Interest of the Alkalinization of the Adrenaline Lidocaine Solution for Conversion of Epidural Analgesia Into Epidural Anesthesia During an Emergency Caesarean

During labor, pain is systematic. In France, epidural analgesia is the gold standard to fight pain.

Sometimes, emergency situations involve the maternal or fetal prognosis and require an emergency fetal extraction by caesarean. When an effective epidural analgesia is in place, an injection of adrenaline lidocaine converts this epidural analgesia into an epidural anesthesia allowing a surgical procedure. Sometimes, the time required to set up the anesthesia cannot be expected and a general anesthesia is performed.

Local anesthetics used during epidural analgesia have Pka between 7.8 and 8.1. In solution, local anesthetics exist in two forms: an un-ionized form and an ionized form. The non-ionized form is liposoluble and crosses the lipid membranes to reach the site of intracellular action. The non-ionized form conditions the time taken to install anesthesia.

When the pH of the solution is equal to Pka, un-ionized and ionized form are present in equal quantity. Commercial local anesthetic solutions have acidic pH and so contained a majority of ionized form. Alkalinization of local anesthetics solution should bring the pH closer to pKa and therefore to favor a greater proportion of non-ionized form.