The Use of Anesthetics in Glaucoma Care
Chat Highlights
January 14, 2004

Norma Devine, Editor

On Wednesday, January 14, 2004, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "The Use of Anesthetics in Glaucoma Care."

Moderator:  Good evening, Dr. Wilson.  Tonight our topic is the use of anesthetics in glaucoma care.

Dr. Rick Wilson:  Good evening, everyone.

Moderator:  Doctor Wilson, what kind of anesthetic is used for  trabeculectomies?  

Dr. Rick Wilson:  For trabeculectomies, a combination of topical anesthetic (drops or gel placed on the surface of the eye) and perhaps a little injected local anesthetic are used.  Or two shots of local anesthetic are placed around the eye.

P:  Is sodium pentothal used?

Dr. Rick Wilson:  Anesthesiologists used to use sodium pentothal to put people to sleep.  It lasted for a while and could make you sick.  Now they have propefal (Diprivan), which is neutralized after only two or three minutes, and people start to awaken.  That allows the patient to be under general anesthesia for the two or three minutes it takes the doctor to inject the local anesthetic around the eye.

P:  When I had my trabeculectomy, I was told that I would be awake, but not remember the surgery afterwards.  I remember everything.  Do your patients remember the details of their surgery?

Dr. Rick Wilson:  It varies, depending upon how much medication the anesthetist or anesthesiologist gives and how rapidly the body metabolizes the medication.  In outpatient surgical centers, where the patients go home shortly after surgery, the tendency is to give less and less anesthesia so the patients will be awake without nausea, and can leave not too long after the end of surgery.

P:  Before I went into the operating room, the anesthesiologist offered me something to relax me before surgery.  I refused, wanting as few drugs as possible.  Perhaps that's why I was so alert during surgery.

Dr. Rick Wilson:  And also remembered everything so much.  When I had sinus surgery, I remember the doctor heading toward me with this long, long, long needle.  The anesthetist said, "Wait a minute.  Let me give him something." And that was the last I remember till I was back in my room.  Versed is the usual medication.  It causes amnesia, along with the calming effect.  If much pain is expected, fentenyl will be added to inhibit pain.

P:  Glad to hear that about Versed.  My doctor said I will love it.

P:  Dr. Wilson, what's the difference between an anesthetist and an anesthesiologist?

Dr. Rick Wilson:  An anesthetist is a nurse with training in anesthesia. They have to function under the supervision of the anesthesiologist, who is an M.D.

P:  What anesthetic is use for laser surgery (trabeculoplasty)?

Dr. Rick Wilson:  The same topical anesthetic ("numbing" drops) is used for glaucoma laser surgery as is used to take intraocular pressure in the office.  

P:  Are there any risks with anesthetics used for cutting surgery or lasers?

Dr. Rick Wilson:  Too much anesthetic can cause cardiac and central nervous system problems, and if injected into the optic nerve can cause the patient to stop breathing.

Moderator:  Are the surgical risks rare?  I do not remember anyone disclosing them to me with any of my surgeries.  Maybe I was just too nervous to remember.

Dr. Rick Wilson:  The risks are rare.  The anesthesiologist does not give the patient enough local anesthetic to cause cardiac or CNS (central nervous system) problems.  There is always the very rare risk of hyperthermia,  where the body's temperature control mechanism goes out of whack and the body temperature can go so high as to cause death.  We now have medicine to treat that, and recognize it early.  Thirty years ago it could be a real problem.

P:  I take phospholine iodide (echothiopate iodide) and have been told that I can't have succinylcholine as an anesthetic.  What could happen and why?

Dr. Rick Wilson:  As I remember, phospholine iodide (PI) prevents the succinylcholine from breaking down, and can cause the paralysis to last far too long.  Nowadays, succinylcholine is not commonly used, so you would probably do well.  If not, you could change to pilocarpine 6%, four times a day, for several weeks before surgery.

P:  Why would the use of succinylcholine be contraindicated for patients on PI, but not for those on other miotic eye drops like pilocarpine and carbachol?  Last year I was having foot surgery, and the anesthesiologist said he would have used succinylcholine had I not told him that I used PI. 

Dr. Rick Wilson:  PI is a different class of medication from pilocarpine, and much stronger than carbachol. 

P:  Thanks.  I was talking about glaucoma surgery, when I had trouble with anesthesia.  What, if anything, can be done to alleviate this problem for my next surgery, which will be soon?

Dr. Rick Wilson:  If the glaucoma is severe, epinephrine is probably not a good idea, as enough of it may get into the blood to slow the circulation to the eye.  For most glaucoma patients, the risk to the eye is minimal and offset by the decreased bleeding and better vision for surgery with its use.

P:  For the two or three minutes under general anesthesia, is intubation necessary for breathing?  Or is the anesthesia not that "deep?"

Dr. Rick Wilson:  The anesthesia is not that deep with the correct dose.  The respiratory center never gets so anesthetized that intubation is required.

