A “New” Automated Bolus Technique for Continuous Popliteal Block: A Prospective, Randomized Comparison with a Continuous Infusion Technique

Abstract

The present investigation demonstrated that local anesthetic administered by an automated bolus technique provided better postoperative pain relief than a continuous infusion technique for continuous popliteal nerve block after foot surgery.

Continuous Femoral Nerve Blocks

“…2–4). This might be viewed as a positive finding if the sensory block—and, therefore, possibly analgesia—was greatly increased in the bolus-only group, in line with previous reports of continuous popliteal-sciatic nerve blocks 12,22. Unfortunately, this was not the case: tolerance to cutaneous electrical current was virtually indistinguishable at Hour 6 between the two groups (fig.…”

“…A second possible explanation for the differing results among studies is the anatomic location of the catheters: local anesthetic deposited in the popliteal fossa in previous studies may have been absorbed by perineural tissue, including blood vessels and the lymphatic system 12,22. Conversely, in the femoral region, the local anesthetic may better pool between the iliac fascia and underlying muscle, providing a conduit and/or reservoir keeping the medication in contact with the femoral nerve.…”

“…The first is in catheter-insertion methodology: the previous studies used nerve stimulation to guide needle placement, but then “blindly” advanced nonstimulating catheters 4–5 cm past the needle tip 12,22. As the previous investigators noted, “the final location of the catheter tip… may have actually been located distant from the targeted nerve… This may render it difficult, or even impossible, for the local anesthetic to traverse the distance between the tip and the two sciatic nerve trunks when a slow continuous infusion with an overall small volume is used… In contrast, the use of an intermittent bolus is accompanied by higher pressure and more volume per time, which may increase the spread of local anesthetic…”12 In contrast, our current study used ultrasound to allow positioning of the catheter tips at a precise (and bilaterally equivalent) location immediately posterolateral to the femoral nerve, resulting in very accurate perineural local anesthetic deposition and possibly improved nerve-anesthetic contact.…”

“…Alternatively, decreasing the concentration of local anesthetic and increasing the delivered volume—to retain total delivered dose—has demonstrated little effect on either sensory or motor block 11. However, one recent study involving continuous popliteal-sciatic nerve blocks following hallux valgus repair reported increased analgesia without a concurrent increase in motor block by administering local anesthetic in repeated 5 ml hourly boluses compared with a 5 ml/h continuous infusion 12. These results raise the exciting possibility of decreasing the fall risk during cFNB by decreasing muscle weakness while maintaining analgesia.…”

Continuous Transversus Abdominis Plane Nerve Blocks: Does Varying Local Anesthetic Delivery Method—Automatic Repeated Bolus Versus Continuous Basal Infusion—Influence the Extent of Sensation to Cold?: A Randomized, Triple-Masked, Crossover Study in Volunteers

“…The superiority of repeated bolus doses over a continuous basal infusion has been demonstrated in some studies for various catheter locations, 17–20 yet not others. 21–23 As with other aspects of continuous peripheral nerve blocks, effects often vary depending upon the anatomy of the catheter location.…”