Kido K, et al. - In this prospective, randomized, double-blind study of 40 patients undergoing orthognathic surgery, researchers investigated the effects of a low dose of ketamine on remifentanil-induced acute opioid tolerance and on the neutrophil–lymphocyte ratio (NLR), a newly recognized biomarker of inflammation. The patients were randomized to receive one of the following anesthetic regimens intraoperatively: high-dose remifentanil (0.6 µg/kg/minute); low-dose remifentanil (0.2 µg/kg/minute); or high-dose remifentanil with ketamine (remifentanil 0.6 µg/kg/minute with 0.5 mg/kg ketamine just after induction followed by an intraoperative infusion of ketamine 5 µg/kg/minute until wound closure). Infusion of low-dose ketamine prevented postoperative acute opioid tolerance induced by high-dose intraoperative remifentanil. Further, they noted an increase in postoperative NLR associated with decreased fentanyl requirement for postoperative pain control, with ketamine infusion.