By the neuraxial route
Near nerves and nerve plexuses,
Under the skin
Levoisomeric LAs can be promoted in different ways and make regional anesthesia safer. These ways are as follows;
• Devazoactive marker epidural test dose,
Fractional peridural doses,
Miscarriage and intrathecal minidosis,
Low volume multiple injections for nerve plexus blocks,
Use of nerve stimulators,
In ultrasound-guided regional anesthesia techniques
Alpha 2 agonists,
Addition of adjuvant drugs such as NMDA receptor antagonists,
Categorize the most important formulas and properties of LAs most commonly used in aesthesiology. This classification is as follows.
Amino Ester LA’lar
The precursor of this group is cocaine. They are characterized by being metabolized by plasmatic esterases, their short half-life and being associated with allergic reactions. The most commonly used are procaine, chloroprocaine, and tetracaine. Benzocaine has no use in regional anesthesia.
Amino Amid LA’lar
They are the most used in regional anesthesia. Lidocaine is the typical anesthetic to which almost all new drugs in this group are compared. Even when they have differences in latency, duration, and toxicity, they have a common mechanism of action in all LAs. They can be divided into two large groups: short-term and long-term ones.
Slow prolonged release of LAs are recent advances in improving postoperative pain management. Nano-structured carriers such as liposomes and polymers facilitate the long-term release of LAs. Exparel® was the first approved liposomal LA to combine racemic bupivacaine with liposomes. Polymersomes have improvements over liposomes with complementary profiles that inspired the emergence of hybrid carriers. In addition, investigation of multilamellar vesicles with ropivacaine is being conducted to prolong its analgesic effect.
It is a short acting LA with medium potency. It is included in the amide group, but contains an additional ester group that is rapidly hydrolyzed by esterases, a chemical property that accelerates its metabolism. The plasma protein binding of articaine and artisainic acid is 70%. IV articaine 80 mg does not cause toxic effects in healthy individuals. It has been used in neuraxial, ocular, intravenous and regional blocks. It is suitable and safe for procedures that require a short duration of action, such as dental procedures and ambulatory spinal anesthesia where a rapid onset of anesthesia is desired. The most common use is dentistry, where it shows efficiency and safety. Complete anesthesia in 90% of cases is achieved using 4% 60-80 mg articaine with 1: 200,000 adrenaline.
It spreads well through soft tissue and bone; The concentration in the alveoli of a tooth in the upper jaw after extraction was about 100 times higher than in the systemic circulation. In comparative clinical studies, their effects were generally not significantly different from other short-acting LAs such as lidocaine, prilocaine, and chloroprocaine. Although frequent cases of persistent paresthesia have been described after the use of Articaine, there is no conclusive evidence of above average neurotoxicity. Saralaya et al. In 50 patients operated in the 3rd molar, 4% articaine with 1: 100,000 epinephrine was compared with 2% lidocaine 1: 100,000 epinephrine. These researchers found that the mean onset time for articaine and lidocaine was 3.16 ± 0.55 and 3.2 ± 0.48 minutes, respectively.
Postoperative analgesia was longer in the articaine group and the duration of action was 289.04 ± 40 and 361.88 ± 40 min compared to lidocaine, which was 144.2 ± 12 and 197.44 ± 25 min, respectively. It also recommends articaine with its stronger and longer duration of action, with better postoperative analgesia and can be considered as an alternative to lidocaine. Even in the presence of pulpitis, articaine has been proven to be more effective than lidocaine in patients undergoing root canal therapy. There is no information on the use of articaine during breastfeeding, so its use is not yet fully recommended.
This drug has mixed properties: LA and & # 956; -opioid partial agonist. It is structurally similar to meperidine. It is mainly a compound still under investigation for spinal anesthesia (N-ethyl-1-hexyl-N-methyl-4-phenyl-4-piperidine carboxamide hydrochloride). Liver hydroxylation is the primary metabolic route and no local neurotoxicity was found in animal studies. Its effect on respiration is directly related to its plasma levels. In healthy volunteers, 25 mg and intrathecal bupivacaine 15 mg had similar effects on resting ventilation.
The ventilatory response to hypoxia and hypercarbia was found to be markedly reduced in the group treated with sameridine. Intravenous doses of 0.73 mg / kg suppress the ventilatory response to hypercarbia. Clinical doses of 150 µg / kg have no significant effect on ventilation. For inguinal surgery and orthopedic surgery, intrathecal doses of 15–25 mg sameridine are sufficient, respectively. Doses of 5-20 mg are comparable to 100 mg intrathecal lidocaine. The advantage is that sameridine produces residual analgesia and reduces the need for opioids in the first hours of the postoperative period, so it can play a role in the management of postoperative pain.
The nonester, chemically known as 4-N-butylamino-1,2,3,4-tetrahydroacridine hydrochloride, is a non-amide LA. Patnaik et al. It is a quinolone derivative drug with LA effects, which was synthesized by it in 1982. It is 5 to 8 times stronger than lidocaine, its LD50 is one quarter of lidocaine. It has vasoconstrictor and antihistamine effects, rapid onset of action (1-3 minutes), prolonged action (2.5 hours), and no cardiotoxicity or neurotoxicity events have been reported. Centbucridine has been investigated for peripheral nerve infiltration, conjunctival surface, neuraxial anesthesia, intravenous regional anesthesia; however, most of the studies are on dental anesthesia. Most studies compare 0.5% centbucridine and 2% lidocaine with similar anesthetic results, but some have found longer duration of anesthesia in patients treated with centbucridine. Centbucridine can be used safely in dental patients who are intolerant of other LAs or when epinephrine is contraindicated.
Maksimum LA Dozu
Another clinical aspect of local anastasis is the maximum doses of each LA. The maximum recommended doses have been arbitrarily determined by the pharmaceutical industry and vary according to the route of administration, the type of anesthetic with or without vasoconstrictor, as well as the type of patient and surgery. With studies conducted specifically to determine the safest and most effective amounts of each, these doses show the maximum recommended doses for the most commonly used LAs without determining them. Sometimes pay attention to variants at significant intervals; While 200 mg of lidocaine is recommended in Europe, this dose reaches 300 mg when epinephrine is not used in the United States. Despite these differences, it is recommended that you stay below the maximum recommended dosage range to avoid unwanted toxic effects.
Adequate Anesthesia Technique
Regional anesthesia techniques are important not only for expected results, but also for reducing the unwanted side effects of LAs. It is known that spinal anesthesia theoretically produces lower plasma concentrations of LA, unlike interpleural injection resulting in higher concentrations and thus may be the procedure that produces more toxic events. However, this is hypothetical because toxic events occur more frequently with peripheral blockages and peridural injections. For different types of nerve blocks, the same total injected dose produces different blood concentrations for mepivacaine, lidocaine, prilocaine and etidocaine; The intercostal block is the block that provides the highest blood absorption, followed by injections in the peridural space.
Writer: Ozlem Guvenc Agaoglu