Department of Anaesthesia and Intensive Care Medicine, St Georges Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK
Corresponding author. E-mail: gnichols@sghms.ac.uk
Accepted for publication: November 23, 2002
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Abstract |
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Methods. Ninety patients were allocated randomly to receive 8 ml of a mixture of equal parts of bupivacaine 0.75% and lidocaine 2% or an equal volume of L-bupivacaine and lidocaine 2%. Hyaluronidase 15 IU ml1 was added to both solutions.
Results. There were significant differences between the groups in clinical end-points. The median time at which the block was adequate to start surgery was 4 min (interquartile range 48 min) in the bupivacaine group and 8 min (512 min) in the L-bupivacaine group (P=0.002). Median ocular and eyelid movement scores were similarly significantly decreased in the bupivacaine group compared with the L-bupivacaine group at all times (P0.03). There was no difference between groups in the incidence of minor complications.
Conclusions. A mixture of bupivacaine 0.75% and lidocaine 2% provides faster onset time than a mixture of L-bupivacaine 0.75% and lidocaine 2%.
Br J Anaesth 2003; 90: 51214
Keywords: anaesthetic techniques, regional, peribulbar; anaesthetics local, levobupivacaine; anaesthetics local, lidocainebupivacaine; surgery, ophthalmological
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Introduction |
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Both racemic bupivacaine and L-bupivacaine have local anaesthetic properties, but the latter drug is associated with a safer side-effect profile.4 5 A recent study has shown that L-bupivacaine 0.75%, when used as a single agent for peribulbar anaesthesia, compared favourably with racemic bupivacaine 0.75% in terms of safety and efficacy.6
However, if bupivacaine or L-bupivacaine is used as a single agent for peribulbar anaesthesia, then the onset of the block may be delayed by up to 13 min, with a corresponding delay in the time to start of surgery of up to 20 min.6 In this study, we compared the rapidity of onset and efficacy of peribulbar block obtained with equal volumes of L-bupivacaine 0.75% and lidocaine 2% with the traditional mixture of racemic bupivacaine 0.75% and lidocaine 2%. Hyaluronidase was added to both solutions. The major clinical end-points were ocular and eyelid movement scores at 8 min and the time to adequate block for surgery.
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Methods and results |
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Patients were not fasted and did not receive any premedication, perioperative sedation or supplementary oxygen. On arrival in the induction room, baseline eyelid and globe movements were assessed. Topical anaesthesia of the conjunctiva and cornea was achieved by administering oxybuprocaine 0.4%, 23 drops. Standard monitoring was started and i.v. access established. Peribulbar block was carried out, by one of two consultant anaesthetists, via a single inferolateral, transcutaneous or transconjunctival injection using a 25 gauge, 25 mm needle. After test aspiration, 8 ml of the local anaesthetic mixture was injected over 3040 s. Manual compression and gentle massage of the eyeball were performed, after which a Visitec intraocular pressure reducer (Sarasota, FL, USA) inflated to 40 mm Hg was applied between scoring, to facilitate spread of the anaesthetic solution and to lower intraocular pressure. Patients were assessed for eyelid and ocular movements at 2 min intervals with a scoring system used by Brahma and colleagues.7 Scoring was carried out by a trained observer, who was blinded as to which local anaesthetic the patient had received.
Ocular movements were scored for each direction of gaze in a superior, inferior, medial and lateral direction with a maximum score for each direction of 3 points and a possible maximum total of 12 points. Ocular and eyelid movements were assessed at 2, 4, 6 and 8 and 10 min, until the block was considered adequate for surgery (eyelid movement score 0 and ocular movement score 2). If the block was inadequate after 10 min, supplementary anaesthesia was provided with a further injection of up to 5 ml of the test solution, by the same technique. The time to adequate surgical anaesthesia and the need for supplementary anaesthesia were noted. It was assumed that, once motor block had been achieved, adequate sensory block was already present as this usually precedes motor block. Complications during or after injection were recorded and patients were specifically questioned about pain during insertion of the block, or during surgery.
The main outcome criteria were the differences in median ocular and eyelid movement scores at 8 min and the time needed to obtain adequate block to start surgery. The differences between groups were analysed with the Wilcoxon rank sum test. The number of patients who reached an ocular movement score of 1, the need for further injections, delays to the start of surgery and the occurrence of complications were compared using the
2-test or Fishers exact test, as appropriate. Statistical analysis was carried out using SPSS for Windows version 8 (SPSS, Chicago, IL, USA).
There were 45 patients in each group and all patient data were included in the statistical analysis. The mean (range) age in the bupivacaine group was 72 (3988) yr and in the L-bupivacaine group 73 (4591) yr. The male:female ratio was 22:23 in the bupivacaine group and 21:24 in the L-bupivacaine group.
Median eyelid movement scores were significantly lower in the bupivacaine group at all times. Ocular movement scores were significantly decreased in the bupivacaine group compared with the L-bupivacaine group at 2 min (P=0.002), 4 min (P=0.001), 6 min (P=0.001) and 8 min (P=0.012) (Table 1). The median (interquartile range) time at which the block was considered adequate to start surgery was 4 (48) min for the bupivacaine group and 8 (512) min for the L-bupivacaine group (P=0.002).
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Comment |
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We were unable to assess the duration of motor block as patients eyes were bandaged and covered postoperatively and they were discharged home 12 h after surgery. If a shorter duration of motor block occurs with L-bupivacaine, this could be advantageous as prolonged paralysis from local anaesthesia leaves the eye vulnerable to drying and trauma.
Peribulbar anaesthesia requires relatively large volumes of local anaesthetic and concerns have been expressed about the potential for systemic toxicity. The incidence of peribulbar blocks requiring supplementary anaesthesia has been reported to be as high as 54%.8 However, L-bupivacaine is less toxic to the myocardium and central nervous system.9 10 While L-bupivacaine may have theoretical advantages in elderly patients with coexisting cardiac disease, the present study did not show any untoward effects with either drug. L-Bupivacaine did not demonstrate any advantages over racemic bupivacaine when used for peribulbar anaesthesia.
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Acknowledgement |
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References |
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