Anesthesia |
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For the VR surgeon to have “peace of mind” during the operation,1 the patient must feel no pain and the eyeball may not move (akinesia, “block”). An anesthesia that permits the sensation of pain or significant eye movement is inadequate for VR surgery.
Pearl
Minimal eye movements are tolerable since the surgeon has rather firm control over the eye by having two instruments inside it. Nevertheless, when fine manipulations are performed, the surgeon should not be forced to divide his attention between the surgical task ahead and the struggle to keep the eye immobile.
There are two types of anesthesia, local and general; both have advantages and disadvantages (see Table 15.1). Either way, the surgeon must have absolute confidence in the anesthesiologist (see the Appendix, Part 2) and look at him as a partner on the team (see Sect. 16.1).
One of the benefits of local anesthesia is that the surgeon can communicate with the wake patient during the operation. For instance, I rather often do this in cases of delayed surgery for severe injury. In such an eye some of the pathologies or their extent may be discovered only intraoperatively,2 and each of the possible treatment options has different implications for the patient; it is preferable to make the decision jointly.
1Allowing him to concentrate on the surgery rather than on the patient who complains of pain or moves because of it.
2Hence the original plan may have to be drastically changed (see Sect. 3.1).
© Springer International Publishing Switzerland 2016 |
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F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,
DOI 10.1007/978-3-319-19479-0_15
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15 Anesthesia |
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Table 15.1 Anesthesia in VR surgery: types and their advantages |
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Anesthesia |
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typea |
Advantage |
Disadvantage |
Local |
Inexpensive |
The akinesia may be imperfect |
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Possible to communicate with the |
The patient may movec or fall asleep |
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patient during surgeryb |
due to the intravenous sedation. The |
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latter is not a problem until the |
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patient suddenly wakes up and then |
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inadvertently moves |
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Easy to change the position of the |
The patient is able to hear everything |
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patient’s head: just ask him to do so |
that is being said in the OR during |
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the operationd |
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Short turnover timee |
Risk of peribulbar hemorrhage or severe |
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chemosis |
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Patient can lie down on the operating |
Risk of needle penetration into the |
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table on his own and enter and leave |
globe |
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the OR on his own foot or in a |
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wheelchair – only rarely is an extra |
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person needed to move the patient |
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The wonders of VR surgery: a few |
Reinjection may be necessary if the |
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patients describe an incredibly |
operation is very long |
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beautiful experience as they can see |
An anesthesiologist should be on the |
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even minute details of what is being |
premises “just in case” |
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done inside their eyef |
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General |
Patient feels absolutely no pain |
Expensive equipment needed |
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Patient will not move body or eyeball |
An anesthesiologist and an extra nurse |
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during the operationg |
are needed (and paid for) |
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The patient’s systemic condition is |
There is an issue with N2O diffusion |
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closely monitored |
into the intravitreal gas (see |
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Chap. 14) |
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The systemic blood pressure is |
There is a risk of a coughing attack after |
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relatively easy to adjusth |
the tube has been removed; an ECH |
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may result |
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If for some reason the machinery |
The turnover time is often more than |
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breaks down or the operation is |
30 min |
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unexpectedly long, there is no extra |
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pressure on the surgeon to finish it |
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Longer postoperative recovery |
aThe patient’s systemic condition is another factor that may be decisive in determining which option to choose. In countries with excellent medical care problems, such as patients showing up with poorly controlled diabetes or blood pressure, almost never occur, but in most countries it is a rather common issue.
bSee the text for more details.
cOften due to back or neck pain. If fine work is being done, such as ILM peeling, movement of even the patient’s leg may lead to movement of the head.
dNot necessarily cursing (although that happens, too) but, for instance, the machine breaking down or the surgeon mentioning last night’s football game (“he is not fully concentrating on me!”).
eIn one of the ORs where I work, the average time between finishing one and being able to start the next operation is 7 min. If the facility is equipped properly, this is also achievable when using general anesthesia, but it requires a lot of expensive extra equipment.
fObviously, this does not represent an indication for, or justification of, local anesthesia, but it nevertheless awards these patients a memory they will never forget.
gThe anesthesiologist must not start waking the patient up until hearing the verbal confirmation from the VR surgeon.
hMostly reduced to the normal range; hypotony in PPV for choroidal melanoma.
15.1 How to Decide the Type of Anesthesia |
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15.1How to Decide the Type of Anesthesia
The patient and the surgeon should decide the type of anesthesia.3 General anesthesia,4 however, is needed or should be considered in the following cases:
•Young patients.5
•Immature, unreliable, mentally challenged, and malicious patients or those who have claustrophobia.
•Patients who undergo repeat PPV, especially if multiple or recent surgery/surgeries.6
•Patients who cannot lie in the supine position for extended periods because of a systemic condition such as a hump or lower back pain.
•A special type of requirement is in place (such as artificial systemic hypotony), which demands tight control and might be unpleasant for the wake patient.
•The operation may require extended or repeated maneuvers that can be difficult to anesthetize locally (360° scleral indentation, cryopexy, disinsertion/hooking of extraocular muscles etc.).
•Patients who request it.
