The pH of local anesthetics and its importance in hand surgery
DOI:
https://doi.org/10.58814/01208845.510Keywords:
Anesthesia, Local, Lidocaine, Epinephrine, Hand Injuries, PainAbstract
Introduction: In Colombia, the most commonly used local anesthetics in hand surgery are lidocaine and bupivacaine, which can be used individually or in combination, and can be mixed with a vasoconstrictor to enhance their intraoperative analgesic and anesthetic effects and reduce latency time and pain at the time of injection and during the postoperative period.
Objective: To analyze the local anesthetics most commonly used in Colombia for hand surgery, their mixtures with other local anesthetics, vasoconstrictors, and buffers based on their pH, in order to determine which mixture is most effective for achieving a pH as close as possible to the physiological level.
Methodology: 14 mixtures of local anesthetics were analyzed. The pH was measured on 3 occasions, during which the temperature was also measured. The measurements were performed in the chemistry laboratory at El Bosque University in Bogotá, Colombia, using an Ohaus benchtop pH meter while adhering to all biosafety protocols.
Results: Of the 14 mixtures, only two (mixtures 3 and 4) yielded pH levels close to physiological (7.33–7.40), with no precipitation during the 1-hour observation period. This reduces pain at the time of injection and shortens the onset of action, while prolonging the duration of the analgesic effect. The remaining mixtures had pH levels that were either very acidic or very alkaline compared to physiological levels.
Conclusion: For patients undergoing hand surgery, the use of 2% lidocaine with epinephrine, either in a 10:1 or 9:1 ratio, plus 1 mL of bicarbonate is recommended, as these mixtures yield a pH close to physiological levels, which, in theory, reduces pain at the time of administration; additionally, they offer the benefits associated with the use of epinephrine.
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