Intravenous regional anesthesia: a review of common local anesthetic options and the use of opioids and muscle relaxants as adjuncts

To provide a review of local anesthetic (LA) agents and adjuncts, opioids and muscle relaxants, and their intraoperative effects and postoperative outcomes in intravenous regional anesthesia (IVRA). A search for prospective, double-blind, randomized controlled trials evaluating LA agents, opioids and muscle relaxants as adjuvants for IVRA, was conducted (MEDLINE(®), Embase). Intraoperative benefits (onset/recovery of sensory and motor block, intraoperative analgesia, tourniquet pain), postoperative benefits (pain score, analgesic consumption, time to first analgesia), and side effects were recorded. A conclusion for overall benefit was made based on statistical significance and clinical relevance. Thirty-one studies were evaluated, with data collected on 1523 subjects. LA agents evaluated were lidocaine, ropivacaine, and prilocaine. Adjuncts evaluated were opioids ( morphine, fentanyl, meperidine, sufentanil, tramadol) and muscle relaxants (pancuronium, atracurium, mivacurium, cisatacurium). There was good evidence that ropivacaine provided effective IVRA and improved postoperative analgesia. Lidocaine and prilocaine were effective LA agents, however they lacked postoperative benefits. Morphine, fentanyl, and meperidine as sole adjuncts did not demonstrate clinically significant benefits or result in an increased risk of side effects. Sufentanil data was limited, but appeared to provide faster onset of sensory block. Tramadol provided faster onset of sensory block and tourniquet tolerance, however postoperative benefits were not consistent and the risk of minor side effects increased. Muscle relaxants improved the quality of motor block, but at the expense of delayed motor recovery. The combination of fentanyl and muscle relaxants can achieve an equivalent quality of IVRA with 50% reduction in LA dose, but at the expense of a potentially slower onset of sensory block. Ropivacaine is effective for IVRA and improves postoperative analgesia. Muscle relaxants enhance the motor block and when combined with fentanyl allow for an equivalent quality of IVRA with 50% reduction in LA dose.