1 West of England Eye Unit and 2 Department of Anaesthesia, Royal Devon and Exeter Hospital, Barrack Road, Exeter EX2 5DW, UK
*Corresponding author. E-mail: pieter@gouws.freeserve.co.uk
Accepted for publication: July 29, 2003
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Abstract |
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Methods. We compared articaine and bupivacaine/lidocaine for sub-Tenons anaesthesia in cataract surgery.
Results. Sub-Tenons anaesthesia using articaine 2% resulted in a more rapid onset of motor block compared with a bupivacaine/lidocaine (P=0.0076). Ocular movement scores were significantly lower from 2 min after injection until the end of surgery (P=0.031 ANOVA).
Conclusion. Articaine 2% is safe and effective for sub-Tenons anaesthesia and is a suitable alternative to the traditional bupivacaine 0.5%/lidocaine 2% mixture.
Br J Anaesth 2004; 92: 22830
Keywords: anaesthetic techniques, regional, sub-Tenons; anaesthetics local, articaine; surgery, ophthalmological
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Introduction |
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In the UK, the majority of cataract extractions are performed under local anaesthesia (86% in 1997)4 and sub-Tenons anaesthesia is gaining popularity in many ophthalmic units. However, sub-Tenon techniques may be associated with limited akinesia (compared with peribulbar anaesthesia) and this has been responsible for at least one case of surgical globe perforation.5 We used the technique described by Stevens6 to compare the effects of local anaesthesia using articaine 2% with a bupivacaine 0.5%/lidocaine 2% mixture. The rapid onset of action and improved tissue diffusion qualities of articaine4 5 suggest that it could be highly suitable for sub-Tenons injection.
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Method |
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Exclusion criteria were age less than 18 yr; previous intraocular surgery; pupil diameter less than 5 mm when fully dilated; pregnant women or those of child-bearing potential; those known to have reduced plasma cholinesterase concentrations (scoline apnoea or taking echothiapate eye drops) as this may affect the metabolism of articaine by plasma esterases; patients unwilling to participate in the study; a history of allergy to amide-type local anaesthetics.
Patients were randomly allocated to one of two groups, using sealed, numbered envelopes and computer randomization. One group received sub-Tenons anaesthesia using articaine 2%; the other received a mixture of equal volumes of bupivacaine 0.5% and lidocaine 2%. Neither group had epinephrine or hyaluronidase as part of their anaesthetic solutions.
Patients were not fasted and did not receive any premedication. All patients had routine monitoring of arterial oxygen saturation, ECG and non-invasive arterial pressure, as well as i.v. access before the administration of anaesthetic. Sedation in the form of midazolam 0.51 mg and alfentanil 250 µg was provided at the request of the patient. Analgesia of the conjunctiva and cornea was achieved by the topical administration of oxybuprocaine 0.4% drops. A sub-Tenons injection of local anaesthetic was then administered by either the ophthalmic specialist registrar (lead author) or consultant anaesthetist, both of whom were blinded to the anaesthetic used. Blunt Westcott scissors were used to make a small nick in the inferonasal conjunctiva 5 mm from the limbus, and a Stevens cannula (BD Visitec Sub-Tenons cannula 1.1 x 25 mm) was then introduced, passing through Tenons fascia and the intermuscular septum. Up to 5 ml of local anaesthetic was injected. The injection was stopped at the first sign of conjunctival chemosis. No compressive device was used but digital massage/pressure was undertaken for 2 min. Ocular movement was then assessed using the scoring system described by Brahma and colleagues7 at 2, 4, 6, 8 and 10 min and at the end of surgery. Ocular movements were scored for each direction of gaze in the superior, inferior, medial and lateral directions, with a maximum score for each direction of 3 points and a possible total maximum of 12 points. Patients were considered to be ready for surgery when the ocular score was 5 or less.
The surgeon (also blinded to the local anaesthetic used) assessed gross visual acuity (assessment by counting fingers, hand movement or perception of light) and the degree of proptosis and chemosis before surgery. After surgery, patients were questioned specifically about pain experienced during insertion of the block and during surgery.
Statistical analysis was performed using SPSS for Windows version 9.0. Age, axial length, volume of local anaesthetic and time to readiness for surgery were compared using the Students t-test; the 2 test was used for sex. Ocular movement scores from injection to the end of surgery were compared using a repeated measures analysis of variance (ANOVA) with P<0.05 taken to be significant.
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Results |
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Ocular movement scores were significantly lower over the study time period in the articaine group compared with the lidocaine/bupivacaine group (P=0.031 ANOVA) (Table 1). Mean time to readiness for surgery was also significantly reduced: 3.5 (SD 2.5) min in the articaine group vs 5.2 (3.4) min in the bupivacaine/lidocaine group (P=0.0076).
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Discussion |
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The use of articaine offers sound advantages over bupivacaine/lidocaine. Increased tissue penetration obviates the need for hyaluronidase,8 reducing costs and potential for allergic reactions. Articaine has very low systemic toxicity. It does not require the addition of epinephrine to reduce systemic absorption and prolong local anaesthetic activity9 thus avoiding additional side-effects such as vasospasm in end arterioles, arrhythmias resulting from inadvertent i.v. injection, and allergy to the metabisulphite preservative.10 Improved block characteristics may also enhance surgical access. Poor akinesia following sub-Tenon anaesthesia has been reported as the cause of at least one case of surgical globe perforation because of inadvertent globe movement.5 It is also possible that enhanced globe immobility following use of articaine may encourage practitioners still using a peribulbar approach to convert to the potentially safer sub-Tenons technique.
In conclusion, articaine 2% is safe and effective for sub-Tenons anaesthesia and is a suitable alternative to the traditional mixture of bupivacaine 0.5%/lidocaine 2%.
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Acknowledgements |
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References |
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4 Desai P, Reidy A, Minassian DC. Profile of patients presenting for cataract surgery: National data collection. Br J Ophthalmol 1999; 83: 8936
5 Ruschen H, Bremner FD, Carr C. Complications after sub-Tenons eye block. Anesth Analg 2003; 96: 2737
6 Stevens JD. A new local anaesthesia technique for cataract extraction by one quadrant sub-Tenons infiltration. Br J Ophthalmol 1992; 76: 6704[Abstract]
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