This comprehensive course will give you the fundamental knowledge needed to begin performing cataract surgery by phacoemulsification and extracapsular removal. Each step from preoperative evaluation to postoperative care will be covered to help prepare you for the operating room.
01.05 - Perioperative Medications
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来自 University of Michigan 的课程
Introduction to Cataract Surgery
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从本节课中
Unit 1: Prior to the Operating Room
This unit describes what needs to take place prior to getting the patient to the operating room. Although this unit may seem trivial, knowing when to make the decision to do surgery, having a good informed consent discussion, selecting an intraocular lens and anesthetic type are critical to a successful surgery and happy patient.
与讲师见面
Elizabeth Du, M.D.Clinical Assistant Professor
Department of Ophthalmology & Visual Sciences, Kellogg Eye Center
Hi, my name is Shahzad Mian.
I'm going to be speaking to you today about perioperative medications for
cataract surgery.
The goal with perioperative medications for cataract surgery,
includes achieving adequate pupillary dilation.
Achieving an anti-infective prophylaxis, anesthesia for
surgery, and anti-inflammatory effects.
In addition, it's also important to be aware of what medications the patient is
already taking prior to surgery, as they may impact the outcomes and
the surgical procedure.
When it comes to pupillary dilation,
the sympathomimetic drops we use tend to stimulate the dilator pupillae muscle.
The most common medication used is 2.5% phenylephrine,
which is an alpha-receptor agonist.
It achieves its maximum dilation in 45 to 60 minutes, and
the recovery time is approximately 3 hours.
Topical use can cause systemic side effects, therefore,
it is important to be aware of patient's cardiac history prior to using the drops.
Additional sympathomimetic drops that can be used,
include intraoperative use of Shugarcaine,
which is a formulation that includes use of lidocaine and epinephrine, as well as
a formulation that we use here in University of Michigan Kellogg Eye Center.
These formulations allow for
intraoperative pupillary dilation by stimulating the dilator pupillae muscle.
In addition to using sympathomimetic agents, parasympatholytic agents,
which are anticholinergic can also be used,
they paralyses sphincter pupillae muscle as well a ciliary muscle.
The common agents use, includes tropicamide,
which in the 1% solution is used commonly prior to surgery, which has a peak
mydriasis 20 to 30 minutes after use and recovery in 4 to 6 hours.
Additional agents that may be used, includes cyclopentolate, homatropine, and
atropine.
It's important to note that the combination of sympathomimetic and
parasympatholytic agents induces greater mydriasis.
Anti-infective prophylaxis is used to address potential sources of microbes that
lead to infection.
And the potential sources, include flora of the conjunctiva, and the skin.
Intraocular anterior chamber contaminants almost always are indigenous and these
include, Staphylococci, Diphtheroids, Streptococcus, and Gram negative bacilli.
The prophylaxis used is due to the need for decreasing or
eliminating the bacterial load on the ocular surface.
We want agents, which can penetrate into the aqueous to treat bacteria
seeded at the time of surgery.
And it is the community standard of care.
The ideal antibiotic would have a broad spectrum of coverage,
minimal side effects or toxicity, and a rapid kill rate.
However there is limited evidence to show that pre-operative drops
actually decrease risk of Endophthalmitis.
We're going to review briefly what endophthalmitis is, because it's important
to recognize this in terms of why we are trying to prevent it.
Often patients present with pain, loss of vision, floaters, and light sensitivity.
The most common signs of endophthalmitis, include lid swelling,
vitreous inflammation, periorbital edema,
ciliary injection, and a layering of white blood cells or a hypopyon.
Most cases of endophthalmitis are culture positive,
however about a third are culture negative.
When they are culture positive bacteria account for
the most common source of endophthalmitis, although rarely can be fungal as well.
In the acute stage that is define as less than 2 weeks, the most common organism
is coag (-) staph, followed by staph aureus, and streptococcus.
In the subacute stage, which is defined by two to six weeks after surgery,
coag (-) staph is the predominant organism.
And chronic endophthamitis is after six weeks,
is caused by propionbacterium acnes.
Endophthamitis can also be caused by toxic materials and
retained lens materials, therefore not being infectious.
Prophylaxis of the endophthalmitis, includes treatment of blepharitis,
since the most common organisms are present on the eyelids,
by using warm compresses, lid hygiene, and oral doxycycline or azithromycin.
