What the Anesthesiologist Should Know before the Operative Procedure
Corneal transplantation is an outpatient procedure utilizing corneal tissue from a cadaver. The graft can be either partial (lamellar keratoplasty) or full (penetrating keratoplasty) and involve synthetic tissue or stem cells. Transplantation is usually indicated after visual loss from corneal cloudiness or distortion in shape secondary to disease and/or injury that is unresolved by corrective lenses.
The most important aspects of the surgery from the anesthesiologist’s perspective are control of intraocular pressure (IOP) and strict control of patient movement.
1. What is the urgency of the surgery?
What is the risk of delay in order to obtain additional preoperative information?
On the day of surgery, the transplant is brought to the operating room for the selected patient. Because the viability of the cadaveral tissue decreases with time, delaying the surgery should be avoided. This is also true for patients who are suffering acute traumatic injury to the globe.
Emergent: If the globe is open/traumatic, stabilization of the globe contents will be the priority because the corneal transplant is an elective procedure.
Urgent: The urgency of the procedure is based on the time between matching the donor with the patient and placement of the surgical graft. The longer the duration before grafting, the less viable is the cornea.
Elective: Surgery is usually elective, scheduled when a donor cornea is identified for the patient. The patient is then scheduled relatively quickly for surgical grafting of the tissue. The patient should be stable enough to undergo general anesthesia or able to lie flat with sedation.
2. Preoperative evaluation
Preoperative evaluation should be used to guide anesthetic management. Rarely should a surgery be cancelled since it is a low-surgical-risk procedure per ACC guidelines. The focus of the examination should be on the patient’s ability to tolerate the anesthetic plan for the comfort of both the anesthesiologist and the ophthalmologist. Conditions that need to be assessed are those that prevent the patient from laying flat and still for prolonged periods or those that require increased dosing of anesthetic.
Medically unstable conditions warranting further evaluation include acute myocardial ischemia or infarction and active COPD exacerbation. Other important conditions necessitating working include recent onset of arrhythmia, stroke, or TIA.
Delaying surgery may be indicated if the patient is currently experiencing unstable cardiac or pulmonary condition; otherwise, surgery should proceed as the transplant has a limited viability span.
3. What are the implications of co-existing disease on perioperative care?
b. Cardiovascular system:
Perioperative evaluation: Because many patients requiring corneal transplants are elderly, there are likely several comorbidities to be concerned about including CAD with unstable angina. In a patient with fulminant CHF or acute signs of ischemia or infarction, the patient must be stabilized before proceeding. Workup includes 12-lead ECG, cardiac enzymes, echocardiogram, and possibly cardiology consultation. Once the patient is stabilized, surgery can proceed.
Perioperative risk reduction strategies: Patients with fragile cardiovascular systems are more likely to benefit from undergoing corneal transplant with MAC and local infiltration of anesthetic rather than general anesthesia. The use of nasal cannula can provide supplemental oxygen as well. If the patient is able to tolerate general anesthesia, the use of an arterial line for beat-to-beat monitoring of blood pressure can help the anesthesiologist to maintain homeostasis. In addition, FiO2 of 100% and generous use of opiate analgesics can assist in reducing cardiac stress.
Baseline coronary artery disease or cardiac dysfunction – goals of management
Assess the severity of their cardiac disease in order to determine whether MAC or general anesthesia would be the appropriate course of anesthetic management. Since there is a possibility of the oculo-cardiac reflex with eye manipulation, proper assessment of cardiac function can be critical in determining the proper course of resuscitation if needed.
Perioperative evaluation: The patient’s functional status is likely the most efficient way to determine status of cardiac disease. The ability of the patient to climb two flights of stairs without shortness of breath is considered stable cardiac health. However, many patients do not exert themselves to such levels, and determining their reasons of restricting activity secondary to chest pain or shortness of breath can help guide anesthetic assessment. Another important question to ask the patient is the ability to lay flat because patients with symptomatic CHF can be difficult patients to operate on under MAC.
Perioperative risk reduction strategies: Reducing cardiovascular impact by either pursuing MAC approach or avoiding fluctuations in blood pressure can lead to a straightforward operation. Ophthalmic procedures are considered low cardiovascular risk, so the focus of cardiac stress from anesthesia should be avoided. Induction with etomidate, maintenance with desflurane, and generous use of opiates for sympathectomy are examples.
