Abstract

Single shot spinal anesthesia is common in obstetric, orthopedic, urologic, and gynecologic surgery, but early postoperative pain and variable block regression hinder recovery. Intravenous (IV) perioperative adjuncts enhance block characteristics and reduce analgesic needs. We aimed to synthesize studies on the analgesic benefits, block effects, and safety of IV adjuncts administered around spinal anesthesia. We conducted this study according to Preferred Reporting Items for Systematic Reviews and Meta Analyses Guidance, electronic databases and reference lists were searched. Studies with adults undergoing surgery with single-shot spinal anesthesia were eligible. Records identified: 1287, included in qualitative synthesis, 48 studies in obstetric and non-obstetric settings. Multiple agents improved early analgesia and delayed the first rescue relative to control. IV dexamethasone and IV dexmedetomidine prolonged sensory block and reduced early analgesic needs; dexmedetomidine was associated with manageable bradycardia and sedation. Magnesium infusions prolonged two-segment regression and reduced opioid use without symptomatic toxicity under monitoring. IV acetaminophen showed mixed results, and IV lidocaine showed context-dependent effects on pain trajectories and recovery outcomes. When integrated into multimodal pathways, selected IV adjuncts administered with spinal anesthesia improve early postoperative analgesia and block characteristics, with agent-specific safety trade-offs.

Key words: Spinal anesthesia, intravenous adjuncts, dexamethasone, dexmedetomidine, magnesium sulfate, ketamine, acetaminophen, lidocaine, postoperative analgesia, PRISMA.