P:  I am having laser cyclophotocoagulation on the 23rd of this month.  What can I expect?

Dr. Rick Wilson:  A laser cyclophotocoagulation will require a shot of local anesthetic behind the eye to numb it.  It sounds terrible, but it is no worse than a shot in the arm and causes very little pain if the anesthetic solution is very, very slowly injected.  My dentist taught me that.  The expansion of the fluid coming out of the needle spreads the muscle fibers apart, causing most of the pain. 

Moderator:  For cutting surgery, does the patient have the option of either being put to sleep or having a local anesthetic?

Dr. Rick Wilson:  Yes, but the local anesthetic is safer, with much less chance of nausea.  I use general anesthesia only on children, patients who cannot speak English or only speak a language nobody in the operating room understands, or is mentally handicapped to the extent that they may not obey instructions.

P:  What about a "block?"  What is that and when is it used?

Dr. Rick Wilson:  A block is just an injection of local anesthetic solution causing a localized numb area -- that is, blocking nerve impulses from the area that is "blocked."

P:  What happens if the injections wear off before the surgery is completed?  I just made it; I could feel the doctor putting in the final stitches.  Ouch!

Dr. Rick Wilson:  Then the doctor switches to topical drops for anesthesia, or gives more anesthesia in the area he is working on.

P:  Though you say risks from anesthesia are rare, I might be a case in point.  It seemed to me that I experienced vision loss following maxillofacial surgery and think that succinylcholine was used as a pre-anesthetic to relax jaw muscles.  This has made me quite afraid of anesthesia.  I understand that succinylcholine raises intraocular pressure for about 5 to 10 minutes after administration.  Can you comment further on this drug, please?

Dr. Rick Wilson:  Just before the muscles are paralyzed, the eye muscles can contract and raise the eye pressure for a brief time. Unless you have quite severe glaucoma, the brief rise is not very dangerous.  Of more concern to patients with severe glaucoma is if their blood pressure drops during surgery and the eye does not get the circulation it craves.

Moderator:  What is succinylcholine?

Dr. Rick Wilson:  Succinylcholine causes paralysis of the muscles, so that people don't react to the tube being put down their windpipe to keep their airway open.

P:  I was told by one of my doctors that if a patient has had several surgeries, it is harder to find the right level of anesthetic.  I had problems with my last surgery and they kept having to kick up the anesthesia a notch.

Dr. Rick Wilson:  If you have had several local anesthetic injections and surgeries around the eyes before, the local anesthetic may be constricted to where it is injected, instead of spreading out around the eye as it should.  The effect will not be as widespread.  If you have had several general anesthesias in a fairly short time, the body steps up its ability to metabolize the anesthetic and the anesthetic will not last as long.

Moderator:  For cataract surgery using topical anesthetic, is it advisable to stop taking blood thinners such as aspirin?  Should blood thinners be stopped before any glaucoma surgery?  

Dr. Rick Wilson:  For standard cataract surgery now, the incision is through clear cornea and the iris is not touched, so no tissues with blood vessels are touched. Therefore, blood thinners need not be stopped.  For trabeculectomy and shunt surgery, it is helpful to stop blood thinners if your medical doctor feels it is relatively safe for the short term.  An ooze of blood under the trabeculectomy flap can glue it down, and will cause more scarring around the shunt. 

P:  When I had my cataract surgery, they said not to take aspirin, but that was because it was a non-steroidal anti-inflammatory (NSAID) and so would conflict with other NSAIDs they were giving, not because it was a blood thinner.  Or at least that's what I thought.  They had me taking NSAIDs before and after surgery. They didn't stop aspirin; they just said not to use it for headache, cold, pain, etc.

Dr. Rick Wilson:  That doesn't hang together for me.  I don't see the need to stop the NSAID for just a cataract surgery.

P:  What is a vitrectomy?

Dr. Rick Wilson:  Aqueous humor, a watery fluid, fills the front of the eye.  Vitreous humor, a jelly-like substance, fills the major space in the eye behind the lens.  Removing the vitreous is called a vitrectomy. 

P:  I had shunt surgery two years ago.  My IOP is still high.  Scarring around the shunt was never mentioned, but now I need laser surgery.  It that common?  And will I need a cornea transplant in a few years due to caused by my contactlens?  Can the eye drops and material in the lens cause cornea damage?

Dr. Rick Wilson:  Shunts infrequently need to be revised or the effect augmented with the laser.  We lose corneal cells throughout our entire lives.   Glaucoma drops and any surgery kill many more cells.  If too many are injured, the corneal clarity will not survive.

Moderator:  Thank you, Dr. Wilson.

Dr. Rick Wilson:  Have to run.  I will be talking to the Connecticut Ophthalmology Society Friday, snow permitting.  Everyone have a good weekend.

End of highlights for January 14, 2004.

On January 21, Dr. Wilson discussed "Pre-operative Care" in the Chat room. Click here for highlights of that meeting.

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