Continuous sciatic nerve block: compartive study between the parasacral, lateral, and anterior approaches for lower limb surgery.

OBJECTIVE: The aim of the present study was to evaluate the ease and reliability of the anterior and lateral approaches to sciatic nerve block compared to the posterior parasacral approach, and their suitability for the specific factors in the patients, positions, and surgeries. Also, the insertion and usefulness of the continuous catheter technique was evaluated.

METHODS: The study was carried out on 120 patients, ASA I, II and III, of both genders, age range between 20 and 70 years, scheduled for orthopedic, general and vascular lower limb surgery. Patients were enrolled in a prospective, randomized, double blind study. Patients were divided into three equal groups, 40 patients each. All the patients received femoral nerve block in addition to sciatic nerve block either parasacral (Posterior group), lateral (Lateral group) or anterior approach (Anterior group). This was followed by continuous femoral and sciatic nerve blocks in the postoperative period. Patients were assessed as regards the time, duration and intensity of the sensory and motor blocks and also the postoperative analgesia offered by the continuous block. They were also assessed for the hemodynamic changes accompanied these blocks. Radiological study was made to demonestrate the spread of different volumes of the drugs alongside the course of the sciatic nerve.

RESULTS: The posterior parasacral approach is the easiest technique to perform and used successfully even in obese patients, but difficult to be done, if at all, in patients with limited movement such as multi-pelvic fractures. The anterior approach was found to be the best for the patients in the supine position, with best results as regards patients' satisfaction and sensory and motor blocks. Only, it is a technique that needs high experience especially in obese patients. The lateral approach was the least performed technique especially its high approach. However, it is useful in patients in supine position, and gives the best results in thin patients. The technique showed to be extremely difficult in obese patients.

CONCLUSION: The insertion of a catheter for continuous nerve block was easy. These blocks provided good or excellent postoperative analgesia for all patients in the different groups and facilitated early mobilization which helped in preventing the lower limb srugery - related morbidity and mortality.