthesia

  • Recovery times are faster, and patients are more awake and can tell you how they are feeling

Drawbacks

  • May be difficult to perform with an uncooperative patient (e.g., children and those with cognitive deficits, language deficits/foreign language) or in more complex eye surgery, or in malformations/deformations of the orbit and surrounding anatomy

  • Depends on skill of the person performing the block

  • Several risks associated with the blocks:

    1. Oculocardiac reflex

      1. Results in bradycardia and possibly resultant hypotension

      2. May be ablated by effective local anesthetic blockade by blocking the afferent pathway

      3. May be triggered following traction or pressure on the eye, by the block itself, or the rapid distention of tissues by solution, or hemorrhage

      4. Blood pressure and heart rate monitoring are essential

      5. Having atropine or glycopyrrolate available may be beneficial

    2. Intravascular Injection

      1. May result in systemic side effects of local anesthetics

      2. Resuscitation measures, including intubation, may be necessary

    3. Retrobulbar hemorrhage

      1. Characterized by a sudden rise in intraocular pressure

      2. Treat with a pressure bandage, and postponement of surgery

    4. Central spread of local anesthetic medications

      1. May result in following symptoms: drowsiness, nausea/vomiting, contralateral blindness (reflux of the local anesthetic to the optic chiasm), seizures, respiratory depression, apnea, neurologic changes, or even cardiac arrest

      2. These symptoms occur rapidly, and appropriate resuscitation equipment and assistance must be readily available

    5. Ruptured globe

      1. May or may not require intervention

General anesthesia

  • Useful in performing in an uncooperative patient, patient anxiety, during pediatric surgery, known allergies to local/topical anesthetics, or other situations when regional/MAC techniques are not possible to achieve above goals for eye surgery.

  • May be performed commonly with endotracheal tube anesthesia and neuromuscular blockade to achieve adequate muscle paralysis

Benefits

  • Achieves relaxation and more than adequate anesthetic depth

  • Patient's airway is secured (when using an endotracheal tube)

Drawbacks

  • Recovery times are longer

  • Possibly more medication side effects as more medications are being utilized

  • Possibly may use medications which increase IOP

Other issues

  • When choosing induction agents, all risks and benefits must be taken into account by the anesthesiologist

  • A combination of induction agents may be used in order to minimize increases in IOP

  • Succinylcholine, while transiently increasing IOP, may still be utilized as it achieves intubating conditions the fastest for this specific surgery

  • Antiemetics may be utilized to avoid postoperative nausea and vomiting and the increases in IOP it may cause

Airway concerns

  • No major airway concerns exist other than what is normal for this patient population

  • Discussion with the ophthalmologist is advisable to discuss placement of endotracheal tube after induction

Monitored anesthesia care

  • Provided often in conjunction with administration of a regional block, as initial placement of the block is often painful

  • Only brief sedation is often necessary, as the procedure may be performed fully without further sedating agents once block is performed and it is often necessary to have patient cooperation during the procedure

  • Often propofol (20-50 mg) or a short-acting IV opioid (eg. remifentanil 20-50 mcg) is enough to accomplish the block

Benefits

  • Allows for pain relief and/or sedation for regional block

  • Allow for quick recovery of sedation and normal breathing patterns and vital signs for duration of procedure

  • Postoperative recovery times are shorter than with GA

Drawbacks

  • Brief periods of apnea may occur, and patients should be monitored carefully throughout

  • Decreases in blood pressure should be anticipated and treated if necessary

Other issues

  • The anesthesiologist must always be ready and able to convert to a general anesthetic if necessary

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

What prophylactic antibiotics should be administered?

  • Antibiotics are generally applied topically by the surgeon prior to surgery

  • One can use topical antibiotics such as fourth-generation fluoroquinolones (e.g., moxifloxacin, gatifloxacin ophthalmic), bacitracin/polymixin B, or aminoglycosides (e.g., tobramycin)

  • Choice of antibiotic is dictated often by the ophthalmologist and the patient's history drug allergies

  • What do I need to know about the surgical technique to optimize my anesthetic care?

Trabeculectomy is the most common procedure performed for glaucoma (goal is to create a fistulous tract between the anterior chamber and the subconjunctival space).

  • An incision is first made in the conjunctiva to expose the sclera.

  • A scleral flap is then created.

  • This is followed by an incision into the anterior chamber of the eye near the scleral flap and a very small portion of sclera is removed.

  • An iridectomy is then performed to prevent part of the iris from herniating into this tract.

  • The flap is then closed and then conjunctiva repaired.

  • Throughout the procedure, it is important to prevent coughing, bucking, vomiting, or anything that may increase IOP, as this could cause potentially catastrophic damage such as hemorrhage or expulsion of intraocular fluid/contents.

What can I do intraoperatively to assist the surgeon and optimize patient care?

  • Make patient comfortable using pillows and padding of pressure points.

  • Constant reassurance of patient about procedure can ease anxiety.

