EditorThe frequency of subconjunctival haemorrhage during posterior sub-Tenon's block is 756%.1 2 This is usually confined to the area of dissection but can spread to other quadrants.2 The incidence is even higher with the use of an anterior sub-Tenon's cannula.3 The damage to fine vessels inevitably severed during conjunctival dissection is the main cause of haemorrhage. It is not uncommon for elderly patients undergoing cataract surgery to receive anticoagulants and this may increase the incidence of haemorrhage.4 Cauterization of conjunctiva by a diathermy is recommended to reduce the incidence5 of subconjunctival haemorrhage but there are no scientific data to support this. Both ophthalmologists and anaesthetists are involved in the delivery of sub-Tenon's block. Ophthalmic surgeons are trained to use diathermy instruments but anaesthetists may not feel comfortable in its use and for some it may be a daunting task. Further, addition of a diathermy will increase the overall cost, the complexity of the technique and morbidity if used by non-trained personnel.
This prospective audit of 50 patients undergoing routine phaecoemulsification cataract surgery with lens implant was conducted to investigate if the use of a diathermy during sub-Tenon's block reduces the incidence of subconjunctival haemorrhage. Informed consent was obtained from patients. Patients who had previous intraocular surgery, received anticoagulant, aspirin and non-steroidal anti-inflammatory drugs were excluded. All patients received sub-Tenon's block in the infero-nasal quadrant with a 25 mm long, blunt curved metal cannula.1 Lidocaine 2%, 4 ml with 1:200 000 epinephrine and hyaluronidase 10 IU ml1 were used in all cases. In the first consecutive 25 patients, the conjunctiva was cauterized using a disposable diathermy before the dissection. The remaining 25 patients received a standard sub-Tenon's block without diathermy. Digital pressure was applied for 2 min. Six minutes after the sub-Tenon's block, an independent observer, who was unaware of the use of diathermy, assessed the grade of subconjunctival haemorrhage using a scoring system (none, minor, moderate or severe). When anaesthesia was judged satisfactory, the patients were taken to the operating theatre. The operating ophthalmologist, who was not aware of diathermy use, also graded subconjunctival haemorrhage using the above scoring system before the start of surgery. Surgeons were also asked if subconjunctival haemorrhage interfered with surgery.
The groups were comparable with respect to age, sex and axial length (Table 1). Subconjunctival haemorrhage was mainly confined to the infero-nasal quadrant. Minor to moderate subconjunctival haemorrhage occurred in 48% and 44%, and spread to other quadrants in 13% and 12%, in standard and diathermy groups, respectively. There was no case of severe haemorrhage. The incidence of subconjunctival haemorrhage noted by independent observers and operating surgeons was similar and did not impede surgery.
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Middlesbrough, UK
Footnotes
An abstract of this study was presented at the 13th World Congress of Anaesthesiologists, Paris, France, April 2004.
References
1 Guise PA. Sub-Tenon anesthesia. Anesthesiology 2003; 98: 9648[CrossRef][ISI][Medline]
2 Roman SJ, Chong Sit DA, Boureau CM, Auclin FX, Ullern MM. Sub-Tenon's anaesthesia: an efficient and safe technique. Br J Ophthalmol 1997; 81: 6736
3 Kumar CM, Dodds C. An anaesthetist evaluation of Greenbaum sub-Tenon's block. Br J Anaesth 2001; 87: 6313
4 Konstantatos A. Anticoagulation and cataract surgery: a review of the current literature. Anaesth Intensive Care 2001; 29: 1118[ISI][Medline]
5 Greenbaum S. Parabulbar anesthesia. Am J Ophthalmol 1992; 114: 776[ISI][Medline]
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