Sciatic nerve blocks

Abstract

Sciatic nerve blocks are infrequently performed by anesthesiologists. These blocks are considered to be more difficult, and they require the use of long needles, causing apprehension to both the patient and the anesthesiologist. However, the use of nerve stimulators significantly facilitates the approach of the sciatic nerve. The nerve can essentially be blocked either high or at the popliteal fossa (popliteal block) before or at its division. Although surgery of the lower extremity does not necessarily require sciatic nerve conduction to be blocked, when indicated, this is a very effective method for controlling pain and reducing the length of hospitalization, the latter leading to substantial savings. Different approaches have been described (eg, posterior, anterior and lateral). Each approach has specific indications that need to be recognized. Consequently it is necessary to be familiar with more than one approach. Thus, a parasacral or classic posterior approach of the sciatic nerve is recommended in lateral positions, whereas the anterior approach is favored in the supine patient. When the strategy of anesthesia is developed or the placement of a catheter is considered, it is important to recognize that sciatic blocks have the slowest onset and longest duration compared with all other peripheral nerve blocks performed by anesthesiologists. For single injections in adults, our preference is a combination of 1.5% lidocaine and 0.75% ropivacaine (equivolumes) with the addition of bicarbonate and epinephrine for a total volume of 20 to 30 mL in adults.