Aseptic technique intraoperatively is
very important with used of 5% povidone iodine because this is bactericidal,
10% may be used as well, however it may have greater endothelial toxicity.
Preoperative use at the time of surgery has been shown to have a significant
benefit in preventing a risk of endophthalmitis.
Prophylactic broad-spectrum antibiotics are used including fluoroquinolones, which
bind to bacterial topoisomerase, thus inhibiting bacterial DNA to supercoil.
There are also bactericidal, and the fourth generation fluoroquinolones have
lower have greater advantages of lower toxicity and
superior penetration through the cornea.
Therefore, providing higher minimum inhibitory
concentrations into the aqueous.
And our broad-spectrum in covering both gram positive and gram negative organisms.
Many different regimens for preoperative antibiotics have been described in
the literature, including one hour prior to surgery,
three days prior to surgery, with different types of fluoroquinolones.
And with postoperative use of different types of fluoroquinolones.
However, when we examine the evidence, and in looking at the American Academy of
Ophthalmology preferred practice patterns, they state that there is no
clear evidence that any of these regimens actually decrease risk of endophthalmitis.
Additional prophylaxis has been described in literature through
the European Society of Cataract Refractive Surgery study
of prophylaxis with intracameral of cefuroxime.
This dosage involved using 1 milligram per point 1 mils at the time of surgery.
In this study, there was a five-fold decrease in the rate of endophthalmitis
in the treatment group as compared to the control group.
Similar data has been reported with use of cefazolin used in intracamerally.
In addition,
prevention of endophthalmitis also involves modifying the surgical technique.
There has been an associated increased risk of endophthalmitis with a transition
from scleral tunnel incisions to scleral corneal incisions.
And use of smaller incisions,
as well as suturing incisions closed may decrease risk of endophthalmitis.
Moving on to anesthetics for cataract surgery,
we commonly use proparacaine eye drops, tetracaine eyedrops,
lidocaine 2% jelly, or intracameral preservative free lidocaine.
In addition, bupivicaine may be used as a peribulbar, or retrobulbar agent.
Topical non-steroidals are used as an anti-inflammatory agent and
their main mechanism of action is to inhibit cyclooxygenase activity
by inhibiting prostaglandin formation in the arachidonic acid pathway.
They're using cataract surgery to maintain adequate pupillary dilation.
Control of inflammation after surgery, as well as prophylaxis and
treatment of pseudophakic cystoid macular edema.
Cystoid macular edema is the most frequent visual complication after
uncomplicated cataract surgery.
All of the incidents was much greater with earlier generations of cataract surgery
techniques.
It still remains relatively high when we look at uncomplicated cataract surgery
risks, where patients who are symptomatic with vision less than 20/40,
having a range of 1 to2%.
There is greater evidence of cystoid macular edema when patients are examined
angiographically or with additional testing including ERG, photostress test,
and contrast sensitivity.
The peak incidents of cystoid macular edema is 6 to 10 weeks postoperatively.
Why does cystoid macular edema occur?
Well, it starts to occur because there is increased perifoveolar capillary
permeability, intraocular vascular instability, and increased production of
prostaglandin that especially released from the anterior uvea.
This results in cystoid spaces, and
lacunar cavities in the outer plexiform layer of Henle.
Because this is a thick layer, which is able to absorb large quantities of fluid.
It is avascular, therefore there's limited capillary absorption of fluid.
And there is a thin fovea and internal limiting membrane in this region,
which increases susceptibility to inflammatory exudates and
toxic products through the vitreous.
What are the risk factors for cystoid macular edema?
Well, there are a number of identified risk factors preoperatively,
including having a epiretinal membrane, and noted prior to surgery.
Hypertension, diabetes, history of uveitis or active uveitis, and
having a history of cystoid macular edema including in the contrary lateral eye.
Intraoperative risk factor, include types of surgery, as I mentioned earlier,
earlier generation cataracts surgery techniques had a higher rate
than newer generation cataracts surgery techniques.
If there is increased vitreomacular traction,
a prolonged case with ultraviolet light exposure,
that's prolonged posterior capsular rupture, vitreous loss,
especially if there's incarceration to the wound or adhesion to the iris.
Even in iris prolapse can increase risk of cystoid macular edema after surgery.
Types of lenses used can also increase the risk earlier generation lenses, which were
iris-supported or closed-loop anterior chamber intraocular lenses have been
reported to have a higher rate of cystoid macular edema after cataract surgery.
