The Opioid-Sparing and Analgesic Effects of IV Acetaminophen in Craniotomy: A Prospective, Randomized, Placebo-Controlled, Double-Blind Study

General anesthesia will be induced by bolus administration of propofol (1.5-2.5 mg/kg IV), and fentanyl (2-3 µg/kg IV). Neuromuscular blockade will be achieved with bolus administration of rocuronium, vecuronium, or succinylcholine. Once the endotracheal tube is secured in place, the patient will be mechanically ventilated to an end-tidal CO2 of 35 mmHg. Additional procedures will include radial arterial line placement for invasive arterial blood pressure monitoring, as well as additional large-bore peripheral IV placements, or central line placement, if indicated. Anesthesia will be maintained with desflurane, propofol, and remifentanil.

Once general anesthesia has been induced, but prior to the first surgical incision, the first dose of the interventional agent will be administered. Repeat doses will be administered every 6 hours until 24 hours from the time that the patient enters the PACU, for a total of up to 6 doses. Once the patient has been positioned and prepped for surgery, the surgeon will infiltrate the scalp with bupivacaine 0.5% with epinephrine 1:200,000 (15-20 ml) before skin incision.

No other opioids or agents with analgesic properties (e.g., ketorolac, dexmedetomidine, ketamine) will be administered at any time during the operation. Additional medications that will be routinely administered for this procedure include dexamethasone 8-12mg IV prior to incision, and ondansetron 4mg IV at skin closure. Anticonvulsant drugs will be administered at the surgeon's request.

Emergence and extubation will occur at the completion of the case per standard guidelines. The time of remifentanil infusion discontinuation and time of extubation will be noted. If necessary, extubation may occur in the post anesthesia recovery unit (PACU); otherwise, extubation will occur in the operating room.

The patient will then be taken directly to the PACU. Inability to extubate a patient within two hours of completion of surgery will result in their withdrawal from the study. Once in the PACU, immediate postoperative vital signs will be recorded, including blood pressure, heart rate, respiratory rate, oxygen saturation, and RASS score.