Original Article
Safety and Efficacy of Subtenon Anesthesia in Anterior
Segment Surgeries
Uzma Fasih, Waqar ul Huda, M.S Fehmi, Arshad
Shaikh, Nisar Shaikh, Atiya Rahman, Asad Raza Jafri
Pak J Ophthalmol 2011, Vol. 27 No. 3
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See end of
article for authors
affiliations …..……………………….. Correspondence
to: Uzma
Fasih Submission of
paper November’ 2010 Acceptance for
publication August’ 2011 …..……………………….. |
Purpose: The objective of the study was to evaluate the
complications of subtenon anesthesia in patients undergoing anterior segment
surgeries Materials and
Methods: The study was conducted in the
department of ophthalmology, Results: A total of 150 patients were operated under subtenon
anesthesia. Majority of the procedures performed were extra capsular cataract
extraction (55.3%) followed by trabaculectomy (24%). Most common complication
in our study was subconjunctival haemorrhage (48%) followed by conjunctival
chemosis (37%). Other complications like inadequate anesthesia were seen in
12 (8%) patients and inadequate akinesia in 18 (12%) patients. A second injection
was required in 12 (8%) patients. Simultaneous use of topical anesthetic was
recorded in 18 (12%) patients. Reterobulbar haemorrhage occurred in a small
percentage (2%) of patients in our study. In addition pupillary constriction
after delivering the nucleus 45 (30%) patients and positive vitreous pressure
leading to raised intra ocular pressure and iris prolapse 3 (2%) patients
were also recorded. 58(39%) patients complained of pain and discomfort during
the injection. Conclusion: Majority of complications encountered in
this study were minor like subconjunctival heamorrhage, conjunctival
chemosis, inadequate anesthesia and akinesia. Major complications like reterobulbar
heamorrhage and positive vitreous pressure leading to raised intraocular pressure
during the surgery were uncommon but present. Subtenon anesthesia though safe
is not devoid of complications. |
There are substantial international variations in the care and
provision of ophthalmic regional anesthesia1-5. In 1884 Herman Knapp
was the first to describe the reterobulbar block6. The complications
related to needle block, such as retrobulbar haemorrhage, globe perforation,
retinal vascular obstruction, cardio-respiratory arrest and even death,
although rare, have been reported7,8.
In 1970s peribulbar block was developed for clinical use9.
Further techniques like topical and subtenon anesthesia10 were
developed in an attempt to minimize potentially serious complications with
retero bulbar and peribulbar anesthesia11-13.
Sub-Tenon’s block is a simple alternative 14 to a sharp
needle block. Subtenon space is a potential space between the tenon capsule and
sclera with capacity of about 1.5 ml. It extends from corneoscleral limbus
anteriorly to the optic nerve posteriorly. It is an ideal space where local
anesthetic can diffuse to secure complete anesthesia of the globe as all the
sensory nerves from the eye cross this space. Additionally the local anesthetic
percolates through the thin area of the tenon capsule around the optic nerve
and has anesthetic effects in the orbit.
The exact frequency of the use of this technique is not known. It
is commonly practiced in certain parts of the world15, 16 but only 7%
of ophthalmic departments in the
Although it is a very safe and effective procedure and common
complications of sub-Tenon’s block are mainly minor, although rare major
complications have also been reported. We conducted this study to evaluate this
procedure.
MATERIALS
AND METHODS
A total of 150 patients were recruited using non probability consecutive
sampling technique from patients presenting in outpatient department who were
planned for anterior segment surgery from January 2009 to June 2010. After
recruitment written informed consent was taken and patients were admitted and
prepared for surgery.
Patients undergoing procedures having less than 60 minutes
duration were included in the study. The patients with clotting abnormalities,
impaired mental status, uncontrolled glaucoma, recent surgical procedure on the
same eye were excluded.
Topical proparcaine 0.5% was instilled thrice with one minute
interval five minutes before subtenon anesthesia for all patients.
Subtenon space was opened using Westcott scissors to expose white
sclera in the supro temporal quadrant of the eye ball. 2 ml of 2% xylocaine
with adrenaline (plain xylocaine where adrenaline was contraindicated) was
injected using a subtenon cannula mounted onto a 5 ml syringe.
We recorded complications including patient discomfort, inadequate
anesthesia, conjunctival chemosis, subconjunctival haemorrhage and retrobulbar haemorrhage
both peroperatively and postoperatively.
RESULTS
A total of 150 patients were operated under subtenon anesthesia.
56% patients were male and 44% were female. (Table 1) Majority of the patients
(45%) were between 50 and 60 years, whereas, 27.3% were between 40 to 50 years
of age. (Table 2)
Majority of the procedures performed were extra capsuler cataract
extraction (55.3%) followed by trabculectomy 24% (Table 3). Common
complications we encountered were subconjunctival haemorrhage 48% followed by
conjunctival chemosis 37%. Other complications like inadequate anesthesia were
seen in 12 (8%) patients and inadequate akinesia in 18 (12%) patients, repeat
injections in 12 (8%) patients were also recorded. Simultaneous use of topical
anesthetic was recorded in 18 (12%) patients. Reterobulbar heamorrhage occurred
in a small percentage (2%) of patients in our study. In addition pupillary
constriction after delivery of the nucleus occurred in 45 (30%) patients and
positive vitreous pressure leading to raised intra ocular pressure and iris
prolapse occurred in 3 (2%) patients. 58 (39%) patients complained of pain and
discomfort during the injection.
