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Anesthesiology:
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Sub-Tenon Eye Block: Approaching the Ideal?

Ripart, Jacques M.D., Ph.D.*; Lefrant, Jean-Yves M.D., Ph.D.; Eledjam, Jean-Jacques M.D.

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In Reply:—
We thank our colleagues for their interest in our work and pertinent comments. The exigency of akinesia and surgical times vary dramatically among teams, but analgesia is much easier to obtain than akinesia. A nonakinetic technique, such as topical anesthesia, may be sufficient in some cases of cataract surgery. Total akinesia is required in other cases. Our study was not aimed to determine whether akinesia is required for cataract surgery. We tried to determine which technique provides the better akinesia.
The rate for reinjections varies from less than 1% to 50%. 1,2 Unless the criteria for those reinjections are controlled using a standardized measure of akinesia, the rate of reinjection is not a good index of block quality to compare different studies. We aimed to obtain total akinesia. This might be considered an increase in the sensitivity of our study: An unperfect block was reinjected, although, in some cases, the surgeon might have dealt with it.
The technique used by Dr. Pinsker is a standard. 1,2 However, it is clear that a single injection may be sufficient in many cases. 1–3 The use of a systematic second injection can be considered a 100% reinjection rate, whether it is useful or not. It theoretically increases the hazards of the puncture twofold. A second injection should be performed only when required.
Lidocaine, 4%, and 0.75% bupivacaine are not available in France because of potential toxicity. The concentrations we used are classic. 1–3 They may contribute to a relatively low success rate. However, with those concentrations, the fact remains that single-injection medial canthus episcleral anesthesia is more efficient than peribulbar anesthesia (100%vs. 61% total akinesia).
Safety of medial canthus episcleral (sub-Tenon) block has to be confirmed. The rate of complications after eye block is more dependent on experience than technique. Regarding the low incidence of complication, a comparison among different techniques is difficult; a randomized study would require thousands of patients. However, since our technique has been described, other teams have used it, and it seems to be relatively safe. 5,6 The perforation rate is estimated between 3/4,000 and 1/16,000. 1,4 At our institution, we did not encounter globe perforation in any of more than 4,000 cases, nor did we observe any symptoms attributable to an impairment in retinal blood supply because of intraocular pressure increase caused by the high volume injected. If such complications occur, theirs frequencies are probably very low.
The use of sedation, although questionable, has been documented in many articles. It should not modify the akinesia scores. We use a very light sedation to help the patient to stay calm, awake, and cooperative when block is performed.
The technique used at Moorfield Eye Hospital necessitates a surgical approach to the episcleral space. Such a surgical approach avoids the risk of blindly inserting a needle. It would be interesting to compare both techniques. We are convinced that the future of eye block is episcleral (sub-Tenon) anesthesia, whichever approach is used.
Jacques Ripart M.D., Ph.D.*
Jean-Yves Lefrant M.D., Ph.D.
Jean-Jacques Eledjam M.D.
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References

1. Davis DB, Mandel MR: Efficacy and complication rate of 16224 consecutive peribulbar blocks: A prospective multicenter study. J Cataract Refract Surg 1994; 20: 327–37

2. Bloomberg LB: Anterior periocular anaesthesia: Five years experience. J Cataract Refract Surg 1991; 17: 508–11

3. Demirok A, Simsek S, Cinal A, Yasar T: Peribulbar anesthesia: one versus two injections. Ophthalmic Surg Lasers 1997; 28: 998–1001

4. Hamilton RC: Complications of ophthalmic regional anesthesia. Ophthalmol Clin North Am 1998; 11: 99–114

5. Truc C, Dieudonné , Vaudelin G, Rigal E, Boulétreau P: Comparative efficacy of peribulbar and episcleral block for cataract surgery (abstract). Br J Anaesth 1999; 82(suppl 1):106

6. Canan F, Ertan S, Melek C, Zuhal A: Caruncular injection in periocular anesthesia (abstract). Br J Anaesth 1999; 82 (suppl 1): 106

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