Perioperative evaluation: Patients with COPD can require greater pulmonary support beyond simple supplemental oxygen. It is therefore important to gauge the patient’s ability to tolerate lying flat on their back for a prolonged period if the MAC approach will be used. The counterargument is whether a patient with severe COPD would be able to be extubated. It is therefore important for the anesthesiologist to have an informed discussion of the risks and benefits of the various methods. Breathing patterns at baseline and results from PFTs can also help guide discussions with the patient and ophthalmologist.
Perioperative risk reduction strategies: Patients should be encouraged to continue their medication through the day of surgery, including inhalers and steroids. The MAC approach will likely be safer for the patient as they will likely be at their baseline and there is less concern about transitions in breathing patterns from the ventilator to spontaneous.
Reactive airway disease (asthma)
Perioperative evaluation: Assessment of how frequently the patient has asthma attacks and what specifically triggers the attacks can help determine the severity of the disease.
Perioperative risk reduction strategies: Using MAC instead of general anesthesia allows the anesthesiologist to avoid instrumenting the airway and thus reducing the chance of bronchospasm in these sensitive airways. If general anesthesia is determined to be the appropriate option, then using of nonpungent inhalants like sevoflurane, suctioning the airway, and extubating while the patient is deep in anesthesia can aid in reducing bronchospasm in this susceptible population.
Perioperative evaluation: These are not usually of concern for ophthalmic cases under MAC unless the patient has severe reflux when laying flat.
Perioperative risk reduction strategies: Communication with the ophthalmologist about some reverse Trendelenburg positioning can decrease chances of reflux in some patients.
Preoperative use of metoclopramide and sodium citrate can help reduce complications of reflux. In patients with renal issues, cautious fluid management will be important because ophthalmic cases have minimal blood loss and thus patients will only have a deficit from being NPO.
Patients with movement disorders need to be identified preoperatively because they are more likely going to need general anesthesia for a successful surgery. Tremors can make it very difficult for the surgeon, which may not become apparent until the patient is at rest. Because the procedure can be done under MAC, the patient needs to have the ability to understand directions and stay still for prolonged period of at least an hour. Concern for dystonic movements from propofol should also be a reason to avoid sedation. Furthermore, sedation in general can lead to spontaneous movements by the patient that may be detrimental to the transplantation.
Perioperative risk reduction strategies: Patients should be kept awake and comfortable under MAC or regional anesthesia; otherwise, general anesthesia with muscle relaxation is necessary.
g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
4. What are the patient's medications and how should they be managed in the perioperative period?
Patients should continue their medications for the surgery except for:
a) Anticoagulants that can cause hemorrhage in locations that can sometimes not be visible. If the patient is on clopidogrel for recent stents, the surgery should be delayed since it is elective and could jeopardize the stent if the medication is stopped. For patients who are on anticoagulants for therapy, these patients should not undergo such elective surgery until the therapy is complete.
Patients who require anticoagulation as part of prophylaxis should have a formal discussion with the ophthalmologist, anesthesiologist, and primary care physician about the risk of clotting if the medication is stopped and the risk of bleeding if the medication is continued. Informed consent is a crucial instrument for patient care, especially if complications were to arise.
b) Oral hypoglycemic drugs that can cause hypoglycemia during the patient’s NPO status. For diabetic patients, preoperative blood sugar should be checked and stabilized prior to proceeding to surgery.
h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
Certain patients may be taking echothiophate for glaucoma, which is an irreversible cholinesterase inhibitor. This will lead to prolongation of action for medications dependent on plasma cholinesterse (succinylcholine and mivacurium) if general anesthesia is used. Other side effects include typical cholinergic effects such as bradycardia and bronchopasm. Reduced dosing or using alternatives is recommended for these patients.
i. What should be recommended with regard to continuation of medications taken chronically?
Cardiac: All cardiac medications should be continued unless it can affect coagulation. The risk of bleeding with the surgery needs to be weighed against the risk of thrombus in a discussion with the patient, surgeon, and cardiologist.
Pulmonary: All pulmonary medications should be continued. Preoperative and intraoperative use of albuterol inhalers should be considered in patients with moderate to severe reactive airways based on history.
Renal: All renal medications should be continued.
Neurologic:All neurologic medications should be continued. It should be noted if the patient is on anticoagulants, then the discussion of bleeding risk should take place.
Antiplatelet: As described above, there is potential for hemorrhaging even though the cornea is avascular. Sources include encroachment of the sclera and rupture of vessels during a retrobulbar block.
