Epidural anaesthesia with mixtures of bupivicaine and lidocaine

In a double-blind trial on 20 human volunteers, the duration of intradermal anaesthesia with bupivacaine 0.25 per cent was compared with duration with a mixture of bupivacaine 0.25 per cent and carbonated lidocaine 1.0 per cent and with a mixture of bupivacaine 0.25 per cent and lidocaine hydrochloride 1.0 per cent.The duration of intradermal anaesthesia produced by bupivacaine mixed with carbonated lidocaine was 114 -56 (mean • 1 SD) minutes and was not significantly shorter than the duration of the bupivacaine 'alone, at 125 • 70 minutes, or duration with the mixture of bupivacaine and lidocaine hydrochloride, which was 112 • 41 minutes.These results indicate that the mixture of bupivacaine with either carbonated lidocaine or lidocaine hydrochloride may be used for local anaesthesia without significant shortening of the duration of action.KEY WORDS: ANAESTHETICS, LOCAL, bupivacaine, lidocaine.LOCAL ANAESTHETICS are often compounded to obtain the benefit of the rapid action of one agent and the longer duration of another. However, it has been shown that the mixing of some local anaesthetics can result in an interaction with consequent shortening of the duration of action.tThe mixing of bupivacaine and carbonated lidocaine has been recommended by Bromage and Gertel for use in brachial plexus blocks 2 and our clinical impression has been that with this mixture the duration of action of the bupivacaine is not markedly reduced. We therefore decided to carry out a trial to establish if this impression was ta'ue, and also to determine whether the mixture of bupivacaine with lidocaine hydrochloride was equally long lasting. Following the injections analgesia to pinprick on the injection site was determined every five minutes until full sensation returned. The duration of action was measured from the time of injection to the last reported analgesia. Statistical analysis was done using the Student t test.A double-blind study was done on 20 healthy young volunteers. Informed consent was obtained from each individual.Intradermal wheals were raised on the volar aspect of the forearm with 0.2 ml of three local anaesthetic solutions. One solution was bupi- RESULTSThe onset of intradermal analgesia was similar with all three solutions, and was uniformly present when tested at five minutes. The mean duration of intradermal analgesia with bupivacaine 0.25 per cent was 125 -+ 70 minutes (mean -1 standard deviation), with the mixture of bupivacaine and carbonated lidocaine 114 -+ 56 minutes and with bupivacaine and lidocaine hydrochloride 112 -41 minutes. The difference between mean duration of action of bupivacaine 481

Muscle fasciculations and pain following the administration of suxamethonium were assessed in a group of patients who performed a series of stretch exercises approximately 1 h before operation. Comparison was made with a group who received suxamethonium but no pretreatment. Fasciculations were significantly reduced in the exercised group, and the incidence of muscle pain decreased from 52% in the untreated group to 12% in the exercised group. A significant relationship was shown between the severity of visible fasciculations and muscle pain.

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