OAS Member, Dr. Maggie Jeffries, was interviewed by EyeWorld reporters this October. She discussed her recent MKO melt study, which was also presented at the 32nd Annual OAS Scientific Meeting this fall.

The study included 611 patients. It was Institutional Review Boards (IRB) approved. The patient were randomized to receive either an MKO melt, valium alone (10 mg), or valium with tramadol and ondansetron. Then her team tracked how much medication the patients needed for pain, anxiety, or both. 

To learn more, watch the interview at ewreplay.org. 

Written by Cagri Besirli, MD, PhD, Department of Ophthalmology and Visual Sciences (University of Michigan)

Intravitreal treatment has been transformative, saving vision for millions of

 patients. The success of anti-VEGF drugs, aging population, diabetes epidemic, and increasing indications have led to a dramatic growth in the number of injections performed, increasing from less than 50,000 a year in the early 2000s to an estimated 6 million injections in 2017.

Current methods of pharmacologic ocular anesthesia used prior to intravitreal injections have several drawbacks, including the need for two patient encounters (the first to administer anesthesia and the second 5-15 minutes later after anesthesia has had time to work), corneal toxicity with blurred vision, and increased rate of hemorrhage seen with subconjunctival lidocaine. In addition, there is concern that certain forms of anesthesia, particularly lidocaine gel and viscous lidocaine drops, may result in suboptimal antiseptic access to the ocular surface, which could theoretically increase the risk of endophthalmitis.

Administering an intravitreal injection safely requires a multi-step process. The anesthesia step is the longest phase and creates a bottleneck in intravitreal injection workflow. Therefore, there is an unmet need for a rapid, non-invasive anesthesia for intraocular injections.  With this in mind, we developed focal cooling as a novel method of non-pharmacologic anesthesia to improve the patient experience. To provide focal cooling on the ocular surface, we designed a portable, battery operated device with a single-use, sterile tip that rapidly cools the ocular surface within 10-20 seconds, temporarily halting nerve conduction. There is a wealth of literature showing that nerve conduction is stopped between 0-8 C, and the temperatures chosen for this study were done based on thermal modeling that showed the ability to achieve this temperature range in the sclera prior to an intravitreal injection.  

To assess the safety and feasibility of focal cooling for ocular anesthesia, we performed a first-in-human feasibility trial.  This was a single center, randomized, unmasked controlled trial that compared non-pharmacologic, ultra-rapid focal cooling to lidocaine-based standard of care anesthesia.  The study included patients older than 18 years of age with a diagnosis of exudative age-related macular degeneration or diabetic macular edema requiring bilateral anti-VEGF therapy.  One eye of each patient was randomized to the focal cooling treatment arm and the fellow eye was randomized to topical lidocaine (lidocaine gel or lidocaine-soaked cotton tipped applicators).  The primary pain outcome was patient reported pain at the time of injection.  The secondary pain outcome was post injection pain measured 4 hours post treatment.

The visual analog scale was used to measure injection and post-injection pain. We found effective pain control in the focal cooling groups, with increasing pain control with colder temperatures and longer treatment duration.  Similar to injection pain, post-injection pain after non-pharmacologic anesthesia was similar to standard of care.  This first-in-human study showed that focal cooling reduced the time patients spent waiting for the injection procedure by approximately 4.5 minutes, which represented a statistically significant improvement, and one that has considerable benefit for patient care.

The first-in-human trial shows that rapid, non-pharmacological anesthesia via focal cooling has the potential to transform the way intravitreal injections are delivered, dramatically improving the patient experience. This technology has now been exclusively licensed to iRenix Medical, with additional development and commercialization planned in the near future. 

Written by Howard Palte, MD, Bascom Palmer Eye Institute (University of Miami)

Today, more than 6 million patients in the USA receive long-term therapy for the prevention of thromboembolism from atrial fibrillation, mechanical heart valves and deep vein thrombosis. Patients undergoing eye surgery are often elderly, have significant comorbidity and receive antiplatelet or anticoagulant therapy. These medications may predispose eye surgery patients to risk of hemorrhagic complications either during the administration of regional anesthesia or intra-orbital intervention. The anesthesia provider is faced with the dilemma of balancing the risk of orbital hemorrhage against the peril of a catastrophic outcome associated with cessation of anticoagulation therapy. In this respect, an appreciation of the pharmacology of the newer anticoagulant agents is key in the management of eye surgery patients.

