Interscalene block anesthesia at an ambulatory surgery center performing predominantly regional anesthesia: a prospective study of one hundred thirty-three patients undergoing shoulder surgery.

Interscalene block (ISB) of the brachial plexus is frequently used for patients undergoing ambulatory shoulder surgery. We previously reported that the incidence of postoperative complaints (neurapraxia) after an ISB was low (3% at 2 weeks), but objective neurologic assessment was not included in the study. The present study combines subjective findings with both preoperative and postoperative objective sensory and motor assessments after an ISB. We prospectively evaluated 133 patients undergoing elective ambulatory shoulder surgery. ISB anesthesia was accomplished by use of 1.5% mepivacaine alone or in combination with bupivacaine (0.5%-0.75%) via a paresthesia technique and a 23-gauge needle. All of the blocks were performed by experienced anesthesiologists. The number of passes with the needle, site of paresthesia, ease of performing the block, and success of the ISB were recorded for each patient. Neurologic assessment was performed preoperatively and up to 2 weeks postoperatively by 1 of 4 health care professionals but not by the anesthesiologists who performed the ISB and included diminished sensation, localized nerve pain, Semmes-Weinstein monofilament pressure threshold sensibility, Weber static 2-point discrimination, and grip strength changes. Patients with postoperative changes were followed up until resolution of symptoms occurred. Successful surgical anesthesia was achieved in 98% of the patients. There was 1 major perioperative complication (0.7%), a seizure that occurred within 5 minutes of the ISB. Two (1.4%) complained of transient postoperative neurapraxias. Neither patient had any changes in objective sensory and motor measurements. Hence, there was no correlation between subjective complaints and objective findings in this study. This study demonstrates that, in the hands of anesthesiologists doing predominantly regional anesthesia, there is a 1.4% incidence of neurologic complications after an ISB. ISB is a safe and effective technique for patients undergoing ambulatory shoulder surgery when an anesthesiologist experienced with regional anesthesia is involved.