Ackerman W E, Ware T R, Juneja M
Department of Anesthesia, University of Cincinnati, College of Medicine, Ohio 45267-0531.
Can J Anaesth. 1992 Apr;39(4):387-9. doi: 10.1007/BF03009051.
The alkalinization of certain local anaesthetics with sodium bicarbonate hastens the onset of epidural analgesia. Increases in both the pH and PCO2 of the local anaesthetic are necessary to hasten onset. However, carbon dioxide can diffuse from local anaesthetic solutions following alkalinization with sodium bicarbonate and change both the pH and PCO2 of the mixture. This study examined changes in pH and PCO2 of three local anaesthetics reported to have a faster onset of analgesia following mixture with sodium bicarbonate and examined the effects of time and the local anaesthetic container air/liquid interface on the pH and PCO2 of the buffered local anaesthetic solutions. Bupivacaine 0.5%, lidocaine 2%, and chloroprocaine 2% were each buffered with sodium bicarbonate. The pH and PCO2 of each solution were measured at time 0 and at 5, 10, 15, 20, 30, 40, 50 and 60 min intervals. The solutions were placed in containers as follows: 30 ml in 40 ml containers, 10 ml in 40 ml containers, 10 ml in 13 ml containers, and 10 ml in polypropylene syringes. The pH and PCO2 increased following alkalinization but gradually decreased in all containers except in polypropylene syringes.
用碳酸氢钠碱化某些局部麻醉药可加速硬膜外镇痛的起效。局部麻醉药的pH值和PCO₂升高对于加速起效是必要的。然而，在用碳酸氢钠碱化后，二氧化碳可从局部麻醉药溶液中扩散出来，从而改变混合液的pH值和PCO₂。本研究检测了三种据报道与碳酸氢钠混合后镇痛起效更快的局部麻醉药的pH值和PCO₂变化，并研究了时间以及局部麻醉药容器的气/液界面缓冲对局部麻醉药溶液pH值和PCO₂的影响。分别用碳酸氢钠对0.5%布比卡因、2%利多卡因和2%氯普鲁卡因进行缓冲。在0、5、10、15、20、30、40、50和60分钟时测量每种溶液的pH值和PCO₂。溶液按以下方式放置在容器中：30 ml置于40 ml容器中、10 ml置于40 ml容器中、10 ml置于13 ml容器中以及10 ml置于聚丙烯注射器中。碱化后pH值和PCO₂升高，但除聚丙烯注射器外，所有容器中的pH值和PCO₂均逐渐下降。
