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Introduction: A combination of sciatic nerve and lumbar plexus block by posterior approach using a neurostimulator is a useful method of providing unilateral anaesthesia for lower extremity surgery [1]. We report the results of the technique using a mixture of mepivacaine and ropivacaine.
Patients and methods: According to the method described by Farny [1] 121 patients ASA class I (54), II (36), III (31) were submitted, after informed consent, to orthopaedic surgery (repair of fractured neck of femur = 47, arthroscopy = 42, ACL repair = 11, foot surgery = 10, total knee replacement = 3, others = 8). The local anaesthetic solution was a 50:50 mixture of mepivacaine 1% and ropivacaine 0.75%. In each patient 30-35 mL of the solution was injected in the lumbar plexus, and 20 mL was placed near the sciatic nerve. Data recorded were expressed as means = SD and range between minimum and maximum values.
Results: Age of patients was 57.8 ± 24 years (range 18-98). Lumbar plexus was identified at the first attempt in 45.4%, at the second in 29%, at the third in 22.2%, at the fourth in 3.3% at a variable depth of 7.9 ± 1.1 cm (range 5.3-12), according to patients' body size. The dosage of mepivacaine was 4.3 ± 2.1 mg kg−1 (range 1.5-9.9); the dosage of ropivacaine was 2.9 ± 0.8 mg kg−1 (range 0.8-4.5). The block was complete (no discomfort during surgery) in 64.5% of the patients, and fair (supplementation with sedatives and/or narcotics) in 31.4%. In five cases (4.1%) the lumbar block failed, but a subsequent anterior approach was successful. Only one patient needed general anaesthesia. The upper level of anaesthesia was located at T10-T12 in 16.5% of cases, at L1-L2 in 79.4% of the cases. The complete block time (patient ready for surgery) was 14.6 ± 6.1 min (range 5-30). For a mean surgery time of 52.7 ± 28.1 min (range 15-125), the duration of anesthesia was always adequate (438 ± 156 min, range 180-950) and the duration of analgesia prolonged (470 ± 168 min, range 200-1080). More than half (52.1%) of the patients did not require postoperative analgesics. Thirteen patients (10.7%) displayed an epidural controlateral spread of the block from two to eight metamers. In no cases was the dura mater accidentally punctured. The subjective acceptance by the patients was good (72.7% very satisfied, 24.8% fairly satisfied). Haemodynamics (HR, BP), respiratory mechanics (RR) and oxygenation (SPO2) were not influenced by the procedure. Neither clinically relevant side effects nor sequelae were observed.
Conclusion: This combination of blocks, using a mixture of mepivacaine and ropivacaince, proved to be a reliable and safe alternative for prolonged, unilateral lower extremity anaesthesia. The learning and execution of these blocks are generally easy.
