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-Postoperative Complications
of Periocular Anesthesia
Ignatius C. Cyriac, M.D.
Roberto Pineda, II, M.D.
Even as current trends move away from retrobulbar blocks and topical
anesthesia gains greater widespread acceptance, ocular anesthesia still is most
commonly administered with a needle. Although rare, numerous complications
associated with the administration of periocular anesthesia have been described,
ranging from the innocuous hemorrhage to life threatening systemic situations.Early recognition is paramount, and judi cious management of these
complications can result in more favorable visual outcomes and significantly less
morbidity.
The local anesthetic ocular complications that are reviewed include
retrobulbar hemorrhage, globe perforation, optic nerve trauma, and mus cl
injury. As systemic complications can be associated with direct central nervous
system (eNS) spread of anesthetic, signs and symptoms of this situation also are
addressed.
Techniques
The aim of retrobulbar anesthesia administration is to direct the tip of theretrobulbar needle toward the orbital apex within the muscle cone to allow
diffusion of anesthetic within this space. When the ocular motor nerves (III and
VI) and sensory nerves (V) are blocked, akinesia and anesthesia is achieved.
Ophthalmic surgery has been performed with local anesthesia for more than
100 years. Herman Knapp was the first to describe retrobulbar anesthesia with
cocaine in 1848. However this method fell into disrepute because of serious and
fatal complications. The modern technique of retrobulbar anesthesia using
lidocaine was described by Atkinson in 1948. This technique of retrobulbar
anesthesia as described by Atkinson has undergone various modifications in
general use but essentially is un-
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86 Cyriac Q,~ Pineda
changed from his original method. Atkinson originally recommended the
technique of positioning the globe in an up and inward gaze using a blunted
needle of no longer than 35 mm. Because of the blind approach of this
technique, Unsold and associates' performed studies that involved scanning
orbits of cadavers after introducing a retrobulbar needle. They demonstrated
the optic nerve, ophthalmic artery, superior orbital vein, and posterior pole of
the globe to be in close proximity to the needle. The authors recommended
placing the globe in primary position or in a down and outward gaze,
suggesting that the optic nerve, vessels, and inferior oblique are placed outside
the path of the anesthetic needle.
Peribulbar anesthesia administration seeks to avoid the optic nerve,
ophthalmic artery and vein, and posterior globe by placing the anesthesia
outside the retrobulbar space just posterior to the equator. Akinesia and
anesthesia is achieved through diffusion of anesthesia in this area. The actual
technique is more varied in its use than is the retrobulbar method of
administration. The technique described by Davis and Mandel/ serves as
representative example of this block. With the eye in primary position, a 12-
mm 27-gauge needle injects a diluted 1 % lidocaine solution into the anteriororbit inferotemporally. In this same area, an 18 to 24-mm 23 to 26-gauge
needle is used to inject a solution of lidocaine, marcaine, and wydase.
Supplemental blocks of this same preparation are administered into the
superonasal or inferonasal orbit as needed.
Peribulbar anesthesia has been believed to be less painful and to result infewer postoperative complications than is retrobulbar anesthesia. Fewer cases
of retrobulbar hemorrhage, globe perforation, and brainstem anesthesia have
been reported.f
Anatomical Considerations
To understand the mechanisms of complications from periocular nerve
blocks first requires knowledge of orbital anatomy. Motor nerves (cranial
nerves III, IV, and VI) insert into rectus muscles between the pos terior and
middle thirds of the muscle belly. Thus, the muscular branches of the third
nerve may be blocked within the muscle cone in the posterior orbit, notably in
the area of the optic nerve and ophthalmic vein, whereas the inferior oblique'snervous and vascular branches insert more anteri orly on the muscle and,
therefore, are more susceptible to damage by blocks provided along the orbital
floor. The origin of the superior oblique in the posterior-superotemporal orbit
and its relative immobility render superotemporal blocks perilous.
Needle length with relation to anatomical dimensions also can increase the
risk of complications for a particular block. It has been shown that the average
length from the lateral one-third of the inferior orbital rim to the orbital apex is
48 mm or less. 4 Also, the intracanalicular portion
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Complications of Periocular , nosia - 87
of the optic nerve is relatively immobile and extends anteriorly from here. Risk
from using long needles then becomes apparent. Using blunt needles was
thought to resolve this risk, but complications have been reported with blunt
needles as well. 5
Local Complications
Hemorrhage
The most common complication of periocular anesthetic administra tion i
retrobulbar and periocular hemorrhage. Incidence of hemor rhages with
retrobulbar blocks is between 1 and 3% and, when combined with peribulbar
blocks, incidences of 1 : 1,000 to 1 : 60 have been re ported." However, most of
these cases are mild in nature. Acquired vascu lar disease is thought to be a risk
factor for this occurrence.
