Epidural anaesthesia with mixtures of bupivicaine and lidocaine.

In a randomized double-blind trial in 30 patients receiving lumbar epidural anaesthesia, the onset and duration of sensory blockade with 0.375 per cent bupivicaine was compared with a mixture of 0.375 per cent bupivicaine and one per cent lidocaine hydrochloride and a mixture of 0.375 per cent bupivicaine and one per cent carbonated lidocaine. Onset (9.3 +/- 1.16 minutes) and complete spread (23.3 +/- 4.8 minutes) for bupivicaine was significantly slower than in the mixtures containing carbonated lidocaine (onset 4.7 +/- 0.48 minutes, complete spread 14.8 +/- 2.49 minutes) and lidocaine hydrochloride (onset 5.0 +/- 0.67 minutes, complete spread 16.3 +/- 3.2 minutes). There was no significant difference in times of onset and complete spread between the two mixtures. The duration of sensory blockade for bupivicaine alone (165 +/- 20 minutes) was not significantly different from the duration in either the mixture containing carbonated lidocaine (161 +/- 51.24 minutes) or lidocaine hydrochloride (143 +/- 33.7 minutes). The results indicate a clinical advantage in speed of onset without significant shortening of duration of action for mixtures of carbonated lidocaine or lidocaine hydrochloride with bupivicaine as compared to bupivicaine alone.

Effect of atropine on bradydysrhythmias induced by succinylcholine following pretreatment with D-tubocurarine.

This study was designed to compare the effectiveness of pretreatment with the combination of d-tubocurarine and atropine with d-tubocurarine alone in preventing changes in cardiac rate and rhythm following repeated administration of succinylcholine. Sixty subjects were randomly divided into three groups of twenty. Group one received d-tubocurarine 0.04 mg.kg-1 and atropine 0.01 mg.kg-1, and group two d-tubocurarine 0.04 mg.kg-1 only, given three minutes before induction of anaesthesia. Group three received no pretreatment. Immediately following thiopentone induction succinylcholine 1 mg.kg-1 was given to all patients. A further dose of succinylcholine 1 mg.kg-1 was given to patients in the pretreatment groups following recovery of neuro-muscular function. Both pretreatment groups showed a small statistically significant fall in mean heart rate after the second dose of succinylcholine. One patient in each pretreatment group showed a fall in heart rate to less than 50 beats min-1; two patients in the group who received both d-tubocurarine and atropine, and three patients in the d-tubocurarine only group, showed a fall in heart rate of 25 per cent or more. It is concluded that the addition of atropine may be unnecessary for prevention of succinylcholine-induced bradydysrhythmias when d-tubocurarine pretreatment is given.

Cardiac effects of self-taming of succinylcholine and repeated succinylcholine administration.

Pretreatment with small (10 mg) doses of succinylcholine ("self-taming") decreases the incidence of muscle fasciculations following succinylcholine administration and may decrease the incidence of other unwanted effects. This study was designed to assess the cardiac effects of such self-taming and to assess the degree of protection afforded against bradydysrhythmias following subsequent succinylcholine administration. Sixty patients were studied and allocated randomly to three groups of twenty. Each group was assigned a different form of pretreatment. Patients in group I received 10 mg of succinylcholine immediately after induction. Patients in group II were treated with d-tubocurarine 0.04k mg . kg-1 three minutes before induction. Patients in group III received no pretreatment. All patients were induced with thiopentone 4 mg . kg-1 followed by succinylcholine 1 mg . kg-1 45 seconds later. A second dose of succinylcholine 1 mg . kg-1 was administered to the patients in the two pretreatment groups between four and five minutes after the first dose of succinylcholine. Following both the first and second doses of succinylcholine patients in the self-taming group showed a significantly greater incidence of bradydysrhythmias when compared to the other two groups. It is concluded that the use of a self-taming technique is potentially hazardous, and that it does not confer protection against repeated succinylcholine administration.

Duration of intradermal anaesthesia with mixtures of bupivacaine 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.