QUALITY OF EPIDURAL BLOCKADE HI: CARBONATED LOCAL ANAESTHETIC SOLUTIONS BY

• Main Authors: P. R. Bromage, M. F. Burfoot, D. E. Crowell, A. P. Truant
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1032.8792; http://bja.oxfordjournals.org/content/39/3/197.full.pdf

The effects of carbon dioxide-enriched local anaesthetics injected epidurally were com-pared in animals and in man. Addition of carbon dioxide at tensions of ^ and 1 atmos-phere shortened by 20-30 per cent the latency of onset and spread of analgesia with lignocaine hydrochloride but did not increase intensity of motor block. The quality of epidural blockade was improved when lignocaine or prilocaine base was dissolved as salts of carbonic acid at a Pco3 of 1 atmosphere. Blockade became complete 33 per cent faster with lignocaine and 24 per cent faster with prilocaine, and the degree of motor block was increased by 42 per cent and 33 per cent, respectively, over control values. A smaller but significant increase (10-15 per cent) in spread and duration of analgesia occurred with carbon dioxide-base solutions also. A high Pco2 increased the uptake of lignocaine in excised frog nerves but not after epidural injection of labelled lignocaine in live dogs. Analysis of uptake of 14C-lignocaine by the neuraxis and meninges in dogs suggests that the improved quality of blockade produced by the carbon dioxide bases is due not to an absolute increase in tissue uptake but to a favourable distribution in tissue. A direct action of carbon dioxide on the axon membrane may be an additional