Selective Spinal Anesthesia: A Comparison of Hyperbaric Bupivacaine 4 mg Versus 6 mg for Outpatient Knee Arthroscopy

he use of spinal anesthesia may lead to the de-velopment of transient neurological symptoms(TNS) especially when short-acting anesthetics(e.g., lidocaine) are used (1–4). In ambulatory surgery,bupivacaine may delay the recovery of motor functionand cause urinary retention, leading to delayed dis-charge (5,6). These concerns have increased interest inthe use of small doses of bupivacaine (6,7) and tech-niques to produce unilateral spinal anesthesia (7–9),but the methods used so far may result in highlyvariable spinal anesthesia (10) or anesthesia of ques-tionable reliability (6,11). Selective spinal anesthesia(SSA) is the practice of using minimal doses of intra-thecal agents so that only the nerve roots supplying aspecific area and only the modalities that require to beanesthetized are affected (5). We hypothesized that4 mg spinal hyperbaric bupivacaine induces a reliableSSA with faster recovery compared with 6 mg foroutpatient knee arthroscopy.