Analgesic Efficacy of Free-opioid Anesthesia for Colorectal Surgery

Free opioid anesthesia (FOA) has been used in many countries around the world, making use of multimodal analgesia therapy which includes hypnotics, N-methyl-D-aspartate (NMDA) antagonists, local anesthetics and anti-inflammatory agents and sympathetic block in surgery. This method was demonstrated to contribute to enhanced recovery after surgery (ERAS). The use of long-acting local anesthetics also enhances postoperative pain relief. As a result, the concept of balanced anesthesia now has a change in three basic components: hypnotics, muscle relaxants and sympathomimetic inhibitors

Opioids have been used as one of three basic components of balanced anesthesia, including anesthetic drugs, pain relievers, and neuromuscular blockade agents (opioid anesthesia). Opioids not only facilitate deep anesthesia but also create the most favorable conditions for surgeries. Fentanyl is a potent opioid used to control pain, reduce the dose of sympathomimetic inhibitors and maintain hemodynamic stability. However, several common side effects of fentanyl are well known: nausea and vomiting, constipation, urinary retention, headache, pruritus, rash, histamine release, biliary spasm and respiratory depression, the most severe adverse effect