Sub-Tenon's anaesthesia: complications and their prevention

Abstract

The advent of a new technique that is considered much safer than previously established one leads to its rapid adoption. This usually leads to the identification of previously unreported complications of the new technique, and a re-assessment of its position in clinical care, which is precisely the state of play with the sub-Tenon's block. The sub-Tenon's block was introduced into the clinical practice in early 1990. A systematic recent search of subject headings such as complications of sub-Tenon's block, subtenon, orbital block, orbital block complications, and orbital anaesthesia was performed in Medline, EMBASE, and Cochrane database. Indeed there are complications of sub-Tenon's block published as case reports and the exact incidence of these complications is not known. Management and preventive measures of these complications are described. Although the sub-Tenon's block appears to be relatively safer than needle-based blocks but a proper prospective, randomized, double-blind controlled trial is essential for scientific proof that sub-Tenon's block is better than needlebased blocks.

Effectiveness of single injection sub-Tenon’s block for Pars Plana Vitrectomy and associated procedures

“…A large sample size, prospective, randomized, double blinded controlled trial comparing variations of volume and sub-Tenon's injections (single vs multiple) would be a more robust methodology, but may not be ethically and logistically feasible. Sub-Tenon's block is associated with minor and clinically insignificant but frequent complications such as chemosis and conjunctival haemorrhage [15]. Presence of swelling and haemorrhage of conjunctiva may deter some surgeons from advocating this method of anaesthesia.…”

“…This block has the advantages of avoiding serious albeit rare but well-known complications of the needle-based blocks [15]. The duration of anesthesia can be extended by simply injecting additional local anaesthetic agent through the initial dissection midway through the procedure on the operating table by the operating surgeon under sterile conditions [1].…”

Non-arteritic Anterior Ischaemic Optic Neuropathy after Uneventful Cataract Extraction

“…It has also been hypothesised that the decrease in ocular blood flow is the result of vasoconstriction caused by the high local concentration of the local anaesthetic drug or inhibition of endothelium-dependent relaxation of the ciliary arteries or even anaesthetic blockade of the vasodilator nerves. 10 This case report of an isolated delayed CEassociated NAION highlights the importance of careful selection, preoperative assessment, and management of patients at higher risk of developing this complication. Aspirin could be used as a prophylactic measure in such cases at a slightly higher dose (100-325 mg/day) than usually administered on a regular basis (75 mg/ day).…”

Comparison of metal and flexible sub-Tenon cannulas

“…Although the technique has gained popularity, 8 it is associated with frequent minor complications, which include pain during injection, chemosis, and subconjunctival hemorrhage. 9 Although rare, sightthreatening and life-threatening complications (eg, brainstem anesthesia and death) with sub-Tenon block have been reported. They are mainly the result of forceful insertion, trauma, or use of an inappropriate technique with a metal posterior sub-Tenon cannula.…”