Psychiatric: All psychiatric medications should be continued. Many medications can prolong QT, which can exacerbate potential arrhythmias from the oculo-cardiac reflex. Since these medications take several weeks to be titrated onto the patient, cessation is not recommended. Fortunately, these medications are usually followed closely by the psychiatrist for potential side effect profiles.
j. How to modify care for patients with known allergies
As with all cases, known allergies should alert the operating room staff to assess all drugs and equipment set up for the case with prompt replacement of such items.
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.
l. Does the patient have any antibiotic allergies – Common antibiotic allergies and alternative antibiotics
m. Does the patient have a history of allergy to anesthesia?
Malignant hyperthermia (MH)
Documented: Avoid all trigger agents such as succinylcholine and inhalational agents. Follow a proposed general anesthetic plan: total intravenous anesthesia with propofol ± opioid infusion ± nitrous oxide. Ensure that an MH cart is available [MH protocol].
Local anesthetics/muscle relaxants: If the patient has an allergy to lidocaine, bupivacaine can be used as the local anesthetic for the regional block of the globe. Alternatively, the patient can undergo general anesthesia and muscle relaxant can be used for akinesis of the ocular muscles. If the patient has an allergy to muscle relaxants and an alternative relaxant is not possible, then regional block of the eye can be used with either general anesthesia or MAC.
5. What laboratory tests should be obtained and has everything been reviewed?
Laboratory tests may not be useful for the anesthesiologist in corneal transplants. There may be a subset of the population who may have liver disease or coagulopathy or are on blood thinners, where a coagulation profile may be helpful. Since bleeding is a complication of the procedure as described above, such patients may be more likely to experience this complication.
Hemoglobin levels: Blood loss is minimal in most cases because the avascular nature of the cornea. Patients should have at least a baseline hemoglobin level that shows 7 g/dL. The possibility of bleeding is still present and can be hidden, so patients should be closely monitored and advised of early symptoms such as ocular pain.
Electrolytes: Electrolyte imbalances can potentiate the arrhythmias associated with the oculo-cardiac reflex and should be normalized before proceeding with surgery. There is not much fluid needed for the case beyond replacing intravascular fluid deficit.
Coagulation panel: Patients who are at risk for bleeding as described above should have a coagulation profile drawn of PT/INR and PTT.
Imaging: No imaging is needed.
Other tests:No further testing is needed, unless the patient is unstable from cardiopulmonary pathology. The surgery should be delayed until the patient has been cleared and stabilized.
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
Corneal transplantation allows the implementation of various anesthetic techniques because of the superficial nature of the surgery and its low cardiovascular risk. Local anesthesia, with a regional block, can be used in the most fragile of patients who can lay still, whereas general anesthesia can be used for cases in which movement disorders or the noncompliant patient complicates management.
It has been described that regional anesthesia can be helpful for patients suffering from severe back or lower extremity pain to receive an epidural for intraoperative pain relief during MAC cases. Another important regional anesthetic is the block of muscles in the globe. In some institutions, the anesthesiologist places the regional block of the globe, rather than the ophthalmologist. There are case reports describing the use of topical anesthesia of the globe as the only means of anesthesia; however, it is still largely used as an adjunct to a regional block.
Benefits: Able to decrease pain from the back or lower extremities, so that patient can lay comfortably during MAC.
Drawbacks:May not be able to perform in patients who cannot sit or lay in lateral decubitus position. Patient may have inherent or medication induced coagulopathy. Another concern is the loss of sympathetic tone in neuraxial anesthesia that can necessitate need for cardiovascular resuscitation.
Issues:May not be sufficient in patients with movement disorders or difficulty with ventilation when supine.
Peripheral nerve block
Benefits: The block of the globe allows anesthesia, akinesia, and decreased intraocular pressures.
Drawbacks: The concern for blocks of the globe is intravascular or intraneural injection, as well as the oculocardiac reflex.
Issues: It is a risky procedure and requires experience.
Preferable in patients who are suitable candidates for undergoing GA. These include patients in stable cardiac and pulmonary health. Patients need to have muscle relaxant on board to have complete akinesia of the ocular muscles for the surgery. For this reason, a nondepolarizing muscle relaxant is preferable. The patient should be kept at no more than a single twitch for the case. Near the end of the case, the patient should be very comfortable with intravenous lidocaine or opiate to prevent bucking on the endotracheal tube. The patient can be completely reversed and allowed spontaneous ventilation while intubated. Once the patient has full reversal with good tidal volumes and regular breathing, extubation while under deep anesthesia is preferable to avoid a situation that can raise intraocular pressure.
