Regional analgesia can often be extremely beneficial for elderly pa¬tients. One advantage of regional techniques is Ihe reduced amount of narcotic needed. The disadvantages include (he hemodynamic changes associated with epidural local anesthetics and the potential for intravas¬cular injection, infection, bleeding, and nerve damage. When a regional anesthetic block is performed before a painful stimulus Ue, surgery) is initialed, pain relief lasts longer than would be expected from the pharmacokinetics of the local anesthelic. When the pain does recur, it is less intense, and lower doses of narcotic can be used. The mechanism for this phenomenon appears to occur at the spinal cord level and in¬volves modulation of the impulses eventually received in the brain.
Regional analgesic techniques range in complexity from instillation of local anesthelic into the surgical incision lo specific nerve blocks to continuous epidural infusions of local anesthetic, a narcotic, or a com¬bination of the two. The choice of technique depends on the surgical site and the relative complexity and potential advantages or disadvan¬tages of a particular technique.
Pain relief after limb surgery is often accomplished with a single-dose nerve block or a continuous infusion. For hand and elbow procedures, the axillary approach is used to block the brachial plexus because this approach can be used with relative ease and it has a lower incidence of complications than the other approaches to this plexus have, if a need for prolonged analgesia is anticipated, a catheter is inserted and an infu¬sion of local anesthetic is begun postoperatively. Often an infusion of bupivcicainc 0.125% is sufficient for complete pain relief. The infusion rate is usually started at X to 10 mL/h and titrated to desired effec¬tiveness.
After knee procedures, a continuous femoral sheath catheter tech¬nique can be used. Although the sciatic nerve is not blocked with this approach, patients still receive adequate analgesia. The femoral cathe-ler infusion may be supplemented by low-dose narcotics or ketorolac. For both the axillary and femoral sheath blocks, a blunt tip needle may be used. The same needle may be used for both single-dose and contin¬uous infusion techniques. The distinct pop felt when the needle enters the sheath signals an excellent end point for proper needle placement. This pop is much more evident with the blunt needles than with the traditional B-bevel needles. Also, with the blunt needles, entering the adjacent artery is more difficult, and the incidence of nerve damage is decreased.