British Journal of Anaesthesia, 2004, Vol. 92, No. 2 296
© 2004 The Board of Management and Trustees of the British Journal of Anaesthesia
Correspondence |
Sub-Tenon’s infiltration using bupivacaine 0.5% decreases acute postoperative pain
1 London, UK 2 Rouen, France
Editor—We would like to thank Calenda and colleagues for contributing the results of their trial to the ongoing controversy over the use of sub-Tenon’s block (STB) in posterior segment eye surgery.1 The use of STB continues to expand into all areas of ophthalmic surgery. A good evidence base for the choice of anaesthetic technique even in cataract surgery is unfortunately missing. The lack of good quality trials has recently been highlighted by others.2 3 Given that Calenda’s study was published as a letter, we accept that we are not given any details about power estimation, patient data, setting of the study, randomization methods, masking, or a description of the block procedure. But, we believe that the authors missed a valuable opportunity to reduce bias by not having a placebo control injection group. In studies assessing pain, this has proved essential. Calenda’s results are solely based on comparing the mean pain scores. We would have liked information about the range as well, as this often reveals a more complete picture. Our most important criticism of the study is the failure to differentiate between the different types of posterior segment surgery. For example, scleral buckling surgery is far more painful postoperatively than a simple vitrectomy. Without these details, their case for using STB in all posterior segment operations is not convincing.
D. A. Celaschi
H. Ruschen
London, UK
Editor—It is always useful to receive constructive comments. The lack of a placebo group is questioned by Celaschi and Ruschen. It is known that sub-Tenon’s (ST) infiltration is a very effective method for performing ophthalmic procedures. The goal of our study was to prove that ST infiltration decreases the visual analogue scores and the consumption of analgesic drugs in the postoperative period. So we chose a group with ST and a group without ST infiltration. Their most important criticism of our study was the failure to differentiate between scleral buckling or simple vitrectomy because scleral buckling is considered a more painful procedure than vitrectomy.4 Our study included 17 patients out of 30 having scleral buckling procedures who received ST infiltration, and 13 patients who did not. As there were more patients having painful procedures in the ST group, we consider that this reduces the bias in our study.
E. Calenda
Rouen, France
References
1 Calenda E, Muraine M, Brasseur G. Sub-Tenon's infiltration using bupivacaine 0.5% decreases acute postoperative pain and opioid requirement after posterior segment surgery. Br J Anaesth 2003; 90: 108–9
2 Friedman DS, Bass EB, Lubomski LH, Fleisher LA. The methodologic quality of clinical trials on regional anesthesia for cataract surgery. Ophthalmology 2001; 108: 530–41[Medline]
3 CanavanKS, Dark A, Garrioch MA. Sub-Tenon’s administration of local anaesthetic: a review of the technique. Br J Anaesth 2003; 90: 787–93
4 Newsom RS, Wainwright AC, Canning CR. Local anaesthesia for 1221 vitreoretinal procedures. Br J Ophthalmol 2001; 85: 225–7
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