Retrobulbar Block Flashcards
What is the primary reason for performing a
retrobulbar block?
To provide anesthesia to the entire globe of the eye.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 554.
How is a retrobulbar block performed?
The patient is supine with their gaze directed supranasally.
Local anesthetic eyedrops are instilled to anesthetize the
conjunctiva. The lower lid is pulled down to expose the globe.
A 25 gauge needle is inserted above the inferior orbital rim and
directed towards the floor of the orbit. Once past the equator of
the eye, the needle is directed more cephalad towards the
muscle cone. After aspirating for blood or CSF, 2-3 mL of local
anesthetic is injected.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 552.
What patient conditions increase the risk for globe
injury during a retrobulbar block?
Myopia or a previous history of scleral buckle surgery increases
the risk of globe penetration by the needle as they both are
associated with an increased anteroposterior length of the
globe. A recessed eyeball also increases the risk of injury.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1385.
Why does intravascular injection during a
retrobulbar block produce symptoms of local
anesthetic toxicity so quickly?
Accidental injection into the opthalmic artery will drive the local
anesthetic in retrograde fashion through the internal carotid
artery and then to the circle of Willis.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1386.
The sudden onset of seizures during or after a
retrobulbar block is probably due to what?
Seizures probably represent the inadvertant intravascular
injection of the local anesthetic during the procedure.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1386.
How is a facial nerve block performed to anesthetize
the orbicularis oculi muscles after performing a
retrobulbar block?
Local anesthetic is injected in a V-shape along the upper and
lower temporal orbital ridge. This blocks the zygomatic
branches of the facial nerve.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 553.
Why is a retrobulbar block performed from an angle
below the globe rather than above it?
The injection is typically only performed below the globe as
most of the vessels are positioned superiorly to the globe
making the risk of puncture higher.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1384-1385.
How deep should the needle be inserted when
performing a retrobulbar block?
The needle should be inserted approximately 1 inch, which
would place the needle tip just posterior to the globe. Inserting
the needle further increases the risk of puncturing a nerve or
vessel in the orbit.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 984-985.
Why is it important for the patient to maintain a
neutral or supranasal gaze during a retrobulbar
block?
The patient should be instructed to look supranasally (up and
toward the nose) or straight ahead (neutral gaze) as the needle
is inserted 1.5 cm. If the patient looks upward, the optic nerve
and vessels are brought forward into the path of the needle.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 984.
What are the potential complications of a retrobulbar
block?
Stimulation of the oculocardiac reflex, retrobulbar hemorrhage,
circumorbital hematoma, penetration of the globe, optic nerve
trauma, optic nerve sheath injection, extraocular muscle injury,
intra-arterial injection, retinal artery occlusion, and inadvertant
brainstem anesthesia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1385.
How does a peribulbar block differ from a retrobulbar
block?
In a peribulbar block, the landmark for inferior injection is the
same as for a retrobulbar block. A second injection is made
superiorly, inserting the needle just inferior and medial to the
supraorbital notch. The needle is directed posteriorly over the
globe to a depth of one inch and another 3-4 mLs of local
anesthetic are injected.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 553.
What is the advantage of a peribulbar block over a
retrobulbar block?
The peribulbar block usually has sufficient local anesthetic
volume injected to block the orbicularis oculi muscles and
prevent eye movement. A retrobulbar block requires an
additional facial nerve block to produce relaxation of the
orbicularis oculi muscles.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 553.
Can topical anesthesia be used for cataract
surgery? Why or why not?
Topical anesthesia is suitable for patients who are alert and can
follow commands. Patients who are demented, photophobic, or
have difficult to access cataracts would not be suitable for this
technique.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1387.
What are the advantages of using topical anesthesia
over retrobulbar anesthesia for cataract surgery?
There is little risk of ocular injury and the technique is perfect for
an anticoagulated patient or a monocular patient who would be
blind from the amaurosis induced by the retrobulbar block.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1387.
What are the disadvantages to using topical
anesthesia over a retrobulbar block for cataract
surgery?
Eye movement may make the surgery difficult and patient
anxiety or discomfort may make a general anesthetic or regional
anesthetic more appropriate.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1387.
