- patients with preexisting neuropathy in the operated limb, ASA greater than III, coagulation disorders, known allergy to local anesthetics, local infection at the puncture site, chronic obstructive pulmonary disease or respiratory failure, pregnancy, breast-feeding and prior surgery in the supraclavicular region, BMI ≥ 35 kg/㎡, uncooperative patients and patients' refusal. an ultrasound view of the perfect circular neural cluster.