Comparison of continuous infusion versus automated bolus for postoperative patient-controlled analgesia with popliteal sciatic nerve catheters.

BACKGROUND: This investigation was designed to compare a new methodology of automated regular bolus with a continuous infusion of local anesthetic for continuous popliteal sciatic block; both regimens were combined with patient-controlled analgesia (PCA). METHODS: Fifty patients undergoing hallux valgus repair were randomly allocated to receive an infusion of 0.125% levobupivacaine administered through a popliteal catheter as an automated regular bolus (n = 25) or as a continuous infusion (n = 25), both combined with PCA. Postoperative pain scores, incremental doses delivered by the PCA, local anesthetic consumed per hour, and the need for rescue tramadol analgesia were recorded. RESULTS: Both dosing regimens provided similar postoperative analgesia. Consumption of local anesthetic (5.14 ml/h, 5-5.75 ml/h) and dose request from the PCA (1, 0-5.4) was lower in the automated bolus group as compared to the continuous infusion group (5.9 ml/h, 5.05-7.8 ml/h; doses by PCA: 6.5, 0-20.5; P < 0.05). The need for rescue tramadol was similar in the two groups. CONCLUSION: In continuous popliteal sciatic block, local anesthetic administered as an automated regular bolus in conjunction with PCA provided similar pain relief as a continuous infusion technique combined with PCA; however, the new dosing regimen reduced the need for additional PCA and the overall consumption of local anesthetic.

Low volume and high concentration of local anesthetic is more efficacious than high volume and low concentration in Labat's sciatic nerve block: a prospective, randomized comparison.

BACKGROUND: Various factors markedly affect the onset time and success rate, of peripheral nerve blockade. This prospective, randomized, double-blind study, compared a dose of mepivacaine 300 mg, in a 20 or 30 mL injection volume for sciatic nerve blockade using Labat's posterior approach. METHODS: A total of 90 patients undergoing foot surgery were randomly allocated to receive sciatic nerve block with 20 mL of 1.5% mepivacaine (n = 45) or 30 mL of 1% mepivacaine (n = 45). All blocks were performed with the use of a nerve stimulator (stimulation frequency 2 Hz; intensity 1.5-0.5 mA). In the two groups, appropriate nerve stimulation was elicited at <0.5 mA and the targeted evoked motor response was plantar flexion of the foot. Time required for onset of sensory and motor block in the distribution of the tibial and common peroneal nerves were recorded. A successful block was defined as a complete loss of pinprick sensation in the sciatic nerve distribution with concomitant inability to perform plantar or dorsal flexion of the foot. RESULTS: A greater success rate was observed with 20 mL of 1.5% mepivacaine (96.6%) than with 30 mL of 1% mepivacaine (68.9%; P < 0.05). Time to onset of complete sensory and motor block was shorter after injection of 20 mL of 1.5% mepivacaine (11 +/- 6 min and 13 +/- 7 min, respectively) than after 30 mL of 1% mepivacaine (17 +/- 8 min and 19 +/- 8 min, respectively, P < 0.05). CONCLUSION: In Labat's sciatic nerve blockade, administering a low volume and a high concentration of local anesthetic (1.5% mepivacaine) is associated with a higher success rate and a shorter onset time than a high volume and a low concentration of solution (1% mepivacaine).

Intraneural hematoma after nerve stimulation-guided femoral block in a patient with factor XI deficiency: case report.

Intraneural hematoma after a peripheral nerve block is a theoretical cause of postoperative nerve injury that has not been previously documented in humans. We report an intraneural hematoma after nerve stimulation-guided femoral block, which occurred in a patient with undiagnosed factor XI deficiency and a slightly prolonged activated partial thromboplastin time. Onset of paralysis several days after surgery prompted early surgical exploration and removal of an intraneural hematoma at the femoral nerve. Improvement in motor function was noted after epineurolysis of the femoral nerve. Early nerve decompression contributed to a satisfactory outcome.

Is ultrasound guidance superior to conventional nerve stimulation for coracoid infraclavicular brachial plexus block?

BACKGROUND AND OBJECTIVES: In different peripheral nerve blocks, it has been speculated that needle guidance by ultrasound improves onset time and success rate compared with the more frequently used nerve stimulation-guided technique. In the present study, we tested the hypothesis that ultrasound guidance improves onset time of coracoid infraclavicular brachial plexus block (IBPB) when compared with a nerve stimulation-guided technique. METHODS: Seventy patients scheduled for hand or forearm surgery were randomly assigned to receive coracoid IBPB using either ultrasound guidance (group U, n = 35), or nerve stimulation (group S, n = 35). Patients were assessed for sensory and motor block every 5 mins after injection of local anesthetic. Onset time, the primary end point, was defined as the time required for complete sensory and motor block. Time required to perform the block, success rate, and time to resolution of motor blockade were also recorded (secondary end points). RESULTS: Onset of complete sensory and motor blockade was similar in the 2 groups (17 mins [8 mins] in group U and 19 mins [8 mins] in group S; P = 0.321). Time required to perform the block was shorter in group U (3 mins [1 min]) as compared with group S (6 mins [2 mins]; P < 0.0001). No differences were observed in success rate (89% in group U and 91% in group S; P = 0.881) and time to resolution of motor blockade (237 mins [45 mins] in group U and 247 mins [57 mins] in group S; P = 0.418). CONCLUSIONS: The present investigation demonstrates that ultrasound guidance and nerve stimulation provide similar onset time, success rate, and duration of motor blockade for coracoid IBPB; however, ultrasound guidance reduces the time required to perform the block.