Comparative Assessment of Block Characteristics and Side Effects of Intrathecal vs. Intravenous Fentanyl for Subarachnoid Block Augmentation in Surgery

Abstract

Although various studies have compared different opioids and fentanyl dosages, research on the two routes of administration, particularly for total abdominal hysterectomy, remains limited. This study compared intrathecal (IT) fentanyl 25µg and intravenous (IV) fentanyl 1µg/kg, both administered with 15 mg of 0.5% hyperbaric bupivacaine for spinal anesthesia. Sensory and motor blockade onset, maximum blockade level and duration, regression times, sedation levels, and time to rescue analgesia were assessed. The onset of sensory and motor blockade was significantly faster in IV fentanyl (p <0.008 and p <0.007, respectively), while IT fentanyl provided prolonged sensory and motor blockade, with a longer time to rescue analgesia (p <0.001). Sedation scores favored IT fentanyl, with 87% of patients having an RSS score of 2 and 13% having an RSS score of 3, compared to 74% and 26% in IV fentanyl. Adverse effects were lower in the IT fentanyl group, with 4% experiencing nausea and vomiting and 13% experiencing hypotension, whereas the IV fentanyl group had higher rates of nausea and vomiting (14%), hypotension (16%), and pruritus (4%). In conclusion, intrathecal fentanyl 25µg, compared to intravenous fentanyl 1µg/kg, prolonged sensory and motor block, extended analgesia duration, and provided better sedation with fewer adverse effects in total abdominal hysterectomy patients.