Comparison of articaine and bupivacaine/lidocaine for sub-Tenon’s anaesthesia in cataract extraction

P. Gouws*,1, P. Galloway1, J. Jacob1, W. English2 and K. G. Allman2

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


    Abstract
 Top
 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
Background. Articaine is the most widely used local anaesthetic for dental anaesthesia in Germany, Italy and The Netherlands and has recently been introduced and licensed for dental use in the UK. We have previously shown articaine to be superior to a standard mixture of bupivacaine 0.5%/lidocaine 2% for peribulbar anaesthesia. Sub-Tenon’s anaesthesia arguably provides a safer method of anaesthetic delivery for cataract surgery. A blunt cannula is used in this technique, thus greatly reducing the risk of globe perforation, intrathecal injection and sight-threatening periocular haemorrhage.

Methods. We compared articaine and bupivacaine/lidocaine for sub-Tenon’s anaesthesia in cataract surgery.

Results. Sub-Tenon’s 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-Tenon’s anaesthesia and is a suitable alternative to the traditional bupivacaine 0.5%/lidocaine 2% mixture.

Br J Anaesth 2004; 92: 228–30

Keywords: anaesthetic techniques, regional, sub-Tenon’s; anaesthetics local, articaine; surgery, ophthalmological


    Introduction
 Top
 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
Articaine was developed in the 1970s1 and is now widely used throughout Europe. It is an amide local anaesthetic agent containing a thiophene ring rather than a benzene ring. This thiophene ring contains an additional ester (2-carbomethoxy) group, which accounts for its rapid metabolism by plasma and tissue esterases. It is licensed for dental use in the UK and has a low systemic toxicity (maximum recommended dose 7 mg kg–1) and short duration and rapid onset of action. It also has increased tissue diffusion properties compared with all other commonly used agents. Articaine has been shown to be safe and effective in peribulbar anaesthesia compared with standard local anaesthetic agents.2 3

In the UK, the majority of cataract extractions are performed under local anaesthesia (86% in 1997)4 and sub-Tenon’s 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-Tenon’s injection.


    Method
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 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
Local research ethics committee approval was granted and a Clinical Trials Exemption Certificate obtained. Eighty patients gave written, informed consent to be included in the trial. All patients underwent routine cataract extraction at the West of England Eye Unit during 2002. The power calculation for a sample of this size shows an 80% chance of detecting a statistically significant (P<0.05) difference of two points for the sums of the ocular movement scores.

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-Tenon’s 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 0.5–1 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-Tenon’s 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-Tenon’s cannula 1.1 x 25 mm) was then introduced, passing through Tenon’s 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 Student’s t-test; the {chi}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.


    Results
 Top
 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
There were 44 patients in the articaine group and 36 patients in the bupivacaine/lidocaine group. All patient data were included in the statistical analysis. Patients in both groups were matched (no statistically significant difference) in age, sex, axial length of eyes, duration of surgery, volume of anaesthetic, proptosis or chemosis following and pain during insertion of block.

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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Table 1 Median ocular movement scores (interquartile range). Scores were assigned in four positions of gaze; 3=full movement; 2=moderate movement; 1=flicker of movement; 0=no movement. P=0.031 (ANOVA)
 
Top-up anaesthesia was required by one patient in the articaine group and by two patients in the bupivacaine/lidocaine group. Sedation was used in 11 patients in the articaine group and 12 patients in the bupivacaine/lidocaine group.


    Discussion
 Top
 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
We have demonstrated that articaine 2% administered by sub-Tenon’s injection provides a more rapid onset of akinesia compared with bupivacaine 0.5%/lidocaine 2%. Time to readiness for surgery was reduced from 5.2 (SD 3.4) min to 3.5 (2.5) min and ocular movement scores were reduced at all time points from injection to the end of surgery in the articaine group. This effect is most likely to be the direct result of increased tissue diffusion of articaine allowing wider distribution within the orbital muscle cone.

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-Tenon’s technique.

In conclusion, articaine 2% is safe and effective for sub-Tenon’s anaesthesia and is a suitable alternative to the traditional mixture of bupivacaine 0.5%/lidocaine 2%.


    Acknowledgements
 
We gratefully acknowledge the support of Deproco UK who provided supplies of articaine free of charge. We also thank the staff of the West of England Eye Unit for their help during the study.


    References
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 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
1 Winther JE, Patirupanusara B. Evaluation of Carticaine – a new local analgesic. Int J Oral Surg 1974; 3: 422–7[Medline]

2 Allman KG, McFadyen JG, Armstrong J, Sturrock GD, Wilson IH. Comparison of articaine and bupivacaine/lidocaine for single medial canthus peribulbar anaesthesia. Br J Anaesth 2001; 87: 584–7[Abstract/Free Full Text]

3 Allman KG, Barker LL, Werrett GC, Gouws P, Sturrock GD, Wilson IH. Comparison of articaine and bupivacaine/lidocaine for peribulbar anaesthesia by inferotemporal injection. Br J Anaesth 2002; 88: 676–8[Abstract/Free Full Text]

4 Desai P, Reidy A, Minassian DC. Profile of patients presenting for cataract surgery: National data collection. Br J Ophthalmol 1999; 83: 893–6[Abstract/Free Full Text]

5 Ruschen H, Bremner FD, Carr C. Complications after sub-Tenon’s eye block. Anesth Analg 2003; 96: 273–7[Abstract/Free Full Text]

6 Stevens JD. A new local anaesthesia technique for cataract extraction by one quadrant sub-Tenon’s infiltration. Br J Ophthalmol 1992; 76: 670–4[Abstract]

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10 Schwartz HJ, Gilbert IA, Lenner KA, Sher TH, McFadden ER. Metabisulfite sensitivity and local dental anaesthesia. Ann Allergy 1989; 62: 83–6[ISI][Medline]