Heparin and Vitamin K Antagonists

Unfractionated heparin and warfarin have been available for more than half a century but impose limitations, such as slow onset of action, interaction with food and drugs, and narrow therapeutic window. Also, Vitamin K antagonists (VKA) have unreliable efficacy and demand routine coagulation monitoring and dose adjustment to maintain the international normalized ration (INR) in the target range. In addition, the slow onset of action means that many patients require perioperative bridging therapy with a rapidly acting agent (e.g. heparin).

Newer Antithrombotic Agents

In addressing these deficiencies, research development has centered on newer oral agents that inhibit two key serine proteases in the coagulation cascade:

1. Thrombin (FIIa)

2. Activated factor X (FXa).

Thrombin (FIIa) plays a central role in coagulation and clot formation by converting fibrinogen to fibrin and feedback activation of factors V, VIII and XI (see Fig. 1).

Factor Xa is a logical target because it is located at the junction of the extrinsic and intrinsic pathways. FXa inhibition attenuates thrombin formation preventing the conversion of fibrinogen to fibrin (see Fig.1).

Figure 1. Newer anticoagulants and their targets in the coagulation pathway (adapted from: Erikson et al. Novel Oral Factor Xa and Thrombin Inhibitors)

Advantages of the new oral anticoagulants over VKA include rapid onset of action and few food interactions. However, the greatest clinical benefit of these new oral anticoagulants is their predictable efficacy in attaining a desired level of anticoagulation, thus obviating the need for routine monitoring.

Thrombin (FII) Inhibitor

1.      Dabigatran (Pradaxa) - direct thrombin inhibitor, oral bioavailability 6%, dose once or twice daily, half-life (t1/2) 12 hours, no inhibition cytochrome P-450 (CYP).

Factor Xa (FXa) Inhibitors

1.      Rivaroxaban (Xarelto)  -  bioavailability 80%, administered once or twice daily, t1/2 12 hours, potent inhibitor CYP3A4.

2.      Apixaban (Eliquis) – bioavailability 66%, dose twice daily, t1/2 12 hours, potent inhibitor CYP3A4.

3.      Edoxaban (Lixiana) – bioavailability 50%, dose once daily, t1/2 10 hours, potent inhibitor CYP3A4.

Bleeding Risks of Ophthalmic Surgery During Continuation Antithrombotic Therapy

The predominant concern surrounding continuation of antithrombotic therapy is the risk of hemorrhage with placement of an ophthalmic block or during surgery. Block-induced hemorrhage can have devastating consequences leading to compressive hematoma, retinal ischemia and loss of vision. However, the main risk factor for periorbital hemorrhage is arterial fragility rather than hemostatic disorders. These devastating complications can be minimized by adopting single injection techniques, short needles (<25G and <25 mm), limited depth of needle insertion, minimal angulation, and injection in the vascular-poor infero-temporal quadrant.

Cataract Surgery

In most centers phacoemulsification surgery is performed under either topical anesthesia alone or with intracameral preservative-free supplementation. A meta-analysis of 11 studies found that patients who continued oral anticoagulants had an increased bleeding risk but these were insignificant (subconjunctival) and self-limiting.

Vitreoretinal Surgery

In recent years there have been a number of studies addressing continued antithrombotic therapy in patients undergoing vitreoretinal surgery. An observational study of 822 patients identified five risk factors for bleeding; male sex, smoking history of proliferative diabetic retinopathy, glaucoma and anticoagulant use. Although anticoagulants were associated with increased risk of intraorbital hemorrhage there were no serious sequela, need for re-operation or surgical failures. Posterior segment surgery is commonly performed under regional anesthesia but the incidence of retrobulbar hemorrhage following an ophthalmic block is exceptionally low. There is no evidence-based data to substantiate that regional ophthalmic anesthesia amplifies risk for retrobulbar hemorrhage.

Glaucoma Surgery

Two recent studies reported a higher incidence of hemorrhage during or after cutaneous surgery in patients on antithrombotic therapy but without serious consequence. For oculoplastic procedures, the incidence is also very low; one American survey found an incidence of 1:2000.

Conclusion

There are no randomized controlled trials that directly compare the rate of thromboembolic events associated with anticoagulant discontinuation against periorbital hemorrhage secondary to ongoing therapy. Severe sight-threatening block-related hemorrhagic complications are rare. Therefore routine cataract, glaucoma, vitreoretinal and oculoplastic procedures appear to be safe in patients on antiplatelet and vitamin K antagonists, as long as the INR is within therapeutic range. On balance there is insufficient data to substantiate firm recommendations for the newer antithrombotic agents (rivaroxaban, dabigatran, apixaban) but clinical experience supports continuation of therapy.

