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Making topical anesthesia work in refractive lens exchange
Short-acting sedatives help to control patients’ involuntary responses during surgery.
Today’s column will be a short, practical description of our “love-hate relationship” with topical anesthesia and how we finally made it work consistently and reliably on our cataract and, more importantly, our refractive lens exchange patients.
Topical, we love you
When topical anesthesia was first introduced in the 1990s, several respected colleagues, including Dave Dillman and Skip Nichamin, began to use it and teach it in our refractive cataract surgery course. The appeal of a non-injection approach was immediately apparent. Not only are the potential risks of retrobulbar hemorrhage or bulbar trauma eliminated, but vision is not interrupted and patching is unnecessary. Once studies clearly showed that the topical and intraocular agents were not toxic, non-injection anesthesia looked to be safer and more efficient. What is not to love? Well, when it came time to implement topical, it turned out to be much less straightforward than it sounded.
Topical, we hate you
Despite apparently achieving excellent ocular anesthesia, involuntary squeezing frequently prevented our technicians from consistently placing the drape so as to eliminate the lids and all lashes from the field. Stop and re-drape.
When the microscope was positioned to begin the procedure, the light often elicited an involuntary response. “Watch the light, Mrs. Jones.” “I’m trying doctor. It’s too bright.” Stop. Reduce the microscope light and slowly increase it.
When performing the capsulorrhexis, I repeatedly reminded the patient to watch the light, all the while holding my breath in anticipation of yet another involuntary movement and the resulting anterior capsular tear.
Initially, we thought that our problems were due to poor patient selection. Those with a low anxiety threshold were not considered to be good candidates. So we began to pre-select our topical patients with very little benefit. We were often unable to predict a patient’s response to the operating room setting or the microscope light. Now we were required to set up for both topical and retrobulbar anesthesia. I could go on, but I suspect that you may already be nodding in recognition, recalling similar circumstances in your own early experience with topical. Our preop routines were disrupted, as was the surgery schedule. The anxiety level was increasing for all concerned.
When I asked patients who had experienced both types of anesthesia — one surgery with retrobulbar anesthesia (with Pentothal, as was our routine) and the other with topical — which they preferred, they overwhelmingly preferred retrobulbar. Clearly neither our staff nor our patients were realizing the anticipated benefits of topical anesthesia. We gradually backed away and returned to what had worked extremely well for us. I had heard similar stories repeated many times in those years and felt comfortable that we had made the right decision for our cataract patients.
Tighter margin of error
As refractive lens exchange (RLE) became an increasingly important part of our surgical practice, I felt a need to revisit that decision. Just as with capsular rupture, with RLE, even the most unlikely complication carries greater significance. As I have emphasized before, this tighter margin of error is the greatest challenge for even the most experienced cataract surgeon who crosses the 20/20 threshold to RLE. Want to get a sense of what this feels like? Imagine the kicker in a national championship game sent in to make the winning field goal. Lining up his kick, he looks up to find a goal post with uprights narrowed to two meters apart. Same kick, but suddenly there is much less margin for error. Similarly, the technique for RLE is essentially the same as for cataract surgery. But when the cataract is removed from the equation, a successful result is defined by a much narrower margin of error. In this context, I was determined to find a way to make non-injection anesthesia work. I felt obliged to eliminate the possibility of any injection-related complications without introducing any new ones. This time we were completely successful. Here is how.
Closer look at failure
Before attempting topical anesthesia again, I took a close look at the specific reasons why we had previously failed with it. Suddenly, our breakthrough jumped out at me. The problems we encountered were not anesthesia related. The eye was numb. Our difficulties were related to the patient’s natural, often involuntary responses to a specific set of very unfamiliar circumstances. Our initial conviction, that topical anesthesia required the measured cooperation of the patient, was the core of our problem.
For us, success came only when we were able to remove the variable of patient input from the equation. We needed to find a way to control that variable, and we did with the proper use of today’s short-acting sedatives. I have asked my nurse anesthetist, Suzy Farrar, to give you the specific formula that she has developed for us.
Sedation: Short and shallow
Much of our sedation effect is not drug related but stems from patient rapport. In the few short minutes I use to tell the patient what he can expect (monitors, sterile prep, drape, etc.), I am sure to speak calmly, slowly and with a warm tone of voice. In short, I “talk Valium” to him, which typically minimizes the amount of sedative required to reach our goal. The rest of the OR staff is sure to avoid any extraneous conversation and maintains a similar relaxing tone of voice when speaking to the patient.
When the patient is comfortably situated with blow-by oxygen and monitors attached, I advise him that I am about to give him a little of that “relaxing medicine” we spoke about earlier. With allowance for weight variance, an initial dose of Versed (midazolam HCl, Roche) 1 mg and Sublimaze (fentanyl citrate, Janssen) 25 mcg is injected into the IV heparin lock. While holding the patient’s hand whenever possible to maintain contact, I monitor his response. The goal is to have him comfortably dozing lightly but readily responding to verbal commands. Before the prep, a second drop of Marcaine (bupivacaine HCl, Abbott) is instilled (the first was instilled 10 minutes earlier). I particularly watch the patient’s response to the sterile prep. If he seems too awake (usually talking and/or blinking frequently), I typically give another 25 mcg of Sublimaze just before the drape is placed. This assures that there will be no lid squeeze and helps ensure proper drape placement so that the lids and lashes can be completely isolated from the surgical field — something Dr. Maloney watches very carefully. If additional sedation is needed, I will typically give between 0.5 mg and 1 mg of Versed at this juncture.
Dr. Maloney is in the room at this point to assure that our timing remains on track. His procedure usually takes between 6 and 10 minutes, so additional medication is rarely necessary. Rarely, if the patient’s eye movement is excessive, Dr. Maloney will silently signal me to give the patient another dose, typically 0.5 mg of Versed. It is important to carefully titrate any supplemental dosage. An overly sedated patient who falls into a deep sleep will be unable to fixate, will often have superior globe rotation and can sometimes awaken with a start. These drugs are metabolized very rapidly, and our patient is typically fully awake, alert and ready for discharge within 10 minutes of the procedure.
Team effort
It should be clear how important Suzy is to this process. I have the luxury of working with the same team every surgery day. If this is not possible in your setting, at least try to have the same anesthetist who understands her central role in this approach.
There you have it. Our love-hate relationship with topical has finally become a long-term commitment. We now use this approach on every patient, cataract or RLE. The only thing that varies is the dosage required for Suzy to reach the short, shallow state of sedation that we now understand is essential to make topical work reliably every time.
Next month:
The risk of retinal detachment in RLE may be greatly overstated. Here is why.