Aim: To study the features of local anesthetic solution spreading during sciatic nerve block in dependence on the anesthetic solution volume. Material and Methods: One hundred and sixty nine cases of sciatic nerve blocks done under ultrasonic visualization control were analyzed. Sciatic nerve blocks were performed by lidocaine in volumes 30; 25; 20; 15; 12.5; 10; 7.5; 6.5; 5; 4.5 ml. The cross-section area, equal to local anesthetic spreading, was determined; the extension of the anesthetic solution spreading along sciatic nerve was calculated. Results: The anesthetic agent solution spreads along sciatic nerve in proximal and distal direction, forming a kind of cylinder. The minimum volume of the local anesthetic, which covers sciatic nerve in the whole, is 5 ml. A rare (1.77%) variation of sciatic nerve structure was described, in which tibial and common peroneal nerves develop directly from the branches of sacral plexus. Conclusion: The decrease of the local anesthetic volume leads to reduction of its spreading distance and cross-section area. Ultrasonic visualization can provide for sciatic nerve anatomical peculiarities, which can have an effect on the block quality.

Background: The aim of the study is to determine the effect of a reduction in dose of local anesthetic blockade on the development of the sciatic nerve. Methods: Forty blocks of sciatic nerve were used in a double-blind randomized research, under ultrasonic guidance, using an electric stimulator with the peripheral nerves. Forty patients were divided into 2 equal groups. In the first group, a sciatic nerve block was performed with 5 ml of 0.75% ropivacaine solution (37.5 mg); in the second group, 10 ml of 0.75% ropivacaine solution (75 mg) was used. The assessment of the time required for developing sensory and motor blocks was carried out from the beginning of local anesthetic solution injection in the fascial sheath of the sciatic nerve. Results: Demographic data of patients were identical in the two sample groups. The time required for achieving a complete sensory block in groups treated with 5 and 10 ml ropivacaine was 45 (40; 48) and 30 (28; 30) min, respectively, (р < 0.01). There was no difference in analgesic duration in the postoperative period among groups at p > 0.05. Conclusions: Complete blockade of the sciatic nerve is developed using 5 ml of 0.75% ropivacaine. Reducing the dose of ropivacaine prolongs the latent period of the LA during the blockade of the sciatic nerve. Time of postoperative analgesia was not significantly changed.

The existing researches in the field of regional anesthesia of the sciatic nerve show that if popliteal sciatic nerve blockade is performed, the time of the development of the sciatic nerve anesthesia is longer in comparison with subgluteal sciatic nerve blockade. Background: The aim of the research is to compare the time of the development of the sciatic nerve blockade performed with 1% lidocaine with epinephrine (1:200,000) in subgluteal and popliteal areas under ultrasound guidance. Materials and Methods: Patients were divided into two groups. In Group A (20 patients), the subgluteal approach to block the sciatic nerve was taken; in Group B (20 patients), the popliteal approach was applied. All blockades of the sciatic nerve were performed with 1% lidocaine (30 ml of lidocaine with epinephrine (1:200,000)) and electrical stimulation of peripheral nerves under ultrasound guidance. We measured the time of the development of sensory and motor blocks. Results: In Group A, the sciatic nerve sensory block developed in 15 (14 -16) minutes, a complete motor block developed in 15.5 (15 -17) minutes. In Group B the sciatic nerve sensory block developed in 40 (38.5 -42.5) minutes while a complete motor block did not develop in any patient. Conclusion: When the sciatic nerve is blocked in subgluteal area with 30 ml of 1% lidocaine with epinephrine (1:200,000) under ultrasound guidance, sensory blocks develop faster than during the popliteal blockade: 15 (14 -16) minutes vs. 40 (38.5 -42.5) minutes respectively. The opportunity to define the place of the introduction of local anesthetic in our research is limited.