DISCUSSION
We conducted this study to assess the complications secondary to subtenon
anesthesia. The complications encountered with this method were minor and
easily manageable but occasional major complications were also encountered.
Most common complication encountered in our study was
sub-conjunctival haemorrhage (48%). The incidence of haemorrhage has been
reported to vary from 20 to 100% in other studies and may depend on the type of
cannula used20. Conjunctival haemorrhage may be caused by
conjunctival dissection. This can be minimized by careful conjunctival
dissection, application of cautery and use of topical epinephrine. Patients
should be warned of the possibility of this complication preoperatively. 39%
patients complained of discomfort and pain during the injection. Pain
experienced during various ophthalmic blocks depends on multiple factors.
Table
1: Gender distribution
|
Sex |
No.
of Patients n (%) |
|
Male |
82 (56) |
|
Female |
68 (44) |
Table 2: Age distribution
|
Age
in Years |
No.
of Patients n (%) |
|
20-30 |
2 (1.3) |
|
30-40 |
2 (1.3) |
|
40-50 |
51 (34) |
|
50-60 |
60 (40) |
|
60-70 |
35 (23.3) |
Table 3: Surgical procedures performed under
subtenon anesthesia
|
Procedure |
No. of Patients n (%) |
|
Trabeculectomy |
36 (24) |
|
ECCE with IOL |
83 (55.3) |
|
Phaco with IOL |
31 (20.7) |
The incidence of pain during sub-Tenon injection reported in
various studies can be up to 44%14,20. Premedication or sedation of
patients during sub-Tenon injection did not help to prevent pain in these
studies. Preoperative explanation of the procedure, good surface anesthesia,
gentle technique, slow injection of warm local anesthetic agent and reassurance
are considered good practice and may reduce the discomfort and anxiety during
the injection22.
Conjunctival chemosis was seen in 37% of the patients. The incidence of chemosis varies from 25%
to 60%14,20 with a posterior cannula and the incidence increases to
100% with shorter cannulae21. Chemosis occurs due to anterior
injection of the anesthetic agent. This usually occurs if a large volume of
local anesthetic is injected and if the Tenon’s capsule is not dissected
properly21. Chemosis may not be confined to the site of injection
and has been known to spread to other quadrants as well21. Chemosis
usually resolve after the application of digital pressure, and no
intra-operative problems have been reported secondary to it. Significant chemosis may compromise the
surgical procedure for glaucoma.
Table 4: Complications of subtenon anesthesia
|
Complications |
No.
of Patients n (%) |
|
Difficulty to reach subtenon space |
18 (12) |
|
Repeat injection |
12 (8) |
|
3.Inadequate anesthesia |
12 (8) |
|
Inadequate akinesia |
18 (12) |
|
Patient discomfort and pain during injection |
58 (39) |
|
Subconjunctival haemorrhage |
72 (48) |
|
Conjunctival chemosis |
55 (37) |
|
Reterobulbar haemorrhage |
3 (2) |
|
Positive vitreous pressure leading to raised intraocular
pressure and iris prolapse |
3 (2) |
|
Pupillary constriction after delivering the nucleus |
45 (30) |
|
Simultaneous use of topical anesthetic |
18 (12) |
Anesthesia with sub tenon block was adequate in most of the cases,
but 8% of the patients required augmentation with more injection.
In our study inadequate akinesia was seen in 12% of the patients.
In other studies akinesia was variable and was not complete23.
Akinesia is volume dependent and if 4-5 ml local anesthetic agent is injected,
a large proportion of patients develop akinesia22. Superior oblique
muscle and lid movements may also remain active in a significant number of
patients22.
We encountered difficulty in reaching sub-tenon space in 12% of
the patients as compared to the study conducted at Larkana in which it was
noticed in 10.8% of the patients. This difficulty was probably due to improper
patient selection and inadequate anesthesia. It was easily overcome by
explaining the procedure to the patient and reassurance.
Positive vitreous pressure leading to raised intraocular pressure
and iris prolapse were found in 2% patients. Similar results were (3.2%) were
seen in a study from Larkana24.
Complications like short term muscle paresis, globe perforation
and cardio respiratory arrest due to central spread of local anesthetic have been
reported but we did not encounter this complication in our study21, 25.
Reterobulbar heamorrhage occurred in 3 (2%) patients in our study.
This complication has also been reported in other studies26-28.
We selected supero-temporal quadrant for subtenon anesthesia in
our study. Access from all quadrants has been reported, supero-temporal by
Fukasaku and Marron, superonasal and infero-temporal by Roman and colleagues14
and the medial canthal side by Ripart and colleagues24. It is not
known how frequently these quadrants are used for access. We found
supero-temporal quadrant anatomically safe and adequate. Moreover, this site is
covered by the upper lid, hiding the subconjunctival heamorrhage and thus
prevents anxiety on first post-op day.
CONCLUSION
In our
study subtenon anesthesia was safe and effective method for anterior segment
intraocular surgery but not devoid of complications. Though majority of
complications were minor and easily manageable but some major complications
like reterobulbar heamorrhage and positive vitreous pressure with iris prolapse
may have adverse effects on the outcome of surgery.
Author’s
affiliation
Dr. Uzma Fasih
Associate Professor
Dr. Waqar ul Huda
Trainee Registrar
Karachi Medical and Dental
College
Dr. M.S Fehmi
Professor
Dr. Arshad Shaikh
Professor
Dr. Nisar Shaikh
Associate Professor
Eye Department
Dr. Atiya Rahman
Assistant Professor
Dr. Asad Raza Jafri
Assistant Professor
Eye Department
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