The vast majority of orbital and periocular hemorrhages are venous in
origin. Usually, they are not vision-threatening and more often require
postponement of surgery than any intervention. Alternatively, arterial he
morrhages can produce proptosis, ecchymosis, and chemosis. In the pres ence o
rapid orbital swelling causing a tight orbit, marked proptosis, oph thalmoplegia,
and blood-staining of periorbital tissues, a retrobulbar hemorrhage of arterial
origin should be suspected. Vision loss occurs as a result of the tamponade
effect of the periorbital swelling wherein the in traorbital pressure rises higher
than does the intraarterial pressure. Also, occlusion of the microvasculature of
the optic nerve can occur, causing a late optic atrophy.
If the diagnosis of retrobulbar hemorrhage is suspected, pressure
measurement and ophthalmoscopy are indicated. Treatment is immedi ate latera
canthotomy-cantholysis and close follow-up of intraocular pres sure (lOP) and
vision. Emergent orbital decompression surgery may be considered if the optic
nerve is compromised.
Permanent impairment of vision in such patients has not been shown to
occur. Direct arterial trauma is the suspected cause, and no modifica tion in
technique has demonstrated avoidance of this complication.
Globe Perforation
Globe perforation is one of the most dreaded complications of local
anesthesia. Several retrospective studies reported isolated cases of globe
perforation. Incidence of globe perforation ranges from 1: 1000 to 1 : 4200 in
reported cases and, in patients with axial lengths greater than 26 mm, the
incidence increases to 1 : 140. 7 In addition, axial myopes also have thinner
sclera, placing them at further risk. Other risk factors for globe perforation
include enophthalmos or nanophthalmos, multiple injections or injection sites,
and a history of a scleral buckling procedure.
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88 Cyr.,.; and Pineda
Whether advantages accrue to sharp rather than blunt needles is un known. Use
of blunt needles has been thought to avoid this risk, but cases of blunt-needle
perforation have occurred. Also, performing strictly peribulbar blocks does not
obviate the risk of perforation, although the incidence is lower with the
peribulbar technique.f Because techniques and needle types vary, determining
the relative risk of globe perforation is difficult. The risk of perforation has not
been proven in any controlled study.
Symptoms of ocular penetration include severe pain and sudden loss of
vision, and signs include hypotony, sudden increase in lOP, and sub -conjunctival hemorrhage. When suspected, indirect ophthalmoscopy should be
performed to confirm the diagnosis, but scleral exploration is not necessary, as
the perforation sites often are small and self-sealing. If the media are not clear
enough to allow visualization of the retina, the sur geon may proceed with
cataract surgery. Otherwise, treatment entails immediate cryopexy or episcleral
implant for anterior perforations or laser photocoagulation to posterior
perforations. Systemic antibiotics should be administered to reduce the risk of
endophthalmitis.
Complications of perforation include subretinal, retinal, and vitreous
hemorrhage; retinal holes; or detachment. The degree of postoperative visual
recovery depends on the location of the perforation (although the majority are
below the fovea), presence of a retinal detachment, and development of
proliferative vitreoretinopathy.
Muscle Injury
Although exceedingly rare, another complication oflocal ocular anes thesia
is direct muscle trauma with subsequent diplopia. The cases reported most
commonly are of inferior rectus palsies or contracture after blocks .m d of
superior rectus overaction. Increased use of peribulbar blocks has been
implicated as a cause, given the multiple injections or injection sites used with
this method; however that the use of hyalu ronidase is thought to improve the
efficacy of this technique, thereby re quiring less injection of anesthetic.
The mechanism of muscle injury is speculative. One theory contends that
direct injection of anesthetic into the recti and subsequent myotoxic ity cause
postoperative strabismus. Studies by Rainin and Carlson" sug gested that
surrounding an isolated rectus muscle with high concentra tions and volume of
anesthetic can cause muscle fiber destruction. Trauma to nerves and needle
damage of the rectus muscles also are spec ulated to be causes of postoperative
strabismus.
Another accepted theory is that muscle injury occurs in one of two ways:
Laceration of anterior ciliary vessels causes a hematoma ora large volume of
anesthetic is injected into this same intramuscular or perimus cular space." The
compressive effect of blood or anesthetic is thought to
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Complications of Periocular, sthesla- 89
result in vascular compromise and subsequent muscle fibrosis and con tracture.Overall, muscle paresis after cataract surgery is noted to be temporary,
but cases of permanent muscle injury have been described. These cases of
permanent strabismus are thought to be the result of a myotoxic effect of the local
anesthetic, but the lack of pathological studies in these cases cannot confirm the
etiology.'?
Optic Nerve Injury
Injury to the optic nerve with the anesthetic needle is a great concern in
administering periocular anesthesia. Severe visual deficit on the first
postoperative day may be the clinical presentation.
Direct needle trauma to the optic nerve is not thought to be the mech anism
optic neuropathy after surgery. In fact, optic nerve injury and dysfunction
occurring after local ocular anesthesia is related inherently to retrobulbar
hemorrhage and to central artery occlusion.