  • Instruct patients to remain silent and to squeeze an assistant's hand whenever possible before a movement is made.

  • Adequately assess patient comfort and safety at all times through verbal communication with the patient as well as close monitoring of the patient's vital signs through ECG, blood pressure, and O2 saturation monitoring, and ETCO2 monitoring to assess respirations if possible.

  • Avoid oversedation of patients, as they may make unconscious movements during surgery or wakeup moving during surgery without being aware of their surroundings.

What are the most common intraoperative complications and how can they be avoided/treated?

Apnea

  • May occur briefly following administration of sedation medication prior to block

  • May resolve spontaneously

  • On some occasions, may require further assistance, in cases of airway obstruction (e.g., chin lift, oral airway, nasal airway, etc.)

  • If unable to arouse, mask ventilation may be necessary, and the anesthesiologist must be ready to convert to a general anesthetic in order to secure the airway if needed

Hypotension

  • May occur during sedation or during block placement

  • Often transient and resolving spontaneously

  • May treat with phenylephrine or ephedrine, guided by patient's history and medications

Coughing

  • Assess preoperatively for history of chronic cough (e.g., in cases of post nasal drip, recent URI, allergies, reflux, or asthma)

  • Consciously tell patient to prevent coughing or warn via hand squeeze of assistant if coughing is going to occur

  • If unable to prevent coughing under MAC/regional block, general anesthesia may be required

Nausea/vomiting

  • Instruct patient to warn anesthesiologist if feeling nauseous

  • Proper treatment with antiemetics when appropriate

Patient discomfort/unable to cooperate

  • Reassurance is key, as is ensuring patient comfort prior to start of procedure

  • If unable to tolerate, may require general anesthesia

  • Small doses of IV anxiolytics (e.g., midazolam 0.5-1 mg IV), may be attempted; however, be careful to avoid oversedation and involuntary movement during surgery

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

In general, as these are such short surgeries mostly performed on an elective basis, no special criteria exist for extubation, other than standard measures (e.g., adequate reversal of neuromuscular blockade, protecting their airway, etc). Prevention of bucking/coughing on the endotracheal tube during wake up is important to minimize increases in IOP and adequate prevention of nausea and vomiting with administration of antiemetics is warranted.

c. Postoperative management

What analgesic modalities can I implement?

  • Fentanyl 25-50 mcg IV or morphine IV 0.1 mg/kg as needed for acute post-operative pain.

  • Oral agents such as Percocet, acetaminophen, or ibuprofen are usually appropriate when patient is able to tolerate oral intake.

What level bed acuity is appropriate?

  • These procedures are generally performed on an outpatient basis, and routine recovery for outpatients is all that is normally required.

What are common postoperative complications, and ways to prevent and treat them?

  • Overfiltration causing hypotony

  • Leakage of bleb

  • Scarring

  • Infection

If any of these complications is suspected, consultation with the opthalmologist is warranted.

What's the Evidence?

Jaffe, RA, Samuels, SI. Ophthalmalogic Surgery-Trabeculectomy. Anesthesiologist's Manual of Surgical Procedures. Lippincott Williams & Wilkins. 2009. pp. 144-6.

(This reference outlines the basics of the surgical treatments for glaucoma, common anesthetic options, and complications of this procedure.)

Barash, PG, Cullen, BF, Stoelting, RK. Anesthesia for Ophthalmologic Surgery: Clinical Anesthesia. Lippincott Williams & Wilkins. 2009. pp. 1324-77.

(This reference outlines the physiology of glaucoma and the effects of various drugs on intraocular pressure, as well as information about the various techniques involved in the anesthetic management of ocular surgery.)

Stoelting, RK, Miller, RD. Ophthalmology and Otolaryngology Basics of Anesthesia. Churchill Livingstone-Elsevier. 2007. pp. 463-8.

(This reference serves as an adjunct to the above, with more information regarding glaucoma physiology and anesthetic management.)

Guidelines for Cataract Practice Section 7.7-Anesthesia.

(This reference outlines the indications for various types of anesthesia for ocular surgery from an eye surgeon's perspective.)

Varvinski, A, Eltringham, R. "Anesthesia for ophthalmic surgery. Part 1: regional techniques". Update Anesth. vol. 6. 1996.

(This reference outlines the procedure for performing regional anesthesia for ophthalmic surgery, including the advantages and disadvantages as well as complications of these techniques.)

Varvinski, A, Eltringham, R. "Anesthesia for ophthalmic surgery. Part 2: general anesthesia". Update Anesth. vol. 8. 1998.

(This reference outlines factors that influence intraocular pressure as well techniques for general anesthesia for ophthalmic surgery.)

Schein, OD. "The value of routine preoperative medical testing before cataract surgery". N Engl J Med. vol. 342. 2000. pp. 168-75.

(This reference provides evidence regarding preoperative medical testing prior to cataract surgery, which is in many aspects similar to the patient population who would undergo glaucoma surgery.)
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