Benefits:Patient will not move and will be the method of choice for delirious patients or those with movement disorders.
Drawbacks:Can cause tube bucking, coughing, and increased intraocular pressures during extubation, which can be detrimental to recovering eye.
Other Issues:Nitrous should be avoided in these patients because any air within the globe will expand with increased pressure and lead to devastating consequences. Succinylcholine can raise intraocular pressure.
Airway Concerns: Patients with perceived difficult airway should strongly be considered for MAC.
Monitored anesthesia care
The preferred method in most patients who are able to follow commands and lay still for an extended period of time. An important aspect of this technique is that patients should not be deeply sedated because of the concern for spontaneous unconscious movements and apnea. The use of an anxiolytic and cautious use of short acting opiates (such as remifentanil) can provide a comfortable surgery for the patient. MAC requires that the patient is given a regional block of the globe.
Benefits:Allows individuals with poor cardiovascular health to complete surgery. Emergence time from anesthesia is reduced, and less chances that the patient would do maneuvers that could increase globe pressure.
Drawbacks: Patient may move and there is no control over the airway.
Other Issues:Because MAC requires a regional block, the oculo-cardiac reflex can be elicited causing bradycardia or another arrhythmia, which may require immediate intervention. The injection should be stopped and appropriate action should be taken if the rhythm does not normalize. Use of remifentanil may enhance the reflex.
6. What is the author's preferred method of anesthesia technique and why?
Based on experience and currently literature, our preferred anesthetic technique is MAC because the procedure is simple, efficient, and well tolerated by most individual, including the common elderly patient with multiple comorbidities. In the holding area, the patient is given a series of eye drops by the nurse including tetracaine 0.5% once and ciprofloxacin 0.3% q5 minutes for 3 doses. The patient also receives mannitol IV 12.5 grams to reduce intraocular pressure. Prior to heading into the OR, 1 to 2 mg of midazolam is administered IV. The stretcher is then taken into the OR, where the standard monitors are placed with a nasal cannula that includes a connection for end tidal carbon dioxide monitoring at 4L/min oxygen flow. After the patient is given a 0.3 to 0.4mcg/kg remifentanil IV bolus, a timer is set for 90 seconds before a regional block of the globe is performed.
At our institution, the ophthalmologist performs the block with a retrobulbar approach using bupivicaine 0.75%. Because the patient is awake and comfortable, he or she can follow commands by looking up as the injection is made. This is the most critical time as both the question of patient’s comfort and the elicitation of the oculo-cardiac reflex can occur. The site is then prepped and draped. The patient is advised not to talk or move during the case. After the completion of the procedure, the monitors are removed and the patient is taken by stretcher to the PACU.
What prophylactic antibiotics should be administered?
In the holding area, the ophthalmologist will have ordered floroquinolone eye drops in preparation of the surgery. Our institution utilizes the ciprofloxacin ophthalmic drops 0.3 %, 1 drop q5 min x3. At the completion of the procedure, polysporin ophthalmic ointment is placed by the surgeon.
What do I need to know about the surgical technique to optimize my anesthetic care?
The techniques of the surgery and blocks do not change the anesthetic management. However, if the surgeon requests the block to be placed by the anesthesiologist, then it must be known that the retrobulbar block works with less local anesthetic but is more difficult to place than the parabulbar block. Both techniques can elicit the oculo-cardiac reflex, with the retrobulbar approach causing more hidden hemorrhaging and possible intraneural or intravascular injection of local anesthetic.
What can I do intraoperatively to assist the surgeon and optimize patient care?
Continued patient reassurance and titrating in midazolam or remifentanil to confirm patient comfort.
What are the most common intraoperative complications and how can they be avoided/treated? Prioritize them by urgency.
Cardiac: The cardiovascuar risk of corneal transplants is very low, however the risk of arrhythmia from the oculo-cardiac reflex (OCR). Routine prophylaxis is considered controversial, especially since it is a reflex more common in children. Premedication with IV glycopyrolate just prior to surgery can reduce the risk of OCR, however the side effect profile can cause discomfort in patients, especially the elderly. The best approach is close intraoperative monitoring of the EKG and immediate cessation of globe manipulation. In most cases, the rhythm resolves after the manipulation is stopped. In rare cases, the need for glycopyrolate or atropine is needed for bradycardia. The possibility of other arrhythmias may require patient stabilization and cardiac resuscitation; hence; it is prudent that the anesthesiologist is prepared for any situation.
