Comparing the efficacy and safety of unilateral versus bilateral spinal anesthesia: a meta-analysis and systematic review

Background Unilateral spinal anesthesia has gained increasing attention in recent years. Emerging evidence suggests that it provides comparable analgesia to conventional bilateral spinal anesthesia while reducing adverse effects, and its efficacy and safety compared to bilateral spinal anesthesia remains controversial.Objective This systematic review and meta-analysis aims to evaluate and compare the efficacy and safety of unilateral versus bilateral spinal anesthesia.Design Systematic reviews and meta-analysis of randomized controlled trials (RCTs).Data sources A systematic search was conducted across PubMed, EMBASE, and Cochrane Library from inception to December 10, 2024.Eligibility criteria Included studies were randomized controlled trials involving adult patients (≥18 years) undergoing surgery under spinal anesthesia, comparing unilateral versus bilateral spinal anesthesia for efficacy and adverse effects. Studies that focused exclusively on either unilateral or bilateral spinal anesthesia were excluded. The comparator group used the same local anesthetic as the experimental group, with no restrictions on adjuncts (e.g. fentanyl, morphine).Results Nineteen randomized controlled trials including 1191 patients met the inclusion criteria. Compared with bilateral spinal anesthesia, unilateral spinal anesthesia has a longer onset of sensory blockade (MD = 2.58, 95% CI: 0.93 to 4.22, p = 0.002), a shorter duration of sensory blockade (MD = −27.83, 95% CI: −39.25 to −16.42, p < 0.00001). In addition, unilateral spinal anesthesia significantly reduced the incidence of hypotension (RR = 0.40, 95% CI: 0.31 to 0.52, p < 0.0001), nausea and vomiting (RR = 0.20, 95% CI: 0.07 to 0.56, p = 0.002), and post-dural puncture headache (RR = 0.44, 95% CI: 0.23 to 0.81, p = 0.009). No statistically significant differences were observed in bradycardia and urinary retention. Collectively, these findings support unilateral spinal anesthesia as a strategy that may enhance perioperative safety while maintaining adequate anesthetic efficacy in appropriately selected patientsConclusions Unilateral spinal anesthesia may offer a favorable balance between anesthetic efficacy and safety compared with bilateral spinal anesthesia, although its clinical utility may depend on surgical duration and patient characteristics.