Prudence dictates assessment on an individual basis, and on occasion, liaison between the anesthesia provider and cardiologist or neurologist. Ultimately, management decisions in regard to perioperative anticoagulation rely on best clinical judgement.

Suggested Reading:

1.      Management of antithrombotic therapies in patients scheduled for eye surgery. Bonhomme et al. European Journal Anaesthesiology. 2013.

2.      Novel oral factor Xa and thrombin inhibitors in the management of thromboembolism. Eriksson et al. Annual Review Medicine. 2011.

3.      Ophthalmic patients on antithrombotic drugs: a review and guide to perioperative management. K-L Kong et al. British Journal Ophthalmology.2015.

4.      Peri-operative management of ophthalmic patients taking antithrombotic therapy. Lip et al. International Journal of Clinical Practice. 2011.

5.      The use of perioperative antithrombotics in posterior segment ocular surgery. McClellan et al. American Journal Ophthalmology. 2014.

Written by Randy Harvey, CRNA, BS

Since Dr. Atkinson described the retrobulbar block in 1936, orbital regional block techniques have continued to undergo refinements that have led to improved patient safety and comfort. The technique of utilizing a parallel approach to orbital blocks has been around for more than 30 years. Gills and Loyd described the technique in, AM Intra-Ocular Implant Soc. J-VOL , Summer 1983, titled "A Technique of Retrobulbar Block with Paralysis of Orbicularis Oculi." Directing the needle tip away from the vital orbital structures is this technique's primary value. Secondarily, the needle is inserted through the conjunctiva avoiding a skin puncture, reducing the potential for lid ecchymosis. 

The needle is inserted with the bevel towards the globe infero-temporally, above the inferior oribital rim, apporximately 3-5mm lateral to the lateral libmic margin of the globe, through the conjunctiva. The needle travels posteriorly, inferior to the globe. After passing the equatorial plane of the globe, the needle is redirected cephalad and advanced into the intra-conal compartment of the mid-orbit to a depth of approximately 25mm. The needle tip rests approximately 5mm posterior to the globe. 

The needle remains parallel to the visual axis and lateral to the lateral limbic margin throughout the technique. Therein lies the difference from the Atkinson needle based technique, which directs the needle tip towards the orbital apex. 

Anatomically, the needle tip rests in an area that has been described as a safe zone, relatively devoid of vital orbital structures. However, the eye should not look medial because it may place the optic nerve in line with the needle tip. In addition, a retrobulbar hemorrhage can still occur if the orbital veins in this area are traumatized. The general proximity of the vital orbital structures in relation to the pathway of the needle tip is illustrated below: 

1. Structures MEDIAL to the needle tip pathway:

Nerves
CN II Optic
CN III Oculomotor
CN IV Trochlear
CN V Trigeminal

Ciliary Ganglion/Nerves

Muscles
Superior Rectus
Inferior Rectus
Medial Rectus
Superior Oblique
Inferior Oblique

Vasculature 
Opthalmic Artery 
Central Retinal Artery
Ciliary Arteries
Superior Ophthalmic Vein
Central Retinal Vein
Venous Vortex Veins

2. Structures LATERAL ot the needle tip pathway: 

Nerves 
CN VI Abducens

Muscles
Lateral Rectus

3. Structures SUPERIOR to the needle tip pathway: 

Nerves
CN V Trigeminal/Lacrimal

Vasculature
Lacrimal Artery
Lacrimal Vein
Superior Ophthalmic Vein

4. The Globe's relationship to the needle tip pathway: 

Superior: The globe is superior to the needle tip, from its insertion point, until after the needle tip passes the equatorial plane of globe and is redirected  cephalad into the intraconal space. 

Posterior: The needle tip becomes posterior to the globe after passing the equatorial plane of the globe. 

Medial: The posterior pole of the globe (macula) remains medial to the needle tip throughout the procedure. Along with the area inferior to the macula where posterior staphylomas may form. 

As practitioners, we understand there is no anesthetic technique that is 100% safe. However, the parallel approach to orbital blocks incorporates a sound anatomical and technically safe approach for our needle tips to enter the intraconal space of the mid-orbit for the administration of the local anesthesia. 

