Field block anesthesia

Field block anesthesia is produced by subcutaneous injection of a solution of local anesthetic such that the region distal to the injection is anesthetized. 

---

Field block anesthesia Produced by subcutaneous injection in such a manner as to anesthetize the region distal to the injection site... 

Field block anesthesia is produced by subcutaneous injection of a solution of local anesthetic in order to anesthetize the region distal to the injection. For example, subcutaneous infiltration of the proximal portion of the volar surface of the forearm results in an extensive area of cutaneous anesthesia that starts 2-3 cm distal to the site of injection. The same principle can be applied with particular benefit to the scalp, the anterior abdominal wall, and the lower extremity. The drugs, concentrations, and doses recommended are the same as for infiltration anesthesia. The advantage of field block anesthesia is that less drug can be used to provide a greater area of anesthesia than when infiltration anesthesia is used. 

Clinical use Ropivacaine is used for local infiltrations such as field block (0.75 % solution) and for nerve block (0.75 %) up to 300 mg and for epidural anesthesia (0.75 and 1.0 %) up to 200 mg. When used for labour analgesia, epidural doses up to 40 mg are recommended. A combination of opioids is often administered via the epidural route for postoperative analgesia. 

Pharmacological Profile. The profile of the ideal local anesthetic agent depends largely on the type and length of the surgical procedure for which it is applied. Procedures could include neuraxial (spinal and epidural) anesthesia, nerve and plexus blocks, or field blocks (local infiltration). In general, tine ideal agent should have a short onset of anesthesia and be useful for multiple indications such as infiltration, nerve blocks. 

Two to three injection sites may be needed to provide adequate anesthesia. For minor surgical procedures of the eyelid, the volume of anesthetic required would be far less than the maximum dose of most local anesthetics (e.g., procaine, lidocaine, and mepivacaine)—approximately 500 mg as a 1% or 2% solution.A ring block or field block may be used to anesthetize around the area of the surgical site in a circumferential manner without injecting... 

In an abaxial sessamoid local anaesthetic model, the highest no-effect dose for the local anaesthetic effect of lidocaine was 4 mg (Harkins et al 1998). For caudal epidural anesthesia, dose rates of lidocaine alone of 0.25 (Csik-Salmon et al 1996) or 0.35mg/kg (Pikes et al 1989) have been proposed (i.e. 6-10 ml of a 2% solution). A maximum of 200 ml should be used for field blocks. The dose rates quoted for i.v. administration of either a 1% or 2% solution of lidocaine (without epinephrine (adrenaline)) are for loading doses of 0.65-5 mg/kg followed by a constant i.v. infusion of 25-100 gg/kg/min (Brianceau et al 2002, Doherty Frazier 1998). 

This consists in the injection of the local anesthetic into or around the nerve trunk or in the area of its distribution, so as to block off sensory impulses from the operative field. Because fatal effects may arise from the absorption of the anesthetic, the smallest amount of the least-toxic agent that is effective should be employed, under conditions that minimize absorption. Procaine with the addition of epinephrine (1 100,000) is generally preferred. A well-planned technique is important. It is not necessary to flood the entire field of operation, as in the earliest methods, nor even to infiltrate the whole line of incision, as in infiltration anesthesia. It is now aimed at confining the anesthetic mainly to the nerves, by placing it where the nerves chiefly run or injecting it into the nerves themselves. 

---