Anesthesia for the Eye

8/8/2019 Anesthesia for the Eye

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ANESTHESIA FOR THE EYEANESTHESIA FOR THE EYE

Scott Taylor, MD


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Requirements of Opthalmic SurgeryRequirements of Opthalmic Surgery Safety

Akinesia

Profound analgesia Minimal bleeding

Avoidance or obtundation ofocularcardiac reflex

Proper control of IOP Awareness of drug interaction

Smooth emergence


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Ocular PhysiologyOcular Physiology The eye is a complex organ with

many intricate physiologic processes

Formation and drainage of the

aqueous humor determines IOP on

both the normal and abnormal eye


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Ocular PhysiologyOcular Physiology Aqueous humor

CSF of the eye

2/3 is formed in the posterior chamber

by the ciliary body

1/3 is formed by passive filtration of

aqueous humor blood vessels


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Opthalamic SurgeryOpthalamic Surgery Intraocular Pressure (IOP)

Normally varies between 10 and 22mmHg and

is considered abnormal above 25 During anesthesia, a rise in IOP can produce

permanent visual loss

3 main factors that influence IOP

External pressure on the eye by contraction of theobicularis oris muscle and tone of extraocular

muscles (coughing, bucking, and vomiting)

Scleral rigidity

Changes in intraocular contents (blood, fluid, tumor)


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Glaucoma

Glaucoma

A condition characterized by

elevated IOP; resulting impairment of

capillary blood flow to optic nerve

can eventually lead to vision loss

Open Angle (Chronic Simple Glaucoma)

Closed Angle (Acute Glaucoma)


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Open AngleG

laucomaOpen AngleG

laucoma Elevated IOP with anatomically open

anterior chamber angle

Sclerosis of trabecular tissue results

in impaired aqueous filtration and

drainage

Treatment is eye drops to stretchtrabecula and produce miosis


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Closed Angle

Glaucoma

Closed Angle

Glaucoma

Caused by mechanical obstruction of

the aqueous outflow

Scopalamine is contraindicated on

narrow angle glaucoma because it

can produce dramatic mydriasis


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Anesthetic Effects on IntraocularAnesthetic Effects on Intraocular

PressurePressure

Inhalational anesthetics

Cause a dose related decrease in IOP

All CNS depressants, including

barbiturates, neuroleptics, tranquilizers,

opioids, and hypnotics all decrease IOP

in the normal and abnormal eye


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Anesthetic Effects on IOPAnesthetic Effects on IOP Etomidate

Produces a significant reduction in IOP

Ketamine

Previously controversial, but current

studies show no increase in IOP

following 2mg/kg IV or 8mg/kg IM


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Anesthetic Effects on IOPAnesthetic Effects on IOP Non-depolarizing Muscle Relaxants

Lower IOP by relaxing extraocular muscles

Succinylcholine Elevates IOP especially in patients with open

eye injuries

Average peak increase of 8mmHG within 1-4

min. and return to baseline within 7 min. Can be attenuated, but not abolished, with

pretreatment of Curare (0.05mg/kg)must weigh the

benefits of rapid establishment of the airway with the

risk of elevated IOP and potential blindness


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Anesthetic Effects on IOPAnesthetic Effects on IOP Hyperventilation

Decreases IOP

Hypoventilation

Increases IOP

Hypothermia

Decreases IOP


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Oculocardiac Reflex (OC

R)Oculocardiac Reflex (OC

R) Reflex triggered by pressure on the globe

and by traction on the extraocular

musclesespecially the medial rectus CNV is the afferent limb

CNX is the efferent limb

Most common manifestation is sinus

bradycardia, but a wide spectrum ofcardiac dysrhythmias may occur


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OC

ROC

R Prophylaxis prior to surgery can

include oral atropine (0.04mg/kg) 1hr

pre-op or IV atropine given 30minpre-op

Current popular practice for pediatric

anesthesia include: Atropine 0.02mg/kg IV

Robinol 0.01mg/kg IV

Prior to commencing surgery


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OC

ROC

R If reflex occurs intra-op:

1st ask the surgeon to cease

manipulation

Next give atropine

With repeated manipulation,

bradycardia is less likely to occursecondary to fatigue of the reflex arc


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Anesthetic Management of SpecificAnesthetic Management of Specific

SituationsSituations

Majority of patients are either

younger than 10 or older than 55

Most ocular procedures demand

profound analgesia, but minimal

skeletal muscle relaxation

The airway must be protected eventhough you are usually distanced from

the airway


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Special SituationsC

ontSpecial SituationsC

ont Must identify underlying illnesses,

especially in geriatric patients

Premedication should be prescribed

with a view towards amnesia,

sedation, and antiemesis

Prophylactic Droperidol

Zofran

Both are reasonable


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Special SituationsC

ontSpecial SituationsC

ont Careful attention is paid to IOP

Must provide a smooth intraoperative

course with no coughing, retching,or vomiting on emergence

Lidocaine is helpful

Brandycardia is extremely common

in strabismus surgery, soprophylaxis is preferable

Avoid nitrous oxide in retinaldetachment surgery


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RETROBULBAR BLOCK

RETROBULBAR BLOCK

Involves injection of anesthesia

behind the eye into the apex

This blocks the nasociliary branch of

the opthalmic nerve (sensory) and also

the ciliary ganglion

Akinesia of the eyelid is by blocking thebranches of the facial nerve that supply

the obicularis oculi


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Retrobulbar BlockRetrobulbar Block Complications

Stimulation of OCR

Retrobulbar reflex Retinal detachment

Central retinal artery occlusion

Penetration of the optic nerve

Inadvertent brainstem anesthesia

Toxicity of local anesthetic

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Anesthesia for the Eye