If intraocular gas tamponade is used, certain caution is needed to avoid a postoperative drop in the fill percentage (see Sect. 14.2).
Fig. 15.1 Preparing the patient for general anesthesia. Especially if the patient’s head is correctly positioned (see 16.6), discharge from the nose may find its way to the conjunctiva and thus into the eye. The nostrils should be tamponaded to eliminate the endophthalmitis risk from this source
3Sometimes the facility preserves the right to determine it.
4Which also means special preparation by the person draping the patient (see Fig. 15.1).
5It is not strictly a question of biological age. A 17-year-old may be mature enough to undergo an operation in local anesthesia, while a 30-year-old may still be “too young” to do the same.
6In inflamed, edematous tissues the efficacy of the anesthetics is reduced.
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15 Anesthesia |
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15.2If Local Anesthesia Is Chosen
Local anesthesia is preferred for most of the cases.7 The surgeon can choose from several potential options, which are discussed in Table 15.2.
Table 15.2 The type of local anesthesia in VR surgery
Anesthesia type |
Comment |
Topical (surface) |
Even if the surface of the eye is fully anesthetized, certain intraocular |
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manipulations will cause pain. Furthermore, the eye remains mobile, |
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and this is a problem the surgeon must face even if complete anesthesia |
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is maintained throughout the operation |
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Summary: this kind of anesthesia is not recommended for VR surgerya |
Sub-Tenon |
The irrigation of the posterior globe surface (through an opening in the |
(parabulbar) |
conjunctiva and Tenon’s capsule) results in immediate anesthesia and |
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after a few-minute delay in akinesia. The medication can be delivered |
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through a blunt metal cannula or a flexible silicone tube |
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Summary: this is a safe and effective technique, but it is usually employed |
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as a supplementary, not primary, option |
Peribulbarb |
The procedure is very effective while keeping the risk of damage to the |
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optic nerve or a major orbital vessel to the minimum. The needle |
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should not be longer than 18 mm |
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Summary: this is the preferable option in local anesthesia |
Retrobulbar |
Deep penetration of the needle into the orbit always has a risk of injury to the |
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optic nerve (especially if the patient is directed to look away from the |
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injection site) or a major orbital vessel. The needle should not be longer |
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than 31 mm |
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Summary: if possible, avoid this technique, but if you must apply it, have |
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the patient look toward the needle or maintain the primary position |
If peribulbar anesthetics need to be added during surgery, remember that the volume of the orbit is limited, and there will be (additional) pressure on the globe. The elevated IOP can be dangerous if the globe is open: make sure the valves of the cannulas do not leak, all incisions are closed, inject gradually, and be careful when reopening the eye
If the PPV is done as a continuation of a cataract surgery (dropped nucleus) that was done in topical anesthesia, place a suture in the phaco wound before the peribulbar injection. Inject no more than 2 ml and then use parabulbar anesthesia to complement it.
aSome surgeons insist that in “short cases” topical anesthesia is acceptable. However, a “short” case can quickly turn into a long one if a complication occurs. I have seen quite a few operations when during the “short case” the surgeon was forced to switch, intraoperatively, to a more robust type of anesthesia. bBoth the periand the retrobulbar injections are given at an inferotemporal location, and the anesthesia is accompanied with intravenous sedation.
7 With rare exceptions (see above), I do all my cases in local anesthesia.
15.2 If Local Anesthesia Is Chosen |
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Q&A
QWho should administer the peribulbar injection: the surgeon, his assistant, or the anesthesiologist?
AThere is no rule, as long as the person is well trained. The only advantage of the surgeon himself giving the injection is that if a complication occurs, he has nobody else to blame. Conversely, it takes away time that he could otherwise use to rest between cases.
It is very important for the surgeon to extensively talk to the patient before, and during, surgery about not moving. I tell my patients the following:
•“No movement” means just that. Not with your head, not with your hands, and not with your feet.
•If you do need to move (because your back hurts or you need to sneeze, cough etc.), tell me in advance. I will then take out the instruments from your eyeball and wait until you tell me that I can continue.
•Keep your other eye closed. Do not squeeze and do not try looking left and right. The eye will be covered with a drape so you will not see anything anyway.
•Extra oxygen will be supplied under the drape so you will not be in danger of suffocating. If you feel you need more oxygen, let me know, and we will increase its flow.
•I may have to do a particularly delicate maneuver during surgery8 when you must be even more motionless, as if you were frozen. From the surface of your retina, the thin film of vision, I have to remove a membrane, which is so thin that if you stack 40 of them on top of each other like bricks in a wall, it is still only as thick as a human hair.9
•You are welcome to ask me any question during the operation, but when you ask the question, make sure that only your lips and tongue move. I will answer you, even if not immediately.
Having performed well over 10,000 surgeries under these conditions, I had only two cases when I was not able to complete a maneuver because of patient movement and no case when I had a serious complication due to patient movement. One important caveat for those operating on patients who are awake: if something goes wrong and you loudly voice your frustration,10 even if the issue is a minor one, the patient will hear you…
8Such as ILM peeling.
9Most patients are unable to envision what “2 μ thick” truly means.
10“Oops!” – or one of those unprintable cusswords.