Safety and Efficacy of Subtenon Anesthesia in Anterior Segment Surgeries

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, Abbasi Shaheed Hospital, from January 2009 to June 2010. 150
Patients were selected amongst those presenting in outpatient department for
anterior segment surgery using non-probability consecutive sampling technique.
Patients were scheduled for elective ophthalmic procedures with an expected
duration of less than 60 min. Patients with clotting abnormalities, impaired
mental status, uncontrolled glaucoma, were excluded from the study. 2 ml of
2% xylocaine with adrenaline (plain xylocaine where adrenaline was
contraindicated) was injected using  a subtenon cannula in supratemporal
quadrant of the eye ball. We recorded complications including patient
discomfort, inadequate anesthesia, conjunctival chemosis, subconjunctival
haemorrhage, reterobulbar haemorrhage.
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.