Vol. 3, Issue 12, Part I (2017)

Materials and Methods: A prospective observational study was performed on 50 adult patients undergoing elective upper or lower limb operations with the use of ultrasound-guided nerve blocks (UGNB). This study was conducted at the Department of Anesthesiology, Sree Lakshmi Narayana Institute of Medical Sciences, Villianur, Puducherry, India from December 2016 to November 2017. The blocks encompassed brachial plexus, femoral, and sciatic nerve blocks. A standardized volume of local anesthetic (bupivacaine 0.5%) combined with a radiopaque contrast agent (iohexol) was delivered. Ultrasound guidance facilitated needle placement and injection, subsequently followed by radiological assessment utilizing fluoroscopy or CT imaging. The distribution pattern (longitudinal, circumferential, or spotty) and magnitude were evaluated. Block efficacy was assessed using sensory and motor evaluation 30 minutes after the operation.

Results: Radiological imaging revealed circumferential spread in 38(76%), longitudinal spread in 9(18%), and patchy spread in 3(6%) of the 50 patients. Complete sensory and motor blocks were substantially associated with circumferential spread (p=0.003), whereas partial or failed blocks were correlated with patchy spread. In the circumferential group, the average onset time was 12.6 ± 3.4 minutes, which was shorter than the others. Vascular puncture and local anesthetic toxicity were not reported as consequences.

Conclusion: The distribution of anesthetics in UGNB can be better understood with the use of radiological imaging. Successful and quick block onset is mainly predicted by a circumferential spread around nerves. It is possible that block prediction and patient outcomes might be improved by using contrast-enhanced imaging in certain circumstances.