Pulmonary: There are no specific pulmonary risks for corneal transplants. End tidal carbon dioxide monitoring should be present continuously intraoperatively since the patient’s head will be toward the surgeon and under the drapes. It may be necessary to prop up the drape caudally to allow outflow of carbon dioxide from gathering over the patient’s face.
Neurologic: The neurologic complications usually arise from the regional block, most commonly the retrobulbar block. Intravascular injection of local anesthetic into the ophthalmic artery may cause enough backflow to enter the cerebral circulation and cause a seizure. Another concern is for postretrobulbar apnea syndrome from intraneural injection of the optic nerve. The local anesthetic can flow through the sheath and into CSF causing loss of consciousness and eventually apnea. Neurologic complications require supportive treatment, with control of the airway and ventilation and cardiac monitoring.
b. If the patient is intubated, are there any special criteria for extubation?
Patient must be extubated without triggering cough or bucking reflex. Deep extubation of patients that were easily intubated is a possibility. The other option is appropriate irritation control with either intravenous opiate and/or lidocaine.
c. Postoperative management
What analgesic modalities can I implement?
The procedure is an elective outpatient procedure and has little postoperative pain. Any mild pain could be treated with acetaminophen. Any indication of unremitting pain should be closely investigated as it could be signs of operative complications.
What level bed acuity is appropriate?
Corneal transplants are outpatient procedures, so patients are able to be discharged home once recovered from anesthesia. The ultimate decision to discharge home versus admission lies with the anesthesiologist and depends on the patient’s postoperative status.
What are common postoperative complications, and ways to prevent and treat them?
1) Graft failure or rejection can occur and is the most important complication. This includes recurrence of corneal disease that may have been the initial indication for transplant. Unfortunately this is a result of forces outside the anesthesiologist’s control. 2) Infection can be decreased by treatment of prophylactic antibiotics, usually administered in the form of eye drops. 3) Fluid leakage can occur if there is improper healing or if increased ocular pressures are created. A smooth extubation can avoid any unnecessary increases in pressure.
What's the Evidence?
Barash, P, Cullen, B, Stoelting, R, Cahalan, M, Stock, M. Clinical anesthesia. 2009. (Information regarding the eye physiology and anesthesia.)
Miller, R, Eriksson, L, Fleisher, L, Wiener-Kronish, J, Young, W. Miller’s Anesthesia. 2009. (Information regarding the eye physiology and anesthesia.)
Rosen, E. “Anaesthesia for ophthalmic surgery”. Br J Ophthalmol. vol. 77. 1993. pp. 542-43. (Paper on anesthetic approach to eye surgery.)
Boskovski, NA, Bormes, P, Landers, DF. “Anesthetic management for the high-risk ophthalmic patient”. J Clin Anesth. vol. 4. 1992. pp. 39-41. (Paper on anesthetic approach to eye surgery.)
Leidinger, W, Schwinn, P, Hofmann, HM, Meierhofer, JN. “Remifentanil for analgesia during retrobulbar nerve block placement”. Eur J Anaesthesiol. vol. 22. 2005. pp. 40-3. (Paper on analgesic approach for regional eye block.)
Spigelman, AV, Doughman, DJ, Lindstrom, RL, Nelson, JD. “Visual loss following suture removal postkeratoplasty”. Cornea. vol. 7. 1988. pp. 214-7. (Paper on complications post eye surgery.)
Brightbill, F, McDonnell, P, McGhee, C, Farjo, A, Serdarevic, O. Corneal surgery: theory, technique and tissue. 2009. (Information regarding the surgery itself.)
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- What the Anesthesiologist Should Know before the Operative Procedure
- 1. What is the urgency of the surgery?
- What is the risk of delay in order to obtain additional preoperative information?
- 2. Preoperative evaluation
- 3. What are the implications of co-existing disease on perioperative care?
- b. Cardiovascular system:
- c. Pulmonary:
- d. Renal-GI:
- e. Neurologic:
- f. Endocrine:
- g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)
- 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?
- i. What should be recommended with regard to continuation of medications taken chronically?
- j. How to modify care for patients with known allergies
- 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.
- l. Does the patient have any antibiotic allergies - Common antibiotic allergies and alternative antibiotics
- m. Does the patient have a history of allergy to anesthesia?
- 5. What laboratory tests should be obtained and has everything been reviewed?
- Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
- 6. What is the author's preferred method of anesthesia technique and why?
- a. Neurologic:
- b. If the patient is intubated, are there any special criteria for extubation?
- c. Postoperative management