Postoperative risk factors for cystoid macular edema, include medications,
if patients are on epinephrine, dipivefrin, or even prostaglandin analogs,
they may be at a higher risk for cystoid macular edema after surgery.
Prolonged inflammation after surgery, as well as hypotony also increase the risk.
Patients often present with decreased vision, they may have mild pain,
redness, light sensitivity.
We are looking for signs of complicated anterior segment surgery,
mild anterior chamber reaction, loss of foveal reflex, yellowish reflex or
spot in the macula, and perifoveal cystoid spaces with red-free light.
A honeycomb lesion appearance, and
perifoveal hemorrhages may also be present.
In addition, capillary microaneurysms, and optic disc edema may also be noted.
The goal standard for detection of cystoid macular edema is fluorescein angiography,
where we can note a petaloid pattern with feathery margins, and
signs of optic disc edema.
However, now the most common method that's used is optical coherence tomography,
which can easily detect cystoid spaces in the outer plexiform layer of henle.
Topical non-steroidals that are used, include flurbiprofen,
which is often used in the preoperative regimen to prevent interoperative miosis.
Additional agent, include diclofenac, ketorolac, nevanac, and bromfenac.
Topical non-steroids are contraindication if there is a known
hypersensitivity a patient may have to non-steroidals.
And a cross reactivity with any other non-steroidal.
Bleeding may also be increased in patients, especially those who
are on anticoagulation, or have a tendency to bleed more easily.
Adverse reactions associated with non-steroidals,
include sterile infiltrates, transient burning and stinging, and keratitis.
So, topical non-steroidals maybe used preoperatively and postoperatively one
to three days pre and postoperatively to reduce risk of cystoid macular edema.
However, the role of preoperative non-steroidal to prevent clinically
significant cystoid macular edema is still controversial.
It is not clear from the literature that routine use
versus using in high risk patients, or never routinely using non-steroidals,
is the best treatment at this time.
It is important to ask patients about what medications they're using, and
which eye drops they are using prior to cataract surgery,
because this can impact the intraoperative surgical treatment.
Anticoagulation, antiplatelet medications may increased risk of medical and
ophthalmic complications.
However, it's low overall, and do not need to be routinely need to be stopped.
You can stop use of anticoagulation if bulbar block's performed.
However, that is also not required.
Flomax, which is a alpha1-blocker, has been shown to cause complete and prolonged
antagonism of the iris dilator muscles by affecting the iris smooth muscle tone.
Other alpha1-adrenoreceptor blockers, such as terazosin and
prazosin are non-selective, however, they also impact the muscle tone.
Stopping these medications prior to surgery does not change the outcome during
surgery.
Additional herbs and vitamins can also have an impact on anticoagulation,
and have antiplatelet effects.
Their effect is not well-characterized, and there's no data to support
whether there's a negative or beneficial impact during cataract surgery.
Caution is necessary on patients on taking multiple herbs and vitamins, and
this needs to be individually assessed with each patient prior to surgery.
Topical prostaglandins can increase risk of pseudophakic cystoid macular
edema by disrupting the blood-aqueous barrier.
This is an important consideration in patients who have glaucoma who
are undergoing cataract surgery, and may need to be stopped especially in
patients who are at higher risk for macular edema after surgery.
In summary, preoperative medications for cataract surgery,
include those agents used for dilation, including phenylephrine 2.5% and
tropicamide 1% because they have a synergistic affect.
Non-steriodals, such as flubriprofen may be used at the time of surgery to
improve dilation, and prevention of myosis.
Topical anesthesia is performed often with proparacaine and lidocaine jelly, however,
additional agents may be used for peribulbar and retrobulbar blocks.
Antibiotics are not routinely recommended prior to cataract surgery because
there is no known benefit of using it preoperatively.
Intraoperatively, anesthesia is achieved with intracameral lidocaine.
Dilation may further be enhance by using balanced salt solution with epinephrine,
or using shugarcaine mixture of epinephrine.
Anti-effective agents such as cefuroxime intraoperatively
had been shown to reduce risk of endophthalmitis after cataract surgery.
Postoperatively antibiotics maybe use,
however the data for this is lacking, and agent such as Polytrim maybe adequate for
providing broad-spectrum bactericidal coverage.
Non-steroidals may be used, especially in patients who are at higher risk for
cystoid macular edema.
And use of topical corticosteroids is recommended to reduce risk of pain,
and controlling inflammation after cataract surgery.
Thank you.
