Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials.
Abrahams MS, Aziz MF, Fu RF, Horn JL.
Br. J. Anaesth. 2009 Jan 26.
Are peripheral and neuroaxial blocks with ultrasound guidance more effective and save in children?
Rubin K, Sullivan D, Sadhasivam S.
Paediatr Anaesth. 2009 Feb;19(2):92-6