Written by George A. Dumas, MD

Since cataract surgery is the most commonly performed operation in the geriatric population, it shouldn’t come as a surprise that this would be a target for payors of medical care.  Most notably, health insurer Anthem has recently stated that it is unnecessary to have an anesthesiologist or nurse anesthetist to administer and monitor sedation in most of these cases.¹ Let’s take a look at aspects of this procedure that have led us to this point.  The American College of Cardiology and the American Heart Association have categorized cataract surgery as a very low-risk procedure.² Cataract surgery is an avascular procedure and considered very low-risk for bleeding complication.  Regional needle blocks during routine use of antithrombotic therapies are generally safe provided that levels are in the usual therapeutic window.³ Most modern day cataract surgeries are performed under topical/intracameral local anesthesia with sedation.  Routine preoperative testing is unnecessary⁴ and the chance of dying from cataract surgery is estimated to be 0.014%.⁵ 

                It can be argued that the involvement of the anesthesia team has led to much of the perceived safety and low mortality rate in cataract surgery.  Many ophthalmologists still utilize needle blocks and sub-Tenon’s blocks for cataract surgery.  Complications may include brainstem anesthesia which will require immediate intubation and resuscitation of the patient.  Patient expectations are high and anxiety, pain, and fear during cataract surgery produce lower patient satisfaction scores.⁶ Sedation and analgesia are often used to supplement suboptimal local anesthesia.  Patient movement and eye block complications account for most of the closed claims for monitored anesthesia care during ophthalmic surgery.⁷

                In a discussion on this topic in Kaiser Health News, Dr. David Glasser, an ophthalmologist stated: “An ophthalmologist cannot administer conscious sedation and monitor the patient and do cataract surgery at the same time.”¹ Anthem states that anesthesia services may be covered for cases of medical necessity which includes: patients <18 years old, patients unable to cooperate or communicate, patients unable to lie flat, and complex surgery.  It should be noted that anesthesia services for cataract surgery are covered by Medicare.  An ophthalmologist will most likely be focused on the eye, not necessarily the patient’s vital signs, respiratory signs, and sedation.  Patient safety experts are concerned.  Leah Binder, president and CEO of the Leapfrog Group, stated that there are better ways for Anthem to save money than keeping anesthesiologists and nurse anesthethetists out of the OR.¹ Her suggestion: “How about identifying surgeons who have the highest complication rates, and letting patients know about them?”¹ This is sure to be a hot-button topic moving forward but as a wise anesthesiologists once told me, just because you can doesn’t mean that you should.

References

1. Andrews, M. Anthem Calls On Eye Surgeons To Monitor Anesthesia During Cataract Surgery. Kaiser Health News. Feb. 20, 2018. https://khn.org/news/anthem-calls-on-eye-surgeons-to-monitor-anesthesia-during-cataract-surgery/

2. Fleisher LA, Fleischmann KE, Auerbach AD, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;64:e77-137.

3. Katz J, Feldman MA, Bass EB, et al. Risks and benefits of anticoagulant and antiplatelet medication use before cataract surgery. Ophthalmology. 2003;110(9):1784-8.

4. Schein OD, Katz J, Bass EB, et al. Study of Medical Testing for Cataract Surgery. The value of routine preoperative medical testing before cataract surgery. N Engl J Med. 2000;342(3):168-75.

5. Keay L, Lindsley K, Tielsch, et al. Routine preoperative medical testing for cataract surgery. Cochrane Database Syst Rev. 2012;3:CD007293.

6. Fung D, Cohen MM, Stewart S, Davies A. What determines patient satisfaction with cataract care under topical local anesthesia and monitored sedation in a community hospital setting? Anesth Analg. 2005;100:1644-50.

7. Bhananker SM, Posner KL, Cheney FW, et al. Injury and liability associated with monitored anesthesia care: A closed claims analysis. Anesthesiology. 2006;104:228-34.

It has been a long winter for many and it seems that finally the spring has arrived along with this newsletter. The Ophthalmic Anesthesia Society continues to grow and we welcome our new president, Tina Tran, MD, Johns Hopkins, who has actively been involved with OAS for a number of years. I wish her good luck in this new role and thank Eric Fry, MD, Fry Eye Associates, for his services.

In this edition of the newsletter, we are sharing expert tips on orbital block techniques from OAS Member Randolf Harvey. We are also tackling a hot topic in the ophthalmology circles -- the Anthem statement. OAS Member George Dumas, MD, offers a meaningful response to the idea that it is unnecessary to have an anesthesiologist or nurse anesthetist to administer and monitor sedation. 

I would also like to share a friendly reminder that now is the best time to register for the 32nd Annual OAS Scientific Meeting in Chicago (September 28-30, 2018).

Please register early and encourage your colleagues to join you. Our program is available online and there is an exciting selection of lectures and workshops this year!

If any of you are interested in writing such commentaries, case reports or articles for the newsletter, please email me or Melissa Graham.  Also, if you have any suggestions on improving the newsletter, please let me know.

With warm regards,

Dr. Vinodkumar Singh, MRCP, FRCA
University of Alabama at Birmingham
Editor, OASIS