Retrobulbar hemorrhage can cause a marked rise in lOP or intraor bi
pressure, thereby causing a central retinal artery occlusion. Intravas cular injectio
of anesthetic also can cause a central vein or artery occlu sion via vasospasm. A
third mechanism for vasoocclusion is the injection of anesthetic into the nerve
sheath, causing a compressive effect first on the venous circulation and later
compromising arterial inflow. Direct needle trauma to the retinal artery in the
posterior orbit, prior to its pen etration of the optic nerve, also is thought to occur.
All these mechanisms cause optic atrophy as a result of vascular compromise.
Needle penetration of the optic nerve rarely causes vision loss but, if
associated with a central retinal artery occlusion, visual dysfunction can be
profound and permanent.
CNS Complications
CNS complications oflocal anesthetic injection can have lethal effects.
In extremely rare instances, after receiving periocular anesthesia, a pa tient m
experience cardiovascular and pulmonary problems, such as hy potension a
respiratory arrest. Drug toxicity can be a cause and may manifest initially as
tremors, agitation, slurred speech, and (eventually) seizure activity. Moreover,
overall nervous system collapse causing respira tory depression an
cardiovascular collapse can occur.
The fisk of nerve trauma or subsequent intrathecal administration of
anesthesia (or both) are thought to be linked. A study of CNS complica tions a
retrobulbar block demonstrated an incidence of 1: 375. Reported rates of CNS
complications range from 0.09% to 1.50%. A life threatening complication ca
occur in 0.13%.11 Effects included apnea
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90 Cyriac and Pineda
and respiratory depression, convulsions, and cardiopulmonary arrest. In -
terestingly, no reported cases occurred in studies wherein a needle length shorter
than 1.5 inch was used. In peribulbar anesthesia, many suggest using needles no
longer than 25 mm.
The clinical picture of CNS anesthesia can be varied. Affected patients may
experience confusion and agitation (which may be normal consider ing
administration of intravenous sedation), dizziness, tremors (ranging from
shivering to marked convulsions), ophthalmoplegia or amaurosis of the fellow
eye, tinnitus or deafness, and problems with speech or breath ing. The onset ofsymptoms usually occurs within a few minutes, peaking at approximately 15
minutes after anesthesia administration. For this rea son, we recommend that the
patient be observed, without drapes, for 15 minutes after administering
anesthesia. The average duration of these symptoms is 2 to 3 hours.
Signs of CNS anesthesia include loss of consciousness, apnea, and limb
paralysis. CNS blockade can manifest as arterial hypertension and tachycardia or
hypotension and bradycardia with cardiac arrest and pul monary edema. These
signs and symptoms can occur in any combination, whereas the earliest findings
are contralateral eye signs and loss of con sciousness. With proper diagnosis and
prompt treatment, full recovery is normal. Treatment is specifically directed
toward seizure control, hemo dynamic support and, in some cases, administration
of cardiopulmonary resuscitation. The nature of this complication of ocular
anesthesia emphasizes the need for careful monitoring of the patient by aqualified anesthesia staff.
The mechanism of this complication is debated. Intravenous or in traarterial
administration has been postulated, but blood levels in patients were not in the
toxic range. Also, doubt has been cast on the intraarterial theory, because no
reports have cited blood in syringes or retrobulbar hemorrhages. Intravascular
injection should produce immediate seizure activity. Grand mal seizure activity
usually is the predominant sign but is not necessarily always present. Respiratory
depression and cardiovascular collapse also should occur injust a few seconds.
This clinical picture after periocular anesthesia has not been reported.
The most widely accepted explanation is direct injection into the nerve
sheath, and it has been shown through orbitography studies using radiocontrast
dye. 12 Anesthetics can gain access to the cranial nerve roots, pons, midbrain, and
spinal cord. Also, the cerebrospinal fluid analysis of patients who developed
respiratory arrest demonstrated lido caine and bupivicaine.P The neurologicalsigns or vision loss from this mechanism are thought to be short-lived, and no
permanent effects have been noted. Direct injection into the subarachnoid space
would cause respiratory arrest within a few minutes, and this is the common
clinical scenario.
Complications of Periocular Anesthesia - 91
Conclusion
No method or technique of local ocular anesthesia is free of compli cation.
We recommend that surgeons perform their preferred technique properly and with
the globe in primary position. The use of blunted, shorter needles 33 mm for
retrobulbar blocks and 20 mm for peribul bar blocks) also is recommended.
Furthermore, the peribulbar technique, although not proved, appears to have an
advantage over the retrobulbar technique in reducing the risk of complications.Many advances in technique have enabled surgeons to achieve excel lent
surgical anesthesia and akinesia. With careful monitoring by qualified individuals
with experience in local ocular anesthesia, the vast majority of cases result in no
serious complication. However, because the administra tion of anesthesia is
essentially a "blind" maneuver, risk of damage to vital neurovascular structures,
orbital tissues, and even to the globe itself is inherent. Therefore, occasional
complications should be expected.
References
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